Tropical Storm Gustav Advisory 15 Plus Forecast Discussion

BULLETIN
TROPICAL STORM GUSTAV ADVISORY NUMBER 15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008
1100 AM EDT THU AUG 28 2008
...GUSTAV CLOSING IN ON JAMAICA...
A HURRICANE WARNING IS IN EFFECT FOR JAMAICA.
A TROPICAL STORM WARNING IS IN EFFECT FOR THE CUBAN PROVINCE OF
GRANMA.
A HURRICANE WATCH IS IN EFFECT FOR ALL OF THE CAYMAN ISLANDS.
INTERESTS IN CENTRAL AND WESTERN CUBA SHOULD CLOSELY MONITOR THE
PROGRESS OF GUSTAV.
FOR STORM INFORMATION SPECIFIC TO YOUR AREA...INCLUDING POSSIBLE
INLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR LOCAL WEATHER OFFICE.
AT 1100 AM EDT...1500Z...THE CENTER OF TROPICAL STORM GUSTAV WAS
LOCATED NEAR LATITUDE 17.9 NORTH...LONGITUDE 76.1 WEST OR ABOUT 45
MILES... 75 KM...EAST OF KINGSTON JAMAICA AND ABOUT 350 MILES...560
KM...EAST-SOUTHEAST OF GRAND CAYMAN.
GUSTAV IS MOVING TOWARD THE WEST NEAR 5 MPH...7 KM/HR...AND A
CONTINUED WESTWARD MOTION WITH A GRADUAL INCREASE IN FORWARD SPEED
IS EXPECTED TODAY. A TURN TOWARD THE WEST-NORTHWEST AND NORTHWEST
IS FORECAST DURING THE NEXT COUPLE OF DAYS. ON THIS TRACK...THE
CENTER OF GUSTAV WILL MOVE NEAR OR OVER JAMAICA TODAY AND
TONIGHT...AND NEAR OR OVER THE CAYMAN ISLANDS FRIDAY NIGHT.
MAXIMUM SUSTAINED WINDS ARE NEAR 70 MPH...110 KM/HR...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT COUPLE OF
DAYS. GUSTAV COULD BECOME A HURRICANE BEFORE MOVING OVER JAMAICA.
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 60 MILES...95 KM
FROM THE CENTER.
THE ESTIMATED MINIMUM CENTRAL PRESSURE BASED ON EARLIER AIRCRAFT
DATA IS 983 MB...29.03 INCHES.
GUSTAV IS EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 6 TO
12 INCHES ACROSS JAMAICA AND THE CAYMAN ISLANDS...WITH ISOLATED
MAXIMUM AMOUNTS OF UP TO 25 INCHES POSSIBLE. THESE RAINS WILL
LIKELY PRODUCE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.
RAINFALL ACCUMULATIONS OF 2 TO 4 INCHES ARE POSSIBLE OVER SOUTHERN
CUBA. RAINFALL WILL BE DIMINISHING OVER HAITI TODAY...WITH AN
ADDITIONAL 1 TO 2 INCHES OF RAINFALL POSSIBLE.
COASTAL STORM SURGE FLOODING OF 1 TO 3 FEET ABOVE NORMAL TIDE LEVELS
CAN BE EXPECTED IN AREAS OF ONSHORE WINDS IN THE HURRICANE
WARNING AREA.
REPEATING THE 1100 AM EDT POSITION...17.9 N...76.1 W. MOVEMENT
TOWARD...WEST NEAR 5 MPH. MAXIMUM SUSTAINED WINDS...70 MPH.
MINIMUM CENTRAL PRESSURE...983 MB.
AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 200 PM EDT FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 500
PM EDT.
