Hurricane Irene A Potentially Historic Storm

000

WTNT34 KNHC 250255
TCPAT4

BULLETIN HURRICANE IRENE ADVISORY NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
1100 PM EDT WED AUG 24 2011

...HURRICANE IRENE DANGEROUSLY APPROACHING THE NORTHWESTERN
BAHAMAS...AT 1100 PM EDT...0300 UTC...THE EYE OF HURRICANE IRENE WAS

.....LOCATED NEAR LATITUDE 23.8 NORTH...LONGITUDE 75.4 WEST. IRENE IS
MOVING TOWARD THE NORTHWEST NEAR 12 MPH...19 KM/H. A TURN TOWARD
THE NORTH-NORTHWEST AND THEN TOWARD THE NORTH ARE EXPECTED ON
THURSDAY. ON THE FORECAST TRACK...THE CORE OF IRENE WILL CONTINUE
TO MOVE ACROSS THE CENTRAL BAHAMAS DURING THE NEXT SEVERAL HOURS
AND MOVE OVER THE NORTHWESTERN BAHAMAS ON THURSDAY.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 120 MPH...195 KM/H...WITH HIGHER
GUSTS. IRENE IS A CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON
HURRICANE WIND SCALE. SOME FLUCTUATIONS IN INTENSITY ARE LIKELY
DURING THE NEXT SEVERAL HOURS...BUT SOME STRENGTHENING IS FORECAST
DURING THE NEXT DAY OR SO. IRENE COULD BECOME A CATEGORY FOUR
HURRICANE ON THURSDAY.

IRENE IS A LARGE TROPICAL CYCLONE. HURRICANE FORCE WINDS EXTEND
OUTWARD UP TO 70 MILES...110 KM...FROM THE CENTER...AND TROPICAL
STORM FORCE WINDS EXTEND OUTWARD UP TO 255 MILES...410 KM.

A RECONNAISSANCE PLANE ESTIMATED A MINIMUM CENTRAL PRESSURE OF 952
MB...28.11 INCHES.
000

FXUS61 KCAR 250250
AFDCAR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CARIBOU ME
1050 PM EDT WED AUG 24 2011.....LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...


PRIMARY CONCERN THIS FORECAST PERIOD IS HURRICANE IRENE. WIND
GRIDS MAIN FOCUS AT THIS POINT. AFTER TALKING WITH OFFICES TO
SOUTH HAVE DECIDED TO GENERATE THE WIND GRIDS WITH GFS40 THEN USE
THE GMOS FOR REMAINDER OF GRIDS. EXPECT HURRICANE IRENE TO MOVE TO
A POSITION OFF THE MID ATLANTIC STATES BY SUNDAY MORNING THEN MOVE
NORTHWARD TO MAINE COAST BY LATE SUNDAY EVENING. WITH WELL OVER
100 HOURS TO THE POSSIBLE ARRIVAL OF THE SYSTEM THERE IS STILL
PLENTY OF UNCERTAIN. HAVE MADE SOME MINOR ADJUSTMENTS TO GMOS POP
AND SKY GRIDS. FOR TIDAL ISSUES THE HIGH TIDE SUNDAY NIGHT IS JUST
PRIOR TO 11:00 PM IS OF MOST CONCERN FOR POSSIBLE COASTAL FLOODING
ISSUES. SO WILL ALSO MONITOR THE TIMING OF IRENE DURING THE NEXT
SEVERAL DAYS SINCE THIS WILL BE CRITICAL WITH LARGE TIDAL RANGE
ALONG EASTERN MAINE COAST.SHORT TERM: HAVE USED A BLEND OF THE NAM12 AND GFS40 FOR WINDS

.MARINE...



.........TRACK OF HURRICANE IRENE WILL BE CRITICAL TO FORECAST SUNDAY
AND SUNDAY NIGHT. FOR WAVES: LONG PERIOD WAVES FROM HURRICANE
IRENE WILL ALREADY BE ARRIVING ALONG THE MAINE COAST AT THE
BEGINNING OF THIS PERIOD AND WILL GRADUALLY INCREASE IN HEIGHT
SATURDAY NIGHT INTO THE DAY SUNDAY. WILL USE WNA/4 WHICH IS IN
LINE WITH HURRICANE VERSION OF WAVE MODEL TO GENERATE THE WAVE
GRIDS.


EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
313 PM EDT WED AUG 24 2011

VALID 12Z SAT AUG 27 2011 - 12Z WED AUG 31 2011

...DANGEROUS HURRICANE IRENE TO AFFECT THE NC OUTER BANKS INTO THE
NORTHEAST THIS WEEKEND...

