ATL: GAMMA - Advisories

[cycloneye]

BULLETIN
Tropical Depression Twenty-Five Advisory Number 1
NWS National Hurricane Center Miami FL AL252020
1100 AM EDT Fri Oct 02 2020

...TROPICAL DEPRESSION FORMS OVER THE NORTHWEST CARIBBEAN...
...WARNINGS AND WATCHES ISSUED FOR A PORTION OF THE YUCATAN
PENINSULA...


SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...18.1N 84.7W
ABOUT 220 MI...355 KM SE OF COZUMEL MEXICO
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The government of Mexico has issued a Tropical Storm Warning for
the Yucatan Peninsula of Mexico from Punta Herrero to Cabo Catoche,
and a Tropical Storm Watch south of Punta Herrero to Puerto Costa
Maya and west of Cabo Catoche to Dzilam.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Punta Herrero to Cabo Catoche

A Tropical Storm Watch is in effect for...
* South of Punta Herrero to Puerto Costa Maya
* West of Cabo Catoche to Dzilam

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM EDT (1500 UTC), the center of Tropical Depression
Twenty-Five was located near latitude 18.1 North, longitude 84.7
West. The depression is moving toward the northwest near 9 mph (15
km/h), and a gradual turn toward the north-northwest with a
decrease in forward speed is expected over the next couple of
days. On the forecast track, the center of the tropical cyclone
should be near the northeastern Yucatan Peninsula on Saturday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some strengthening is forecast, and the depression is expected to
become a tropical storm by Saturday morning.

The estimated minimum central pressure is 1005 mb (29.68 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for the depression can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT5 and WMO header WTNT45 KNHC.

RAINFALL: The depression is expected to produce rainfall of 4 to 8
inches with isolated maximum amounts of 12 inches in portions of the
Yucatan Peninsula and far western Cuba. A separate area of
significant rain is expected to develop well away from the center in
the Mexican states of Campeche, Tabasco, and northern Chiapas, with
rainfall of 8 to 12 inches and isolated maximum amounts of 20
inches. This rainfall may produce life-threatening flash floods and
mudslides.

Rainfall of 1 to 3 inches with maximum amounts of 5 inches is
expected in the Bay Islands of Honduras.

WIND: Tropical storm conditions are expected within the Tropical
Storm Warning area by early Saturday, and are possible within the
Tropical Storm Watch area on Saturday and Sunday.


NEXT ADVISORY
-------------
Next intermediate advisory at 200 PM EDT.
Next complete advisory at 500 PM EDT.

$$
Forecaster Pasch


Tropical Depression Twenty-Five Discussion Number 1
NWS National Hurricane Center Miami FL AL252020
1100 AM EDT Fri Oct 02 2020

Visible satellite images show that cloudiness and showers associated
with the low pressure area over the northwestern Caribbean Sea have
become significantly better organized since yesterday, with
convective banding features becoming prominent. Moreover, low cloud
motions suggest that a closed circulation has become better defined.
Therefore, advisories are being initiated on Tropical Depression
Twenty-Five at this time. The initial intensity estimate is 30 kt
based on Dvorak T-numbers, but an Air Force Reserve Hurricane Hunter
aircraft is scheduled to investigate the system later today to
provide a better intensity estimate. Sea surface temperatures are
very warm, near 30 deg C, and vertical shear should remain low for
at least the next couple of days, so the cyclone is likely to become
a tropical storm by the time it nears the Yucatan Peninsula
tomorrow. The main impediment to strengthening over the next few
days should be the interaction with land. Given the uncertainties
about how far offshore the center will be over the next several
days, the official intensity forecast is conservative.

Since there is still a lot of scatter in the center fixes, the
initial motion estimate, 315/8 kt, is rather uncertain. For the
next couple of days, the system is expected to move northwestward to
north-northwestward on the southwestern edge of a mid-level high
pressure area. This would take the center near or over the
northeastern Yucatan Peninsula. After about 48 hours, the steering
currents are not well-defined and there is considerable spread in
the track models. At this time, it appears the cyclone should move
slowly westward over the latter part of the forecast period in
response to weak ridging over the north-central Gulf of Mexico. The
official forecast is near or a little north of the corrected and
simple model consensus predictions.

Tropical Storm Warnings and Watches have been issued for a portion
of the Yucatan Peninsula.

KEY MESSAGES:

1. The system is expected to produce heavy rainfall that could
result in life-threatening flash flooding over portions of the
Yucatan Peninsula, far western Cuba and well away from the center in
the Mexican states of Campeche, Tabasco, and northern Chiapas.

2. The depression is forecast to become a tropical storm and bring
tropical storm conditions to portions of the Yucatan Peninsula on
Saturday, where a Tropical Storm Warning is in effect.

FORECAST POSITIONS AND MAX WINDS

INIT 02/1500Z 18.1N 84.7W 30 KT 35 MPH
12H 03/0000Z 18.9N 85.6W 30 KT 35 MPH
24H 03/1200Z 19.8N 86.6W 35 KT 40 MPH
36H 04/0000Z 20.6N 87.2W 40 KT 45 MPH...INLAND
48H 04/1200Z 21.4N 87.5W 40 KT 45 MPH...INLAND
60H 05/0000Z 22.0N 87.6W 40 KT 45 MPH
72H 05/1200Z 22.0N 88.2W 45 KT 50 MPH
96H 06/1200Z 21.5N 90.5W 45 KT 50 MPH
120H 07/1200Z 21.5N 92.5W 45 KT 50 MPH

$$
Forecaster Pasch

[cycloneye]

BULLETIN
Tropical Depression Twenty-Five Advisory Number 2
NWS National Hurricane Center Miami FL AL252020
400 PM CDT Fri Oct 02 2020

...DEPRESSION LIKELY TO BECOME A TROPICAL STORM TONIGHT...


SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...18.8N 85.3W
ABOUT 155 MI...250 KM SE OF COZUMEL MEXICO
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Punta Herrero to Cabo Catoche Mexico

A Tropical Storm Watch is in effect for...
* South of Punta Herrero to Puerto Costa Maya Mexico
* West of Cabo Catoche to Dzilam Mexico

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 400 PM CDT (2100 UTC), the center of Tropical Depression
Twenty-Five was located near latitude 18.8 North, longitude 85.3
West. The depression is moving toward the northwest near 9 mph (15
km/h), and a gradual turn toward the north-northwest with a decrease
in forward speed is expected over the next couple of days. On the
forecast track, the center of the tropical cyclone should be near
the northeastern Yucatan Peninsula on Saturday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some strengthening is forecast, and the depression is expected to
become a tropical storm tonight.

The estimated minimum central pressure is 1005 mb (29.68 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for the depression can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT5 and WMO header WTNT45 KNHC.

RAINFALL: The depression is expected to produce rainfall of 4 to 8
inches with isolated maximum amounts of 12 inches in portions of the
Yucatan Peninsula and far western Cuba. A separate area of
significant rain is expected to develop well away from the center in
the Mexican states of Campeche, Tabasco, and northern Chiapas with
rainfall of 8 to 12 inches and isolated maximum amounts of 20
inches. This rainfall may produce life-threatening flash floods and
mudslides.

Rainfall of 1 to 3 inches with maximum amounts of 5 inches is
expected in the Bay Islands of Honduras and over the Cayman Islands.

WIND: Tropical storm conditions are expected within the Tropical
Storm Warning area by Saturday morning, and are possible within the
Tropical Storm Watch area on Saturday and Sunday.


NEXT ADVISORY
-------------
Next intermediate advisory at 700 PM CDT.
Next complete advisory at 1000 PM CDT.

$$
Forecaster Pasch


Tropical Depression Twenty-Five Discussion Number 2
NWS National Hurricane Center Miami FL AL252020
400 PM CDT Fri Oct 02 2020

Convective banding features have become a little better defined
over the southern portion of the circulation, but otherwise the
system has not changed much in organization since earlier today.
The current intensity estimate remains at 30 kt in agreement with a
Dvorak estimate from TAFB, and scatterometer observations
from a few hours ago. The SHIPS model output now shows some
south-southwesterly shear affecting the system during the next few
days. Otherwise, the environment should favor at least gradual
strengthening, and the cyclone is likely to become a tropical storm
prior to moving near the Yucatan Peninsula. The official intensity
forecast is within the range of most of the model guidance.

The initial motion estimate is the same as in the morning advisory,
315/8 kt. The depression should move along the southwestern
periphery of a mid-tropospheric high pressure area for the next
couple of days, causing the cyclone to move on a northwestward to
north-northwestward heading. Later in the forecast period, the
global models build a weak ridge across the northern half of the
Gulf of Mexico. This should induce the cyclone to turn westward or
even a little south of west in 3-5 days. The latest NHC forecast
lies between the simple and corrected dynamical model consensus
predictions, TVCA and HCCA, and is quite similar to the previous
official forecast.

At this time, the biggest threat from this slow-moving system is
rain and flooding, particularly near and over mountainous terrain.


KEY MESSAGES:

1. The system is expected to produce heavy rainfall that could
result in life-threatening flash flooding over portions of the
Yucatan Peninsula, far western Cuba and well away from the center in
the Mexican states of Campeche, Tabasco, and northern Chiapas.

2. The depression is forecast to become a tropical storm and bring
tropical storm conditions to portions of the Yucatan Peninsula on
Saturday, where a Tropical Storm Warning is in effect.


