[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 102356
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI 10 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
2332 UTC.

...SPECIAL FEATURE...

HURRICANE IVAN CENTERED NEAR 17.3N 76.5W OR ABOUT 45 MILES SSE
OF KINGSTON JAMAICA AT 11/0000 UTC MOVING WNW 10 KT. MAXIMUM
SUSTAINED WIND SPEED HAS INCREASED TO 130 KT WITH GUSTS TO 160
KT. THE LATEST MINIMUM CENTRAL PRESSURE REPORTED FROM A
RECONNAISSANCE AIRPLANE IS 926 MB...A 14 MB DROP OVER A 4-5 HOUR
PERIOD. SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC OR
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SATELLITE IMAGERY
INDICATES THAT IVAN IS BECOMING BETTER ORGANIZED. AFTER
APPEARING A BIT RAGGED EARLIER TODAY...THE EYE HAS BECOME MUCH
MORE DISTINCT AND DEEP CONVECTION IS NOW WRAPPING AROUND THE W
PORTION OF THE STORM PRODUCING A MORE SYMMETRIC APPEARANCE.
CLOUD TOP TEMPERATURES HAVE BEEN FLUCTUATING THROUGHOUT THE DAY
AND ARE CURRENTLY IN THE -70 TO -80 CELSIUS RANGE. IVAN IS
GENERATING INTENSE CONVECTION WITHIN 125-150 NM OVER THE E
SEMICIRCLE AND 75-100 NM OVER THE W SEMICIRCLE. THE ACTIVITY IS
CURRENTLY SPREADING OVER JAMAICA AND CONDITIONS ARE RAPIDLY
DETERIORATING OVER THE ISLAND. OUTER RAINBANDS EXTEND AS FAR N
AS THE S BAHAMAS AND TURKS/CAICOS INCLUDING S PORTIONS OF
HISPANIOLA AND E CUBA. IN THE UPPER LEVELS...IVAN CONTINUES TO
BE FLANKED BY AN UPPER LEVEL TROUGH TO THE WEST AND ANTICYCLONE
TO THE E. THIS REGIME IS MAINTAINING LOW SHEAR AND GOOD UPPER
LEVEL OUTFLOW ESPECIALLY TO THE NORTH WITH A WELL-DEFINED
POLEWARD OUTFLOW JET EXTENDING ACROSS E CUBA AND THE SRN BAHAMAS
INTO THE ATLC. AN UPPER LOW NE OF THE BAHAMAS DRIFTING SW MAY
IMPINGE UPON THE OUTFLOW DURING THE NEXT DAY OR SO.
OTHERWISE...THE ENVIRONMENT APPEARS FAVORABLE FOR IVAN TO REMAIN
A MAJOR HURRICANE AS IT TRACKS OVER OR NEAR JAMAICA THEN TOWARDS
W CUBA.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC JUST E OF THE CAPE VERDE ISLANDS
ALONG 21W/22W S OF 22N MOVING W 10-15 KT. AN EARLIER QUIKSCAT
PASS INDICATES A WEAK LOW MAY ACCOMPANY THE WAVE NEAR 10N/11N.
HOWEVER...CONVECTION IS LIMITED AND POORLY ORGANIZED AT THIS
TIME. WIDELY SCATTERED MODERATE CONVECTION FROM 5N-13N BETWEEN
21W-28W.

CENTRAL ATLC TROPICAL WAVE ALONG 40W/41W S OF 18N MOVING W 15-20
KT. THE WAVE IS BROAD AND LOW-AMPLITUDE WITH ASSOCIATED
CONVECTION REMAINING DISORGANIZED. THERE ARE NO SIGNS OF
DEVELOPMENT. WIDELY SCATTERED MODERATE CONVECTION FROM 3N-9N
BETWEEN 38W-43W AND FROM 12N-17N BETWEEN 40W-48W.

