Caribbean-On-Line's Caribbean Hurricane Blog



HURRICANE IRENE DISCUSSION NUMBER 9

Published on August 22, 2011 5:58 PM | Comments

This is turning into a beast:

HURRICANE IRENE DISCUSSION NUMBER 9
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 PM AST MON AUG 22 2011

DATA FROM THE LAST AIR FORCE HURRICANE HUNTER AIRCRAFT AROUND 1700
UTC INDICATE THAT THE CENTRAL PRESSURE WAS STEADY AND THE WINDS
HAVE NOT CHANGED DURING THE DAY. SINCE THEN...HIGH RESOLUTION
SATELLITE IMAGES REVEAL SOME CONVECTIVE BANDS WRAPPING AROUND A
CLUSTER OF DEEP CONVECTION NEAR THE CENTER...SUGGESTING THAT IRENE
COULD BE SLOWLY INTENSIFYING. HOWEVER...DVORAK T-NUMBERS ARE 4.0
AND 4.5 WHICH SUPPORTS KEEPING THE INITIAL INTENSITY AT 70 KNOTS.
ANOTHER PLANE WILL CHECK THE HURRICANE AROUND 0000 UTC TONIGHT.
WITH THE EXCEPTION OF THE DISRUPTION OF THE OUTER CIRCULATION BY
THE HIGH TERRAIN OF HISPANIOLA...WHICH PROBABLY WILL SLOW DOWN THE
INTENSIFICATION PROCESS DURING THE NEXT 12 TO 24 HOURS...ALL OF THE
INGREDIENTS ARE CONDUCIVE FOR IRENE TO INTENSIFY OVER THE NEXT FEW
DAYS. THE OFFICIAL FORECAST CALLS FOR IRENE TO BECOME A STRONG
CATEGORY 2 OR CATEGORY 3 HURRICANE ON THE SAFFIR-SIMPSON HURRICANE
WIND SCALE AS IRENE MOVES ACROSS THE CENTRAL AND NORTHWESTERN
BAHAMAS. IN FACT...BOTH THE GFS AND THE ECMWF GLOBAL MODELS INSIST
ON MAKING IRENE A LARGE AND STRONG HURRICANE WITH MINIMUM PRESSURES
AROUND 945 MB AND 952 MB...RESPECTIVELY.

IRENE IS MOVING TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 11
KNOTS. CURRENTLY...THE MOTION OF THE HURRICANE IS BEING CONTROLLED
BY A NARROW SUBTROPICAL RIDGE TO ITS NORTH. HOWEVER...THE FUTURE
TRACK WILL DEPEND ON THE DEVELOPMENT OF A LARGE MID- TO UPPER-LEVEL
TROUGH ALONG THE EAST COAST OF THE UNITED STATES. THIS PATTERN WILL
INDUCE A GRADUAL NORTHWESTWARD AND THEN NORTHWARD TRACK THROUGH THE
FORECAST PERIOD WITH A SLIGHT DECREASE IN FORWARD SPEED. THERE IS
MORE CONFIDENCE IN THE FORECAST SINCE MOST OF THE TRACK MODELS...
WITH THE EXCEPTION OF THE GFDL...HAVE NOW FOLLOWED THE LEAD OF THE
ECMWF MODEL. THE GUIDANCE IS NOW IN BETTER AGREEMENT IN TURNING
IRENE NORTHWARD ALONG 78 OR 79 DEGREES LONGITUDE. ALTHOUGH IT IS
STILL TOO EARLY TO BE CERTAIN...THE GUIDANCE TREND CONTINUES TO
LESSENS THE THREAT TO SOUTH FLORIDA BUT INCREASES THE THREAT TO THE
CAROLINAS.

DO NOT TO FOCUS ON THE EXACT FORECAST TRACK...ESPECIALLY AT DAYS 4
TO 5...SINCE THE MOST RECENT 5-YEAR AVERAGE ERRORS AT THOSE FORECAST
TIMES ARE 200 AND 250 MILES...RESPECTIVELY.



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