FORECAST POSITIONS AND MAX WINDS

INIT 02/2100Z 18.8N 85.3W 30 KT 35 MPH
12H 03/0600Z 19.5N 86.1W 35 KT 40 MPH
24H 03/1800Z 20.5N 87.0W 40 KT 45 MPH
36H 04/0600Z 21.6N 87.5W 40 KT 45 MPH
48H 04/1800Z 22.3N 87.7W 40 KT 45 MPH
60H 05/0600Z 22.5N 88.0W 45 KT 50 MPH
72H 05/1800Z 22.5N 88.8W 50 KT 60 MPH
96H 06/1800Z 22.5N 91.0W 50 KT 60 MPH
120H 07/1800Z 22.0N 92.5W 50 KT 60 MPH

$$
Forecaster Pasch

[cycloneye]

BULLETIN
Tropical Storm Gamma Intermediate Advisory Number 2A
NWS National Hurricane Center Miami FL AL252020
700 PM CDT Fri Oct 02 2020

...DEPRESSION BECOMES TROPICAL STORM GAMMA OVER THE NORTHWESTERN
CARIBBEAN SEA...


SUMMARY OF 700 PM CDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...18.8N 85.8W
ABOUT 135 MI...220 KM SSE OF COZUMEL MEXICO
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Punta Herrero to Cabo Catoche Mexico

A Tropical Storm Watch is in effect for...
* South of Punta Herrero to Puerto Costa Maya Mexico
* West of Cabo Catoche to Dzilam Mexico

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 700 PM CDT (0000 UTC), the center of Tropical Storm Gamma was
located near latitude 18.8 North, longitude 85.8 West. Gamma is
moving toward the northwest near 9 mph (15 km/h), and a gradual turn
toward the north-northwest with a decrease in forward speed is
expected over the next couple of days. On the forecast track, the
center of the tropical cyclone should be near the northeastern
Yucatan Peninsula on Saturday.

Maximum sustained winds are near 40 mph (65 km/h) with higher
gusts. Slow strengthening is forecast during the next few days.

The estimated minimum central pressure based on data from the Air
Force Hurricane Hunters is 1000 mb (29.53 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce rainfall of 4 to 8
inches with isolated maximum amounts of 12 inches in portions of the
Yucatan Peninsula and far western Cuba. A separate area of
significant rain is expected to develop well away from the center in
the Mexican states of Campeche, Tabasco, and northern Chiapas with
rainfall of 8 to 12 inches and isolated maximum amounts of 20
inches. This rainfall may produce life-threatening flash floods and
mudslides.

Rainfall of 1 to 3 inches with maximum amounts of 5 inches is
expected in the Bay Islands of Honduras and over the Cayman Islands.

WIND: Tropical storm conditions are expected within the Tropical
Storm Warning area by Saturday morning, and are possible within the
Tropical Storm Watch area on Saturday and Sunday.


NEXT ADVISORY
-------------
Next complete advisory at 1000 PM CDT.

$$
Forecaster Cangialosi

[cycloneye]

BULLETIN
Tropical Storm Gamma Advisory Number 3
NWS National Hurricane Center Miami FL AL252020
1000 PM CDT Fri Oct 02 2020

...GAMMA FORECAST TO STRENGTHEN BEFORE LANDFALL IN THE YUCATAN
PENINSULA TOMORROW...
...HEAVY RAINFALL EXPECTED TO BE THE MAIN THREAT...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.1N 86.1W
ABOUT 110 MI...175 KM SSE OF COZUMEL MEXICO
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Punta Herrero to Cabo Catoche Mexico

A Tropical Storm Watch is in effect for...
* South of Punta Herrero to Puerto Costa Maya Mexico
* West of Cabo Catoche to Dzilam Mexico

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1000 PM CDT (0300 UTC), the center of Tropical Storm Gamma was
located near latitude 19.1 North, longitude 86.1 West. Gamma is
moving toward the northwest near 9 mph (15 km/h). A slower
northwestward motion is expected during the next couple of days,
followed by a turn to the west or west-southwest. On the forecast
track, the center of Gamma should be near the northeastern
Yucatan Peninsula on Saturday.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts.
Some strengthening is expected before Gamma moves inland over the
northeastern Yucatan Peninsula on Saturday. After landfall, slight
weakening or little change in strength is expected.

Tropical-storm-force winds extend outward up to 45 miles (75 km)
from the center.

The estimated minimum central pressure based on data from the Air
Force Hurricane Hunters is 998 mb (29.47 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce rainfall of 4 to 8 inches
across portions of the Yucatan Peninsula and far western Cuba, with
maximum rainfall amounts as high as 10 to 15 inches possible across
the northeastern portion of the Mexican state of Quintana Roo. This
rainfall may produce life-threatening flash floods.

A separate area of significant rain is expected to develop well away
from the center in the Mexican states of Campeche, Tabasco, and
northern Chiapas with rainfall of 8 to 12 inches and isolated
maximum amounts of 20 inches. This rainfall may produce
life-threatening flash floods and mudslides.

Rainfall of 1 to 3 inches with maximum amounts of 5 inches is
expected in the Bay Islands of Honduras and over the Cayman Islands.

WIND: Tropical storm conditions are expected within the Tropical
Storm Warning area by Saturday morning, and are possible within the
Tropical Storm Watch area on Saturday and Sunday.


NEXT ADVISORY
-------------
Next intermediate advisory at 100 AM CDT.
Next complete advisory at 400 AM CDT.

$$
Forecaster Cangialosi


Tropical Storm Gamma Discussion Number 3
NWS National Hurricane Center Miami FL AL252020
1000 PM CDT Fri Oct 02 2020

A few hours ago, the Air Force Hurricane Hunters found maximum
winds of around 35 kt in the northeastern quadrant of the cyclone,
which was the reason why it was upgraded to Tropical Storm Gamma.
Since then, there have been no stronger winds reported so the
initial intensity remains 35 kt. The minimum pressure estimated by
the aircraft is quite low at 998 mb, so it seems likely that
the winds will increase soon. The storm also has better banding
features compared to hours ago and deep convection has also been
persisting near the center.

Fixes from the aircraft indicate that Gamma has jogged to the left
recently, but smoothing through the short-term jog suggests an
initial motion of 310/8 kt. The tropical storm is expected to
remain on the western periphery of a subtropical high during the
next couple of days, and that should cause the storm to move slowly
northwestward during that time period. This track should take Gamma
across the northern Yucatan Peninsula and perhaps over the extreme
south-central Gulf of Mexico this weekend. By early next week, a
mid-level ridge is expected to build to the north of the storm while
another low pressure area is forecast to develop to the east of
Gamma. This change in the steering pattern is expected to cause the
storm to make a sharp left turn toward the Bay of Campeche, but
continue to move at a fairly slow forward speed. The models have
shifted well to the south from 48-120 hours this cycle, and the NHC
track forecast has been adjusted in that direction. Despite the
shift, most of the reliable models are south of the new official
track forecast, and future southward adjustments could be necessary.

Environmental conditions appear generally favorable for additional
strengthening until the cyclone reaches the Yucatan Peninsula on
Saturday, and the NHC intensity forecast shows a slightly higher
landfall intensity there. Once the system moves over the Yucatan
Peninsula and the extreme southern Gulf of Mexico, the combination
of land interaction, an increase in shear, and drier air should
limit the amount of strengthening into next week. At this point,
no model shows Gamma becoming a hurricane, and the NHC intensity
forecast shows little change in strength for much of the forecast
period.

The biggest threat from this large and slow-moving storm is the
the potential for heavy rainfall and flooding, particularly near
and over mountainous terrain.


KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall that could result in
life-threatening flash flooding over portions of the Yucatan
Peninsula, far western Cuba and well away from the center in
the Mexican states of Campeche, Tabasco, and northern Chiapas.

2. Gamma is forecast to bring tropical storm conditions to portions
of the Yucatan Peninsula on Saturday, where a Tropical Storm
Warning is in effect.


FORECAST POSITIONS AND MAX WINDS

INIT 03/0300Z 19.1N 86.1W 35 KT 40 MPH
12H 03/1200Z 19.8N 86.9W 45 KT 50 MPH
24H 04/0000Z 20.8N 87.6W 45 KT 50 MPH...INLAND
36H 04/1200Z 21.6N 88.0W 40 KT 45 MPH...INLAND
48H 05/0000Z 22.0N 88.3W 40 KT 45 MPH
60H 05/1200Z 21.9N 88.9W 40 KT 45 MPH
72H 06/0000Z 21.7N 90.0W 45 KT 50 MPH
96H 07/0000Z 21.0N 91.8W 45 KT 50 MPH
120H 08/0000Z 20.3N 92.8W 45 KT 50 MPH

$$
Forecaster Cangialosi

[cycloneye]

BULLETIN
Tropical Storm Gamma Advisory Number 4
NWS National Hurricane Center Miami FL AL252020
400 AM CDT Sat Oct 03 2020

...GAMMA CONTINUES TO STRENGTHEN AS IT MOVES TOWARD THE YUCATAN
PENINSULA...
...HEAVY RAINFALL EXPECTED TO BE THE MAIN THREAT...


SUMMARY OF 400 AM CDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...19.4N 86.9W
ABOUT 75 MI...120 KM S OF COZUMEL MEXICO
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...992 MB...29.29 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The Government of Mexico has issued a Tropical Storm Warning for
the north coast of the Yucatan Peninsula from Cabo Catoche to
Dzilam, and a Tropical Storm Watch for the north coast of the
Yucatan Peninsula west of Dzilam to Progreso.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Punta Herrero to Dzilam Mexico

A Tropical Storm Watch is in effect for...
* South of Punta Herrero to Puerto Costa Maya Mexico
* West of Dzilam to Progreso Mexico

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 400 AM CDT (0900 UTC), the center of Tropical Storm Gamma was
located near latitude 19.4 North, longitude 86.9 West. Gamma is
moving toward the northwest near 9 mph (15 km/h), and this motion
should continue at a slower forward speed today. A turn toward the
north is expected on Sunday, followed by a turn to the west or
west-southwest Sunday night or Monday. On the forecast track, the
center of Gamma should move inland over the northeastern Yucatan
Peninsula later today, and be near the north coast of the Yucatan
Peninsula on Sunday.

