ATL: BONNIE - Post-Tropical - Discussion

[Hammy]

Discussion should be interesting--it still didn't appear closed as of the last pass.

[cycloneye]

TROPICAL DEPRESSION TWO DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016
500 PM EDT FRI MAY 27 2016

An Air Force Reserve reconnaissance aircraft investigating the low
pressure system located about 400 n mi southeast of Charleston,
South Carolina, indicated that the system has developed a
well-defined closed circulation. With this afternoon's increase in
convection near the center, the system is now a tropical cyclone
and advisories have been initiated. The strongest reliable SFMR
surface wind measured was 30 kt, and that is the intensity set for
this advisory.

The initial motion estimate is 300/11 kt. A strong deep-layer ridge
to the northeast of the depression is forecast to remain
oriented northwest-southeast across the Carolinas through 36 hours
or so, which should keep the depression moving in a general
west-northwestward direction during that time. By 48 hours, however,
a mid-level shortwave trough ejecting northeastward out of the
south-central United States is forecast to erode the ridge,
resulting in a significant weakening of the steering currents and a
sharp decrease in forward speed as the cyclone is approaching the
coast of South Carolina. By day 3 and beyond, the cyclone is
forecast to move slowly northeastward or eastward off of the coast
of North Carolina as a weakening system. The models are in good
agreement on this track scenario, with only small differences in
forward speed. The official track forecast is close to the consensus
model TVCN and has incorporated the slightly slower speed of the
ECMWF model.

The depression will be moving over somewhat cooler sea surface
temperatures of near 25C during the next 24 hours or so before
moving over the warmer Gulfstream by 36 hours, where SSTs are
27C-28C. Over the next day or so, the cyclone will also be moving
into weaker vertical wind shear conditions. The net result is
expected to be slow strengthening to tropical storm status prior to
landfall. The NHC intensity forecast is similar to the SHIPS model
through 48 hours, and then closely follows the Decay-SHIPS model
after that.

FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 28.5N 74.7W 30 KT 35 MPH
12H 28/0600Z 29.5N 76.4W 35 KT 40 MPH
24H 28/1800Z 30.7N 78.3W 40 KT 45 MPH
36H 29/0600Z 32.0N 79.7W 40 KT 45 MPH
48H 29/1800Z 32.8N 80.2W 40 KT 45 MPH...INLAND
72H 30/1800Z 33.6N 78.7W 30 KT 35 MPH...OVER WATER
96H 31/1800Z 34.0N 77.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 01/1800Z 34.7N 75.6W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart

[floridasun78]

i see cone bigger after 5 days so going swift in area?

[SouthDadeFish]

I guess the circulation was defined enough for the NHC to consider TD 2 to have formed. It will be interesting to see how TD 2 handles incoming dry air intrusions over the next few days as the environmental wind shear drops to more favorable magnitudes.

[TheAustinMan]

i see cone bigger after 5 days so going swift in area?

Remember the cone is just based on the average track error for the National Hurricane Center from the last 5 years: based on those trends, a storm would have a 2/3rds chance of being in that cone. It does not change during the hurricane season, and does not change according to the forecaster's confidence.

Generally slow-moving storms make the cone seem "bigger" but this is just a consequence of the error circles swept out by the forecast points being close to one another.

[tatertawt24]

Another one of those weird early-year east coast storms.

[floridasun78]

GFDL-P,HWRF-P show mess left behide td2 close Bahamas spin other low send it ne http://www.tropicaltidbits.com/analysis/models/

[cycloneye]

BULLETIN
TROPICAL DEPRESSION TWO INTERMEDIATE ADVISORY NUMBER 1A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL022016
800 PM EDT FRI MAY 27 2016

...DEPRESSION MOVING WEST-NORTHWESTWARD TOWARD THE SOUTHEAST U.S.
COAST...


SUMMARY OF 800 PM EDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...28.8N 75.1W
ABOUT 400 MI...645 KM SE OF CHARLESTON SOUTH CAROLINA
ABOUT 405 MI...655 KM ESE OF HILTON HEAD ISLAND SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES


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

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Savannah River to Little River Inlet South Carolina

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

For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 800 PM EDT (0000 UTC), the center of Tropical Depression Two was
located near latitude 28.8 North, longitude 75.1 West. The
depression is moving toward the west-northwest near 13 mph (20
km/h), and this general motion is expected to continue for the next
24 hours. A reduction in forward speed is expected by Saturday
night as the system nears the coast.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some strengthening is forecast during the next 48 hours, and the
depression is expected to become a tropical storm later tonight or
on Saturday.

The estimated minimum central pressure is 1009 mb (29.80 inches).


HAZARDS AFFECTING LAND
----------------------
WIND: Tropical storm conditions are expected to first reach the
coast within the warning area by Saturday night, making outside
preparations difficult.

