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HURRICANE IRENE PUBLIC ADVISORY & DISCUSSION NUMBER 11

By: National Hurricane Center
By: National Hurricane Center

BULLETIN
HURRICANE IRENE ADVISORY NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
1100 PM AST MON AUG 22 2011

...CENTER OF IRENE JUST NORTH OF THE DOMINICAN REPUBLIC...EXPECTED
TO MOVE OVER THE SOUTHEASTERN BAHAMAS TUESDAY...

SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.9N 69.2W
ABOUT 165 MI...265 KM SE OF GRAND TURK ISLAND
ABOUT 100 MI...155 KM E OF PUERTO PLATA DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...100 MPH...160 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...980 MB...28.94 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...
* NORTH COAST OF THE DOMINICAN REPUBLIC FROM THE HAITI BORDER
EASTWARD TO CABO ENGANO
* TURKS AND CAICOS ISLANDS...SOUTHEASTERN AND CENTRAL BAHAMAS

A HURRICANE WATCH IS IN EFFECT FOR...
* NORTH COAST OF HAITI FROM LE MOLE ST. NICHOLAS EASTWARD TO THE
DOMINICAN REPUBLIC BORDER
* NORTHWESTERN BAHAMAS

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* SOUTH COAST OF THE DOMINICAN REPUBLIC FROM SANTO DOMINGO EASTWARD
TO CABO ENGANO
* ALL OF HAITI

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

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 PM AST...0300 UTC...THE CENTER OF HURRICANE IRENE WAS
LOCATED BY AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT NEAR
LATITUDE 19.9 NORTH...LONGITUDE 69.2 WEST. IRENE IS MOVING TOWARD
THE WEST-NORTHWEST NEAR 12 MPH...19 KM/H...AND THIS MOTION IS
EXPECTED TO CONTINUE THROUGH TUESDAY FOLLOWED BY A TURN TOWARD THE
NORTHWEST TUESDAY NIGHT AND WEDNESDAY. ON THE FORECAST TRACK...THE
CORE OF IRENE WILL MOVE JUST TO THE NORTH OF THE DOMINICAN REPUBLIC
AND HAITI TONIGHT...NEAR OR OVER THE TURKS AND CAICOS ISLANDS AND
THE SOUTHEASTERN BAHAMAS ON TUESDAY...AND NEAR THE CENTRAL BAHAMAS
EARLY WEDNESDAY.

DATA FROM THE HURRICANE HUNTER AIRCRAFT INDICATE THAT MAXIMUM
SUSTAINED WINDS REMAIN NEAR 100 MPH...160 KM/H...WITH HIGHER
GUSTS. IRENE IS A CATEGORY TWO HURRICANE ON THE SAFFIR-SIMPSON
SCALE. ADDITIONAL STRENGTHENING IS FORECAST DURING THE NEXT 48
HOURS...AND IRENE COULD BECOME A MAJOR HURRICANE ON TUESDAY.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 45 MILES...75 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 185
MILES...295 KM.

THE MINIMUM CENTRAL PRESSURE BASED ON DATA FROM THE HURRICANE HUNTER
AIRCRAFT IS 980 MB...28.94 INCHES.

HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS WILL CONTINUE TO SPREAD OVER THE
NORTHERN PORTIONS OF DOMINICAN REPUBLIC TONIGHT AND LOCALIZED
HURRICANE CONDITIONS ARE EXPECTED OVER THE NORTHERN PORTIONS OF THE
DOMINICAN REPUBLIC TONIGHT AND EARLY TUESDAY. THE HIGHEST WINDS
ARE LIKELY TO OCCUR OVER AREAS OF ELEVATED TERRAIN. TROPICAL STORM
CONDITIONS ARE EXPECTED TO REACH THE SOUTHEASTERN BAHAMAS AND THE
TURKS AND CAICOS ISLANDS TUESDAY MORNING WITH HURRICANE CONDITIONS
EXPECTED TUESDAY. TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH
THE CENTRAL BAHAMAS BY TUESDAY NIGHT WITH HURRICANE CONDITIONS
EXPECTED BY WEDNESDAY. TROPICAL STORM CONDITIONS ARE POSSIBLE IN
THE NORTHWESTERN BAHAMAS BY LATE WEDNESDAY...WITH HURRICANE
CONDITIONS POSSIBLE BY THURSDAY.

RAINFALL...IRENE IS EXPECTED TO PRODUCE ADDITIONAL RAINFALL
ACCUMULATIONS OF 1 TO 2 INCHES ACROSS PUERTO RICO AND THE VIRGIN
ISLANDS. RAINFALL AMOUNTS OF 3 TO 6 INCHES ARE EXPECTED OVER
NORTHERN HISPANIOLA...WITH ISOLATED MAXIMUM AMOUNTS OF UP TO 10
INCHES POSSIBLE OVER HIGHER TERRAIN. THESE RAINS COULD CAUSE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES IN AREAS OF STEEP
TERRAIN. RAINFALL ACCUMULATIONS OF 5 TO 10 INCHES ARE EXPECTED IN
THE SOUTHEASTERN AND CENTRAL BAHAMAS...AND THE TURKS AND CAICOS
ISLANDS.

STORM SURGE...A STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 9
TO 13 FEET ABOVE NORMAL TIDE LEVELS OVER THE SOUTHEASTERN AND
CENTRAL BAHAMAS...AND THE TURKS AND CAICOS ISLANDS. STORM SURGE
WILL ALSO RAISE WATER LEVELS BY AS MUCH AS 2 TO 4 FEET ABOVE NORMAL
TIDE LEVELS ALONG THE ENTIRE COAST OF THE DOMINICAN REPUBLIC. NEAR
THE COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE AND DANGEROUS
WAVES.

NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...200 AM AST.
NEXT COMPLETE ADVISORY...500 AM AST.

$$
FORECASTER BRENNAN/CANGIALOSI

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

HURRICANE IRENE DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
1100 PM AST MON AUG 22 2011

AFTER DEEPENING QUICKLY EARLIER THIS EVENING...THE INTENSITY OF
IRENE APPEARS TO HAVE LEVELED OFF A BIT OVER THE PAST HOUR OR TWO.
THE CENTRAL PRESSURE HAS DECREASED TO 980 MB ...AND MAXIMUM WINDS
HAVE NOT INCREASED SINCE THE EARLIER MAXIMUM OF 106 KT AT 850 MB.
THEREFORE...THE INTENSITY WILL REMAIN 85 KT FOR THIS ADVISORY.
OVERALL THE STRUCTURE OF THE CYCLONE HAS CONTINUED TO IMPROVE...
WITH A LARGE CDO FORMING NEAR AND NORTH OF THE CENTER AND THE
AIRCRAFT REPORTING A CLOSED EYEWALL. SOUTHERLY SHEAR OF ABOUT 10
KT IS PRESENT OVER IRENE ACCORDING TO SATELLITE ANALYSIS FROM
UW-CIMSS AND THE SHIPS MODEL...BUT OTHERWISE THE ENVIRONMENT
APPEARS CONDUCIVE FOR CONTINUED STRENGTHENING. THE NHC INTENSITY
FORECAST IS UNCHANGED FROM THE PREVIOUS SPECIAL ADVISORY AND SHOWS
IRENE BECOMING A MAJOR HURRICANE WITHIN 24 HOURS AND REACHING A
PEAK OF 115 KT IN 72 HOURS...FOLLOWED BY SLOW WEAKENING LATE IN THE
PERIOD. THE NHC FORECAST IS HIGHER THAN MOST OF THE GUIDANCE
THROUGH 48 HOURS AND IS CLOSE TO A BLEND OF THE GFDL AND HWRF
MODELS AFTER THAT TIME.

AIRCRAFT FIXES INDICATE THAT THE CENTER WAS LOCATED A LITTLE TO THE
RIGHT OF THE PREVIOUS TRACK AND THAT THE FORWARD MOTION HAS SLOWED
A BIT...WITH AN INITIAL MOTION ESTIMATE OF 295/10. OVERALL THE
TRACK FORECAST SCENARIO HAS NOT CHANGED...AS IRENE WILL CONTINUE
MOVING WEST-NORTHWESTWARD FOR THE NEXT DAY OR SO ON THE SOUTHWEST
PERIPHERY OF A WEAKENING MID-LEVEL RIDGE. A MID- TO UPPER-LEVEL
TROUGH LOCATED EAST OF NORTH AMERICA WILL LIFT OUT WITHIN 24
HOURS...LEAVING A PRONOUNCED WEAKNESS IN THE RIDGE OVER THE
BAHAMAS. THIS SHOULD ALLOW IRENE TO GRADUALLY TURN NORTHWESTWARD
AND NORTH-NORTHWESTWARD BY DAYS 2 AND 3. AFTER THAT TIME...THE
TRACK OF IRENE APPEARS TO BE SENSITIVE TO THE TIMING AND AMPLITUDE
OF SEVERAL SHORTWAVE TROUGHS MOVING EASTWARD ACROSS THE UNITED
STATES/CANADIAN BORDER. THE MODELS ARE SHOWING SOME RUN-TO-RUN
VARIABILITY IN HOW MUCH THESE SHORTWAVES WILL AMPLIFY AND DEEPEN
THE MEAN TROUGH OVER THE NORTHEASTERN UNITED STATES...WHICH WILL BE
CRITICAL TO HOW SOON IRENE TURNS NORTHWARD OR EVEN EAST OF DUE
NORTH AT DAYS 4 AND 5. OVERALL...THE SPREAD OF THE GUIDANCE SUITE
HAS DECREASED THIS CYCLE...AND THE COMBINATION OF THE SLIGHT
RIGHTWARD ADJUSTMENT OF THE INITIAL POSITION AND A SLIGHT WESTWARD
SHIFT IN THE MODEL CONSENSUS RESULTS IN ONLY MINOR ADJUSTMENTS TO
THE NEW NHC TRACK FORECAST. THE BIGGEST CHANGE IS A SLOWER FORWARD
SPEED AT THE END OF THE PERIOD FOLLOWING THE BULK OF THE GUIDANCE
THAT KEEPS THE CYCLONE OFFSHORE AT DAY 5.

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

OF NOTE...SYNOPTIC SURVEILLANCE FLIGHTS FROM THE NOAA G-IV AND AN
AIR FORCE RESERVE C-130 AIRCRAFT PROVIDED NUMEROUS DROPSONDES FOR
ASSIMILATION INTO THE 0000 UTC MODEL CYCLE. THIS SHOULD IMPROVE
THE ANALYSIS OF THE ENVIRONMENT AROUND AND UPSTREAM OF IRENE.

FORECAST POSITIONS AND MAX WINDS

INIT 23/0300Z 19.9N 69.2W 85 KT 100 MPH
12H 23/1200Z 20.4N 70.6W 95 KT 110 MPH
24H 24/0000Z 21.1N 72.4W 105 KT 120 MPH
36H 24/1200Z 22.2N 74.2W 110 KT 125 MPH
48H 25/0000Z 23.5N 75.6W 110 KT 125 MPH
72H 26/0000Z 26.5N 78.0W 115 KT 135 MPH
96H 27/0000Z 30.0N 79.0W 105 KT 120 MPH
120H 28/0000Z 33.5N 78.5W 100 KT 115 MPH

$$
FORECASTER BRENNAN


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