Reports from an Air Force Reserve Hurricane Hunter aircraft
indicate that maximum sustained winds have increased to near 50 mph
(85 km/h) with higher gusts. Additional strengthening is expected
before Gamma makes landfall on the Yucatan Peninsula. After
landfall, a slight weakening is expected.

Tropical-storm-force winds extend outward up to 80 miles (130 km)
from the center.

The minimum central pressure extrapolated by the Hurricane Hunter
aircraft is 992 mb (29.29 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce rainfall of 4 to 8 inches
across portions of the Yucatan Peninsula and far western Cuba, with
maximum rainfall amounts as high as 10 to 15 inches possible across
the northeastern portion of the Mexican state of Quintana Roo. This
rainfall may produce life-threatening flash floods.

A separate area of significant rain is expected to develop well away
from the center in the Mexican states of Campeche, Tabasco, and
northern Chiapas with rainfall of 8 to 12 inches and isolated
maximum amounts of 20 inches. This rainfall may produce
life-threatening flash floods and mudslides.

Rainfall of 1 to 3 inches with maximum amounts of 5 inches is
expected in the Bay Islands of Honduras and over the Cayman Islands.

WIND: Tropical storm conditions are spreading into the Tropical
Storm Warning area on the east coast of the Yucatan Peninsula, and
these conditions should spread across the remainder of the warning
area through Sunday. Tropical Storm conditions are possible
within the Tropical Storm Watch area later today and on Sunday.


NEXT ADVISORY
-------------
Next intermediate advisory at 700 AM CDT.
Next complete advisory at 1000 AM CDT.

$$
Forecaster Beven



Tropical Storm Gamma Discussion Number 4
NWS National Hurricane Center Miami FL AL252020
400 AM CDT Sat Oct 03 2020

Satellite imagery and reports from an Air Force Reserve Hurricane
Hunter aircraft indicate that Gamma is strengthening. A central
dense overcast with cloud tops to -85C has formed, along with an
outer convective band in the eastern semicircle. The aircraft has
reported maximum 850 mb flight-level winds of 58 kt and reliable-
looking surface wind estimates from the Stepped Frequency Microwave
Radiometer of 40-45 kt. Based on this, the initial intensity is
increased to 45 kt.

The initial motion is again a little to the left of the previous
advisory, 305/8 kt. During the next 24-36 h, Gamma is expected to
turn northward as it tries to recurve into a break in the
subtropical ridge caused by a mid-latitude trough over the eastern
United States. The track guidance, however, is in good agreement
that the trough will bypass the tropical cyclone, with a ridge
building to the north after 36 h. This should cause Gamma to turn
westward or southwestward between the ridge and the Central
American cyclonic gyre to the south. There is uncertainty as to
whether Gamma will move over the Gulf of Mexico before this turn
occurs, as the ECMWF keeps the center inland or very near the
coast. The new forecast track is north of the ECMWF, but a little
to the south of the previous track. The foreast track calls for
landfall on the northeastern Yucatan Peninsula in about 12 h,
followed by the center reaching the Gulf of Mexico in about 36 h
and a track near the coast of the Yucatan Peninsula thereafter.

Conditions appear favorable for strengthening until landfall, and
the forecast 12-h intensity of 50 kt could be conservative given
current trends. The remainder of the intensity forecast is quite
uncertain due to the possibility of land interaction, dry air
entrainment, shear, and possible interaction with another system to
the east. The intensity guidance again does not show much
strengthening if Gamma emerges into the Gulf of Mexico, and that
part of the new intensity forecast has only minor adjustments from
the previous one. It should be noted that several models show a low
pressure area over the northern Gulf of Mexico after 120 h. Whether
this will be Gamma or a new system is unclear at this time.

The biggest threat from this large and slow-moving storm is the
the potential for heavy rainfall and flooding, particularly near
and over mountainous terrain.


KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall that could result in
life-threatening flash flooding over portions of the Yucatan
Peninsula, far western Cuba and well away from the center in
the Mexican states of Campeche, Tabasco, and northern Chiapas.

2. Gamma is forecast to bring tropical storm conditions to portions
of the Yucatan Peninsula today and Sunday, where a Tropical Storm
Warning is in effect.


FORECAST POSITIONS AND MAX WINDS

INIT 03/0900Z 19.4N 86.9W 45 KT 50 MPH
12H 03/1800Z 20.2N 87.4W 50 KT 60 MPH
24H 04/0600Z 21.1N 87.9W 45 KT 50 MPH...INLAND
36H 04/1800Z 21.7N 88.0W 40 KT 45 MPH...OVER WATER
48H 05/0600Z 21.8N 88.4W 40 KT 45 MPH
60H 05/1800Z 21.6N 89.3W 45 KT 50 MPH
72H 06/0600Z 21.2N 90.5W 45 KT 50 MPH
96H 07/0600Z 20.5N 92.4W 45 KT 50 MPH
120H 08/0600Z 19.5N 93.5W 40 KT 45 MPH

$$
Forecaster Beven

[cycloneye]

BULLETIN
Tropical Storm Gamma Intermediate Advisory Number 4A
NWS National Hurricane Center Miami FL AL252020
700 AM CDT Sat Oct 03 2020

...GAMMA STRENGTHENS SOME MORE AS IT APPROACHES THE EAST COAST OF
THE YUCATAN PENINSULA...


SUMMARY OF 700 AM CDT...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...19.7N 87.2W
ABOUT 40 MI...65 KM SSE OF TULUM MEXICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...987 MB...29.15 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Punta Herrero to Dzilam Mexico

A Tropical Storm Watch is in effect for...
* South of Punta Herrero to Puerto Costa Maya Mexico
* West of Dzilam to Progreso Mexico

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 700 AM CDT (1200 UTC), the center of Tropical Storm Gamma was
located near latitude 19.7 North, longitude 87.2 West. Gamma is
moving toward the northwest near 9 mph (15 km/h), and this motion
should continue at a slower forward speed today. A turn toward the
north is expected on Sunday, followed by a turn to the west or
west-southwest Sunday night or Monday. On the forecast track, the
center of Gamma should move inland over the eastern Yucatan
Peninsula later today, and be near the north coast of the Yucatan
Peninsula on Sunday.

Reports from an Air Force Reserve Hurricane Hunter aircraft
indicate that maximum sustained winds have increased to near 65 mph
(100 km/h) with higher gusts. Some slight additional strengthening
is possible before Gamma makes landfall on the Yucatan Peninsula
today. After landfall, some weakening is expected.

Tropical-storm-force winds extend outward up to 80 miles (130 km)
from the center.

The minimum central pressure estimated from Hurricane Hunter
observations is 987 mb (29.15 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce rainfall of 4 to 8 inches
across portions of the Yucatan Peninsula and far western Cuba, with
maximum rainfall amounts as high as 10 to 15 inches possible across
the northeastern portion of the Mexican state of Quintana Roo. This
rainfall may produce life-threatening flash floods.

A separate area of significant rain is expected to develop well away
from the center in the Mexican states of Campeche, Tabasco, and
northern Chiapas with rainfall of 8 to 12 inches and isolated
maximum amounts of 20 inches. This rainfall may produce
life-threatening flash floods and mudslides.

Rainfall of 1 to 3 inches with maximum amounts of 5 inches is
expected in the Bay Islands of Honduras and over the Cayman Islands.

WIND: Tropical storm conditions are spreading into the Tropical
Storm Warning area on the east coast of the Yucatan Peninsula, and
these conditions should spread across the remainder of the warning
area through Sunday. Tropical Storm conditions are possible
within the Tropical Storm Watch area later today and on Sunday.


NEXT ADVISORY
-------------
Next complete advisory at 1000 AM CDT.

$$
Forecaster Pasch

[cycloneye]

BULLETIN
Tropical Storm Gamma Advisory Number 5
NWS National Hurricane Center Miami FL AL252020
1000 AM CDT Sat Oct 03 2020

...GAMMA CLOSE TO HURRICANE STRENGTH AS IT NEARS THE EAST COAST
OF THE YUCATAN PENINSULA...


SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...20.0N 87.3W
ABOUT 20 MI...30 KM SE OF TULUM MEXICO
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...983 MB...29.03 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The government of Mexico has issued a Hurricane Warning for the
east coast of the Yucatan Peninsula from north of Punta Allen to
Cancun, including Cozumel.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Hurricane Warning is in effect for
* North of Punta Allen to Cancun Mexico, including Cozumel

A Tropical Storm Warning is in effect for...
* Punta Herrero to Punta Allen Mexico
* North and west of Cancun to Dzilam Mexico

A Tropical Storm Watch is in effect for...
* South of Punta Herrero to Puerto Costa Maya Mexico
* West of Dzilam to Progreso Mexico

A Hurricane Warning means that hurricane conditions are expected
somewhere within the warning area, in this case within the next 6
hours. Preparations to protect life and property should be rushed
to completion.

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1000 AM CDT (1500 UTC), the center of Tropical Storm Gamma was
located near latitude 20.0 North, longitude 87.3 West. Gamma is
moving toward the northwest near 9 mph (15 km/h), and this motion
should continue at a slower forward speed today. A turn toward the
north-northwest is expected on Sunday, followed by a turn to the
west or west-southwest Sunday night or Monday. On the forecast
track, the center of Gamma should move inland over the eastern
Yucatan Peninsula later today, and be near the north coast of
the Yucatan Peninsula on Sunday.

Maximum sustained winds have increased to near 70 mph (110 km/h)
with higher gusts. Gamma is likely to be near or at hurricane
strength when it makes landfall in the eastern Yucatan Peninsula.
Some weakening is expected after landfall.

