[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 281500
TCDAT2
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.



FORECAST POSITIONS AND MAX WINDS

INITIAL      28/1500Z 17.9N  76.1W    60 KT
 12HR VT     29/0000Z 17.9N  77.1W    65 KT...NEAR JAMAICA
 24HR VT     29/1200Z 18.4N  79.0W    70 KT
 36HR VT     30/0000Z 19.1N  80.8W    80 KT
 48HR VT     30/1200Z 20.2N  82.6W    95 KT
 72HR VT     31/1200Z 23.5N  86.0W   100 KT
 96HR VT     01/1200Z 27.0N  89.0W   100 KT
120HR VT     02/1200Z 29.5N  91.0W   100 KT...NEAR COAST OF LA

$$
FORECASTER KNABB

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