[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 262046
TCDAT3

HURRICANE RINA DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL182011
400 PM CDT WED OCT 26 2011

RECENT SATELLITE IMAGERY...DATA FROM THE BELIZE CITY RADAR...AND
REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SUGGEST
THAT RINA HAS CHANGED LITTLE IN STRENGTH DURING THE PAST FEW HOURS.
THE AIRCRAFT HAS REPORTED 700 MB FLIGHT-LEVEL WINDS OF 79 KT AND
SFMR SURFACE WIND ESTIMATES OF 75-78 KT...WHILE AN EYEWALL
DROPSONDE SUGGESTS SURFACE WINDS NEAR 70 KT.  THE INITIAL INTENSITY
OF 75 KT IS A COMPROMISE BETWEEN THESE DATA. THE AIRCRAFT DATA
SUGGEST THE VORTEX IS TILTED WITH HEIGHT...AS DROPSONDES AT THE
FLIGHT-LEVEL CENTER HAVE CONSISTENTLY REPORTED 25-30 KT SURFACE
WINDS.  THIS TILT IS LIKELY DUE TO 20 KT OF SOUTHERLY VERTICAL WIND
SHEAR DEPICTED IN ANALYSES FROM CIMSS AT THE UNIVERSITY OF
WISCONSIN.

RITA HAS CONTINUED ITS SLOW RIGHT TURN...AND THE INITIAL MOTION IS
NOW 310/5.  THE FORECAST TRACK AND PHILOSOPHY ARE UNCHANGED FOR THE
FIRST 48 HOURS...WITH THE HURRICANE FORECAST TO MOVE SLOWLY
NORTHWARD AND THEN NORTH-NORTHEASTWARD NEAR OR OVER THE
NORTHEASTERN PORTION OF THE YUCATAN PENINSULA AS AN UPPER-LEVEL
TROUGH AND ASSOCIATED COLD FRONT MOVE ACROSS THE SOUTHEASTERN
UNITED STATES AND THE GULF OF MEXICO.  THE TRACK FORECAST BECOMES
VERY PROBLEMATIC AFTER 48 HOURS DUE TO UNCERTAINTIES OF HOW RINA
INTERACTS WITH THE TROUGH AND HOW LONG IT HOLDS TOGETHER
VERTICALLY.  THE GFDL AND GFDN MODELS CONTINUE TO FORECAST THE
SYSTEM TO MOVE EAST-NORTHEASTWARD OVER FLORIDA OR THE FLORIDA
STRAITS INTO THE ATLANTIC.  THE ECMWF...NOGAPS...UKMET...AND
CANADIAN MODELS NOW FORECAST RINA OR ITS REMNANTS TO MAKE A HAIRPIN
TURN AND MOVE SOUTHWARD NEAR THE EAST COAST OF YUCATAN.  THE
GFS...GFS ENSEMBLE MEAN...AND HWRF MODELS ARE BETWEEN THESE
EXTREMES...FORECASTING THE CYCLONE TO MOVE SLOWLY EASTWARD AND THEN
SOUTHEASTWARD NEAR OR OVER WESTERN CUBA.  THE NEW FORECAST TRACK
FOLLOWS THESE MODELS AND IS THUS SHIFTED SOUTH OF THE PREVIOUS
TRACK.  THIS LATTER PART OF THE FORECAST TRACK REMAINS A LOW
CONFIDENCE FORECAST.

RINA IS FORECAST TO BE IN A MODERATE SHEAR ENVIRONMENT FOR THE NEXT
24-36 HOURS.  THIS...COMBINED WITH EXPECTED LAND INTERACTION...
SUGGESTS IT SHOULD SLOWLY WEAKEN DURING THIS TIME.  AFTER 36
HOURS...THE CYCLONE SHOULD ENCOUNTER STRONG SHEAR AS THE
MID/UPPER-LEVEL FLOW TRIES TO STEER IT EAST-NORTHEASTWARD AND THE
LOW-LEVEL FLOW TRIES TO STEER IT SOUTHWARD OR SOUTHWESTWARD.  THIS
SHOULD CAUSE RINA TO WEAKEN IN AGREEMENT WITH ALL THE INTENSITY
GUIDANCE.  THE NEW INTENSITY FORECAST CALLS FOR A FASTER WEAKENING
THAN PREVIOUSLY SHOWN...IN BEST AGREEMENT WITH THE DECAY SHIPS
MODEL.  IT IS POSSIBLE THAT THIS RELATIVELY SMALL SYSTEM COULD
WEAKEN FASTER THAN CURRENTLY FORECAST AND BECOME A REMNANT LOW BY
120 HOURS OR EARLIER.

FORECAST POSITIONS AND MAX WINDS

INIT  26/2100Z 18.2N  85.9W   75 KT  85 MPH
 12H  27/0600Z 18.7N  86.5W   75 KT  85 MPH
 24H  27/1800Z 20.0N  86.9W   70 KT  80 MPH
 36H  28/0600Z 21.4N  86.9W   60 KT  70 MPH...INLAND
 48H  28/1800Z 22.5N  86.5W   60 KT  70 MPH...OVER WATER
 72H  29/1800Z 23.0N  84.5W   50 KT  60 MPH
 96H  30/1800Z 22.5N  83.0W   35 KT  40 MPH...INLAND
120H  31/1800Z 22.5N  83.0W   25 KT  30 MPH...INLAND

$$
FORECASTER BEVEN


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