HURRICANE RITA DISCUSSION NUMBER 14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT TUE SEP 20 2005
DATA FROM AN AIR FORCE RESERVE UNIT RECON AIRCRAFT AT 21/0020Z IN
THE NORTHEAST QUADRANT INDICATED 700 MB FLIGHT-LEVEL WINDS OF 103
KT...ROUGHLY 93 KT SURFACE WINDS. DOPPLER RADAR VELOCITIES FROM KEY
WEST HAVE BEEN AS HIGH AS 113 KT AT 9500 FEET IN SPOTS...WITH THE
MAJORITY OF THE HIGHEST VALUES IN THE 105-107 KT RANGE...WHICH
EQUALS ABOUT 95 KT SURFACE WINDS. A RECON PASS THROUGH THE 28 NMI
DIAMETER EYE AT 0204Z INDICATED A SURFACE PRESSURE OF 965 MB...
WHICH ROUGHLY EQUALS 95 KT. THEREFORE...THE INITIAL INTENSITY HAS
BEEN INCREASED TO 95 KT...OR JUST BELOW MAJOR HURRICANE STRENGTH.
THE INITIAL MOTION IS 275/11. RITA IS EXPECTED TO CONTINUE MOVING A
LITTLE NORTH OF DUE WEST FOR THE NEXT 36-48 HOURS AS THE STRONG
RIDGE TO THE NORTH REMAINS INTACT ALONG THE GULF COAST AND INTO
CENTRAL AND NORTHERN TEXAS. THE 18Z GFS AND GFS-ENSEMBLE MODELS
HAVE SHIFTED EASTWARD TO NEAR THE TEXAS-LOUISIANA BORDER. HOWEVER
...BOTH MODELS WERE FORECASTING THE 21/00Z 500 MB HEIGHTS ACROSS
TEXAS TO DECREASE BY 20 METERS...WHEN IN FACT... 21/00Z UPPER-AIR
DATA INDICATE THE HEIGHTS DID NOT CHANGE AND THE MID-LEVEL HIGH
OVER NORTHWEST TEXAS HAS REMAINED QUITE STRONG WITH HEIGHTS NEAR
6000 METERS. AS A RESULT...LESS WEIGHT WAS PALCED ON THE GFS MODEL
...SINCE IT APPEARS TO BE DECREASING THE STRENGTH OF THE RIDGE TOO
QUICKLY...THE OFFICIAL FORECAST TRACK IS JUST AN UPDATE AND
EXTENSION OF THE PREVIOUS ADVISORY TRACK...AND IS CLOSE TO THE NHC
MODEL CONSENSUS.
THE PREVIOUS ADVISORY INDICATING RAPID INTENSIFICATION FOR THE NEXT
24 HOURS APPEARS TO BE ON TRACK. DURING THE PAST 14 HOURS...THE
CENTRAL PRESSURE HAS DECREASED 20 MB...OR AT A RATE OF ABOUT 2
DVORAK T-NUMBERS PER 24 HOURS. WHILE SUCH A LARGE PRESSURE FALL
TREND RARELY OCCURS FOR MORE THAN 24 HOURS...THE VERY FAVORABLE
UPPER-LEVEL OUTFLOW PATTERN AND 30C-31C SSTS BENEATH RITA SUGGEST
THAT RAPID INTENSIFICATION SHOULD CONTINUE FOR AT LEAST ANOTHER 24
HOURS. A POLEWARD OUTFLOW CHANNEL IS WELL ESTABLISHED WITH OUTFLOW
ACCUMULATING INTO A LARGE UPPER-LEVEL LOW...OR MASS SINK...EAST OF
THE BAHAMAS. IN ADDITION... AN EQUATORWARD OUTFLOW CHANNEL ALSO
APPEARS TO BE DEVELOPING. GIVEN THE DUAL OUTFLOW PATTERN THAT IS
EXPECTED TO PERSIST FOR THE NEXT 36-48 HOURS...STRENGTHENING INTO A
CATEGORY 5 HURRICANE IS A DISTINCT POSSIBILITY. BY 72 HOURS... A
GRADUAL INCREASE IN THE SOUTHWESTERLY VERTICAL SHEAR IS EXPECTED TO
BRING ABOUT SOME WEAKENING. HOWEVER...THE GFS-BASED SHIPS MODEL
THAT IS INDICATING 25-30 KT OF SHEAR MAY BE INCLUDING THE WINDS
ASSOCIATED WITH THE STRONG OUTFLOW PATTERN DEPICTED BY THE MODEL.
THIS WOULD MEAN THAT THE GFS SHEAR IS TOO HIGH...AND THUS...THE
SHARP GFS WEAKENING OF RITA DOWN TO 99 KT AT LANDFALL WOULD BE
PREMATURE. THE OFFICIAL INTENSITY FORECAST LEANS CLOSER TO THE FSU
SUPERENSEMBLE INTENSITY FORECAST OF 122 KT IN 48 HOURS AND 126 KT
IN 60 HOURS.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 21/0300Z 24.1N 83.2W 95 KT
12HR VT 21/1200Z 24.2N 85.2W 105 KT
24HR VT 22/0000Z 24.4N 87.5W 120 KT
36HR VT 22/1200Z 24.6N 89.4W 125 KT
48HR VT 23/0000Z 25.1N 91.4W 125 KT
72HR VT 24/0000Z 27.1N 94.7W 120 KT
96HR VT 25/0000Z 30.5N 96.5W 60 KT...INLAND
120HR VT 26/0000Z 34.5N 96.5W 25 KT...DISSIPATING INLAND
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