ATL: CRISTOBAL - Advisories

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 13
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 PM EDT TUE AUG 26 2014

As Cristobal has moved northward around the eastern side of the
upper trough it is currently interacting with, the shear has
decreased over the cyclone and deep convection has redeveloped near
the center. The latest NOAA Hurricane Hunter aircraft found that
the pressure had fallen to 984 mb and reported a partial eyewall.
The initial intensity of 65 kt is based on a peak 8,000-ft
flight-level wind of 75 kt and SFMR winds around 60 kt. Aircraft
data and a partial ASCAT pass show that the wind field of Cristobal
has expanded significantly in the eastern semicircle, and the
initial and forecast wind radii have been adjusted outward.

Conditions should be favorable for some strengthening as a tropical
cyclone during the next couple of days before the cyclone moves over
cooler waters and into a higher shear environment. After that time,
the GFS, ECMWF, and UKMET all show an impressive extratropical
transition of Cristobal, as it interacts synergistically with a
powerful mid-latitude trough in about 3 days. This should result in
Cristobal maintaining hurricane-force winds for a time as an
extratropical cyclone.

The initial motion estimate is 010/12. Cristobal jogged north-
northeastward earlier today, but is now moving a bit more to the
left. The dynamical model guidance shows a bit of a northward jog
tonight as the cyclone moves east of the upper-trough. After that
time an acceleration toward the northeast is expected as the
subtropical ridge to the southeast propels Cristobal into the mid
latitudes by 48 hours. A quick northeastward motion is expected to
continue through 4 days with a bend back toward the north-northeast
shown at day 5. The track model guidance has shifted a bit to the
west this cycle in the short range, and the NHC forecast has been
nudged in that direction for the first 36 hours, but lies on the
east side of the guidance envelope. At 48 hours and beyond the NHC
forecast is largely an update of the previous one and is close to a
consensus of the GFS and ECMWF models.

FORECAST POSITIONS AND MAX WINDS

INIT 26/2100Z 28.8N 71.4W 65 KT 75 MPH
12H 27/0600Z 30.7N 71.2W 70 KT 80 MPH
24H 27/1800Z 32.9N 70.4W 70 KT 80 MPH
36H 28/0600Z 35.2N 67.6W 75 KT 85 MPH
48H 28/1800Z 38.0N 62.4W 75 KT 85 MPH
72H 29/1800Z 45.5N 47.0W 70 KT 80 MPH...POST-TROP/EXTRATROP
96H 30/1800Z 52.5N 35.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
120H 31/1800Z 60.0N 26.0W 55 KT 65 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brennan

[TheEuropean]

000
WTNT34 KNHC 262344
TCPAT4

BULLETIN
HURRICANE CRISTOBAL INTERMEDIATE ADVISORY NUMBER 13A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
800 PM EDT TUE AUG 26 2014

...CRISTOBAL STRENGTHENS A LITTLE...


SUMMARY OF 800 PM EDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...29.7N 71.5W
ABOUT 435 MI...700 KM WSW OF BERMUDA
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...983 MB...29.03 INCHES


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

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* BERMUDA

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE IN THE NEXT 24 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 PM EDT...0000 UTC...THE CENTER OF HURRICANE CRISTOBAL WAS
LOCATED NEAR LATITUDE 29.7 NORTH...LONGITUDE 71.5 WEST. CRISTOBAL
IS MOVING TOWARD THE NORTH NEAR 16 MPH...26 KM/H. A NORTHWARD TO
NORTH-NORTHEASTWARD MOTION IS EXPECTED TONIGHT AND WEDNESDAY. A
TURN TOWARD THE NORTHEAST IS FORECAST WEDNESDAY NIGHT...FOLLOWED BY
A FASTER NORTHEASTWARD MOTION ON THURSDAY. ON THE FORECAST
TRACK...THE CENTER OF CRISTOBAL IS EXPECTED TO PASS NORTHWEST OF
BERMUDA ON WEDNESDAY AND WEDNESDAY NIGHT.

OBSERVATIONS FROM A NOAA HURRICANE HUNTER AIRCRAFT INDICATE THAT THE
MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 80 MPH...130 KM/H...
WITH HIGHER GUSTS. SOME ADDITIONAL STRENGTHENING IS FORECAST DURING
THE NEXT 48 HOURS.