TROPICAL WAVE LOCATED JUST E OF THE LEEWARD/WINDWARD ISLANDS
ALONG 57W S OF 21N MOVING W 15-20 KT. A 1011 MB LOW ACCOMPANIES
THE WAVE NEAR 15N. THE NRN PORTION OF THE WAVE IS INTERACTING
WITH AN UPPER LEVEL LOW WHICH IS PRODUCING CONVECTION N OF 20N.
S OF 20N...CONVECTION IS WEAKER AND LESS NUMEROUS WITH SCATTERED
MODERATE ACTIVITY WITHIN 60 NM EITHER SIDE OF A LINE FROM
BARBADOS TO 20N57W. THIS ACTIVITY IS MOVING WEST AND MAY AFFECT
THE LESSER ANTILLES OVERNIGHT.

...ITCZ...

ITCZ AXIS EXTENDS ACROSS W AFRICA TO THE MAURITANIA/WESTERN
SAHARA BORDER...THEN SWD ALONG 11N25W 12N40W 15N50W 7N60W 8N70W
7N80W. ASIDE FROM CONVECTION OUTLINED WITH TROPICAL
WAVES...SCATTERED MODERATE CONVECTION FOR MUCH OF
COLOMBIA...PANAMA...AND COSTA RICA.

...DISCUSSION...

GULF OF MEXICO...
A PERSISTENT SURFACE TROF...FROM THE FLORIDA PANHANDLE TO THE
COAST OF MEXICO NEAR VERACRUZ...CONTINUES TO PLAGUE THE GLFMEX
AND N FLORIDA WITH SCATTERED SHOWERS/THUNDERSTORMS.
ADDITIONALLY...A WEAK UPPER LEVEL TROUGH RETROGRADING ACROSS THE
YUCATAN PENINSULA IS PRODUCING INCREASING SHOWERS/THUNDERSTORMS
OVER S PORTIONS OF MEXICO AND THE BAY OF CAMPECHE.  IN
FACT...MUCH OF THE AREA E OF A LINE FROM TAMPICO MEXICO TO THE
FLORIDA/ALABAMA BORDER IS EXPERIENCING SCATTERED
SHOWERS/THUNDERSTORMS SAVE THE S PORTION OF FLORIDA WHERE DRY
AIR HAS MOVED IN FROM THE BAHAMAS.  OVER THE NW GLFMEX...STRONG
MIDDLE TO UPPER LEVEL SUBSIDENCE AND DRY AIR ASSOCIATED WITH A
MID-LATITUDE TROUGH OVER THE MISSISSIPPI VALLEY IS LIMITING
SIGNIFICANT CONVECTION.  THIS UPPER LEVEL TROUGH WEAKENS/SPLITS
A MID-LEVEL RIDGE WHICH EXTENDS FROM THE W ATLC SW OVER FLORIDA
AND THE CENTRAL GLFMEX.  THIS WEAKNESS IN THE MID-LEVEL RIDGE IS
EXPECTED TO REMAIN OVER THE CENTRAL GLFMEX DURING THE NEXT DAY
OR SO THEN GRADUALLY SHIFT EWD COURTESY OF A SHORTWAVE TROUGH
DROPPING SEWD FROM THE CENTRAL UNITED STATES. THIS EVOLUTION
WILL PLAY A PIVOTAL ROLE IN THE EVENTUAL TRACK OF HURRICANE
IVAN. MEANWHILE...THE RETROGRADING UPPER TROUGH OVER THE YUCATAN
PENINSULA WILL MOVE SLOWLY OVER THE BAY OF CAMPECHE ENHANCING
SHOWER/THUNDERSTORMS ACTIVITY S OF 25N.

