Tropical Cyclone Discussion
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WTNT44 KNHC 280232
TCDAT4

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




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