[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 162358
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU 16 SEP 2004

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM JEANNE IS CENTERED NEAR 19.2N 69.4W...OR 65 MILES
NE OF SANTO DOMINGO DOMINICAN REPUBLIC...AT 17/0000 UTC DRIFTING
TO THE NW. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO
75 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB. SEE LATEST
NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC FOR MORE
DETAILS. THE CENTER OF JEANNE IS JUST BARELY VISIBLE ON THE 2 KM
RADAR IMAGERY FROM SAN JUAN PUERTO RICO...AND IT LOOKS LIKE IT
IS ALONG THE N COAST OF THE DOMINICAN REPUBLIC OVER CABO SAMANA.
JEANNE IS A SMALL STORM WITH A CLOUD FIELD THAT ONLY EXTENDS OUT
ABOUT 100 NM FROM THE CENTER...BUT A PERSISTENT TRAILING BAND
HAS BEEN SITTING TO THE E OVER PARTS OF THE VIRGIN ISLANDS AND
PUERTO RICO ALL DAY. THE AIRPORT IN CHARLOTTE AMALIE ST. THOMAS
AIRPORT STOPPED REPORTING AROUND 1730 UTC...BUT SEVERAL USGS
GAUGES ACROSS THE ISLAND HAVE REPORTED ANYWHERE BETWEEN 7-8.5"
OF RAIN OVER THE PAST 24 HOURS. EVEN MORE IMPRESSIVE...THE
ISLAND OF VIEQUES HAS REPORTED A STORM TOTAL ACCUMULATION OF
JUST OVER 23" AND IT'S STILL RAINING! (THANKS TO WFO SAN JUAN
FOR THIS INFORMATION). THERE IS NO DOUBT THAT VERY HEAVY
RAINFALL IS ALSO FALLING OVER THE DOMINICAN REPUBLIC...
ESPECIALLY NOW THAT VERY STRONG CONVECTION IS NOW DEVELOPING TO
THE SE OF THE CENTER OF CIRCULATION. SCATTERED MODERATE/STRONG
CONVECTION FROM 17N-21N BETWEEN 67W-71W OVER THE DOMINICAN
REPUBLIC AND COASTAL WATERS. SCATTERED STRONG FROM 16N-20N
BETWEEN 63.5W-67W EXTENDING ACROSS THE BRITISH AND U.S. VIRGIN
ISLANDS AND FAR E PUERTO RICO.

TROPICAL STORM IVAN IS CENTERED NEAR 33.1N 87.0W...OR 25 MILES
SSW OF BIRMINGHAM ALABAMA...AT 16/2100 UTC MOVING NNE 12 KT.
MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO 50 KT WITH GUSTS
TO 60 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 980 MB. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. THE LARGE CLOUD SHIELD
ASSOCIATED WITH IVAN HAS EXPANDED NWD ACROSS MUCH OF THE OHIO
VALLEY... MID-ATLANTIC...AND SOUTHEAST UNITED STATES. WSR-88D
IMAGERY INDICATES THAT THE LARGE AREA OF VERY HEAVY RAINFALL HAS
SHIFTED FROM A LINE THROUGH CENTRAL MISSISSIPPI/ALABAMA/GEORGIA
NWD INTO TENNESSEE AND ERN KENTUCKY WITH MORE SCATTERED
SHOWERS/TSTMS IN BANDS ACROSS SE ALABAMA/SW GEORGIA AS WELL AS
ACROSS THE CAROLINAS. ONE PARTICULARLY STRONG SPIRAL BAND IS
ROTATING THROUGH NRN GEORGIA...NOW JUST E OF ATLANTA...AND COULD
BE PRODUCING TORNADOES WELL E OF THE CENTER OF CIRCULATION.
NUMEROUS MODERATE CONVECTION FROM 32.5N-38N BETWEEN 82.5W-89W
AND WIDELY SCATTERED MODERATE ELSEWHERE FROM 30N-36N BETWEEN
79W-86W.