CRISTOBAL HAS A LARGE WIND FIELD. HURRICANE FORCE WINDS EXTEND
OUTWARD UP TO 60 MILES...95 KM...FROM THE CENTER...AND TROPICAL
STORM FORCE WINDS EXTEND OUTWARD UP TO 240 MILES...390 KM.

THE HURRICANE HUNTER AIRCRAFT RECENTLY REPORTED A MINIMUM CENTRAL
PRESSURE OF 983 MB...29.03 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...CRISTOBAL IS EXPECTED TO PRODUCE ADDITIONAL RAINFALL
AMOUNTS OF 2 TO 4 INCHES OVER BERMUDA.

WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE ON BERMUDA WEDNESDAY
AND WEDNESDAY NIGHT.

SURF...SWELLS GENERATED BY CRISTOBAL ARE AFFECTING BERMUDA AND
PORTIONS OF THE U.S. EAST COAST FROM CENTRAL FLORIDA NORTHWARD TO
NORTH CAROLINA...AND WILL SPREAD NORTHWARD ALONG THE U.S. EAST COAST
OVER THE NEXT FEW DAYS. THESE SWELLS ARE LIKELY TO CAUSE
LIFE-THREATENING SURF AND RIP CURRENT CONDITIONS. FOR MORE
INFORMATION...PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER
OFFICE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1100 PM EDT.

$$
FORECASTER PASCH

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
1100 PM EDT TUE AUG 26 2014

A NOAA Hurricane Hunter aircraft investigated Cristobal earlier
this evening, and found that the hurricane had strengthened a bit.
Based on SFMR-observed surface winds and dropsonde data from the
aircraft, the intensity was increased to 70 kt. Since the time of
the aircraft mission, the convective cloud tops have warmed
somewhat -- but this is likely a diurnal fluctuation. The
dynamical guidance indicates that the vertical shear over Cristobal
will remain modest through about 36 hours, but increase
substantially thereafter. Therefore the hurricane has a window of
opportunity for strengthening that should last through tomorrow
night. The official wind speed forecast is close to the latest
intensity model consensus. Later in the forecast period, as
Cristobal nears and undergoes extratropical transition, strong
baroclinic forcing should result in a powerful post-tropical storm
with hurricane-force winds over the north Atlantic later this week.

Aircraft fixes indicate a northward motion of about 360/13 kt. The
track forecast philosophy is essentially unchanged from the
previous advisory package. Over the next day or two, Cristobal
should move through a weakness between 2 subtropical anticyclones.
Thereafter, the cyclone should turn northeastward ahead of a
mid-tropospheric shortwave trough moving off of the northeastern
United States, and accelerate in the mid-latitude westerlies. The
latest track model guidance has shifted a bit to the left, and the
official forecast remains near the right side of the guidance suite.

FORECAST POSITIONS AND MAX WINDS

INIT 27/0300Z 30.4N 71.5W 70 KT 80 MPH
12H 27/1200Z 32.0N 71.2W 70 KT 80 MPH
24H 28/0000Z 34.3N 69.7W 75 KT 85 MPH
36H 28/1200Z 36.6N 66.5W 75 KT 85 MPH
48H 29/0000Z 39.5N 60.0W 75 KT 85 MPH
72H 30/0000Z 47.5N 45.5W 70 KT 80 MPH...POST-TROP/EXTRATROP
96H 31/0000Z 54.0N 33.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
120H 01/0000Z 62.0N 23.0W 55 KT 65 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 15
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 AM EDT WED AUG 27 2014

The cloud pattern has changed from 12 hours ago when there was deep
and symmetric convection near the center. Currently, the satellite
presentation resembles a subtropical cyclone with weak convection
which is not concentrated near the center. However, an Air Force
plane recently penetrated Cristobal and found a minimum pressure of
983 mb and a partial eyewall. The strong winds of 75 to 80 kt
measured by the plane at flight level were not observed at the
surface during this time. Given such uncertainty, the initial
intensity has been kept at 70 kt at this time. The hurricane has a
small window of opportunity for strengthening before it moves to
higher latitudes and over cooler waters in a couple of days. The NHC
wind speed forecast is close to the latest intensity model
consensus and similar to the previous official one. After that time,
Cristobal is forecast to become a strong post-tropical storm with
hurricane-force winds over the north Atlantic later this week.