Tropical-storm-force winds extend outward up to 80 miles (130 km)
from the center. A station at Cancun, Mexico, reported a sustained
wind of 46 mph (74 km/h) and a gust to 55 mph (89 km/h) within the
past few hours. A station at Xcaret Park near Playa del Carmen
recently reported a sustained wind of 39 mph (63 km/h) and a gust to
54 mph (87 km/h).

The minimum central pressure estimated from Hurricane Hunter
observations is 983 mb (29.03 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce rainfall of 4 to 8 inches
across portions of the Yucatan Peninsula and far western Cuba, with
maximum rainfall amounts as high as 10 to 15 inches possible across
northeastern Quintana Roo and northern Yucatan. This rainfall may
produce life-threatening flash floods.

A separate area of significant rain is expected to develop well away
from the center in the Mexican states of Campeche, Tabasco, northern
Chiapas, and southeast Veracruz, with rainfall of 6 to 8 inches and
isolated maximum amounts of 12 inches. This rainfall may produce
life-threatening flash floods and mudslides. The storm will also
result in an area of heavy rains to the south that will affect the
Gulf of Fonseca region between eastern El Salvador, southern
Honduras, and northwest Nicaragua with accumulation of 4-6 inches
and isolated maximum amounts of 8 inches.

Additional rainfall of 1 to 3 inches with maximum amounts of 5
inches is expected over the Cayman Islands.

WIND: Hurricane conditions are expected within the Hurricane
Warning area during the next few hours. Tropical storm conditions
are spreading into the Tropical Storm Warning area on the east coast
of the Yucatan Peninsula, and these conditions should spread across
the remainder of the warning area through Sunday. Tropical Storm
conditions are possible within the Tropical Storm Watch area later
today and on Sunday.

STORM SURGE: A dangerous storm surge will raise water levels by
as much as 1 to 3 feet above normal tide levels along the immediate
coast near and to the north of where the center makes landfall.
Near the coast, the surge will be accompanied by large and
destructive waves.


NEXT ADVISORY
-------------
Next intermediate advisory at 100 PM CDT.
Next complete advisory at 400 PM CDT.

$$
Forecaster Pasch/Berg




Tropical Storm Gamma Discussion Number 5
NWS National Hurricane Center Miami FL AL252020
1000 AM CDT Sat Oct 03 2020

Observations from both the Air Force and NOAA Hurricane Hunters
indicate that Gamma has continued to strengthen this morning. The
cloud pattern has continued to become better organized, with an eye
trying to become evident on high-resolution satellite images from
the GOES-16 mesoscale sectors. Flight-level and SFMR-observed
surface winds from the aircraft support an intensity of 60 kt, and
the storm could strengthen a little more as long as the center
remains over water. Since Gamma will be near or at hurricane
intensity when it makes landfall later today, the government of
Mexico has issued a Hurricane Warning for a portion of the
northeastern Yucatan Peninsula. Gamma should weaken some while it
moves over land tonight. Some re-intensification is likely after
the center moves into the southern Gulf of Mexico. However, the
numerical guidance does not show much strengthening during the next
few days, possibly due to the influence of drier air and/or the
interaction with another area of low pressure to the east of Gamma.
The official intensity forecast is near or above the model
consensus.

Gamma continues northwestward at near 8 kt. The cyclone is
expected to turn north-northwestward and move through a break in
the subtropical ridge through 36 hours or so. Thereafter, a trough
to the north moves eastward, bypassing Gamma, and later in the
forecast period a ridge builds weakly over the Gulf of Mexico.
This should cause the cyclone to turn toward the west and
southwest. The official track forecast is close to the multi-model
consensus, TVCN.

Although Gamma has strengthened, its biggest threat continues to be
torrential rains, flooding, and mudslides especially near and over
mountainous terrain.


KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall for several
days over portions of southeastern Mexico, the Yucatan
Peninsula, Central America, and far western Cuba. This
rainfall could result in life-threatening flash flooding
and mudslides, particularly in the mountainous regions of
southeastern Mexico and Central America.

2. Gamma is very near hurricane strength and will be near or at
hurricane intensity when the center moves inland over the Yucatan
Peninsula later today. A Hurricane Warning is now in effect
for portions of the east coast of the Yucatan Peninsula, where
tropical storm conditions are already occurring. Tropical storm
conditions are expected along the north coast of the Yucatan
Peninsula within the Tropical Storm Warning area later today
and on Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT 03/1500Z 20.0N 87.3W 60 KT 70 MPH
12H 04/0000Z 20.8N 87.8W 55 KT 65 MPH...INLAND
24H 04/1200Z 21.8N 88.1W 40 KT 45 MPH...OVER WATER
36H 05/0000Z 22.2N 88.3W 40 KT 45 MPH
48H 05/1200Z 22.3N 88.8W 45 KT 50 MPH
60H 06/0000Z 22.1N 89.7W 50 KT 60 MPH
72H 06/1200Z 22.0N 91.0W 50 KT 60 MPH
96H 07/1200Z 21.0N 92.5W 45 KT 50 MPH
120H 08/1200Z 20.0N 93.5W 40 KT 45 MPH

$$
Forecaster Pasch

[cycloneye]

Tropical Storm Gamma Tropical Cyclone Update
NWS National Hurricane Center Miami FL AL252020
1200 PM CDT Sat Oct 03 2020

...GAMMA MAKES LANDFALL NEAR TULUM, MEXICO...

Surface observations and satellite images indicate that the center
of Tropical Storm Gamma made landfall in the northeast Yucatan
Peninsula near Tulum, Mexico, around 1145 AM CDT. The storm was
very close to hurricane strength at landfall, with maximum
sustained winds near 70 MPH (110 MPH) with higher gusts.

A weather station at Xel-Ha Park, along the Yucatan coast just
north of Tulum, reported a sustained wind of 55 mph (89 km/h) and a
gust to 68 mph (109 km/h) within the past hour.


SUMMARY OF 1200 PM CDT...1700 UTC...INFORMATION
---------------------------------------------------
LOCATION...20.2N 87.5W
ABOUT 0 MI...0 KM N OF TULUM MEXICO
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...980 MB...28.94 INCHES

$$
Forecaster Pasch

[cycloneye]

BULLETIN
Tropical Storm Gamma Advisory Number 6
NWS National Hurricane Center Miami FL AL252020
400 PM CDT Sat Oct 03 2020

...GAMMA MOVING OVER THE NORTHEASTERN YUCATAN PENINSULA...


SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...20.7N 87.7W
ABOUT 35 MI...60 KM NNW OF TULUM MEXICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NW OR 325 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The government of Mexico has changed the Hurricane Warning to a
Tropical Storm Warning north of Punta Allen to Cancun Mexico,
including Cozumel, and discontinued all watches and warnings from
Punta Allen southward.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* North and west of Punta Allen to Dzilam Mexico, including Cozumel

A Tropical Storm Watch is in effect for...
* West of Dzilam to Progreso Mexico

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 400 PM CDT (2100 UTC), the center of Tropical Storm Gamma was
located near latitude 20.7 North, longitude 87.7 West. Gamma is
moving toward the northwest near 8 mph (13 km/h), and a turn toward
the north-northwest with decreasing forward speed is expected
tonight and Sunday, followed by a turn to the west or west-southwest
Sunday night or Monday. On the forecast track, the center of Gamma
will continue to move over the northeastern Yucatan Peninsula
through tonight, move into the southern Gulf of Mexico on Sunday,
and pass near or north of the northern coast of the Yucatan
Peninsula Sunday night and Monday.

Maximum sustained winds have decreased to near 65 mph (100 km/h)
with higher gusts. Additional weakening is forecast tonight and
Sunday, followed by some re-intensification by Monday.

Tropical-storm-force winds extend outward up to 80 miles (130 km)
from the center.

The estimated minimum central pressure is 985 mb (29.09 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce rainfall of 4 to 8 inches
across portions of the Yucatan Peninsula and far western Cuba, with
maximum rainfall amounts as high as 10 to 15 inches possible across
northeastern Quintana Roo and northern Yucatan. This rainfall may
produce life-threatening flash floods.

A separate area of significant rain is possible in the Mexican
states of Campeche, Tabasco, northern Chiapas, and southeast
Veracruz, with rainfall of 6 to 8 inches and isolated maximum
amounts of 12 inches. This rainfall may produce life-threatening
flash floods and mudslides. The storm will also result in an area of
heavy rains to the south that will affect the Gulf of Fonseca
region between eastern El Salvador, southern Honduras, and
northwest Nicaragua with accumulation of 4 to 6 inches and isolated
maximum amounts of 8 inches.

Rainfall of 1 to 3 inches with maximum amounts of 5 inches is
expected over the Cayman Islands.

WIND: Tropical storm conditions should continue within the Tropical
Storm Warning area on the east coast of the Yucatan Peninsula for
the next several hours, and these conditions should spread across
the remainder of the warning area through Sunday. Tropical Storm
conditions are possible within the Tropical Storm Watch area on
Monday.



NEXT ADVISORY
-------------
Next intermediate advisory at 700 PM CDT.
Next complete advisory at 1000 PM CDT.

$$
Forecaster Pasch


Tropical Storm Gamma Discussion Number 6
NWS National Hurricane Center Miami FL AL252020
400 PM CDT Sat Oct 03 2020

Surface observations from the Yucatan Peninsula along with
high-resolution visible satellite imagery indicated that the center
of Gamma made landfall in the vicinity of Tulum, Mexico, shortly
before 1700 UTC. Earlier aircraft observations and pressure
measurements from Tulum showed that the system was very near
hurricane strength when it made landfall. A ragged eye appeared in
the visible images shortly after the center crossed the coast, but
that feature has since become obscured. Since Gamma has likely
been slowly weakening while moving over land, the current intensity
has been set to 55 kt. Continued gradual weakening is likely into
Sunday while the center either moves over land or interacts with
nearby land. Some re-strengthening is expected to begin by
Monday, but the numerical guidance is not very enthusiastic about
intensification over the Gulf, probably due to the combination of
drier air and the interaction with another low pressure system to
the east. The official intensity forecast is not much different
from the model consensus.