TROPICAL DEPRESSION TWELVE HAS FORMED NEAR 11.4N 32.8W...OR 670
MILES WSW OF THE CAPE VERDE ISLANDS...AT 16/2100 UTC MOVING W 14
KT. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. THE DEPRESSION HAS MAINTAINED A SIZEABLE BAND
OF CONVECTION OVER ITS N AND W QUADRANTS BUT MORE STRONG
CONVECTION HAS RECENTLY BEEN DEVELOPING CLOSER TO THE LOW-LEVEL
CENTER. WATER VAPOR IMAGERY INDICATES THAT THE OUTFLOW IS MOST
IMPRESSIVE OVER THE NW SEMICIRCLE...WHICH PARTLY INDICATES THAT
THERE IS A SLIGHT AMOUNT OF ELY SHEAR OVER THE SYSTEM. SCATTERED
MODERATE/STRONG CONVECTION FROM 9.5N-16N BETWEEN 29W-37W.

...TROPICAL WAVES...

CENTRAL ATLANTIC TROPICAL WAVE ALONG 49W/50W S OF 20N MOVING W
15 KT. THE WAVE CONTINUES TO MOVE W IN TANDEM WITH THE LEADING
EDGE OF AN EXTENSIVE SAHARAN AIR LAYER (SAL)...WHICH EXTENDS
ALONG A NW/SE LINE FROM 22N54W TO 14N50W 10N40W. SOME TSTMS HAVE
PERSISTED ALONG THE MAIN WAVE AXIS WITH SCATTERED MODERATE
CONVECTION IN A SMALL AREA FROM 13N-15.5N BETWEEN 47.5W-50W.
OTHER WIDELY SCATTERED MODERATE HAS DEVELOPED FARTHER N ALONG
THE SAL FRONT FROM 18N-22N BETWEEN 49W-54W.

A WEAK TROPICAL WAVE IS MOVING ACROSS BELIZE AND GUATEMALA ALONG
89W S OF 19N MOVING W 10 KT. THE WAVE'S POSITION HAS BEEN HELD
BACK COMPARED TO THE PREVIOUS POSITION BASED ON A LOW-LEVEL
CIRCULATION S OF EL SALVADOR IN THE E PACIFIC. ISOLATED MODERATE
CONVECTION OVER PARTS OF HONDURAS...GUATEMALA...AND SE MEXICO.

...ITCZ...

ITCZ EMERGES FROM THE COAST OF GUINEA-BISSAU ALONG 11.5N16W
12N20W 14N30W...THEN ALONG 8N32W 13N46W...THEN ALONG 9N51W 7N63W
9N76W. SCATTERED MODERATE CONVECTION S OF THE AXIS FROM 4N-10N
BETWEEN 16W-23W. WIDELY SCATTERED MODERATE FROM 5N-8N BETWEEN
24W-30W AND FROM 4N-10N BETWEEN 36W-42W. SCATTERED MODERATE OVER
N COLOMBIA AND THE ADJACENT COASTAL WATERS FROM 8N-12N BETWEEN
72W-76W.

...DISCUSSION...

GULF OF MEXICO...
HURRICANE IVAN HAS EXITED THE AREA AND IS NOW DUMPING VERY HEAVY
FLOODING RAINFALL ACROSS THE SOUTHEAST U.S. AND TENNESSEE
VALLEY. SURFACE WINDS ACROSS THE GULF ARE GENERALLY W/SWLY
AROUND THE PERIPHERAL CIRCULATION OF IVAN...AND SOME OF THE
BUOYS ACROSS THE E GULF ARE STILL REPORTING SUSTAINED WINDS
BETWEEN 20 AND 30 KT. THE GOOD NEWS IS THAT THE WEATHER HAS
IMPROVED GREATLY ACROSS THE AREA WITH MOSTLY FAIR SKIES...WITH
THE EXCEPTION OF PATCHY SHOWERS WITHIN 180 NM OF THE MEXICAN
COAST. AN UPPER LEVEL RIDGE HAS BEEN LEFT BEHIND IN THE WAKE OF
IVAN AND EXTENDS FROM AN ANTICYCLONE ALONG THE NE MEXICO COAST
EWD ACROSS CNTRL FLORIDA INTO THE W ATLC. THE VERY DRY AIR WHICH
EXTENDS W OF ABOUT 85W IS BEING REINFORCED BY MODERATE/STRONG
SUBSIDENCE ALONG THE LOUISIANA/TEXAS COAST WHERE A SHORTWAVE
TROF IS PUSHING IVAN TO THE NE.

