Tropical Storm CRISTOBAL

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TROPICAL STORM CRISTOBAL DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042014
500 AM EDT MON AUG 25 2014

Cristobal is a sheared tropical cyclone with all of the associated
convection located over the southeastern portion of the
circulation. During the past few hours, deep convection has formed a
little closer to the center and reconnaissance aircraft data
indicate that Cristobal has strengthened a little.  The Air
Force Reserve aircraft has measured peak 850 mb flight-level winds
of 55 kt, and believable SFMR winds of around 45 kt.  Therefore, the
initial wind speed is set at 45 kt for this advisory.  The north
to northwesterly vertical wind shear that has been affecting the
cyclone is forecast to decrease during the next day or so.  This
should allow a more favorable environment for strengthening.  The
NHC intensity forecast brings Cristobal to hurricane intensity in
a couple of days, which is close to the SHIPS guidance and model
consensus.  Late in the forecast period, Cristobal is expected to
become an extratropical cyclone.

Aircraft fixes between 0000 and 0600 UTC showed that the cyclone
meandered southeastward or a center reformation occurred. The last
few fixes indicate that Cristobal has resumed a slow northward
motion of about 3 kt.  The tropical storm is expected to begin
moving north-northeastward today ahead of a mid- to upper-level
trough between Bermuda and the United States east coast.  By
Tuesday the trough is forecast to lift out and Cristobal should
begin moving faster north-northeastward around the western
periphery of a building ridge over the central Atlantic.  Later in
the period, the cyclone should turn northeastward and accelerate
when another trough approaches the coast of the northeastern United
States.  The track guidance has shifted eastward during the first
48 hours, and the official forecast has been adjusted accordingly.
After that time, the track is similar to, but faster than, the
previous advisory since the track guidance has once again trended
toward a faster northeastward motion.

FORECAST POSITIONS AND MAX WINDS

INIT  25/0900Z 24.5N  72.8W   45 KT  50 MPH
 12H  25/1800Z 25.2N  72.5W   50 KT  60 MPH
 24H  26/0600Z 26.8N  71.7W   55 KT  65 MPH
 36H  26/1800Z 29.3N  70.9W   60 KT  70 MPH
 48H  27/0600Z 31.5N  70.4W   65 KT  75 MPH
 72H  28/0600Z 35.2N  66.0W   65 KT  75 MPH
 96H  29/0600Z 40.5N  53.5W   65 KT  75 MPH
120H  30/0600Z 48.5N  41.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown

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