Gamma has been moving northwestward, but it is expected to turn
north-northwestward while moving near and into a weakness in the
subtropical ridge over the next day or so. The global models
predict that a trough to the north of the tropical cyclone will
lift northeastward and bypass Gamma. In a couple of days, a ridge
is forecast to build back, albeit weakly, across the Gulf of
Mexico. This is expected to cause the system to turn westward to
southwestward over the latter part of the forecast period. The
more reliable global models show the system meandering over the
southern Bay of Campeche in 4 to 5 days, and so does the official
forecast.


KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall for several days over
portions of southeastern Mexico, the Yucatan Peninsula, Central
America, and far western Cuba. This rainfall could result in
life-threatening flash flooding and mudslides, particularly in the
mountainous regions of southeastern Mexico and Central America.

2. Even though Gamma has moved inland, tropical storm conditions
will continue along the east coast of the Yucatan Peninsula through
this evening and are expected to spread along the north coast within
the Tropical Storm Warning area tonight and on Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT 03/2100Z 20.7N 87.7W 55 KT 65 MPH...INLAND
12H 04/0600Z 21.3N 88.0W 45 KT 50 MPH...INLAND
24H 04/1800Z 22.0N 88.2W 40 KT 45 MPH...OVER WATER
36H 05/0600Z 22.1N 88.4W 40 KT 45 MPH
48H 05/1800Z 22.0N 89.1W 45 KT 50 MPH
60H 06/0600Z 21.6N 90.4W 50 KT 60 MPH
72H 06/1800Z 21.0N 91.5W 50 KT 60 MPH
96H 07/1800Z 20.0N 92.0W 45 KT 50 MPH
120H 08/1800Z 20.0N 93.0W 40 KT 45 MPH

$$
Forecaster Pasch

[cycloneye]

BULLETIN
Tropical Storm Gamma Advisory Number 7
NWS National Hurricane Center Miami FL AL252020
1000 PM CDT Sat Oct 03 2020

...GAMMA DRENCHING THE NORTHERN YUCATAN PENINSULA...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...21.3N 88.0W
ABOUT 85 MI...135 KM NNW OF TULUM MEXICO
ABOUT 110 MI...175 KM E OF PROGRESO MEXICO
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NW OR 325 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...990 MB...29.24 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* North and west of Punta Allen to Dzilam Mexico, including Cozumel

A Tropical Storm Watch is in effect for...
* West of Dzilam to Progreso Mexico

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1000 PM CDT (0300 UTC), the center of Tropical Storm Gamma was
located near latitude 21.3 North, longitude 88.0 West. Gamma is
moving toward the northwest near 7 mph (11 km/h) and a turn
toward the north-northwest with decreasing forward speed is expected
on Sunday, followed by a turn to the west or west-southwest
Sunday night or Monday. On the forecast track, the center of Gamma
will move offshore of the Yucatan Peninsula and over the southern
Gulf of Mexico on Sunday, and pass near or north of the northern
coast of the Yucatan Peninsula Monday and Tuesday.

Maximum sustained winds are near 60 mph (95 km/h) with higher gusts.
Little change in strength is forecast during the next few days.

Tropical-storm-force winds extend outward up to 105 miles (165 km)
from the center.

The estimated minimum central pressure is 990 mb (29.24 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce storm total rainfall of 4 to
8 inches across portions of the Yucatan Peninsula and far western
Cuba, with maximum rainfall amounts as high as 10 to 15 inches
possible across northeastern Quintana Roo and northern Yucatan. This
rainfall may produce life-threatening flash floods.

A separate area of significant rain is possible in the Mexican
states of Campeche, Tabasco, northern Chiapas, and southeast
Veracruz, with rainfall of 6 to 8 inches and isolated maximum
amounts of 12 inches. This rainfall may produce life-threatening
flash floods and mudslides. The storm will also result in an area of
heavy rains to the south from southern Guatemala towards the Gulf of
Fonseca region between eastern El Salvador, southern Honduras, and
northwest Nicaragua, with accumulations of 4 to 6 inches and
isolated maximum amounts of 8 inches.

WIND: Tropical storm conditions should continue within the Tropical
Storm Warning area on the east coast of the Yucatan Peninsula for
the next few hours, and on the north coast of the Yucatan through
Sunday. Tropical Storm conditions are possible within the Tropical
Storm Watch area on Monday.


NEXT ADVISORY
-------------
Next intermediate advisory at 100 AM CDT.
Next complete advisory at 400 AM CDT.

$$
Forecaster Cangialosi



Tropical Storm Gamma Discussion Number 7
NWS National Hurricane Center Miami FL AL252020
1000 PM CDT Sat Oct 03 2020

Tropical Storm Gamma remains over the northern portion of the
Yucatan Peninsula, and the cyclone has been inland for about 10
hours now. Although the storm has weakened some, satellite images
show that Gamma still has an intact central dense overcast feature
and spiral bands on the north side of the circulation. The initial
intensity is estimated to be 50 kt, but there is quite of bit of
uncertainty in this value. The tropical storm is drenching the
northern portion of the Yucatan Peninsula, and heavy rainfall is
likely to continue there into Sunday.

The tropical storm is moving northwestward at 6 kt on the
southwestern periphery of an Atlantic subtropical ridge. Gamma is
expected to move very slowly to the northwest or north-northwest
toward a weakness in the ridge during the next 12 to 24 hours, and
that should take the core of the tropical storm over the extreme
southern Gulf of Mexico by early Sunday. By Sunday night and
Monday, a combination of a building low- to mid-level ridge over the
Gulf of Mexico and a developing low pressure area over the
northwestern Caribbean Sea should cause Gamma to turn fairly sharply
to the west or southwest early next week. A slow southwest or west
motion is likely to continue into the middle of next week, and some
of the models suggest that Gamma could become nearly stationary by
the end of the forecast period. The NHC track forecast is largely
an update of the previous one and lies near the TVCA and HCCA
consensus models.

The intensity forecast seems tricky. The tropical storm still
appears well organized despite its time over land and since it will
be moving back over water soon, it could re-strengthen. However,
none of the intensity models show much strengthening, in fact, most
of them show Gamma gradually weakening throughout the forecast
period. On one hand, the storm is going to be over the warm Gulf
of Mexico waters for several days, which favors strengthening. On
the other hand, there is a fair amount of dry air over the western
Gulf of Mexico and this could entrain into the circulation. Another
complicated factor is how Gamma interacts with a developing low over
the northwestern Caribbean Sea and a disturbance to its south.
Based on these complexities, the NHC intensity forecast shows no
change in strength through the forecast period, and lies near the
high end of the guidance near the SHIPS model.

KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall for several days over
portions of southeastern Mexico, the Yucatan Peninsula, Central
America, and far western Cuba. This rainfall could result in
life-threatening flash flooding and mudslides, particularly in the
mountainous regions of southeastern Mexico and Central America.

2. Even though Gamma is inland, tropical storm conditions will
continue across portions of the Yucatan Peninsula tonight
and Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0300Z 21.3N 88.0W 50 KT 60 MPH
12H 04/1200Z 21.8N 88.2W 50 KT 60 MPH
24H 05/0000Z 22.2N 88.5W 50 KT 60 MPH
36H 05/1200Z 22.1N 88.9W 50 KT 60 MPH
48H 06/0000Z 21.8N 89.9W 50 KT 60 MPH
60H 06/1200Z 21.3N 90.9W 50 KT 60 MPH
72H 07/0000Z 20.7N 91.7W 50 KT 60 MPH
96H 08/0000Z 20.0N 92.5W 50 KT 60 MPH
120H 09/0000Z 19.9N 93.3W 50 KT 60 MPH

$$
Forecaster Cangialosi

[cycloneye]

BULLETIN
Tropical Storm Gamma Advisory Number 8
NWS National Hurricane Center Miami FL AL252020
400 AM CDT Sun Oct 04 2020

...GAMMA LOCATED OVER THE EXTREME SOUTHERN GULF OF MEXICO...
...TORRENTIAL RAINS OCCURRING OVER THE NORTHERN YUCATAN PENINSULA...


SUMMARY OF 400 AM CDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...22.0N 88.2W
ABOUT 110 MI...175 KM ENE OF PROGRESO MEXICO
ABOUT 30 MI...45 KM N OF RIO LAGARTOS MEXICO
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...N OR 355 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...995 MB...29.39 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The government of Mexico has discontinued the Tropical Storm
Warning south of Cancun.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* North and west of Cancun to Dzilam Mexico

A Tropical Storm Watch is in effect for...
* West of Dzilam to Progreso Mexico

A Tropical Storm Warning means that tropical storm conditions are
occurring somewhere within the warning area.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 400 AM CDT (0900 UTC), the center of Tropical Storm Gamma was
located near latitude 22.0 North, longitude 88.2 West. Gamma is
moving toward the north near 5 mph (7 km/h), and this general
motion with a further decrease in forward speed is forecast today.
Gamma should turn toward the west or west-southwest tonight or
Monday. On the forecast track, the center of Gamma will meander
offshore of the northern Yucatan Peninsula and over the extreme
southern Gulf of Mexico today, and pass near or just offshore of
the northern coast of the Yucatan Peninsula on Monday and Tuesday.

Maximum sustained winds are near 50 mph (85 km/h) with higher gusts.
Some re-strengthening is expected today, followed by weakening
tonight or Monday, which should continue into Wednesday.

Tropical-storm-force winds extend outward up to 115 miles (185 km),
mainly north and east of the center.

