Hurricane Isabel weak (still strong Cat 4) 9/13/03

000 WTNT33 KNHC 130842 TCPAT3 BULLETIN HURRICANE ISABEL ADVISORY NUMBER 29 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM AST SAT SEP 13 2003

AT 5 AM AST...0900Z...THE EYE OF HURRICANE ISABEL WAS LOCATED NEAR LATITUDE 22.0 NORTH...LONGITUDE 60.4 WEST OR ABOUT 455 MILES...730 KM...NORTHEAST OF SAN JUAN PUERTO RICO.

ISABEL IS MOVING TOWARD THE WEST NEAR 9 MPH...15 KM/HR...AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE DURING THE NEXT 24 HOURS.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 150 MPH...240 KM/HR...WITH HIGHER GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 24 HOURS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 85 MILES...140 KM... FROM THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 185 MILES...295 KM.

LATEST MINIMUM CENTRAL PRESSURE REPORTED BY AN AIR FORCE RECONNAISSANCE PLANE WAS 935 MB...27.61 INCHES.

LARGE OCEAN SWELLS AND DANGEROUS SURF CONDITIONS ARE LIKELY OVER PORTIONS OF THE LEEWARD ISLANDS...THE VIRGIN ISLANDS...AND PUERTO RICO OVER THE NEXT SEVERAL DAYS.

REPEATING THE 5 AM AST POSITION...22.0 N... 60.4 W. MOVEMENT TOWARD...WEST NEAR 9 MPH. MAXIMUM SUSTAINED WINDS...150 MPH. MINIMUM CENTRAL PRESSURE... 935 MB.

FORECASTER AVILA000 WTNT43 KNHC 130843 TCDAT3 HURRICANE ISABEL DISCUSSION NUMBER 29 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT SAT SEP 13 2003

THE MUCH ANTICIPATED WEAKENING HAS OCCURRED. DATA FROM A RECONNAISSANCE PLANE INDICATE THAT THE CENTRAL PRESSURE HAS RISEN TO 935 MB AND FLIGHT-LEVEL PEAK WINDS ARE 139 KNOTS. INITIAL INTENSITY HAS BEEN LOWERED TO 130 KNOTS AND THIS IS PROBABLY ON THE HIGH SIDE. THE RECON ALSO CONFIRMED THE PRESENCE OF TWO CONCENTRIC EYEWALLS OF 25 AND 35 NMI AND A BAND OF MAXIMUM WINDS ASSOCIATED WITH EACH EYEWALL...RESPECTIVELY. THERE IS NO SKILL IN PREDICTING IF THE CURRENT EYEWALL CYCLE WILL RESULT IN FURTHER WEAKENING OR IN ANOTHER ROUND OF INTENSIFICATION. BEST BET IS TO INDICATE SOME FLUCTUATIONS IN INTENSITY IN THE NEXT DAY OR TWO WITH A WEAKENING TREND DUE TO COOLER SSTS OR SHEAR THEREAFTER. NEVERTHERELESS... ISABEL IS EXPECTED TO REMAIN A MAJOR HURRICANE THROUGHOUT THE FORECAST PERIOD.

ISABEL IS MOVING TOWARD THE WEST OR 280 DEGREES AT 8 KNOTS AROUND THE PERIPHERY OF A STRONG DEEP-LAYER ANTICYCLONE. THIS PATTERN IS EXPECTED TO STEER THE HURRICANE TOWARD THE WEST WITH A GRADUAL TURN TO THE WEST-NORTHWEST AS INDICATED IN THE OFFICIAL FORECAST. IT APPEARS THAT THE TROUGH WHICH IS CURRENTLY ERODING THE WESTERN PORTION OF THE RIDGE WILL WEAKEN AND THE HIGH WILL EXPAND WESTWARD. THIS EXPANSION OF THE RIDGE WILL CONTROL HOW CLOSE ISABEL APPROACHES THE U.S EAST COAST.

HIGH UNCERTAINTIES CONTINUE AT LONGER RANGE. THE CONSISTENT AND GOOD PERFORMER UK MODEL HAS THE HURRICANE NEAR THE COAST OF NORTH CAROLINA BETWEEN 5 AND 6 DAYS. ON THE OTHER HAND...THE RELIABLE GFDL TURNS ISABEL NORTHWARD IN FIVE DAYS AT A GOOD DISTANCE AWAY FROM THE U.S EAST COAST. BECAUSE BOTH MODELS HAVE BEEN VERY GOOD SO FAR...THE OFFICIAL FORECAST IS IN BETWEEN THESE TWO MODELS. AT THIS TIME...I WOULD NOT EVEN DISCUSS THE GFS WHICH MOVES THE HURRICANE EASTWARD FOR THE FIRST 12 TO 18 HOURS IN THE LATEST 00Z RUN AND ISABEL IS ALREADY WEST OF 60 DEGREES WEST. HOWEVER...THE LARGE SCALE PATTERN PROVIDED BY THE GFS IS QUITE REASONABLE.

