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TROPICAL STORM OLGA DISCUSSION NUMBER  33
NATIONAL WEATHER SERVICE MIAMI FL
4 PM EST SUN DEC 02 2001
 
OLGA HAS CHANGED LITTLE DURING THE PAST 6 HOURS.  THE SYSTEM LOOKS 
QUITE IMPRESSIVE IN VISIBLE IMAGERY AND HAS THE APPEARANCE OF A 
HURRICANE...COMPLETE WITH A BANDED-EYE FEATURE.  HOWEVER...DEEP 
CONVECTION IS LACKING AROUND THE LOW-LEVEL CENTER AND A 02/1559Z 
TRMM OVERPASS ONLY INDICATED SURFACE WINDS OF 35 TO 40 KT AND...  
THEREFORE...THE INITIAL INTENSITY IS MAINTAINED AT 40 KT.  UPPER- 
LEVEL OUTFLOW REMAINS SYMMETRICAL AND HAS IMPROVED SLIGHTLY.
 
THE INITIAL MOTION IS 345/09.  THERE IS NO SIGNIFICANT CHANGE TO THE 
PREVIOUS FORECAST TRACK OR REASONING. FOR THE FIRST TIME IN SEVERAL 
DAYS...OLGA HAS ACTUALLY TRACKED IN A STRAIGHT LINE FOR MORE THAN 6 
HOURS.  HOWEVER...THIS RECENT STEADY MOTION WILL BE SHORT-LIVED 
SINCE A STRONG SHORTWAVE TROUGH CURRENTLY APPROACHING THE 
MID-ATLANTIC COAST AT 40 TO 50 KT WILL RAPIDLY BYPASS THE CYCLONE. 
THE RESULT WILL BE A RAPID WEAKENING/FILLING OF THE SUBTROPICAL 
RIDGE LOCATED TO THE NORTH OF OLGA AND CREATE A WEAK STEERING FLOW 
PATTERN IN 24 TO 36 HOURS...IF NOT SOONER.  OLGA IS FORECAST TO MAKE 
A SMALL ANTICYCLONIC LOOP...OR STALL AGAIN...AND THEN GRADUALLY TURN 
BACK TO THE WEST OR WEST-SOUTHWEST BY 48 HOURS.  ONLY THE GENERAL 
TRENDS AND NOT THE SPECIFIC FORECAST TRACKS FROM ALL OF THE GLOBAL 
MODELS WERE USED SINCE THEY ALL APPEAR TO WEAKEN OLGA TOO QUICKLY.  
THE 12Z MODEL RUNS SHOULD HAVE BEEN INITIALIZED WITH A CENTRAL 
PRESSURE OF 1001 MB INSTEAD OF 1010 MB BY THE AVN...1011 MB BY THE 
UKMET...AND 1008 MB BY NOGAPS. THE HIGHER INITIAL PRESSURE HAS 
RESULTED IN A RAPID DECAY OF THE CYCLONE BY ALL OF THE MODELS IN 12 
TO 24 HOURS...WHICH CAUSES OLGA TO BE INFLUENCED MORE BY THE 
LOW-LEVEL STEERING FLOW. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE 
PREVIOUS TRACK AND THE AVN-NOGAPS-GFDN CONSENSUS SINCE THE UKMET AND 
GFDL MODELS DISSIPATE OLGA IN ABOUT 24 AND 48 HOURS...RESPECTIVELY.
 
THE INTENSITY FORECAST REMAINS AS COMPLICATED AS THE TRACK FORECAST. 
DUE TO THE HIGHER THAN ACTUAL CENTRAL PRESSURE...ALL OF THE GLOBAL 
MODELS RAPIDLY WEAKEN OLGA.  HOWEVER...INSPITE OF THE POOR MODEL 
INITIALIZATION...THE AVN AND GFDN MODELS KEEP OLGA AT OR SLIGHTLY 
ABOVE TROPICAL STORM STRENGTH. THIS SEEMS REASONABLE WHETHER OR NOT 
OLGA WILL BE A TROPICAL OR SUBTROPICAL CYCLONE DURING THE FORECAST 
PERIOD.  HOWEVER...GIVEN THE OVERALL IMPRESSIVE STRUCTURE AND THE 
CLOUD PATTERN NOTED IN VISIBLE AND MICROWAVE IMAGERY...IT WOULD NOT 
TAKE MUCH CONVECTION TO DEVELOP NEAR THE CENTER TO GET OLGA INTO A 
RAPID INTENSIFICATION MODE. IN FACT...SOME MODERATE CONVECTION HAS 
ALREADY FILLED IN THE DRY SLOT IN THE EASTERN SEMICIRCLE AND WATER 
VAPOR IMAGERY SUGGESTS THAT THE DRY SLOT IS BEGINNING TO THIN OUT TO 
THE WEST OF THE CENTER. OF EQUAL CONCERN IN THE LONG TERM IS THE 200 
MB ANTICYCLONE NOW FORECAST TO DEVELOP EAST OF FLORIDA NEAR 29N75W 
BY ALL THREE OF THE GLOBAL MODELS. SHOULD OLGA SURVIVE THE NEXT 48 
HOURS TRACK BENEATH THAT UPPER-LEVEL ANTICYCLONE...THEN THE 
DECREASING VERTICAL SHEAR AND FAVORABLE OUTFLOW PATTERN COULD RESULT 
IN SIGNIFICANT RE-STRENGTHENING...POSSIBLY TO NEAR HURRICANE 
STRENGTH AGAIN.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     02/2100Z 26.8N  69.6W    40 KTS
12HR VT     03/0600Z 27.8N  69.9W    45 KTS
24HR VT     03/1800Z 29.0N  69.7W    45 KTS
36HR VT     04/0600Z 29.4N  68.9W    40 KTS
48HR VT     04/1800Z 28.8N  69.0W    40 KTS
72HR VT     05/1800Z 28.0N  72.0W    35 KTS
 
 
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