TROPICAL STORM GUSTAV DISCUSSION NUMBER 15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008
1100 AM EDT THU AUG 28 2008
THE LAST AIRCRAFT FIX AT ABOUT 1130 UTC SHOWED THE CIRCULATION
CENTER HAD BEEN MOVING VERY LITTLE EARLIER THIS MORNING. MY SENSE
FROM VISIBLE IMAGERY SINCE THEN IS THAT GUSTAV HAS STARTED MOVING
SLOWLY WESTWARD...PERHAPS 265/4. IT IS NOT CLEAR IF THE CENTER
WILL PASS DIRECTLY OVER JAMAICA OR WILL HUG THE SOUTH OR NORTH
COAST...BUT WITH A WEAK MID-LEVEL RIDGE OVER FLORIDA...ALL MODELS
FORECAST GUSTAV TO CONTINUE GENERALLY WESTWARD FOR THE NEXT DAY OR
SO. A WEAKNESS IN THE RIDGE OVER THE EASTERN GULF OF MEXICO SHOULD
ALLOW GUSTAV TO GRADUALLY TURN TO THE RIGHT DURING THE FOLLOWING
FEW DAYS. THE MODELS ALSO FORECAST A MID-LATITUDE RIDGE TO
PROPAGATE EASTWARD ACROSS THE EASTERN U.S. DURING THE 3-5 DAY TIME
FRAME...BUT SUFFICIENTLY PROGRESSIVE SUCH THAT IT WOULD NOT BLOCK
GUSTAV'S NORTHWARD PROGRESS. THE MODELS ARE IN GENERALLY GOOD
AGREEMENT ON A TRACK ACROSS THE NORTHWESTERN CARIBBEAN...NEAR OR
OVER THE WESTERN TIP OF CUBA...AND ACROSS THE CENTRAL GULF OF
MEXICO. SOME OF THE MODELS HINT THAT THE HIGH TO THE NORTH LATE IN
THE FORECAST PERIOD COULD FORCE GUSTAV TO TURN A LITTLE BACK TO THE
WEST OVER THE NORTHERN GULF...BUT THESE MODELS ARE CURRENTLY IN THE
MINORITY. THE NEW OFFICIAL TRACK FORECAST DOES SHOW A SLOWING OF
THE FORWARD MOTION AS GUSTAV APPROACHES THE NORTHERN GULF
COAST...AND IS NUDGED JUST A LITTLE TO THE EAST TO BE IN LINE WITH
THE CONSENSUS. RELIABLE MODELS REMAIN ON EITHER SIDE OF THE
FORECAST TRACK...SO ONE SHOULD NOT FOCUS ON THE EXACT OFFICIAL
TRACK.
THE ADVISORY INTENSITY IS KEPT AT 60 KT BASED ON THE EARLIER
AIRCRAFT DATA...AND ANOTHER AIR FORCE PLANE WILL ARRIVE ON THE
SCENE THIS AFTERNOON. VISIBLE IMAGERY SUGGESTS THE CYCLONE
CONTINUES TO REORGANIZE...BUT THE INTERACTION WITH JAMAICA DURING
THE NEXT DAY OR SO MIGHT LIMIT INTENSIFICATION...ALTHOUGH ONLY A
SLIGHT INCREASE IN STRENGTH COULD MAKE GUSTAV A HURRICANE AT ANY
TIME TODAY. AFTER PASSING JAMAICA...GUSTAV WILL ENCOUNTER THE VERY
WARM WATERS OF THE NORTHWESTERN CARIBBEAN WITH ANTICYCLONIC FLOW
ALOFT...FAVORING INTENSIFICATION. ANY INTERACTION WITH THE NARROW
LANDMASS OF WESTERN CUBA SHOULD NOT HAVE MUCH INFLUENCE ON THE
STRENGTH OF GUSTAV OVER THE GULF OF MEXICO...WHERE WATERS WILL BE
WARM BUT WIND SHEAR COULD SLOWLY INCREASE. THE NEW OFFICIAL
INTENSITY FORECAST CALLS FOR A LITTLE FASTER STRENGTHENING OVER THE
NORTHWESTERN CARIBBEAN...BUT IS SIMILAR TO THE PREVIOUS ADVISORY
AND THE INTENSITY CONSENSUS THEREAFTER.