Aircraft and satellite fixes indicate that Cristobal slowed down
earlier this morning, but as anticipated, it has resumed a northward
motion or 010 degrees at 10 knots. The steering pattern has not
changed and Cristobal should begin to move toward the northeast in
about 24 hours with an increase in forward speed as it becomes
embedded in the mid-latitude westerlies. The NHC forecast is very
close to the multi-model consensus and similar to the GFS ensemble
mean AEMI, which has been performing quite well with this storm so
far. The forecast beyond 72 hours follows the input from the Ocean
Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT 27/0900Z 30.9N 71.9W 70 KT 80 MPH
12H 27/1800Z 32.4N 71.6W 70 KT 80 MPH
24H 28/0600Z 34.7N 69.2W 75 KT 85 MPH
36H 28/1800Z 37.5N 63.5W 75 KT 85 MPH
48H 29/0600Z 40.5N 56.5W 75 KT 85 MPH
72H 30/0600Z 48.0N 43.0W 70 KT 80 MPH...POST-TROP/EXTRATROP
96H 31/0600Z 53.0N 32.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 01/0600Z...ABSORBED

$$
Forecaster Avila

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
1100 AM EDT WED AUG 27 2014

Some deep convection has redeveloped near the center of Cristobal
during the past few hours, mainly in the western semicircle.
Satellite imagery shows dry air wrapping south and east of the
center interspersed with a couple of convective bands. The initial
intensity remains 70 kt, and another aircraft will be investigating
the cyclone this afternoon. There is still some potential for
Cristobal to strengthen as a tropical cyclone during the next day or
so before it begins extratropical transition, which should be
complete shortly after 48 hours. Cristobal is expected to be a
powerful extratropical cyclone by Friday night or Saturday, and then
slowly weaken before being absorbed by another cyclone at the end of
the period. The NHC intensity forecast is similar to the previous
one and close to the IVCN intensity consensus while Cristobal
remains a tropical cyclone.

Cristobal has wobbled a little to the left this morning, with an
initial motion estimate of 355/10. All of the guidance is unanimous
in turning Cristobal north-northeastward and then northeastward
during the next 24 hours and accelerating the cyclone into the
mid-latitude westerlies. A continued northeasterly motion is
expected through the remainder of the cyclone's life cycle. The
track model guidance is tightly clustered, but the NHC forecast has
shifted to the left of the previous one by about a half a degree due
to the initial position and motion being to the left of the previous
track. The new NHC track is close to a consensus of the GFS and
ECMWF models through 72 hours, and a little south of that consensus
at 96 hours.

The extratropical portion of the forecast has been coordinated with
the Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT 27/1500Z 31.8N 72.2W 70 KT 80 MPH
12H 28/0000Z 34.0N 70.8W 70 KT 80 MPH
24H 28/1200Z 36.5N 66.7W 75 KT 85 MPH
36H 29/0000Z 39.6N 59.9W 75 KT 85 MPH
48H 29/1200Z 43.5N 52.0W 75 KT 85 MPH
72H 30/1200Z 50.0N 40.5W 70 KT 80 MPH...POST-TROP/EXTRATROP
96H 31/1200Z 56.0N 29.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 01/1200Z...ABSORBED

$$
Forecaster Brennan

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 17
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 PM EDT WED AUG 27 2014

Deep convection continues to be confined mostly near and to the west
of the center of Cristobal, with dry air persisting in the eastern
semicircle. After rising a bit earlier this afternoon, the central
pressure has fallen back down to 984 mb. The initial intensity of 65
kt is based on several 60-65 kt SFMR winds from the hurricane hunter
aircraft. The intensity forecast shows gradual intensification to 75
kt in 36 to 48 hours, as Cristobal will have the opportunity to
intensify as a tropical cyclone and then via baroclinic processes
during extratropical transition. Global model fields show Cristobal
deepening during transition and acquiring a warm seclusion structure
in 48 to 72 hours. Slow decay is expected after 72 hours before the
cyclone is absorbed at high latitudes.

Cristobal has begun moving north-northeastward, with an initial
motion estimate of 030/13. The cyclone should continue to accelerate
around the subtropical ridge into the mid-latitude westerlies
tonight and remain on a general northeastward heading through 72
hours before bending northward. The track model guidance remains in
good agreement on this scenario, and the NHC track is close to the
previous forecast and the middle of the guidance envelope.

The extratropical portion of the forecast has been coordinated with
the Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 32.7N 71.4W 65 KT 75 MPH
12H 28/0600Z 34.4N 69.2W 65 KT 75 MPH
24H 28/1800Z 37.3N 63.7W 70 KT 80 MPH
36H 29/0600Z 41.0N 55.3W 75 KT 85 MPH
48H 29/1800Z 45.3N 47.8W 75 KT 85 MPH...POST-TROPICAL
72H 30/1800Z 53.5N 34.5W 70 KT 80 MPH...POST-TROP/EXTRATROP
96H 31/1800Z 60.0N 27.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 01/1800Z...ABSORBED

$$
Forecaster Brennan

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
1100 PM AST WED AUG 27 2014

Cristobal has a fairly circular area of deep convection over the
estimated low-level center, with cloud tops occasionally to -70 deg
C. The initial intensity is kept at 65 kt, in agreement with a
Dvorak estimate from TAFB. The symmetric appearance of the cloud
pattern suggests that vertical shear has not yet become very
strong, but the latest SHIPS guidance indicates a significant
increase in shear in 18-24 hours. The hurricane could strengthen
some over the next day or two as a tropical cyclone, or due to
baroclinic processes. The official intensity forecast is close to
the intensity model consensus through 36 hours, and a little above
it thereafter. Extratropical transition is likely to have occurred
by 48 hours since the global models depict the system as fully
embedded within a frontal zone by that time. Post-tropical Cristobal
is likely to be an intense extratropical cyclone with winds to
hurricane force over the north Atlantic in a couple of days.

The hurricane is beginning to accelerate northeastward, and the
motion estimate is 050/17. The track forecast is unchanged from
the previous advisory. Cristobal is currently rounding the
northwestern periphery of a subtropical anticyclone over the
west-central Atlantic. A mid-latitude shortwave trough to the
northwest of the hurricane should cause the hurricane, or its
post-tropical counterpart, to accelerate further and move into the
higher-latitude westerlies. The official forecast track is in good
agreement with the multi-model consensus TVCA.

The track, intensity and wind structure forecasts have been
coordinated with the Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT 28/0300Z 34.1N 69.9W 65 KT 75 MPH
12H 28/1200Z 36.1N 66.6W 65 KT 75 MPH
24H 29/0000Z 39.3N 59.6W 70 KT 80 MPH
36H 29/1200Z 43.4N 51.5W 75 KT 85 MPH
48H 30/0000Z 47.5N 44.5W 70 KT 80 MPH...POST-TROP/EXTRATROP
72H 31/0000Z 56.0N 32.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
96H 01/0000Z 62.5N 25.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 02/0000Z...ABSORBED

$$
Forecaster Pasch

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 AM AST THU AUG 28 2014

Cristobal's satellite presentation is more typical of a tropical
cyclone tonight than yesterday at this time. There is a symmetric
area of very deep convection concentrated near the center, and
Dvorak T-numbers from TAFB and SAB support an initial intensity of
65 kt. There is a small opportunity for intensification as
indicated by some models, but it is becoming more likely that it
will be enhanced by baroclinic processes as the cyclone interacts
with a frontal zone. Cristobal will move over 17-degree Celsius
waters and lose tropical characteristics in about 36 hours. It
should then become an intense extratropical cyclone with winds of
hurricane force over the north Atlantic in a couple of days.

The hurricane is already embedded within the mid-latitude westerlies
and is moving toward the northeast or 055 degrees at 25 knots and
accelerating. There is no reason to change the track forecast from
the previous one, and the official forecast track continues to be in
good agreement with the multi-model consensus TVCA and the GFS
ensemble mean.

The track, intensity and wind radii forecasts have been coordinated
with the Ocean Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT 28/0900Z 35.6N 67.8W 65 KT 75 MPH
12H 28/1800Z 37.8N 63.2W 70 KT 80 MPH
24H 29/0600Z 41.5N 55.0W 75 KT 85 MPH
36H 29/1800Z 46.0N 47.0W 75 KT 85 MPH...POST-TROP/EXTRATROP
48H 30/0600Z 50.0N 40.0W 70 KT 80 MPH...POST-TROP/EXTRATROP
72H 31/0600Z 59.5N 28.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
96H 01/0600Z 63.0N 21.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 02/0600Z...ABSORBED

$$
Forecaster Avila

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 20
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
1100 AM AST THU AUG 28 2014

The satellite presentation of Cristobal has become much more
symmetric than at any earlier time during its life. The center is
embedded within an area of deep convection and a warm spot has
become evident in recent visible satellite images. T-numbers from
both SAB and TAFB are 4.0 on the Dvorak Scale and the initial
intensity is set at 65 kt. Some strengthening is expected
today while the hurricane remains over warm water. The cyclone will
begin to interact with a frontal zone tonight and should complete
extratropical transition on Friday. The global models indicate that
the extratropical low will remain a powerful cyclone over the north
Atlantic during the next few days. The low is forecast to merge
with another large extratropical cyclone over the north Atlantic in
3 to 4 days.

Cristobal is moving northeastward at about 23 kt. The cyclone
should continue to accelerate northeastward in the mid-latitude
westerlies during the next day or so. The updated NHC track is
close to the previous advisory and near the middle of the guidance
envelope. The track, intensity and wind radii forecasts of the
extratropical low have been coordinated with the Ocean Prediction
Center.

FORECAST POSITIONS AND MAX WINDS

INIT 28/1500Z 36.9N 65.9W 65 KT 75 MPH
12H 29/0000Z 39.7N 59.9W 75 KT 85 MPH
24H 29/1200Z 43.8N 51.2W 75 KT 85 MPH
36H 30/0000Z 48.0N 43.5W 70 KT 80 MPH...POST-TROP/EXTRATROP
48H 30/1200Z 51.5N 36.5W 65 KT 75 MPH...POST-TROP/EXTRATROP
72H 31/1200Z 61.1N 25.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
96H 01/1200Z...MERGED WITH ANOTHER EXTRATROPICAL LOW

$$
Forecaster Brown

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 21
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 PM AST THU AUG 28 2014

The satellite presentation of Cristobal looked its best in visible
imagery shortly after the release of the previous advisory, when the
eye became more apparent. Since that time, the eye has become a
little more ragged, but a blend of the latest subjective and
objective Dvorak intensity estimates yields an initial wind speed
of 70 kt. Although the official forecast does not explicitly show
any additional intensification, there is a small window of
opportunity this evening for the hurricane to get a little
stronger. After that time, Cristobal will be moving across the
north wall of the Gulf Stream -- and over much colder waters. An
upper-level trough and cold front approaching the cyclone from the
northwest should cause Cristobal to transform into an extratropical
cyclone on Friday. The extratropical cyclone is expected to
continue to produce hurricane-force winds during the next couple of
days before it merges with another large extratropical cyclone over
the north Atlantic in about 3 days.

The hurricane continues to accelerate, and is now moving
east-northeastward at 31 kt. The cyclone should continue to
accelerate tonight and remain on an east-northeastward to
northeastward heading during the next 2 to 3 days. The updated NHC
track is in good agreement with the tightly clustered guidance,
but the forecast has been adjusted slightly to the right due to a
more eastward 1800 UTC initial position. The track, intensity and
wind radii forecasts of the extratropical low have been coordinated
with the Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT 28/2100Z 38.5N 61.5W 70 KT 80 MPH
12H 29/0600Z 41.0N 54.7W 70 KT 80 MPH
24H 29/1800Z 45.2N 46.0W 70 KT 80 MPH...POST-TROP/EXTRATROP
36H 30/0600Z 49.3N 38.4W 70 KT 80 MPH...POST-TROP/EXTRATROP
48H 30/1800Z 54.0N 31.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
72H 31/1800Z 62.0N 23.5W 60 KT 70 MPH...POST-TROP/EXTRATROP
96H 01/1800Z...MERGED WITH ANOTHER EXTRATROPICAL LOW

$$
Forecaster Brown

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
1100 PM AST THU AUG 28 2014

Remarkably, Cristobal still has a well-organized appearance on
satellite imagery with a central dense overcast and some banding
features. The current intensity estimate is increased to 75 kt in
agreement with Dvorak estimates from TAFB and SAB. The
hurricane will soon encounter much cooler waters, which would cause
significant weakening as a tropical cyclone. However, it is
expected that the cyclone will be able to maintain at least some of
its strength due to baroclinic forcing. Post-tropical Cristobal
will likely remain a powerful, albeit extratropical, cyclone over
the north Atlantic through Saturday. Beyond that time, the system
is forecast to merge with another low near southern Greenland and
lose its identity.

The hurricane has continued to accelerate, and the motion is now
near 065/40 kt as Cristobal moves within the mid-latitude
westerlies. Dynamical track guidance indicates a slight turn toward
the northeast as the tropical or post-tropical cyclone interacts
with the low near southern Greenland in the next day or two. The
official track forecast is close to a consensus of the GFS and
ECMWF model solutions.

The wind radii were adjusted based on data from a recent ASCAT
overpass.

FORECAST POSITIONS AND MAX WINDS

INIT 29/0300Z 40.2N 56.6W 75 KT 85 MPH
12H 29/1200Z 43.1N 49.9W 70 KT 80 MPH
24H 30/0000Z 47.5N 42.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
36H 30/1200Z 51.5N 34.5W 65 KT 75 MPH...POST-TROP/EXTRATROP
48H 31/0000Z 56.5N 27.5W 60 KT 70 MPH...POST-TROP/EXTRATROP
72H 01/0000Z...MERGED WITH ANOTHER CYCLONE

$$
Forecaster Pasch

[cycloneye]

HURRICANE CRISTOBAL DISCUSSION NUMBER 23
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 AM AST FRI AUG 29 2014

Cristobal has begun extratropical transition. The cloud pattern has
become much less symmetric and central convection has decreased,
along with dry air eroding the southern flank of the cyclone. Dvorak
classifications are a little lower and support an intensity of about
70 kt for this advisory. The hurricane has now moved across the
north wall of the Gulf Stream over much colder waters. This
change in environment usually causes a significant weakening of
a tropical cyclone, but in this case strong baroclinic forcing
should delay the cyclone's demise. Post-tropical Cristobal will
likely remain a powerful extratropical cyclone over the north
Atlantic through early Sunday. Beyond that time, the system is
forecast to merge with another low near southern Greenland
and lose its identity.

The hurricane continues to accelerate, and the motion is now
055/43 kt with Cristobal moving rapidly within the mid-latitude
flow. Dynamical track guidance indicates that this general motion
will continue during the next couple of days with a decrease
in forward speed and a small leftward turn due to Cristobal
interacting with the low near southern Greenland in the next day or
two. The official track forecast is close to the dynamical model
consensus and the latest guidance from the Ocean Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT 29/0900Z 42.1N 51.7W 70 KT 80 MPH
12H 29/1800Z 45.4N 45.4W 65 KT 75 MPH...POST-TROP/EXTRATROP
24H 30/0600Z 49.3N 39.1W 65 KT 75 MPH...POST-TROP/EXTRATROP
36H 30/1800Z 52.9N 32.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 31/0600Z 59.0N 24.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 01/0600Z...ABSORBED

$$
Forecaster Blake

[cycloneye]

POST-TROPICAL CYCLONE CRISTOBAL DISCUSSION NUMBER 24
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
1100 AM AST FRI AUG 29 2014

Cristobal has completed its transformation into an extratropical
cyclone with all of the cold cloud tops located well north and
northwest of the exposed center. A frontal boundary has also
wrapped around the southern portion of the circulation. A recent
ASCAT pass revealed a large area of 50-60 kt winds to the southeast
of the center. Based on these data, the initial intensity is set at
65 kt. Although some gradual weakening is forecast during the next
day or so, the low is expected to remain a large and powerful
cyclone over the north Atlantic until it merges with another large
low near Iceland in 36 to 48 hours.

The cyclone has been moving northeast at more than 40 kt during the
past 6 to 12 hours. However, the low is expected to slow down some
while it continues on a northeastward heading in deep layer
southwesterly flow during the next day or so. The official track
forecast lies between the ECMWF and GFS solution and has been
coordinated with guidance from the Ocean Prediction Center.

This is the last NHC advisory 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 and WMO header FZNT01 KWBC.

FORECAST POSITIONS AND MAX WINDS

INIT 29/1500Z 45.5N 47.1W 65 KT 75 MPH...POST-TROP/EXTRATROP
12H 30/0000Z 48.2N 41.8W 65 KT 75 MPH...POST-TROP/EXTRATROP
24H 30/1200Z 51.5N 35.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
36H 31/0000Z 55.0N 27.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
48H 31/1200Z...MERGED WITH ANOTHER LOW

$$
Forecaster Brown