[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 240846
TCDAT4

HURRICANE IRENE DISCUSSION NUMBER  16
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092011
500 AM EDT WED AUG 24 2011

THE LAST PENETRATION OF THE EYE BY THE AIR FORCE HURRICANE HUNTERS
WAS JUST AFTER 0500 UTC...AND THEY FOUND THAT THE CENTRAL PRESSURE
HAD DROPPED TO 966 MB.  THEY ALSO MEASURED 700 MB FLIGHT-LEVEL WINDS
OF 92 KT OUTBOUND IN THE SOUTHEAST QUADRANT.  IT IS LIKELY THAT
HIGHER WINDS WERE OCCURRING OVER THE NORTHEAST QUADRANT OF THE
HURRICANE.  OVER THE PAST FEW HOURS..THE SATELLITE PRESENTATION OF
IRENE HAS BECOME QUITE IMPRESSIVE WITH THE EYE EMBEDDED WITHIN VERY
COLD CLOUD TOPS.  DVORAK INTENSITY ESTIMATES FROM BOTH TAFB AND SAB
ARE 100 KT.  COMBINING THE ABOVE INFORMATION...THE CURRENT
INTENSITY IS SET CONSERVATIVELY AT 95 KT FOR THIS ADVISORY.  ANOTHER
HURRICANE HUNTER MISSION IS SCHEDULED FOR 1200 UTC TO MEASURE THE
INTENSITY OF THE HURRICANE.  ALTHOUGH THE NUMERICAL GUIDANCE
INDICATES SOME SOUTH-SOUTHWESTERLY SHEAR OVER THE AREA...THIS SHEAR
IS NOT EXPECTED TO PREVENT FURTHER STRENGTHENING AND IT SEEMS
HIGHLY LIKELY THAT IRENE WILL INTENSIFY TO CATEGORY 3 STATUS LATER
TODAY.  SOME FLUCTUATIONS IN STRENGTH COULD OCCUR IN 1 TO 2 DAYS
DUE TO EYEWALL REPLACEMENTS.  IN FACT...THE UW-CIMSS OBJECTIVE
TECHNIQUE SHOWS A CONSIDERABLY HIGHER THAN CLIMATOLOGICAL
PROBABILITY OF SECONDARY EYEWALL FORMATION WITHIN 24 TO 48 HOURS.
THE OFFICIAL INTENSITY FORECAST IS CLOSE TO THE NUMERICAL CONSENSUS
AND LIES BETWEEN THE GFDL/HWRF MODELS AND THE LGEM GUIDANCE.

SATELLITE ANIMATION AND CENTER FIXES SHOW THAT THE EYE OF IRENE HAS
BEEN WOBBLING BETWEEN A WEST AND NORTHWEST HEADING OVER THE PAST
SEVERAL HOURS.  SMOOTHING THROUGH THESE WOBBLES YIELDS A MORE
REPRESENTATIVE MOTION OF ABOUT 295/8.  THERE HAS BEEN LITTLE CHANGE
TO THE TRACK FORECAST REASONING FROM THE PAST FEW ADVISORIES.  OVER
THE NEXT COUPLE OF DAYS...THE HURRICANE IS EXPECTED TO GRADUALLY
TURN TOWARD THE NORTHWEST AND NORTH AS IT MOVES THROUGH A
PRONOUNCED WEAKNESS IN THE SUBTROPICAL RIDGE.  AROUND 72 HOURS...A
SHORTWAVE TROUGH MOVING THROUGH THE GREAT LAKES SHOULD BEGIN TO
INDUCE AT LEAST A SLIGHT TURN TOWARD THE NORTH-NORTHEAST WITH SOME
ACCELERATION AFTERWARDS.  THE DYNAMICAL TRACK MODEL CONSENSUS
HAS...AGAIN...SHIFTED A LITTLE TO THE EAST FROM THE PREVIOUS
PACKAGE.  THE OFFICIAL FORECAST IS NOT SUBSTANTIALLY DIFFERENT FROM
THE PREVIOUS ONE AND LIES A LITTLE TO THE LEFT OF THE CONSENSUS.

USERS ARE REMINDED THAT SIGNIFICANT ERRORS ARE POSSIBLE WITH
FORECASTS AT LONGER LEAD TIMES...SO ONE SHOULD NOT FOCUS ON THE
EXACT FORECAST POSITIONS AT 96 AND 120 HOURS.


FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 21.6N  72.9W   95 KT 110 MPH
 12H  24/1800Z 22.5N  74.1W  105 KT 120 MPH
 24H  25/0600Z 24.1N  75.4W  110 KT 125 MPH
 36H  25/1800Z 25.8N  76.6W  110 KT 125 MPH
 48H  26/0600Z 27.7N  77.0W  110 KT 125 MPH
 72H  27/0600Z 32.0N  76.8W  105 KT 120 MPH
 96H  28/0600Z 36.5N  75.0W   90 KT 105 MPH
120H  29/0600Z 42.0N  71.5W   70 KT  80 MPH...INLAND

$$
FORECASTER PASCH/KIMBERLAIN



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