TROPICAL STORM OMAR DISCUSSION NUMBER 5

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL152008

1100 AM EDT TUE OCT 14 2008

SATELLITE AND RADAR DATA INDICATE THE DEPRESSION HAS CONTINUED TO

BECOME BETTER ORGANIZED AND CLOUD TOPS HAVE COOLED SIGNIFICANTLY

WITH SOME TOPS TO -86C NEAR THE CENTER. OUTFLOW HAS ALSO IMPROVED

IN ALL QUADRANTS AND IS LESS RESTRICTED TO THE NORTHWEST NOW. THE

INITIAL ADVISORY OF 35 KT IS BASED ON A CONSENSUS T2.5/35 KT

SATELLITE ESTIMATE FROM TAFB AND SAB FOR THE PAST 12 HOURS...PLUS

SEVERAL BELIEVABLE 30-34 KT QUIKSCAT WIND VECTORS NOTED IN THE

NORTHWEST QUADRANT AROUND 1036Z THIS MORNING. THUS...TROPICAL

DEPRESSION FIFTEEN HAS BEEN UPGRADED TO TROPICAL STORM OMAR.

THE INITIAL MOTION ESTIMATE IS 115/02. OMAR HAS BEEN DRIFTING SOUTH

TO SOUTHEASTWARD THE PAST 12 HOURS...AND CURRENTLY SHOWS NO SIGN OF

CHANGING THAT MOTION. HOWEVER...ALL OF THE AVAILABLE MODEL GUIDANCE

INDICATES THAT A BROAD DEEP MID-LATITUDE TROUGH OVER THE CENTRAL

AND WESTERN ATLANTIC WILL CONTINUE TO DROP SOUTHWARD AND GRADUALLY

PICK UP OMAR AND NUDGE IT TO THE EAST DURING THE NEXT 12 HOURS...

AND THEN ACCELERATE IT TO THE NORTHEAST AFTER THAT. THE LATEST

TREND IN WATER VAPOR IMAGERY SUPPORTS THIS SCENARIO AS A PIECE OF

SHORTWAVE ENERGY ALONG 70W LONGITUDE CAN BE SEEN DIGGING DUE SOUTH.

NHC MODEL GUIDANCE IS TIGHTLY CLUSTERED CROSS-WISE...BUT THERE ARE

SIGNIFICANT DIFFERENCES IN THE FORWARD SPEED AND JUST HOW SOON OMAR

GETS PICKED UP BY THE AFOREMENTIONED TROUGH. THE OFFICIAL FORECAST

TRACK HAS BEEN SHIFTED TO THE EAST OR RIGHT OF THE PREVIOUS TRACK

...MAINLY DUE TO THE MORE EASTWARD INITIAL POSITION...BUT NOT AS FAR

EAST OR AS FAST AS THE MODEL CONSENSUS.

RECENT DEVELOPMENT OF A CDO-LIKE AREA OF CENTRAL DEEP CONVECTION

SUGGESTS THAT OMAR MAY BE STARTING A PERIOD OF RAPID STRENGTHENING.

IN ADDITION...A LARGE MASS OF CONVECTION IN THE EASTERN SEMICIRCLE

THAT HAS BEEN DISRUPTING INFLOW INTO THE CIRCULATION CENTER HAS

WEAKENED CONSIDERABLY...WHICH SHOULD ALLOW FOR MORE CONVECTIVE

FORCING TO OCCUR NEAR THE LOW-LEVEL CENTER. THE IMPROVING OUTFLOW

PATTERN AND A FORECAST OF DECREASING VERTICAL WIND SHEAR OF LESS

THAN 10 KT FOR THE NEXT 24 HOURS FURTHER SUPPORTS A FORECAST OF

STEADY INTENSIFICATION OF AT LEAST ONE T-NUMBER PER DAY FOR THE

NEXT 24 HOURS. AFTER THAT...SOUTHWESTERLY VERTICAL WIND SHEAR AHEAD

OF THE LARGE MID-LATITUDE TROUGH IS EXPECTED TO INCREASE TO GREATER

THAN 20 KT...SO THE INTENSIFICATION TREND SHOULD SLOW DOWN BY DAY 2

AND BEYOND. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE

PREVIOUS ADVISORY AND IS A BLEND OF THE SHIPS...GFDL...AND HWRF

MODELS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 14/1500Z 14.0N 69.0W 35 KT

12HR VT 15/0000Z 14.7N 68.3W 45 KT

24HR VT 15/1200Z 15.8N 67.3W 55 KT

36HR VT 16/0000Z 17.3N 65.6W 60 KT

48HR VT 16/1200Z 19.1N 63.6W 65 KT

72HR VT 17/1200Z 23.8N 60.0W 65 KT

96HR VT 18/1200Z 28.0N 58.0W 65 KT

120HR VT 19/1200Z 33.0N 55.0W 65 KT

$$

FORECASTER STEWART