396
WTNT41 KNHC 191500
TCDAT1
TROPICAL STORM OSCAR DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL162024
1100 AM EDT SAT OCT 19 2024
THINGS HAVE BEEN QUICKLY EVOLVING WITH A SMALL AREA OF LOW PRESSURE
LOCATED JUST TO THE EAST OF THE TURKS AND CAICOS ISLANDS. EARLIER
THIS MORNING, THERE WAS A 0556 UTC AMSR2 PASSIVE MICROWAVE IMAGE
THAT SUGGESTED THE SYSTEM'S STRUCTURE HAD BECOME QUITE A BIT BETTER
ORGANIZED COMPARED TO PRIOR IMAGES, WITH PROMINENT CURVED BANDS ON
THE 37 GHZ LOW-LEVEL CHANNEL THAT SUGGEST A WELL-DEFINED CIRCULATION
WAS DEVELOPING. WHILE THE OVERNIGHT C-BAND SCATTEROMETER IMAGERY
MISSED THE SMALL CIRCULATION JUST TO THE WEST, THERE WAS A KU-BAND
SCATTEROMETER THAT SUGGESTED A CLOSED CIRCULATION HAD FORMED. FIRST
LIGHT GOES-16 MESO-SECTOR IMAGERY ALSO SUGGESTS A TIGHT CIRCULATION
HAS FORMED, WITH BUBBLING HOT TOWERS WITHIN A SMALL CENTRAL DENSE
OVERCAST TAKING SHAPE. ALL THESE DATA SUGGEST A TROPICAL CYCLONE HAS
FORMED, AND BASED ON THE EARLIER 12 UTC TAFB T2.5/35 KT DVORAK
ESTIMATE, ADVISORIES ARE BEING STARTED ON TROPICAL STORM OSCAR WITH
A 35 KT INITIAL INTENSITY.
OSCAR IS ESTIMATED TO BE MOVING DUE WESTWARD AT 270/11 KT. THIS
MOTION SHOULD CONTINUE FOR THE REMAINDER OF THE DAY AS THE SYSTEM IS
INITIALLY STEERED BY A NARROW MID-LEVEL RIDGE POSITIONED TO THE
NORTH. HOWEVER, A DIGGING EAST-TO-WEST LONGWAVE TROUGH IS SOON
EXPECTED TO ERODE THE EASTWARD SIDE OF THIS RIDGE, CAUSING OSCAR TO
SLOWDOWN AND POTENTIALLY STALL NEAR THE NORTHEASTERN COAST OF CUBA
IN 36-48 HOURS. THEREAFTER, THAT SAME TROUGH IS EXPECTED TO CONTINUE
AMPLIFYING OR EVEN RETROGRADE WESTWARD, AND IF OSCAR IS VERTICALLY
DEEP ENOUGH, THIS SHOULD INDUCE STEERING THAT BRINGS THE TROPICAL
CYCLONE NORTHEASTWARD. THE TRACK FORECAST LIES CLOSE TO THE SIMPLE
TCVA CONSENSUS AID, WHICH IS QUITE CLOSE TO THE MOST RECENT ECMWF
FORECAST. ITS WORTH MENTIONING, THERE IS QUITE A BIT OF
SOUTHWEST-TO-NORTHEAST SPREAD IN THE ENSEMBLE GUIDANCE, WITH WEAKER
MEMBERS SLOWER AND FURTHER WEST AND STRONGER MEMBERS BEING CAPTURED
BY THE TROUGH.
INTENSITY-WISE, OSCAR ONLY APPEARS TO HAVE A 24 H WINDOW FOR
STRENGTHENING AS SHEAR REMAINS LOW ENOUGH. THE FIRST NHC INTENSITY
FORECAST SHOWS THE SYSTEM PEAKING AS A 45-KT STORM AS IT NEARS THE
EASTERN COAST OF CUBA. SHEAR OUT OF THE NORTHWEST INCREASES QUITE
RAPIDLY AFTER THAT TIME, DUE TO THE AFOREMENTIONED TROUGH TO ITS
NORTH, WITH THE INTENSITY LIKELY LEVELING OFF AROUND THEN. THERE
COULD ALSO BE SOME LAND INTERACTION WITH CUBA THAT COULD DISRUPT THE
CIRCULATION. HOWEVER OSCAR IS A VERY SMALL TROPICAL CYCLONE, AND
COULD BE PRONE TO RAPID CHANGES IN INTENSITY, BOTH UP AND DOWN.
AFTER 72 H, THE MUCH LARGER TROUGH IS LIKELY TO ABSORB THE SMALL
OSCAR, WITH THIS OCCURRING BY THE END OF THE FORECAST PERIOD BY THE
MIDDLE OF NEXT WEEK.
KEY MESSAGES:
1. OSCAR IS EXPECTED TO BRING TROPICAL STORM CONDITIONS TO PORTIONS
OF THE SOUTHEASTERN BAHAMAS, TURKS AND CAICOS ISLANDS, AND EASTERN
CUBA DURING THE NEXT DAY OR SO. A TROPICAL STORM WARNING HAS BEEN
ISSUED FOR THOSE LOCATIONS.
2. LOCALLY HEAVY RAINFALL IS POSSIBLE ACROSS THE TURKS AND CAICOS
ISLANDS AND THE SOUTHEASTERN BAHAMAS LATER TODAY AND TONIGHT. THESE
RAINS ARE EXPECTED TO SPREAD TO EASTERN CUBA ON SUNDAY.
FORECAST POSITIONS AND MAX WINDS
INIT 19/1500Z 21.3N 70.2W 35 KT 40 MPH
12H 20/0000Z 21.4N 71.9W 40 KT 45 MPH
24H 20/1200Z 21.2N 73.8W 45 KT 50 MPH
36H 21/0000Z 20.9N 74.9W 45 KT 50 MPH
48H 21/1200Z 21.0N 75.8W 45 KT 50 MPH
60H 22/0000Z 21.6N 75.9W 45 KT 50 MPH
72H 22/1200Z 22.5N 75.0W 40 KT 45 MPH
96H 23/1200Z 25.1N 72.6W 35 KT 40 MPH
120H 24/1200Z...DISSIPATED
FORECASTER PAPIN
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