NOTE: THERE ARE NO DYNAMICAL MODELS SUGGESTING THAT ISABEL MIGHT EVER REACH FLORIDA.

INITIAL 13/0900Z 22.0N 60.4W 130 KT 12HR VT 13/1800Z 22.2N 61.6W 130 KT 24HR VT 14/0600Z 23.0N 63.7W 130 KT 36HR VT 14/1800Z 23.5N 65.5W 130 KT 48HR VT 15/0600Z 24.5N 67.5W 130 KT 72HR VT 16/0600Z 26.0N 70.0W 120 KT 96HR VT 17/0600Z 28.5N 72.0W 115 KT 120HR VT 18/0600Z 32.0N 74.5W 105 KT

The models suggest wide unpredictability about Isabel. See http://www.wrel.com/modelmap.htm for the latest guesses of some of the models. If you believe one of them, Florida is not out of the woods yet... and if you believe the rightmost one will slide further to the right, those members of the elistist board blown halfway away by Fabian may be in for a rude resurprise.

Actually, the models are unusually close together for a storm this far out. Much less unpredictability than usual.

And there's a real problem with people who don't really know anything about any of the models simply looking at maps with colored lines.

The only models pointing at Florida are the completely useless ones.

BAMM is the Beta-and-Advection Model, MEDIUM Layer. It's designed for BADLY SHEARED weak tropical storms. It's useless for Hurricanes. It only shows the low and medium level steering flow.

And the A98E is the oldest and most useless model that is still run. It incorporates a lot of climo (based on history of previous storms, rather than current weather conditions.

In Andrew, the Climo models showed Andrew curving harmlessly out to sea. The Dynamical models showed Andrew hitting Florida five days before it did.

As Avila noted in the latest discussion, there are no global dynamical models getting Isabel anywhere near Florida.

Not that high.. Ocean City/Norfolk would be the closest brush if it does stroll by Hatteras... Even if it did a Wilmington/Beaufort NC strike (again), all DC would get (if Norfolk did not) is tropical-force winds (and the seemingly inevitable southern Potomac tornadoes) and of course the power going out again in places.

000
WTNT33 KNHC 131448
TCPAT3
BULLETIN
HURRICANE ISABEL ADVISORY NUMBER 30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM AST SAT SEP 13 2003

...POWERFUL CATEGORY 4 HURRICANE ISABEL GETTING A LITTLE BETTER
ORGANIZED AS IT MOVES WESTWARD...

AT 11 AM AST...1500Z...THE CENTER OF HURRICANE ISABEL WAS LOCATED
NEAR LATITUDE 22.2 NORTH...LONGITUDE 61.5 WEST OR ABOUT 405 MILES
...650 KM...NORTHEAST OF SAN JUAN PUERTO RICO.

ISABEL IS MOVING TOWARD THE WEST NEAR 10 MPH...17 KM/HR...AND THIS
GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 150 MPH...240 KM/HR...WITH HIGHER
GUSTS. SOME SLIGHT STRENGTHENING IS POSSIBLE DURING THE NEXT
24 HOURS. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS
SCHEDULED TO INVESTIGATE THE DANGEROUS HURRICANE THIS AFTERNOON.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 85 MILES...140 KM...
FROM THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP
TO 175 MILES...280 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 935 MB...27.61 INCHES.

LARGE OCEAN SWELLS AND DANGEROUS SURF CONDITIONS ARE LIKELY OVER
PORTIONS OF THE LEEWARD ISLANDS...THE VIRGIN ISLANDS...PUERTO RICO
...AND THE DOMINICAN REPUBLIC OVER THE NEXT SEVERAL DAYS.

REPEATING THE 11 AM AST POSITION...22.2 N... 61.5 W. MOVEMENT
TOWARD...WEST NEAR 10 MPH. MAXIMUM SUSTAINED
WINDS...150 MPH. MINIMUM CENTRAL PRESSURE... 935 MB.

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER
AT 5 PM AST.

FORECASTER STEWART
000
WTNT43 KNHC 131439
TCDAT3
HURRICANE ISABEL DISCUSSION NUMBER 30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT SAT SEP 13 2003

ISABEL HAS COMPLETED AN EYEWALL REPLACEMENT CYCLE BASED ON A
13/1102Z SSMI OVERPASS SHOWING A CLOSED 35 NMI DIAMETER EYE. THE
INTENSITY IS MAINTAINED AT 130 KT BASED ON CONTINUITY WITH THE
PREVIOUS DATA...A CONSENSUS SATELLITE INTENSITY ESTIMATE OF 127
KT...RAW ODT VALUES OF T6.5...OR 127 KT...AND THE FACT THAT THE EYE
HAS CLEARED OUT NICELY AND SURROUNDING EYEWALL CLOUD TOPS HAVE
COOLED TO -70C AND COLDER ONCE AGAIN. NEXT RECON MISSION IS AT 18Z.