The estimated minimum central pressure is 995 mb (29.39 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce an additional 2 to 4 inches
with isolated maximum amounts of 6 inches across portions of
northern Yucatan and far western Cuba through early Tuesday. This
rainfall may prolong or enhance any ongoing flash flooding.

Through the middle of the week, a separate area of significant rain
is possible in the Mexican states of Campeche, Tabasco, northern
Chiapas, and southeast Veracruz, with rainfall of 6 to 8 inches and
isolated maximum amounts of 12 inches. This rainfall may produce
life-threatening flash floods and mudslides. Another area of heavy
rain will impact southern Guatemala towards the Gulf of Fonseca
region between eastern El Salvador, southern Honduras, and northwest
Nicaragua, with accumulations of 4 to 6 inches and isolated maximum
amounts of 8 inches.

WIND: Tropical storm conditions should continue within the Tropical
Storm Warning area on northern coast of the Yucatan through today.
Tropical Storm conditions are possible within the Tropical Storm
Watch area on Monday.


NEXT ADVISORY
-------------
Next intermediate advisory at 700 AM CDT.
Next complete advisory at 1000 AM CDT.

$$
Forecaster Stewart


Tropical Storm Gamma Discussion Number 8
NWS National Hurricane Center Miami FL AL252020
400 AM CDT Sun Oct 04 2020

Tropical Storm Gamma has moved back over open water, just offshore
the northern Yucatan Peninsula in the extreme southern Gulf of
Mexico. Although deep convection has been increasing near the
center, the overall convective cloud shield is now strung out to
the north and northeast due to southerly to southwesterly vertical
wind shear in excess of 15 kt. The initial intensity of 45 kt is
based on an earlier ASCAT pass showing 39-kt surface winds just
offshore the northeastern tip of Yucatan, and these winds were
likely under-sampled due to their proximity to the coast. Satellite
classifications from both TAFB and SAB were T3.0/45 kt, which
further supports the 45-kt intensity assessment.

The initial motion estimate is 355/04 kt. As the day progresses,
Gamma is expected to move further into a slight weakness in
subtropical ridge located to the north of the cyclone and slow down,
possibly stalling by this afternoon. The trough over the
southeastern U.S. that is creating the weakness is forecast to move
offshore the U.S. east coast by tonight, causing the ridge to build
back in and force Gamma westward to west-southwestward from Monday
through Thursday. The new NHC track forecast follows the TVCA and
FSSE consensus models, and is similar to but slightly slower and a
little to the right/north of the previous advisory track.

Now that Gamma is back out over open water, some slight
re-strengthening is expected today. However, strong southerly
vertical wind shear is forecast to increase across the cyclone by
tonight and especially on Monday, and continue for the next few
days. The result should be a slow but gradual weakening trend on
Monday through the end of the forecast period. The new official
intensity forecast follow the downward trend of the simple- and
corrected-consensus models, but is slightly higher than the IVCN,
HCCA, FSSE intensity models.

KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall for several days over
portions of southeastern Mexico, the Yucatan Peninsula, Central
America, and far western Cuba. This rainfall could result in
life-threatening flash flooding and mudslides, particularly in the
mountainous regions of southeastern Mexico and Central America.

2. Even though Gamma is offshore, tropical storm conditions will
continue across portions of the Yucatan Peninsula today.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0900Z 22.0N 88.2W 45 KT 50 MPH
12H 04/1800Z 22.6N 88.3W 50 KT 60 MPH
24H 05/0600Z 22.7N 88.6W 45 KT 50 MPH
36H 05/1800Z 22.4N 89.4W 45 KT 50 MPH
48H 06/0600Z 22.0N 90.2W 40 KT 45 MPH
60H 06/1800Z 21.5N 90.9W 40 KT 45 MPH
72H 07/0600Z 21.0N 91.6W 40 KT 45 MPH
96H 08/0600Z 20.4N 92.5W 40 KT 45 MPH
120H 09/0600Z 20.4N 93.4W 40 KT 45 MPH

$$
Forecaster Stewart

[cycloneye]

BULLETIN
Tropical Storm Gamma Advisory Number 9
NWS National Hurricane Center Miami FL AL252020
1000 AM CDT Sun Oct 04 2020

...GAMMA FORECAST TO MEANDER JUST NORTH OF THE NORTHERN COAST OF
THE YUCATAN PENINSULA OVER THE NEXT DAY OR SO...


SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...22.2N 88.2W
ABOUT 40 MI...65 KM N OF RIO LAGARTOS MEXICO
ABOUT 115 MI...185 KM ENE OF PROGRESO MEXICO
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 2 MPH...4 KM/H
MINIMUM CENTRAL PRESSURE...996 MB...29.42 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* North and west of Cancun to Dzilam Mexico

A Tropical Storm Watch is in effect for...
* West of Dzilam to Progreso Mexico

A Tropical Storm Warning means that tropical storm conditions are
occurring somewhere within the warning area.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1000 AM CDT (1500 UTC), the center of Tropical Storm Gamma was
located near latitude 22.2 North, longitude 88.2 West. Gamma is
moving toward the north near 2 mph (4 km/h), and this general motion
with a further decrease in forward speed is expected today. Gamma
should turn toward the west or west-southwest tonight or Monday,
and a slow southwestward motion should continue Monday night
through early Wednesday. On the forecast track, the center of
Gamma will meander offshore of the northern Yucatan Peninsula and
over the extreme southern Gulf of Mexico today, and pass near or
just offshore of the northern coast of the Yucatan Peninsula on
Monday and Tuesday.

Data from an Air Force Reserve reconnaissance aircraft indicate that
the maximum sustained winds are near 60 mph (95 km/h) with higher
gusts. Little change in strength is expected through this evening.
Gradual weakening is anticipated to begin later tonight or on
Monday and continue into Tuesday.

Tropical-storm-force winds extend outward up to 115 miles (185 km)
from the center.

The latest minimum central pressure reported by Air Force Reserve
reconnaissance aircraft is 996 mb (29.42 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce an additional 2 to 4 inches
with isolated maximum amounts of 6 inches across portions of
northern Yucatan and far western Cuba through early Tuesday. This
rainfall may prolong or enhance any ongoing flash flooding.

Through the middle of the week, a separate area of significant rain
is possible in the Mexican states of Campeche, Tabasco, and
southeast Veracruz, with rainfall of 4 to 6 inches and isolated
maximum amounts of 8 inches. This rainfall may produce
life-threatening flash floods and mudslides. Another remote area of
heavy rain associated with Gamma is expected to bring additional
accumulations of 1 to 3 inches and isolated maximum amounts of 5
inches in southern Guatemala towards the Gulf of Fonseca region
between eastern El Salvador, southern Honduras, and northwest
Nicaragua.

WIND: Tropical storm conditions should continue within portions
of the Tropical Storm Warning area on northern coast of the Yucatan
through today. Tropical Storm conditions are possible within the
Tropical Storm Watch area later today through Monday.


NEXT ADVISORY
-------------
Next intermediate advisory at 100 PM CDT.
Next complete advisory at 400 PM CDT.

$$
Forecaster Brown


Tropical Storm Gamma Discussion Number 9
NWS National Hurricane Center Miami FL AL252020
1000 AM CDT Sun Oct 04 2020

An Air Force Reserve reconnaissance aircraft has found the center
of Gamma over the far southern Gulf of Mexico, just north of the
Yucatan Peninsula. Early morning visible satellite imagery has
revealed decent banding structure over the northern and western
portions of the circulation. The aircraft has measured a peak 850
mb flight-level wind of 66 kt and SFMR winds of 47 kt. A blend of
these data support an initial intensity of 50 kt, which is also in
line with the latest Dvorak classifications of T3.0 and T3.5 from
SAB and TAFB, respectively.

Gamma appears to be slowing down as anticipated, with an initial
motion estimate of 360/3 kt. Gamma is expected to meander over the
southern Gulf of Mexico, just north of the northern coast of the
Yucatan peninsula during the next 12-24 hours. By late Monday, the
western portion of a subtropical ridge is expected to build
westward over the northern Gulf of Mexico. This should cause Gamma
to turn westward to west-southwestward through the remainder of the
forecast period. The dynamical model guidance is in general
agreement on this scenario, but there are some differences in how
close Gamma tracks to the northwestern portion of the Yucatan
peninsula. The NHC track splits these differences and is a blend
TCVA multi-model consensus and the HFIP corrected consensus. The
new track forecast is very close to the previous official forecast.

Although Gamma has re-strengthened this morning, increasing
southerly wind shear is expected over the cyclone by tonight.
This unfavorable upper-level environment is likely to cause
some gradual weakening by late tonight and Monday. Since the
vertical shear expected to remain moderate to strong through the
latter portion of the forecast period, little overall change in
strength is shown after 48 hours.


KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall for several days over
portions of southeastern Mexico, the Yucatan Peninsula, Central
America, and far western Cuba. This rainfall could result in
life-threatening flash flooding and mudslides, particularly in the
mountainous regions of southeastern Mexico and Central America.

2. Even though Gamma is offshore, tropical storm conditions will
continue across portions of the northern coast of the Yucatan
Peninsula today.


FORECAST POSITIONS AND MAX WINDS

INIT 04/1500Z 22.2N 88.2W 50 KT 60 MPH
12H 05/0000Z 22.6N 88.2W 50 KT 60 MPH
24H 05/1200Z 22.6N 88.5W 45 KT 50 MPH
36H 06/0000Z 22.3N 89.3W 40 KT 45 MPH
48H 06/1200Z 22.0N 90.2W 40 KT 45 MPH
60H 07/0000Z 21.5N 91.0W 40 KT 45 MPH
72H 07/1200Z 21.0N 91.6W 40 KT 45 MPH
96H 08/1200Z 20.4N 92.5W 40 KT 45 MPH
120H 09/1200Z 20.4N 93.0W 40 KT 45 MPH

$$
Forecaster Brown

[cycloneye]

Tropical Storm Gamma Discussion Number 10
NWS National Hurricane Center Miami FL AL252020
400 PM CDT Sun Oct 04 2020

The last aircraft reconnaissance fix, recorded a couple of hours
ago, indicated that Gamma's center had wobbled a little to the
right of the previous 6-hour motion and is located near the
southeastern edge of the convective canopy. Flight-level winds
adjusted to the surface, SFMR wind data, and a blend of Dvorak
satellite intensity estimates from TAFB and SAB still support an
initial intensity of 50 kt for this advisory.

