[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 031817
TWDAT

TROPICAL WEATHER DISCUSSION...CORRECTION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 03 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION GUSTAV IS DRIFTING NORTH-NORTHEAST WITH
HEAVY RAIN CONTINUING OVER THE LOWER MISSISSIPPI VALLEY. AT
3/1500Z...ITS CENTER IS LOCATED NEAR 33.8N 94.3W OR ABOUT 30
MILES...50 KM...NORTHWEST OF TEXARKANA ARKANSAS AND ABOUT 105
MILES...170 KM...SOUTH OF FORT SMITH ARKANSAS MOVING N-NE AT
NEAR 2 KT...5 KM/HR. THIS MOTION WILL CONTINUE WITH A GRADUAL
TURN TOWARD THE NORTHEAST AND AN INCREASE IN FORWARD SPEED TODAY
AND THURSDAY. MAXIMUM SUSTAINED WINDS ARE 22 KT WITH HIGHER
GUSTS. THE MINIMUM CENTRAL PRESSURE IS 997 MB. FLASH FLOOD
WARNINGS ARE IN EFFECT FOR A LARGE PART OF CENTRAL AND
NORTHEASTERN LOUISIANA...WESTERN MISSISSIPPI...SOUTHEASTERN
ARKANSAS...PORTIONS OF EASTERN OKLAHOMA AND NORTHWESTERN
ARKANSAS. STORM TOTAL RAINFALL AMOUNTS UP TO 16 INCHES HAVE BEEN
REPORTED IN PARTS OF LOUISIANA. SATELLITE PICTURES AND DOPPLER
RADAR CONTINUE TO SHOW THE CIRCULATION OF GUSTAV WITH A NARROW
OUTER RAINBAND OVER THE NW CORNER OF THE GULF.

AT 03/1800 TROPICAL STORM HANNA IS CENTERED NEAR 21.4N 72.0W
WEST OR JUST SOUTH OF THE CAICOS ISLANDS. HANNA IS MOVING TOWARD
THE N-NW AT 9 KT. A TURN TO THE NORTHWEST WITH AN INCREASE IN
FORWARD SPEED IS EXPECTED OVER THE NEXT 24 HOURS. ON THE
FORECAST TRACK...THE CENTER OF HANNA SHOULD BE MOVING THROUGH OR
JUST EAST OF THE CENTRAL AND NORTHWESTERN BAHAMAS OVER THE NEXT
COUPLE OF DAYS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB.
MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT.
LITTLE CHANGE IN STRENGTH IS FORECAST TODAY...BUT HANNA COULD
REGAIN HURRICANE STRENGTH TOMORROW OR ON FRIDAY. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
FOR MORE DETAILS. HANNA IS EXPECTED TO PRODUCE RAINFALL TOTALS
OF 4 TO 8 INCHES...WITH MAXIMUM ISOLATED AMOUNTS OF 12
INCHES...OVER THE SOUTHEASTERN BAHAMAS...THE TURKS AND CAICOS
ISLANDS...AND EASTERN CUBA. RAINFALL TOTALS OF 6 TO 10
INCHES...WITH ISOLATED MAXIMUM AMOUNTS OF UP TO 15 INCHES...ARE
POSSIBLE OVER
HISPANIOLA...WHERE THESE RAINS COULD CAUSE LIFE-THREATENING
FLASH FLOODS AND MUD SLIDES. MODERATE TO LOCALLY HEAVY RAINFALL
IS POSSIBLE ALONG THE EAST COAST OF FLORIDA BY FRIDAY MORNING.