WEST ATLANTIC...
BROAD N/NE UPPER LEVEL FLOW EXTENDS WELL E OF HURRICANE IVAN AND
IS PRODUCING A CONSIDERABLE AMOUNT OF STRONG NELY SHEAR NEAR THE
BAHAMAS. IN ADDITION...A REMNANT UPPER TROF SNAKES ITS WAY
ACROSS THE AREA ALONG 26N60W 24N67W 21N73W WITH DRY AIR
EXTENDING UP TO 250 NM N OF T.S. JEANNE. JEANNE ITSELF IS TRYING
TO ESCAPE THE RUGGED TERRAIN OF HISPANIOLA AND IF IT DOES THIS
SUCCESSFULLY...IT WILL THEN HAVE TO CONTEND WITH THE HOSTILE
ENVIRONMENT AHEAD OF IT.

CARIBBEAN...
THE BROAD NELY UPPER FLOW OVER THE W ATLC EXTENDS ALL THE WAY
DOWN INTO THE W CARIBBEAN...OR JUST TO THE W OF AN INVERTED
UPPER TROF WHICH EXTENDS FROM E PANAMA TO 17N72W JUST S OF
HISPANIOLA. THERE IS SOME DRY AIR ACROSS PARTS OF THE CARIBBEAN
BASIN BUT ALL IN ALL THERE IS ENOUGH MOISTURE MILLING AROUND TO
ALLOW SPORADIC TSTMS ESPECIALLY OVER LAND AREAS OF SOUTH
AMERICA...CENTRAL AMERICA...AND CUBA. AN UPPER HIGH IS LOCATED
TO THE E OF T.S. JEANNE OVER THE NRN LEEWARD ISLANDS AND THE
ASSOCIATED DIVERGENCE HAS ALLOWED VERY HEAVY TSTMS TO PERSIST
OVER THE SAME AREAS FOR THE PAST 2 DAYS.

SUBTROPICS E OF 60W...
A TIGHTLY-WOUND MID/UPPER LOW IS LOCATED ABOUT 800 NM NE OF T.S.
JEANNE NEAR 27N57W BUT IS ATTACHED TO A MUCH LARGER TROF
EXTENDING INTO THE AREA BETWEEN 54W-64W. UPPER LEVEL MOISTURE
FROM JEANNE IS BEING DRAWN NEWD ON THE E SIDE OF THE LOW/TROF
AND BROAD DIFFLUENCE IS SUPPORTING WIDELY SCATTERED MODERATE
CONVECTION WITHIN 250 NM ON EITHER SIDE OF A SFC TROF ALONG
31N48W 25N62W. SFC RIDGING EXTENDS INTO THE AREA FARTHER E ALONG
28N45W 32N31W WITH TWO DISTINCT MID/UPPER LOWS MEANDERING OVER
THE AREA NEAR 28N33W AND 29N17W (OVER THE CANARY ISLANDS). THE
EASTERNMOST LOW DEVELOPED AS A CUT-OFF FROM A MUCH LARGER TROF
WHICH IS MOVING ACROSS EUROPE...AND IS BRINGING MUCH DRIER AIR
IN THE UPPER LEVELS N OF 20N E OF 28W.

TROPICAL ATLANTIC...
AN UPPER LEVEL RIDGE EXTENDS TO THE SE OF T.S. JEANNE FROM THE
WINDWARD ISLANDS NEWD BEYOND 20N53W...AND BROAD NELY FLOW TO THE
W OF THE RIDGE AXIS COVERS THE AREA S OF 16N BETWEEN 37W-62W.
THE SRN END OF AN UPPER TROF EXTENDS S OF ONE OF THE SUBTROPICAL
UPPER LOWS ALONG 22N40W 17N47W. FARTHER E...STRONGER RIDGING IS
DEVELOPING OVER THE E ATLC AS T.D. TWELVE INTENSIFIES AND AN
UPPER HIGH MAY BE LOCATED NEAR 14N30W. THE HIGH IS INCREASING
THE DIVERGENCE OVER THE DEPRESSION AND THUS IS SUPPORTING THE
STRONG CONVECTIVE BANDING.

$$
BERG


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