IRENE CONTINUES TO STRENGTHEN AS A CATEGORY 3 HURRICANE OVER THE
BAHAMAS AND AS OF 18Z WAS PACKING SUSTAINED WINDS OF 120 MPH WITH
HIGHER GUSTS. IRENE COULD REACH CATEGORY 4 STATUS BY THURSDAY.
PLEASE REFER A UPDATES FROM THE NATIONAL HURRICANE CENTER AND
LOCAL WEATHER OFFICE/AGENCIES FOR ADDITIONAL INFORMATION ON IRENE.

DUE IN PART TO MORE FREQUENT SAMPLING OF THE ENVIRONMENTAL
CONDITIONS SURROUNDING HURRICANE IRENE BY MULTIPLE AIRPLANE
PLATFORMS ALONG WITH CONTINUATION OF SUPPLEMENTAL UPPER AIR RAOBS
ACROSS PARTS OF THE EASTERN CONUS EVERY 6 HOURS...THE MODEL
SOLUTION SPREAD FOR THE TRACK OF IRENE FOR MOST GUIDANCE OVER THE
NEXT 4-5 DAYS OVERALL SEEMS REDUCED FOR THE LONGER RANGES. THAT
SAID...EVEN RELATIVELY SMALL DIFFERENCES CAN MAKE A SIGNIFICANT
DIFFERENCE ON THE EXTENT OF SYSTEM EFFECT LOCALLY AS TRACKS VARY
FROM RUN TO RUN WITH RESPECT TO HOW FAR TO THE WEST/INLAND IRENE
MAY GO.

IN ADDITION TO IRENE INTENSITY IN GUIDANCE...ONE OF THE LARGEST
REMAINING UNCERTAINTIES IN THE MEDIUM RANGE PERIOD HOWEVER IS THE
EXACT SPEED AND STRENGTH OF A STRONG SHORTWAVE TROUGH CURRENTLY
ENTERING WESTERN CANADA. THIS TROUGH IS EXPECTED TO AMPLIFY DOWN
FROM ONTARIO/QUEBEC BY DAY 3/SAT AND PICK UP IRENE. THE GFS/ECMWF
HAVE NEARLY CONVERGED WITH THE DETAILS OF THIS TROUGH...WITH THE
GFS ONLY SLIGHTLY FASTER AND SUPPORTED BY THE CANADIAN...THUS
ACCELERATING IRENE NORTHWARD INTO THE NORTHEAST/NEW ENGLAND AND
BEYOND MORE QUICKLY THAN THE ECMWF. HOWEVER...RUN-TO-RUN
VARIABILITY WITH THE MORE UNCERTAIN HIGHER LATITUDE FLOW IS TO BE
EXPECTED...WITH RECENT GFS/ECMWF 4-CYCLE LAGGED AVERAGE FORECASTS
SHOWING 500 MB HEIGHT VARIABILITIES AVERAGING 50 TO 70 DECAMETERS
ACROSS THE UPPER GREAT LAKES...ENOUGH TO SUPPORT DIFFERING
INFLUENCES ON IRENE.

GFS/ECMWF AGREEMENT ELSEWHERE SEEMED SUFFICIENT TO USE NEARLY
EQUALLY FOR THE PRELIMINARY AND NOW FINAL PRESSURES/FRONTS OVERALL
ACROSS MUCH OF THE CONUS. THIS APPROACH WORKS WELL FOR THE WESTERN
AND CENTRAL CONUS IN PARTICULAR AS THE STRONG FLOW ACROSS THE
NORTHERN PACIFIC IS EXPECTED TO SUPPORT CONTINUED STRENGTH AND
TIMING DIFFERENCES OF INDIVIDUAL SHORTWAVE TROUGHS WHICH ARE BEST
RESOLVED WITH AN INTERMEDIATE APPROACH. ONE DIFFERENCE SEEN IN THE
LATEST GUIDANCE IS FOR GREATER AMPLIFICATION OF A SIGNIFICANT
SHORTWAVE TROUGH ACROSS THE PACIFIC NORTHWEST DAYS 6/7...WITH THE
ECMWF FASTER IN EJECTING THE LEADING EDGE OF THE TROUGH OUT OF THE
NORTHWEST COMPARED TO THE GFS...WHICH THEN LEADS TO GROWING
DIFFERENCES DOWNSTREAM. THE 00Z CANADIAN AND THE GLOBAL ENSEMBLE
MEANS PROVIDE GOOD SUPPORT FOR A SOLUTION CLOSEST TO THE
GFS...LEANING AWAY FROM THE 00/12 UTC ECMWF THERE STARTING DAY
6/TUE...AND INSTEAD BLEND THE GFS/GEFS MEAN SOLUTIONS FOR DAYS
6/7.

JAMES/SCHICHTEL