TROPICAL STORM IKE IS ALMOST A HURRICANE. AT 3/1500 UTC... ITS
CENTER IS NEAR 20.8N 51.2W OR ABOUT 645 NM EAST-NORTHEAST OF THE
LEEWARD ISLANDS MOVING W-NW AT 16 KT. THIS GENERAL MOTION IS
EXPECTED TO CONTINUE THROUGH THURSDAY...FOLLOWED BY A TURN TO
THE WEST ON FRIDAY...TAKING IKE OVER THE OPEN WATERS OF THE
WEST-CENTRAL ATLANTIC DURING THE NEXT COUPLE OF DAYS. IT IS TOO
EARLY TO DETERMINE WHAT IF ANY LAND AREAS MIGHT BE DIRECTLY
AFFECTED BY IKE. ESTIMATED MINIMUM CENTRAL PRESSURE IS 991 MB.
MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT.
STRENGTHENING IS FORECAST DURING THE NEXT DAY OR TWO...AND IKE
IS FORECAST TO BECOME A HURRICANE LATER TODAY. STEADY
STRENGTHENING IS FORECAST AT DAYS 3-5...AND IKE COULD REACH
MAJOR HURRICANE STATUS BEFORE FIVE DAYS PASS. SEE LATEST NHC
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS. IKE IS WRAPPING UP SOME SOLID CONVECTIVE
BANDING AS VIEWED IN VISIBLE IMAGERY. IT IS MOVING ALONG THE
SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE OVER THE CENTRAL
ATLANTIC.

TROPICAL STORM JOSEPHINE IS CENTERED NEAR 13.8N 28.8W AT 03/1500
UTC OR ABOUT 265 NM...485 KM...W-SW OF THE SOUTHERNMOST CAPE
VERDE ISLANDS MOVING W AT 9 KT. A TURN TOWARD THE WEST-NORTHWEST
WITH AN INCREASE IN FORWARD SPEED IS EXPECTED DURING THE NEXT
COUPLE OF DAYS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB.
MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 KT.
LITTLE CHANGE IN STRENGTH IS FORECAST THROUGH THURSDAY...BUT A
WEAKENING TREND IS FORECAST TO BEGIN ON FRIDAY. WATER VAPOR
IMAGERY SHOWS UPPER-LEVEL WESTERLY FLOW...ASSOCIATED WITH A
TROUGH TO THE WEST...IS BEGINNING TO AFFECT JOSEPHINE. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS. CONVECTION HAS SLIGHTLY
DIMINISHED OVER THE PAST FEW HOURS...AND JOSEPHINE NOW LOOKS
LESS ORGANIZED THAN THIS MORNING.

...TROPICAL WAVES...
THE TROPICAL WAVE THAT WAS ALONG 62W ON THE 0600 UTC SURFACE MAP
IS NO LONGER DISCERNIBLE. IT WAS ABSORBED BY THE LARGE
CIRCULATION OF T.S. HANNA.

A NEW TROPICAL WAVE IS JUST MOVING OFF THE AFRICAN COAST. THE
VERTICAL SOUNDING FROM DAKAR IS STILL SHOWING NE WINDS AT LOW
LEVELS. AN EARLIER QSCAT PASS INDICATED A CYCLONIC CIRCULATION
NEAR 11N16W. WILL WAIT FOR MORE DATA BEFORE PLACING THE WAVE ON
THE SURFACE MAP.

...THE ITCZ...

THE ITCZ AXIS IS PRETTY WEAK TODAY. IT IS ANALYZED ALONG 7N12W
10N25W 10N32W 8N45W 10N60W. ONLY ISOLATED MODERATE CONVECTION IS
SEEN ALONG THE AXIS. MOST THE MODERATE TO STRONG CONVECTION IS
RELATED TO THE TROPICAL CYCLONES MENTIONED ABOVE.

...DISCUSSION...