CARIBBEAN...
THE MAJOR FEATURE OVER THE CARIBBEAN IS HURRICANE IVAN WHICH IS
NOW APPROACHING THE ISLANDS OF JAMAICA. ASSOCIATED RAINBANDS AND
CONTINUE TO AFFECT S PORTIONS OF HISPANIOLA AND ARE LIKELY
PRODUCING STRONG WINDS AND LOCALLY HEAVY RAINFALL. OUTER
RAINBANDS ARE ALSO BEGINNING TO AFFECT THE E CUBA.  THE REST OF
THE CARIBBEAN IS UNDER MODERATE/STRONG SUBSIDENCE IN THE
MID-UPPER LEVELS EFFECTIVELY CAPPING SIGNIFICANT
CLOUDS/CONVECTION.

SUBTROPICAL ATLANTIC...
THE BIG FEATURE OVER THE SUBTROPICAL ATLC IS THE MID-OCEANIC
UPPER TROUGH WHICH CONTINUES TO FRACTURE FORMING A VERY LARGE
UPPER LOW NEAR 29N60W.  THE UPPER LOW IS NOW RETROGRADING
QUICKLY WESTWARD AND ERODING THE MID/UPPER LEVEL RIDGE WHICH HAS
PERSISTED OVER THE W ATLC FOR SEVERAL DAYS.  STRONG SUBSIDENCE
AND DRY AIR WITH THE UPPER LOW IS SPREADING WESTWARD AND NOW
COVERS A GOOD PORTION OF THE W ATLC TO THE SE UNITED STATES
COAST.  AS A RESULT...DRY/TRANQUIL WEATHER PREVAILS W OF 65W.
OVER THE CENTRAL ATLC...DIFFLUENT UPPER LEVEL FLOW IS PRODUCING
CLOUDINESS AND SHOWERS/THUNDERSTORMS NEAR A SURFACE TROUGH ALONG
55W.  THIS ACTIVITY EXTENDS FROM 20N-30N AND IS BOUNDED BY
50W-60W.  FURTHER E...AN E/W ORIENTED RIDGE LIES ALONG 27N
BETWEEN AFRICA AND 50W.  A WEAKNESS EXIST IN THE RIDGE FROM THE
CANARY ISLANDS TO THE CAPE VERDE ISLANDS COURTESY OF AN UPPER
TROUGH.  SUBSIDENCE AND DRY AIR WITH THE TROUGH IS LIMITING
CONVECTIVE ACTIVITY E OF 30W.  THE UPPER TROUGH WILL LIKELY BE
REINFORCED BY A MID-LATITUDE TROUGH CURRENTLY DROPPING SEWD OVER
THE AZORES. THIS WILL CAUSE FURTHER DEGRADATION OF THE MID-LEVEL
RIDGE OVER THE E ATLC.  AT THE SURFACE...SUBTROPICAL RIDGE
REMAINS DISRUPTED OVER THE CENTRAL ATLC BY A TROUGH ALONG 55W. A
WEAK RIDGE EXISTS OVER THE W ATLC FROM JUST W OF BERMUDA TO
CENTRAL FLORIDA. EARLIER VISIBLE SATELLITE IMAGERY SHOWS A LARGE
AREA OF AFRICAN DUST AND DRY AIR E OF 50W MOVING WESTWARD.

TROPICAL ATLANTIC...
THE UPPER LEVEL FLOW OVER THE TROPICS IS DOMINATED BY AN
EXPANSIVE MID-UPPER LEVEL RIDGE EXTENDING FROM E CUBA ENE
20N20W.  AN UPPER LEVEL TROUGH EXTENDING SWD FROM THE CANARY
ISLANDS TO THE JUST W OF THE CAPE VERDE ISLANDS IS PRODUCING A
WEAKNESS IN THE MID-LEVEL RIDGE E OF 35W.  MODERATE SUBSIDENCE
AND DRY MIDDLE TO UPPER LEVEL AIR IS SUPPRESSING ITCZ/TROPICAL
WAVE ACTIVITY E OF 35W.  ADDITIONALLY...AFRICAN DUST AND DRY
AIR IS NOTED N OF THE ITCZ E OF 50W.

$$
RHOME



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