THE INITIAL MOTION IS 280/08. OVER THE PAST 72 HOURS...ISABEL HAS
BEEN MOVING AT 275 DEGREES. THE HURRICANE MADE A SLIGHT NORTHWARD
WOBBLE DURING THE EARLIER EYEWALL REPLACEMENT CYCLE...BUT IT NOW
APPEARS TO HAVE RESUMED A 275-280 DEGREES MOTION. ALL OF THE GLOBAL
AND REGIONAL MODELS HAVE HAD A DISTINCT RIGHT-OF-TRACK BIAS BY AS
MUCH AS 10 DEGREES...AND EACH MODEL RUN HAS BEEN A LITTLE FARTHER
WEST AND SLOWER. THE EXCEPTION IS THE 06Z GFDL RUN WHICH MADE A
MAJOR SHIFT WESTWARD BY MORE 200 NMI IN THE LATER FORECAST PERIODS
...WHILE THE 06Z NOGAPS MODEL ACCELERATED ISABEL AND HAS THE
HURRICANE ONSHORE THE SOUTHEAST COAST OF NORTH CAROLINA IN 120
HOURS. HOWEVER...THE MODEL CONSENSUS IS SLOWER AND FARTHER WEST
BEFORE A TURN TO THE NORTHWEST OCCURS IN THE LATER PERIODS. THE
MODELS OBVIOUSLY HAVE NOT BEEN HANDLING THE STRONG RIDGING TO THE
NORTH OF ISABEL VERY WELL. THIS MAY BE DUE TO THE OUTFLOW ON THE
NORTH SIDE BEING DRAWN NORTHWARD AND SINKING ALONG 30N-33N...WHICH
MAY HAVE HELPED TO STRENGTHEN THE SUBTROPICAL RIDGE. WATER VAPOR
IMAGERY INDICATES THIS PATTERN HAS PERSISTED FOR MORE THAN 72 HOURS
AND CONTINUES TO SHIFT WESTWARD WITH ISABEL. THEREFORE...A GENERAL
WESTWARD MOTION SHOULD CONTINUE FOR ANOTHER 36 HOURS OR SO.
AFTERWARDS...THERE REMAINS CONSIDERABLE DIVERGENCE AMONG THE MODELS
AND HOW THEY HANDLE THE CURRENT SHORTWAVE TROUGH/LOW OVER THE
SOUTHEASTERN U.S. WATER VAPOR IMAGERY INDICATES THE TROUGH HAS
BECOME NEGATIVELY TILTED IN AN EAST-WEST ORIENTATION. THIS WOULD
SUGGEST THAT THE LOW SHOULD BEGIN TO LIFT OUT AND ALLOW THE RIDGE
NORTH OF ISABEL TO GRADUALLY BUILD WESTWARD...WHICH IS SIMILAR TO
THE 06Z GFS...GFDL...AND ETA...AND 00Z UKMET SOLUTIONS. THE KEY
WILL BE HOW THE CENTRAL U.S. TROUGH EVOLVES AND HOW DEEP IT DIGS
INTO THE SOUTHERN U.S. AND GULF OF MEXICO. THE OFFICIAL FORECAST
WAS ADJUSTED SLIGHTLY TO THE LEFT OF AND SLOWER THAN THE PREVIOUS
FORECAST...WHICH IS CONSISTENT WITH THE GUNA MODEL CONSENSUS.
HOWEVER...IT IS STILL TOO EARLY TO DETERMINE WHEN OR WHERE ISABEL
WILL MAKE LANDFALL. HOPEFULLY...THE NOAA GULFSTREAM-IV SYNOPTIC
DATA MISSION AT 14/00Z WILL PROVIDE BETTER MODEL CONVERGENCE.

ALTHOUGH ISABEL HAS A RATHER LARGE EYE DIAMETER...CONDITIONS APPEAR
FAVORABLE FOR AT LEAST SOME SLIGHT ADDITIONAL STRENGTHENING OVER
THE NEXT COUPLE OF DAYS AS THE HURRICANE MOVES OVER WARMER WATER.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL 13/1500Z 22.2N 61.5W 130 KT
12HR VT 14/0000Z 22.6N 63.0W 135 KT
24HR VT 14/1200Z 23.0N 64.8W 135 KT
36HR VT 15/0000Z 23.7N 66.7W 130 KT
48HR VT 15/1200Z 24.5N 68.7W 130 KT
72HR VT 16/1200Z 26.0N 71.0W 125 KT
96HR VT 17/1200Z 28.5N 73.0W 120 KT
120HR VT 18/1200Z 31.5N 75.0W 110 KT

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