RAINFALL: The depression is expected to produce total rainfall
accumulations of 2 to 4 inches from the upper coast of Georgia
through eastern South Carolina and into southeastern North Carolina.

STORM SURGE: Storm surge inundation of 1 to 2 feet above ground
level is expected within the tropical storm warning area.

SURF: This system is expected to produce life-threatening surf and
rip current conditions along portions of the southeastern United
States coast through the weekend. Please consult products from your
local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM EDT.

$$
Forecaster Brennan

[SeGaBob]

I don't understand this...
Sunday:
Tropical storm conditions possible. A slight chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 87. Northwest wind 5 to 10 mph. Chance of precipitation is 20%.

Why would they put that there when the storm will be nowhere around here?

[Hammy]

I don't understand this...
Sunday:
Tropical storm conditions possible. A slight chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 87. Northwest wind 5 to 10 mph. Chance of precipitation is 20%.

Why would they put that there when the storm will be nowhere around here?

You don't seem to be that far inland from where the TS warning is so that was probably factored into it.

[Alyono]

Discussion should be interesting--it still didn't appear closed as of the last pass.

was clearly closed. When recon reports a VDM, not only does that mean the center is closed, but it is also quite well defined

[cycloneye]

I forgot to post something very important and that is the VDM that helped to get ex 91L classified


URNT12 KNHC 272032
VORTEX DATA MESSAGE AL912016
A. 27/20:17:10Z
B. 28 deg 15 min N
074 deg 44 min W
C. NA
D. 22 kt
E. 063 deg 58 nm
F. 135 deg 32 kt
G. 056 deg 84 nm
H. EXTRAP 1009 mb
I. 22 C / 305 m
J. 22 C / 303 m
K. NA / NA
L. NA
M. NA
N. 1234 / 1
O. 0.02 / 6 nm
P. AF307 01AAA INVEST OB 14
MAX FL WIND 32 KT 056 / 84 NM 19:49:30Z
SLP EXTRAP FROM BELOW 1500 FT
MAX FL TEMP 22 C 084 / 11 NM FROM FL CNTR
SHORT CURVED BANDS ON RADAR NEAR CENTER
;

[CrazyC83]

I don't understand this...
Sunday:
Tropical storm conditions possible. A slight chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 87. Northwest wind 5 to 10 mph. Chance of precipitation is 20%.

Why would they put that there when the storm will be nowhere around here?

That probably is because the models show it mostly missing but the chance is there that it could go off track. However, not sure if it is worth mentioning on a 20% chance though.

[AJC3]

I don't understand this...
Sunday:
Tropical storm conditions possible. A slight chance of showers and thunderstorms after 2pm. Partly sunny, with a high near 87. Northwest wind 5 to 10 mph. Chance of precipitation is 20%.

Why would they put that there when the storm will be nowhere around here?

This has to do with the 34KT wind probabilities. When they reach a certain threshold for a given location, it automatically triggers wording in the formatters for the Zone, Coastal Waters, and Point-and-Click Forecasts. The same logic applies for 64KT wind probablities.

There are three conditional phrases used in our public forecasts for expressing uncertainty about Tropical Storm and Hurricane conditions.

In order of increasing likelihood, they are: "...Possible", "...Likely" and "...Expected".

There are several references available for you to learn more about this. Here's one (Powerpoint)....
http://www.srh.noaa.gov/images/mfl/rese ... ummary.ppt

[cycloneye]

Still a TD at 00z Best track.

AL, 02, 2016052800, , BEST, 0, 288N, 752W, 30, 1009, TD

[SeGaBob]

Good read, and thanks for that informaton.

[tarheelprogrammer]

Convection is looking like it is dying off. Will it ever make it to named status? This thing has struggled a lot with keeping convection around it.

[Nimbus]

This morning when TD2 passed near a buoy it looked as though the pressure gradient was kind of broad and shallow.
Sea surface temperature is only 26 or 27 degrees and there is still some light shear from that ULL near Cuba.
Maybe once it gets over the warmer gulf stream it will tighten up.
Could make it to TS strength by landfall but I'm not sure I would forecast that.

[TheStormExpert]

Latest Video Discussion from Tropical Tidbits Levi Cowan.

Friday evening video discussion on Tropical Depression #2: http://www.tropicaltidbits.com/blog/2016/05/28/tropical-depression-2-forms-primary-threat-heavy-rain-and-dangerous-coastal-waters/

[cycloneye]

SUMMARY OF 1100 PM EDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...29.0N 75.9W
ABOUT 355 MI...575 KM SE OF CHARLESTON SOUTH CAROLINA
ABOUT 360 MI...580 KM SE OF HILTON HEAD ISLAND SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES