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Tropical Storm CRISTOBAL (Text)

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TROPICAL STORM CRISTOBAL DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042014
1100 AM EDT MON AUG 25 2014

Cristobal remains a sheared tropical cyclone with the low-level
center fully exposed on the north side of the deep convective cloud
mass. Earlier reconnaissance data indicated maximum 850 mb
flight-level winds of 61 kt in the southeast quadrant where SFMR
winds of near 50 kt were observed. Therefore, the initial intensity
has been increased to 50 kt. A NOAA aircraft reported a central
pressure of 996 mb, but the dropsonde also reported a 33-kt surface
wind. As a result, the central pressure is estimated to be 993 mb.

Aircraft fixes indicate that Cristobal is moving erratically
north-northeastward or 015/02 kt. Strong northerly shear has been
impeding the forward motion of Cristobal for the past several hours
by keeping the deep convection displaced to the south of the center,
and this is expected to continue through today. On Tuesday, however,
a deep trough just of the U.S. east coast is forecast to capture
Cristobal and gradually lift out the cyclone to the northeast while
the Bermuda-Azores ridge builds westward to the south of the system.
The NHC model guidance is in very good agreement on this developing
scenario with only minor differences in forward speed. The official
track forecast is similar to the previous advisory track, and lies
close to a blend of the GFS and ECMWF solutions.

The GFS-based SHIPS model indicates northerly shear of 23 kt has
been affecting Cristobal. The shear is forecast to gradually subside
to around 10 kt during the next 12-24 hours, during which time some
slight strengthening could occur. However, by 48-72 hours, the shear
is forecast to decrease more significantly, allowing Cristobal to
strengthen further, becoming a hurricane as the cyclone passes to
the west and north of Bermuda on Wednesday and Thursday. On Days 4
and 5, Cristobal will be passing over much cooler waters and
encountering strong southwesterly wind shear as the cyclone becomes
embedded in the mid-latitude westerlies, which will result in
extratropical transition by 120 hours.

Owing to the slow motion of Cristobal, heavy rainfall and possible
flooding will remain a threat for the southeastern Bahamas and the
Turks and Caicos through Tuesday.

FORECAST POSITIONS AND MAX WINDS

INIT  25/1500Z 24.6N  72.7W   50 KT  60 MPH
 12H  26/0000Z 26.0N  72.2W   50 KT  60 MPH
 24H  26/1200Z 27.8N  71.5W   55 KT  65 MPH
 36H  27/0000Z 30.0N  70.9W   60 KT  70 MPH
 48H  27/1200Z 32.2N  69.7W   65 KT  75 MPH
 72H  28/1200Z 36.5N  63.5W   65 KT  75 MPH
 96H  29/1200Z 42.7N  50.1W   65 KT  75 MPH
120H  30/1200Z 49.5N  39.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart

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