GULF OF MEXICO...
A WEAK SURFACE RIDGE IS POSITIONED ACROSS THE GULF OF MEXICO IN
THE WAKE OF T.D. GUSTAV THAT IS INLAND OVER THE LOWER
MISSISSIPPI VALLEY. AN AREA OF SHOWERS WITH ISOLATED TSTMS HAS
DEVELOPED OVER THE BAY OF CAMPECHE LIKELY ASSOCIATED WITH A 1007
MB SFC LOW THAT IS LOCATED NEAR 19N94W AND A DIFFLUENT PATTERN
ALOFT. AN UPPER-LEVEL HIGH CENTERED OVER THE BAY OF CAMPECHE IS
ENHANCING THIS CONVECTIVE ACTIVITY. THIS HIGH EXTENDS A RIDGE NE
OVER MOST OF THE GULF...THE SE CONUS...FLORIDA...WEST-CENTRAL
CUBA...THE NW CARIBBEAN AND MOST OF CENTRAL AMERICA. MODERATE TO
STRONG SUBSIDENCE/DRY AIR IS NOTED OVER THE WESTERN GULF N OF
23N W OF 90W.

CARIBBEAN SEA...
THE MAIN WEATHER MAKER ACROSS THE BASIN IS T.S. HANNA. AREAS OF
HEAVY RAINFALL...GUSTY WINDS AND LOCALIZED FLOODING...ASSOCIATED
WITH THE OUTER RAINBANDS OF THIS TROPICAL CYCLONE HAVE BEEN
AFFECTING LARGE SECTIONS OF PUERTO RICO AND THE US/UK VIRGIN
ISLANDS AS WELL AS PARTS OF DOMINICAN REPUBLIC PARTICULARLY THE
SOUTH COAST AND COASTAL WATERS...INCLUDING ALSO THE MONA AND
ANEGADA PASSAGES. RAINBANDS ASSOCIATED WITH THE OVERALL
CIRCULATION OF HANNA AREA ALSO NOTED OVER THE EAST AND CENTRAL
CARIBBEAN. WESTERLY SHEAR AND DRY AIR ASSOCIATED WITH THE UPPER
LOW SPINNING OVER THE CENTRAL BAHAMAS CONTINUES TO INHIBIT THE
DEVELOPMENT OF HANNA...BUT THESE CONDITIONS SHOULD DIMINISH OVER
THE NEXT COUPLE OF DAYS. STRONG UPPER NLY WINDS DOMINATES THE
WESTERN CARIBBEAN. STRONG SW WINDS ARE BLOWING ACROSS THE N
CENTRAL CARIBBEAN...ESPECIALLY IN THE WINDWARD PASSAGE WHILE
UNUSUAL W WINDS ARE OBSERVED WELL S TOWARD THE COAST OF COLOMBIA
DUE TO HANNA'S LARGE CIRCULATION.

ATLANTIC OCEAN...
THREE TROPICAL STORMS ARE LOCATED IN THE DISCUSSION AREA. FROM
EAST TO WEST...JOSEPHINE...IKE AND HANNA. THE LAST ONE IS
IMPACTING THE SE BAHAMAS. SEE SPECIAL FEATURES ABOVE FOR
DETAILS. UPPER RIDGE CENTERED IN THE BAY OF CAMPECHE EXTENDS
INTO THE WRN ATLC W OF 78W. AN UPPER-LEVEL LOW OVER THE CENTRAL
BAHAMAS HAS A TROUGH EXTENDING SOUTH OVER EASTERN CUBA. A LARGE
UPPER LEVEL HIGH CENTERED NEAR 30N48W EXTENDS A RIDGE AXIS INTO
THE TROPICAL ATLC REACHING 10N. AN UPPER LEVEL TROUGH EXTENDS SW
ACROSS THE ERN ATLC FROM AN UPPER LEVEL LOW NOW LOCATED NEAR
22N31W. LOCATED NORTH OF THE CANARY ISLANDS NEAR 31N17W.
UPPER-LEVEL ELY WINDS DOMINATE MOST OF THE DEEP TROPICS W OF
35W. AT THE SURFACE...A 1027 MB HIGH LOCATED NEAR 36N40W EXTENDS
A RIDGE OVER PARTS OF THE CENTRAL AND ERN ATLC E OF 48W. THE
TAIL END OF A FRONT...AS A SURFACE TROUGH...ENTERS THE AREA NEAR
31N62W THEN CONTINUES SW TO 28N65W.

$$
GR





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