The UW-CIMSS shear analysis reveals stiff 20-25 kt southerly shear
impinging on the south portion of the cyclone. Subsequently, the
large-scale models and the ECMWF/GFS statistical-dynamical
intensity guidance show the shear magnitude increasing during the
next 24 hours. This inhibiting upper wind pattern should induce
weakening soon. Although the shear is predicted to decrease
somewhat around mid-period, Gamma should exhibit little change in
strength through the remaining period which is in best agreement
with all of the skilled intensity guidance. As mentioned in
previous advisories, it cannot be stressed enough the relatively
high level of uncertainty in this intensity forecast, and that it's
primarily dependent on whether or not the cyclone moves back over
the Yucatan Peninsula.

Gamma should continue to move little, or meander over the
southern Gulf of Mexico, near the northern coast of the
Yucatan Peninsula through most of tomorrow. By Monday night,
the global models are in good agreement with the western extent of
a subtropical ridge reestablishing temporarily over the central
Gulf of Mexico. This change in the synoptic steering pattern
should cause the cyclone to turn and move west-southwestward
through the 72 hour forecast period. After a brief reduction in
forward speed late Wednesday, while Potential-Tropical Cyclone
Twenty-Six moves into the central Gulf of Mexico, a turn toward the
northwest is expected on Thursday as the ridge, once again, builds
back over the central Gulf in response to PTC Twenty-Six
approaching the northern Gulf coast. The official track forecast
is adjusted to the left of the previous one through the 60 hour
period to agree more with the HCCA consensus, and shifted to the
right through day 5.


KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall for several days over
portions of southeastern Mexico, the Yucatan Peninsula, Central
America, and far western Cuba. This rainfall could result in
life-threatening flash flooding and mudslides, particularly in the
mountainous regions of southeastern Mexico and Central America.

2. Even though Gamma is just offshore, tropical storm conditions
will continue across portions of the northern coast of the Yucatan
Peninsula today.


FORECAST POSITIONS AND MAX WINDS

INIT 04/2100Z 22.4N 87.8W 50 KT 60 MPH
12H 05/0600Z 22.3N 88.1W 45 KT 50 MPH
24H 05/1800Z 22.1N 88.6W 40 KT 45 MPH
36H 06/0600Z 21.7N 89.4W 40 KT 45 MPH
48H 06/1800Z 21.3N 90.4W 40 KT 45 MPH
60H 07/0600Z 20.8N 91.1W 40 KT 45 MPH
72H 07/1800Z 20.1N 91.4W 40 KT 45 MPH
96H 08/1800Z 21.0N 92.1W 40 KT 45 MPH
120H 09/1800Z 22.2N 92.7W 40 KT 45 MPH

$$
Forecaster Roberts

[cycloneye]

BULLETIN
Tropical Storm Gamma Advisory Number 11
NWS National Hurricane Center Miami FL AL252020
1000 PM CDT Sun Oct 04 2020

...GAMMA CONTINUES TO DRIFT JUST NORTH OF THE YUCATAN PENINSULA...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...22.8N 87.2W
ABOUT 190 MI...305 KM ENE OF PROGRESO MEXICO
ABOUT 160 MI...255 KM N OF COZUMEL MEXICO
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...E OR 90 DEGREES AT 2 MPH...4 KM/H
MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The government of Mexico has issued a Tropical Storm Watch from
Progreso to Campeche Mexico.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* North and west of Cancun to Dzilam Mexico

A Tropical Storm Watch is in effect for...
* West of Dzilam to Campeche Mexico

A Tropical Storm Warning means that tropical storm conditions are
occurring somewhere within the warning area.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1000 PM CDT (0300 UTC), data from an Air Force Reserve Hurricane
Hunter aircraft indicated that the center of Tropical Storm Gamma
was located near latitude 22.8 North, longitude 87.2 West. The
tropical storm is drifting toward the east near 2 mph (4 km/h).
Gamma is forecast to gradually turn toward the southwest or
west-southwest on Monday and move slowly in that direction through
mid-week. On the forecast track, the center of Gamma will continue
to meander offshore of the northern Yucatan Peninsula tonight and
pass near or just offshore of the northern coast of the Yucatan
Peninsula on Monday and Tuesday.

Maximum sustained winds are near 60 mph (95 km/h) with higher gusts.
Some weakening is forecast during the next 48 hours. Gradual
weakening is anticipated to begin on Monday and continue into
Tuesday. Afterward, little change in strength is forecast.

Tropical-storm-force winds extend outward up to 160 miles (260 km)
from the center.

The estimated minimum central pressure based on measurements from
the hurricane hunter plane is 998 mb (29.47 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Tropical Storm Gamma can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT5, WMO header WTNT45
KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT5.shtml.

RAINFALL: Gamma is expected to produce an additional 3 to 6 inches
of rainfall, with isolated maximum amounts of 8 inches, across
portions of the Mexican states of Yucatan, Campeche and Tabasco.
This rainfall may enhance any ongoing flash flooding and result in
new areas of flash flooding into the middle of the week.

WIND: Tropical storm conditions are likely in portions of the
Tropical Storm Warning area along the northern coast of the Yucatan
Peninsula on Monday. Tropical Storm conditions are possible within
the Tropical Storm Watch area late Monday and Tuesday.


NEXT ADVISORY
-------------
Next intermediate advisory at 100 AM CDT.
Next complete advisory at 400 AM CDT.

$$
Forecaster Zelinsky



Tropical Storm Gamma Discussion Number 11
NWS National Hurricane Center Miami FL AL252020
1000 PM CDT Sun Oct 04 2020

Gamma has moved much farther northeast than previously anticipated.
With little in the way of low or mid-level large-scale steering flow
currently in place, it seems likely that upper-level
southwesterlies, also responsible for the shear affecting the
tropical storm, are causing this recent northeastward motion. This
may be either through reformations of the center closer to the
convection or a direct contribution to the net steering. An Air
Force Reserve Hurricane Hunter aircraft is currently investigating
Gamma and so far has found max SFMR winds of 47 kt but flight level
winds of only 45 kt. Given the data so far, there is no indication
that Gamma is any stronger than the 50 kt intensity, but it seems
prudent to let the plane finish its pattern before lowering the
winds at this time.

Gamma's future track is highly uncertain. The track guidance spread
is much higher than usual, and confidence in the forecast is
accordingly low. Most of the global models indicate that Gamma will
soon begin moving generally west-southwestward as a mid-level ridge
briefly builds over the eastern and central Gulf of Mexico.
Unfortunately, there is little agreement on exactly when this will
happen or how fast Gamma will move once it turns. After about 48 h,
Gamma could interact with Tropical Depression Twenty-Six, which is
forecast to move over the northwestern Caribbean Sea at that time.
Current dynamical models are notoriously bad at forecasting such
interactions, but if the two systems do interact it will likely
cause Gamma to move inland over the Yucatan.

Whether such an interaction occurs or not, continued shear and
proximity to land should cause the tropical storm to gradually
weaken, and Gamma could dissipate if it moves over land (and stays
there) in a few days, as shown by the GFS. The ECMWF shows the
vortex remaining over water but dissipating nonetheless, while a
couple other global models maintain the vortex longer and show it
moving north over the central Gulf of Mexico late in the forecast
period. The NHC forecast is a compromise between those solutions,
showing a remnant low moving north over the southern Gulf of Mexico
by day 5. In general, the NHC intensity forecast is similar to the
previous one, but slightly lower to account for the system
potentially moving inland.

Due to the uncertainty in the forecast at this time, future
advisories may feature larger than normal changes to the track or
intensity forecast. It is also worth noting that several dynamical
model trackers appear to lose Gamma and jump to tracking Tropical
Depression Twenty-Six when it reaches the Gulf of Mexico, resulting
in unrealistic depictions of the intensity and track forecasts.

KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall for several days over
portions of southeastern Mexico, the Yucatan Peninsula, Central
America, and far western Cuba. This rainfall could result in
life-threatening flash flooding and mudslides, particularly in the
mountainous regions of southeastern Mexico and Central America.

2. Even though Gamma is just offshore, tropical storm conditions
are likely along portions of the northern coast of the Yucatan
Peninsula on Monday.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0300Z 22.8N 87.2W 50 KT 60 MPH
12H 05/1200Z 22.7N 87.7W 45 KT 50 MPH
24H 06/0000Z 22.3N 88.5W 45 KT 50 MPH
36H 06/1200Z 21.8N 89.5W 40 KT 45 MPH
48H 07/0000Z 21.3N 90.3W 40 KT 45 MPH
60H 07/1200Z 20.3N 90.7W 35 KT 40 MPH
72H 08/0000Z 20.2N 90.1W 30 KT 35 MPH...INLAND
96H 09/0000Z 22.0N 90.7W 30 KT 35 MPH...OVER WATER
120H 10/0000Z 24.0N 91.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Zelinsky

[cycloneye]

Tropical Storm Gamma Discussion Number 12
NWS National Hurricane Center Miami FL AL252020
400 AM CDT Mon Oct 05 2020

Gamma is a strongly sheared tropical storm that has been meandering
just north of the northern coast of the Yucatan Peninsula of Mexico.
Strong convective cloud tops colder than -80 deg C are located more
than 60 nmi north and northeast of the well-defined and fully
exposed low-level circulation center. An Air Force Reserve
reconnaissance aircraft investigating the cyclone found maximum
850-mb flight-level winds of only 44 kt along with peak SFMR surface
winds of 47 kt. In addition, a 0329Z ASCAT-A pass revealed peak
surface winds of 41 kt. Allowing for undersampling by the
scatterometer instrument and blending it with the SFMR winds
supports lowering the initial intensity to 45 kt. The central
pressure of 999 mb is based on a center dropsonde reports of 1000 mb
and 10-12 kt winds.

