Tropics I WCTV Eyewitness News: Tallahassee, Thomasville, Valdosta

HURRICANE IRENE ADVISORY & FORECAST DISCUSSION NUMBER 18

By: National Hurricane Center
By: National Hurricane Center

BULLETIN
HURRICANE IRENE ADVISORY NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 PM EDT WED AUG 24 2011

...DANGEROUS HURRICANE IRENE HITTING THE SOUTHEASTERN
BAHAMAS HARD...

SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...23.1N 74.7W
ABOUT 30 MI...45 KM ESE OF LONG ISLAND
ABOUT 215 MI...345 KM SE OF NASSAU
MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...954 MB...28.17 INCHES

WATCHES AND WARNINGS
--------------------
CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY...

NONE

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* THE SOUTHEASTERN...CENTRAL...AND NORTHWESTERN BAHAMAS

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE TURKS AND CAICOS ISLANDS

INTERESTS FROM THE CAROLINAS NORTHWARD THROUGH NEW ENGLAND SHOULD
MONITOR THE PROGRESS OF IRENE.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 PM EDT...2100 UTC...THE CENTER OF HURRICANE IRENE WAS LOCATED
NEAR LATITUDE 23.1 NORTH...LONGITUDE 74.7 WEST. IRENE IS MOVING
TOWARD THE NORTHWEST NEAR 12 MPH...19 KM/H...AND THIS GENERAL MOTION
IS EXPECTED TO CONTINUE THROUGH TONIGHT. A TURN TOWARD THE
NORTH-NORTHWEST AND THEN NORTH ARE EXPECTED THURSDAY AND THURSDAY
NIGHT. ON THE FORECAST TRACK...THE CORE OF IRENE WILL MOVE ACROSS
THE SOUTHEASTERN AND CENTRAL BAHAMAS TONIGHT AND OVER THE
NORTHWESTERN BAHAMAS ON THURSDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 120 MPH...195 KM/H...WITH HIGHER
GUSTS. IRENE IS A CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON
SCALE. SOME ADDITIONAL STRENGTHENING IS FORECAST DURING THE NEXT
DAY OR SO AND IRENE COULD BECOME A CATEGORY FOUR HURRICANE BY
THURSDAY.

IRENE IS A LARGE TROPICAL CYCLONE. HURRICANE FORCE WINDS EXTEND
OUTWARD UP TO 60 MILES...95 KM...FROM THE CENTER...AND TROPICAL
STORM FORCE WINDS EXTEND OUTWARD UP TO 230 MILES...370 KM. A WIND
GUST TO 60 MPH...95 KM/H WAS RECENTLY REPORTED AT GREAT EXUMA IN
THE BAHAMAS.

ESTIMATED MINIMUM CENTRAL PRESSURE WAS 954 MB...28.17 INCHES.

HAZARDS AFFECTING LAND
----------------------
WIND...HURRICANE CONDITIONS ARE OCCURRING OVER PORTIONS OF THE
SOUTHEASTERN BAHAMAS. TROPICAL STORM CONDITIONS WILL CONTINUE TO
SPREAD OVER THE CENTRAL BAHAMAS...WITH HURRICANE CONDITIONS
EXPECTED BY TONIGHT. TROPICAL STORM CONDITIONS ARE EXPECTED IN THE
NORTHWESTERN BAHAMAS BY LATE TONIGHT...WITH HURRICANE CONDITIONS
EXPECTED ON THURSDAY.

STORM SURGE...IN AREAS OF ONSHORE WINDS NEAR THE CENTER OF
IRENE...AN EXTREMELY DANGEROUS STORM SURGE WILL RAISE WATER LEVELS
BY AS MUCH AS 7 TO 11 FEET ABOVE NORMAL TIDE LEVELS OVER THE
BAHAMAS. NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE
AND DANGEROUS WAVES.

RAINFALL...IRENE IS EXPECTED TO PRODUCE ADDITIONAL RAINFALL
ACCUMULATIONS OF 1 TO 3 INCHES ACROSS HISPANIOLA WITH ISOLATED
MAXIMUM STORM TOTAL AMOUNTS OF 15 INCHES POSSIBLE. THESE RAINS
COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES IN AREAS
OF STEEP TERRAIN. RAINFALL ACCUMULATIONS OF 6 TO 12 INCHES ARE
EXPECTED IN THE BAHAMAS AND THE TURKS AND CAICOS ISLANDS.

SURF...SWELLS GENERATED BY IRENE WILL BEGIN AFFECTING PORTIONS OF
THE COAST OF THE SOUTHEASTERN UNITED STATES ON THURSDAY. THESE
SWELLS ARE EXPECTED TO CAUSE LIFE-THREATENING SURF AND RIP CURRENT
CONDITIONS. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER
OFFICE.

NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...800 PM EDT.
NEXT COMPLETE ADVISORY...1100 PM EDT.

$$
FORECASTER BROWN

===================================

HURRICANE IRENE DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 PM EDT WED AUG 24 2011

THE SATELLITE PRESENTATION OF THE HURRICANE HAS CONTINUED TO IMPROVE
THIS AFTERNOON. A LARGE AREA OF DEEP CONVECTION WITH VERY COLD
CLOUD TOPS HAS EXPANDED NEAR THE EYEWALL AND NOW SOLIDLY SURROUNDS
THE EYE. BEFORE DEPARTING IRENE...THE AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT MEASURED A PEAK 700 MB FLIGHT-LEVEL WIND OF 116 KT
IN THE NORTHEASTERN EYEWALL AND A DROPSONDE MEASURED A MINIMUM
PRESSURE OF 954 MB. THESE DATA SUPPORT AN INITIAL INTENSITY OF
105 KT.

ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN FAVORABLE FOR SOME
ADDITIONAL STRENGTHENING DURING THE NEXT DAY OR TWO. THE UW-CIMMS
OBJECTIVE SECONDARY EYEWALL FORMATION TECHNIQUE CONTINUES TO
PREDICT A HIGH CHANCE OF AN EYEWALL REPLACEMENT DURING THE NEXT DAY
OR SO. IN FACT...A RECENT TRMM MICROWAVE PASS SHOWED SOME EVIDENCE
OF A SECONDARY EYEWALL. THESE EYEWALL CYCLES CAN PRODUCE HARD TO
PREDICT FLUCTUATIONS IN INTENSITY. FOR NOW...THE NEW INTENSITY
FORECAST CALL FOR SOME ADDITIONAL STRENGTHENING FOLLOWED BY A
LEVELING OFF OF THE INTENSITY. IN 3-4 DAYS....INCREASING
SOUTHWESTERLY SHEAR AND COOLER SSTS SHOULD INDUCE GRADUAL
WEAKENING...ALTHOUGH IRENE IS EXPECTED TO REMAIN A LARGE AND
POWERFUL HURRICANE...OR EVEN GROW IN SIZE...AS IT NEARS NEW
ENGLAND.

THE HURRICANE HAS BEEN MOVING NORTHWESTWARD OR 310/10 KT. IRENE IS
EXPECTED TO TURN TOWARD THE NORTH-NORTHWEST THEN NORTH THROUGH A
BREAK IN THE SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC DURING
THE NEXT COUPLE OF DAYS. AFTER THAT TIME...THE HURRICANE IS
FORECAST TO TURN NORTH-NORTHEASTWARD AROUND THE NORTHWESTERN SIDE
OF THE RIDGE. BETWEEN 72 AND 96 HOURS...THERE REMAINS UNCERTAINTY
AS TO WHETHER IRENE TURNS BACK TOWARD THE NORTH AHEAD OF A
MID-LATITUDE TROUGH MOVING INTO THE GREAT LAKES REGION AT THAT
TIME. THE NEW ECMWF SHOWS MUCH MORE AMPLIFICATION OF THE TROUGH...
WHICH HAS RESULTED IN ITS TRACK SHIFTING OVER 100 MILES TO THE
WEST...AND THIS SKILLFUL LONG-RANGE MODEL NOW DEFINES THE WESTERN
EDGE OF THE GUIDANCE ENVELOPE. OVERALL...THE GUIDANCE ENVELOPE HAS
SHIFTED A LITTLE WESTWARD AT DAYS 4 AND 5. THE NEW TRACK FORECAST
IS CLOSE TO THE PREVIOUS ADVISORY AND IS BETWEEN THE GFS
AND ECMWF MODELS. THIS IS ALSO CLOSE TO THE TVCA AND EXPERIMENTAL
HURRICANE FORECAST IMPROVEMENT PROJECT...HFIP...CONSENSUS TRACKS.

FORECAST POSITIONS AND MAX WINDS

INIT 24/2100Z 23.1N 74.7W 105 KT 120 MPH
12H 25/0600Z 24.3N 75.8W 110 KT 125 MPH
24H 25/1800Z 26.1N 76.8W 115 KT 135 MPH
36H 26/0600Z 28.2N 77.3W 115 KT 135 MPH
48H 26/1800Z 30.1N 77.3W 110 KT 125 MPH
72H 27/1800Z 34.3N 75.8W 100 KT 115 MPH
96H 28/1800Z 39.5N 73.0W 85 KT 100 MPH
120H 29/1800Z 47.0N 69.0W 55 KT 65 MPH...POST-TROP/EXTRATROP

$$
FORECASTER BROWN


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