[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 240243
TCDAT3

TROPICAL STORM RINA DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL182011
1100 PM EDT SUN OCT 23 2011

EARLIER REPORTS FROM AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT
INDICATED BELIEVABLE SFMR WINDS OF 33-35 KT OUTSIDE OF THE
CONVECTION IN THE SOUTHWESTERN QUADRANT OF THE CYCLONE...BUT THESE
WINDS COULD HAVE BEEN GUSTS. THE AIRCRAFT ALSO HAD TO AVOID STRONG
THUNDERSTORMS TO THE NORTH OF THE CENTER AND WAS... THEREFORE...
UNABLE TO SAMPLE THE WINDS IN THAT AREA. SINCE THEN... HOWEVER...
DEEP CONVECTION HAS INCREASED MARKEDLY IN THE NORTHERN SEMICIRCLE
AND CONVECTION HAS ALSO DEVELOPED IN THE SOUTHWESTERN QUADRANT...
WHICH IS LIKELY HELPING TO SUSTAIN THE STRONGER WINDS IN THAT
REGION AS REPORTED PREVIOUSLY. UW-CIMSS ADT ESTIMATES HAVE BEEN
STEADILY INCREASING...AND THE MOST RECENT 2-HOUR AVERAGE IS T2.7/39
KT. AS A RESULT...THE DEPRESSION HAS BEEN UPGRADED TO TROPICAL
STORM RINA...THE SEVENTEENTH NAMED STORM OF THE SEASON.

RINA IS FORECAST TO REMAIN OVER SSTS OF NEAR 30C FOR THE NEXT 72-96
HOURS. IN ADDITION...DURING THE 24-48 HOUR TIME PERIOD...THE
CYCLONE WILL BE MOVING OVER SOME VERY HIGH UPPER-OCEAN CONTENT THAT
IS MORE THAN 10 TIMES THE VALUE THE STORM IS CURRENTLY TRAVERSING.
THE UPPER-LEVEL OUTFLOW HAS BEEN STEADILY INCREASING AND IS
EXPECTED TO IMPROVE EVEN MORE THROUGH 72 HOURS AS RINA MOVES UNDER
AN UPPER-LEVEL RIDGE AXIS THAT WILL PRODUCE OUTFLOW CHANNELS TO THE
NORTH AND SOUTH. SO THERE IS PLENTY OF HEAT AND VENTILATION
AVAILABLE FOR STRENGTHENING TO OCCUR. THE ONLY POSSIBLE INHIBITING
FACTOR IS VERY DRY MID-LEVEL AIR LOCATED OVER THE SOUTHERN GULF OF
MEXICO AND YUCATAN CHANNEL...WHICH COULD BE ENTRAINED INTO THE
CYCLONE AT 48 HOURS AND BEYOND. AS A RESULT...THE INTENSITY
FORECAST WILL REMAIN ON THE CONSERVATIVE SIDE AND LIES CLOSE TO THE
INTENSITY CONSENSUS MODEL ICON...AND THE STATISTICAL-DYNAMICAL
MODEL...LGEM.

THE INITIAL MOTION ESTIMATE IS 335/7 KT BASED ON RECON FIXES. THE
FORECAST TRACK DEPENDS HEAVILY ON THE INTENSITY FORECAST. SINCE THE
OFFICIAL INTENSITY FORECAST IS MUCH MORE ROBUST THAN WHAT THE
GFS...NOGAPS...CANADIAN...AND GFDL MODELS ARE FORECASTING FOR THE
NEXT 48 HOURS AND BEYOND...THOSE MODEL SOLUTIONS OF A WESTWARD OR
EVEN WEST-SOUTHWESTWARD MOTION FROM THE CURRENT POSITION HAVE BEEN
DISCOUNTED. IN CONTRAST...THE HWRF AND UKMET MODELS ARE FORECASTING
A STRONGER AND DEEPER CYCLONE THROUGHOUT THE THE FORECAST PERIOD...
WHICH LOOKS MORE LIKELY GIVEN THE RECENT UPWARD TRENDS IN SATELLITE
AND UPPER-AIR DATA. AS A RESULT...THE EXPECTED FORECAST SCENARIO
CALLS FOR RINA TO MOVE NORTHWESTWARD THROUGH A WEAKNESS IN THE
SUBTROPICAL RIDGE FOR THE NEXT 12 HOURS OR SO. AS A VIGOROUS
SHORTWAVE TROUGH CURRENTLY MOVING EASTWARD ACROSS THE CENTRAL AND
EASTERN GULF OF MEXICO PASSES EAST OF FLORIDA TOMORROW...THE RIDGE
SHOULD BUILD BACK IN TO THE NORTH OF RINA...FORCING THE CYCLONE ON
A SLOW WEST-NORTHWESTWARD TRACK UNTIL DAY 4. AFTER THAT...ANOTHER
STRONG SHORTWAVE TROUGH IS FORECAST TO DIG SOUTHEASTWARD FROM THE
SOUTHERN PLAINS AND INTO THE GULF OF MEXICO...WHICH IS EXPECTED TO
WEAKEN THE SUBTROPICAL RIDGE ONCE AGAIN AND ALLOW RINA TO TURN
NORTHWARD NEAR THE YUCATAN PENINSULA. THE OFFICIAL FORECAST TRACK
LIES TO THE RIGHT OF THE PREVIOUS ADVISORY TRACK AND THE CONSENSUS
MODELS..AND IS CLOSE TO A BLEND OF THE UKMET...HWRF...AND ECMWF
MODEL TRACKS.

IN THE SHORT TERM...HEAVY RAINFALL AND FLOODING WILL BE SIGNIFICANT
THREATS FOR NORTHERN HONDURAS WHERE 8-15 INCHES OF RAIN HAVE
ALREADY FALLEN DURING THE PAST 3 DAYS.


FORECAST POSITIONS AND MAX WINDS

INIT  24/0300Z 16.4N  82.2W   35 KT  40 MPH
 12H  24/1200Z 16.8N  82.6W   40 KT  45 MPH
 24H  25/0000Z 17.3N  83.4W   45 KT  50 MPH
 36H  25/1200Z 17.5N  84.3W   50 KT  60 MPH
 48H  26/0000Z 17.7N  85.1W   55 KT  65 MPH
 72H  27/0000Z 17.9N  86.2W   60 KT  70 MPH
 96H  28/0000Z 18.9N  87.4W   65 KT  75 MPH
120H  29/0000Z 20.0N  87.4W   65 KT  75 MPH

$$
FORECASTER STEWART



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