The initial motion estimate is an uncertain 240/02 kt. Gamma's
future track remains highly uncertain after day 2. For the next 48
hours or so, the cyclone is forecast to move slowly southwestward to
west-southwestward and weaken due to strong southerly vertical wind
shear. Thereafter, TD-26 to the east is forecast to strengthen into
a hurricane, accompanied by a corresponding increase in the size of
that cyclone's circulation, which is expected to result in some
binary interaction between the two tropical cyclones. Due to Gamma's
expected smaller size on days 3 and 4, the cyclone is forecast to be
pulled eastward and then northward, making landfall on and then
moving over the northwestern Yucatan Peninsula. By day 5, Gamma is
expected to degenerate into a remnant low and then be absorbed by
the larger circulation of the expected central Gulf of Mexico
hurricane that is currently TD-26. The new NHC track forecast is
similar to but a little slower than the previous advisory track, and
lies close to the southern edge of the guidance envelope.

Strong southerly wind shear, combined with drier and more stable air
just to the west of Gamma, is expected to weaken the cyclone further
over the next few days. If land interaction occurs sooner than
expected, then the cyclone could weaken and dissipate sooner than
currently forecast. For now, the intensity forecast maintains
continuity with the previous advisory and shows dissipation by 120
hours as Gamma interacts with what is expected to be a significant
hurricane over the central Gulf of Mexico by 96 hours, which could
end up absorbing the smaller Gamma tropical cyclone.

Due to the uncertainty in the forecast at this time, future
advisories may feature larger-than-normal changes to the track or
intensity forecast. It is also worth noting that several dynamical
model trackers appear to lose Gamma and jump to tracking Tropical
Depression Twenty-Six when it reaches the Gulf of Mexico, resulting
in unrealistic depictions of the model intensity and track
forecasts.

KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall through midweek over
portions of southeast Mexico, including the Mexican states of
Yucatan, Campeche, and Tabasco. This rainfall could result in
significant flash flooding.

2. Even though Gamma is just offshore, tropical storm conditions
are likely along portions of the northern coast of the Yucatan
Peninsula later today.


FORECAST POSITIONS AND MAX WINDS

INIT 05/0900Z 22.7N 87.5W 45 KT 50 MPH
12H 05/1800Z 22.5N 88.0W 40 KT 45 MPH
24H 06/0600Z 22.1N 88.9W 40 KT 45 MPH
36H 06/1800Z 21.4N 89.8W 35 KT 40 MPH
48H 07/0600Z 20.8N 90.4W 35 KT 40 MPH
60H 07/1800Z 20.3N 90.5W 30 KT 35 MPH...INLAND YUCATAN
72H 08/0600Z 20.7N 90.1W 30 KT 35 MPH...INLAND YUCATAN
96H 09/0600Z 22.5N 90.0W 30 KT 35 MPH...OVER WATER
120H 10/0600Z...DISSIPATED

$$
Forecaster Stewart

[cycloneye]

Tropical Storm Gamma Discussion Number 13
NWS National Hurricane Center Miami FL AL252020
1000 AM CDT Mon Oct 05 2020

Air Force Reserve reconnaissance aircraft investigating Gamma found
maximum 850 mb flight-level winds of 37 kt and surface SFMR peak
winds of 40 kt, and the central pressure has increased to 1003 mb.
Therefore, the initial intensity is lowered to 40 kt for this
advisory.

Stiff, persistent southerly shear, and an inhibiting thermodynamic
surrounding environment should prevent Gamma from restrengthening,
although, the Decay SHIPS intensity model does indicate a very
brief period of decreasing shear magnitude just prior to landfall
around the 24 hour period. Afterward, the shear, once again,
increases. Gamma is expected to make landfall over the
northwestern Yucatan peninsula on Tuesday and further weakening
to a remnant low is forecast Wednesday as the cyclone remains
inland over the northern Mexican State of Yucatan. Dissipation is
likely to occur Friday over the region, if not sooner.

The initial motion is estimated to be a south-southwestward drift,
or 205/2 kt. A turn southwestward or west-southwestward is
expected by tonight and this general motion should continue through
Wednesday morning while moving inland over the northern Mexican
State of Yucatan. The large-scale models still insist on some
binary interaction occurring with Tropical Storm Delta commencing
Tuesday night/Wednesday morning. This should cause Gamma to
gradually turn cyclonically through Thursday while remaining over
the Northern Yucatan peninsula. If there is a delay in Gamma's
landfall, or the cyclone does remain just offshore, similar to the
outlier UKMET, then Tropical Storm Delta could end up absorbing the
smaller Gamma tropical cyclone toward the end of the week. For
now, the NHC forecast will side with a landfall scenario which
agrees with the HCCA consensus and the GFS/ECMWF solutions.

KEY MESSAGES:

1. Gamma is expected to produce heavy rainfall through midweek over
portions of southeast Mexico, including the Mexican states of
Yucatan, Campeche, and Tabasco. This rainfall could result in
significant flash flooding.

2. Even though Gamma is just offshore, tropical storm conditions
are likely along portions of the northern coast of the Yucatan
Peninsula later today.


FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 22.3N 87.6W 40 KT 45 MPH
12H 06/0000Z 22.1N 88.4W 40 KT 45 MPH
24H 06/1200Z 21.6N 89.2W 35 KT 40 MPH
36H 07/0000Z 20.9N 89.9W 30 KT 35 MPH...INLAND
48H 07/1200Z 20.2N 90.2W 25 KT 30 MPH...POST-TROP/INLAND
60H 08/0000Z 20.3N 89.8W 25 KT 30 MPH...POST-TROP/INLAND
72H 08/1200Z 21.0N 89.5W 20 KT 25 MPH...POST-TROP/INLAND
96H 09/1200Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

Tropical Depression Gamma Discussion Number 14
NWS National Hurricane Center Miami FL AL252020
400 PM CDT Mon Oct 05 2020

The last couple of legs of the Air Force Reserve reconnaissance
aircraft mission and recent METOP-A and C scatterometer passes
support lowering Gamma's initial intensity to 30 kt for this
advisory. Conventional satellite imagery reveals that the cyclone
has been devoid of deep convection for nearly 10 hours and is on
its way to becoming a post-tropical remnant low. Strong southerly
shear and a stable, relatively dry surrounding air mass should
prevent any significant convective regeneration as the system
approaches the northern coast of the northwestern Yucatan peninsula
tomorrow. After the remnants of Gamma makes landfall, dissipation
is likely to occur Wednesday as larger, Tropical Storm Delta
approaches the Yucatan Channel.

The initial motion is estimated to be southwestward, or 230/4 kt.
A continued southwestward or west-southwestward motion is expected
through Wednesday morning while moving inland over the northern
Mexican State of Yucatan. The NHC forecast track is basically an
update of this morning's package and is based on the various
multi-model consensus aids.

KEY MESSAGES:

1. Gamma is expected to produce areas of heavy rainfall through
midweek over portions of southeast Mexico, including the Mexican
states of Yucatan, Campeche, and Tabasco. This rainfall could result
in areas of flash flooding.

2. Gusty winds are likely along portions of the northern coast of
the Yucatan Peninsula later today through Tuesday.


FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 22.1N 88.1W 30 KT 35 MPH
12H 06/0600Z 21.6N 88.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 06/1800Z 20.9N 89.6W 25 KT 30 MPH...POST-TROP/INLAND
36H 07/0600Z 20.0N 90.1W 20 KT 25 MPH...POST-TROP/INLAND
48H 07/1800Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

BULLETIN
Post-Tropical Cyclone Gamma Advisory Number 15
NWS National Hurricane Center Miami FL AL252020
1000 PM CDT Mon Oct 05 2020

...GAMMA BECOMES POST TROPICAL NEAR THE NORTHERN COAST OF THE
YUCATAN PENINSULA...
...PERIODS OF HEAVY RAINFALL POSSIBLE TONIGHT...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...21.6N 88.4W
ABOUT 85 MI...140 KM ENE OF PROGRESO MEXICO
ABOUT 125 MI...200 KM NW OF COZUMEL MEXICO
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...SW OR 220 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1000 PM CDT (0300 UTC), the center of Post-Tropical Cyclone Gamma
was located near latitude 21.6 North, longitude 88.4 West. The
post-tropical cyclone is moving toward the southwest near 6 mph (9
km/h), and this general motion is expected to continue for the next
day or so. The post-tropical cyclone is currently centered along
the northern coast of the Yucatan peninsula and will move inland
through Monday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Gradual weakening is anticipated and Gamma is forecast to dissipate
by Wednesday.

The estimated minimum central pressure is 1005 mb (29.68 inches).


HAZARDS AFFECTING LAND
----------------------
RAINFALL: Through midweek, the remnants of Gamma are expected to
produce an additional 2 to 4 inches of rainfall with isolated
maximum amounts of 8 inches across portions of the Mexican states of
Yucatan, Campeche, and Tabasco. This rainfall may produce areas of
flash flooding.


NEXT ADVISORY
-------------
This is the last public advisory issued by the National Hurricane
Center on this system. Additional information on this system can be
found in High Seas Forecasts issued by the National Weather Service,
under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php

$$
Forecaster Zelinsky