[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 270847
TCDAT2

TROPICAL STORM PHILIPPE DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 AM AST TUE SEP 27 2011

PHILIPPE HAS TAKEN ON THE APPEARANCE OF A SHEARED TROPICAL CYCLONE
THIS MORNING. NIGHT CHANNEL VISIBLE IMAGERY AND RECENT MICROWAVE
DATA INDICATE THAT THE LOW-LEVEL CENTER IS LOCATED NEAR THE WESTERN
EDGE OF THE DEEP CONVECTION. THIS ASYMMETRIC CLOUD PATTERN IS DUE
TO ABOUT 20 KT OF WEST-SOUTHWESTERLY WIND SHEAR...ACCORDING TO THE
SHIPS MODEL. THE SATELLITE CLASSIFICATIONS HAVE CHANGED LITTLE
SINCE THE TIME OF THE 2304 UTC ASCAT OVERPASS...SO THE INITIAL
INTENSITY IS MAINTAINED AT 45 KT. THE AFOREMENTIONED SHEAR...WHICH
IS BEING PRODUCED BY A DEEP-LAYER TROUGH TO THE NORTH OF
PHILIPPE...IS NOT EXPECTED TO CHANGE MUCH DURING THE NEXT SEVERAL
DAYS. AS A RESULT...THE SHIPS AND LGEM MODELS SHOW A VERY GRADUAL
WEAKENING THROUGHOUT THE FORECAST PERIOD. CONVERSELY...THE REGIONAL
HURRICANE MODELS SHOW PHILIPPE GAINING STRENGTH...ESPECIALLY BEYOND
A COUPLE OF DAYS. GIVEN THE EXPECTED UNFAVORABLE ATMOSPHERIC
ENVIRONMENT...THE OFFICIAL FORECAST FAVORS THE LGEM/SHIPS GUIDANCE
AND IS AN UPDATE OF THE PREVIOUS ONE.

THE TROPICAL STORM IS MOVING NORTHWESTWARD AT ABOUT 6 KT...LOCATED
NEAR THE SOUTHWESTERN PERIPHERY OF A RIDGE OVER THE EASTERN
ATLANTIC. THE RIDGE IS EXPECTED TO BUILD WESTWARD DURING THE NEXT
24 TO 36 HOURS AS THE TROUGH TO THE NORTH OF PHILIPPE LIFTS OUT.
THIS FLOW PATTERN COULD ALLOW THE CYCLONE TO TURN A BIT TO THE LEFT
WITH SOME INCREASE IN FORWARD SPEED DURING THAT TIME PERIOD. IN TWO
TO THREE DAYS...ANOTHER TROUGH IS EXPECTED TO APPROACH BUT THEN
BYPASS PHILIPPE...CAUSING IT TO TURN NORTHWARD. IN ITS WAKE...THE
SUBTROPICAL RIDGE IS FORECAST TO REBUILD ONCE AGAIN...TURNING
PHILIPPE BACK TOWARD THE NORTHWEST BY DAY 5. ALTHOUGH SIGNIFICANT
SPREAD STILL EXISTS AMONGST THE MODELS...THEY HAVE COME INTO BETTER
AGREEMENT IN THE OVERALL SYNOPTIC STEERING PATTERN. THE OFFICIAL
FORECAST IS VERY CLOSE TO THE PREVIOUS ONE AND LIES A LITTLE TO THE
WEST OF THE MULTI-MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT  27/0900Z 16.1N  35.1W   45 KT  50 MPH
 12H  27/1800Z 16.7N  35.9W   45 KT  50 MPH
 24H  28/0600Z 17.6N  37.1W   40 KT  45 MPH
 36H  28/1800Z 18.7N  38.6W   40 KT  45 MPH
 48H  29/0600Z 19.9N  39.6W   40 KT  45 MPH
 72H  30/0600Z 22.3N  40.9W   35 KT  40 MPH
 96H  01/0600Z 24.0N  41.5W   35 KT  40 MPH
120H  02/0600Z 25.0N  42.5W   35 KT  40 MPH

$$
FORECASTER CANGIALOSI


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