[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 110604
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT 11 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0345 UTC.

...SPECIAL FEATURE...

HURRICANE IVAN CENTERED NEAR 17.4N 77.3W OR ABOUT 50 MILES SW OF
KINGSTON JAMAICA AT 11/0600 UTC MOVING WNW AT 9 KT. MAXIMUM
SUSTAINED WIND SPEED IS 135 KT WITH GUSTS TO 165 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 920 MB. 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 REMAINS WELL ORGANIZED.
THE EYE REMAINS DISTINCT WITH DEEP CONVECTION MORE SYMMETRICAL
IN APPEARANCE. CLOUD TOP TEMPERATURES REMAIN IN THE -70 TO -80
CELSIUS RANGE WITHIN 75/90 NM OF THE CENTER. SCATTERED STRONG
CONVECTION IS WITHIN 120/140 NM OF THE CENTER. SCATTERED
MODERATE CONVECTION IS E OF THE SYSTEM FROM 16N-20N BETWEEN
70W-75W INCLUDING ALL OF HAITI. THE UPPER LEVELS...IVAN
CONTINUES TO BE FLANKED BY A MID/UPPER LEVEL TROUGH TO THE
SW...A SMALL UPPER LEVEL HIGH TO THE NW...AND A BROAD MID/UPPER
LEVEL HIGH TO THE E. THIS REGIME IS MAINTAINING LOW SHEAR AND
GOOD UPPER LEVEL OUTFLOW ESPECIALLY TO THE NW. AN UPPER TROUGH
EXTENDING ACROSS THE BAHAMAS IS FORCING STRONG SUBSIDENCE OVER
THE BAHAMAS TO CENTRAL CUBA AND 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
TOWARDS W CUBA.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC JUST E OF THE CAPE VERDE ISLANDS
IS ALONG 21W/22W S OF 21N MOVING W 10-15 KT. SCATTERED CLUSTERS
OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 7N-16N
BETWEEN 21W-28W.

CENTRAL ATLC TROPICAL WAVE IS ALONG 43W/44W S OF 17N MOVING W
15-20 KT. THE WAVE IS BROAD AND LOW-AMPLITUDE WITH ASSOCIATED
CONVECTION BECOMING BETTER ORGANIZED. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF LINE FROM
12N40W-14N46W.

TROPICAL WAVE LOCATED JUST E OF THE LEEWARD/WINDWARD ISLANDS
ALONG 59W S OF 20N MOVING W 15-20 KT. A 1009 MB LOW IS ALONG THE
WAVE NEAR 16N. A SINGLE BAND OF SCATTERED MODERATE/STRONG
CONVECTION IS WITHIN 60 NM OF LINE FROM 17N47W-19N52W. CLUSTERS
OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM
13N-18N BETWEEN 56W-61W MOVING INTO THE WINDWARD ISLANDS.

...ITCZ...

ITCZ AXIS EXTENDS ALONG 16N10W 7N30W 11N46W 13N57W 10N62W.
SCATTERED MODERATE/STRONG CONVECTION IS MOVING OFF THE COAST OF
AFRICA WITHIN 120 NM FROM 7N-17N. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS WITHIN 45/60 NM OF 5.5N FROM 22W-27W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYERED TROUGH AXIS OVER THE E UNITED STATES INTO THE N
GULF EXTENDS FROM ALONG THE MISSISSIPPI VALLEY. A STRONG UPPER
LEVEL HIGH OVER MEXICO WITH THE ASSOCIATED UPPER LEVEL RIDGE
AXIS EXTENDING N OVER THE CENTRAL U.S. IS FORCING STRONG
SUBSIDENCE S INTO THE NW GULF LIMITING ANY SHOWER ACTIVITY. THE
PERSISTENT SURFACE TROF...FROM THE NE FLORIDA ACROSS THE GULF TO
THE COAST OF MEXICO NEAR VERACRUZ...CONTINUES TO PLAGUE THE GULF
AND N FLORIDA WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS.
ADDITIONALLY...A WEAK UPPER LEVEL TROUGH RETROGRADING FROM THE
YUCATAN PENINSULA INTO THE BAY OF CAMPECHE IS PRODUCING
INCREASING SHOWERS/THUNDERSTORMS OVER S PORTIONS OF MEXICO AND
THE BAY OF CAMPECHE. THE SMALL UPPER LEVEL HIGH TO THE NW OF
HURRICANE IVAN CENTERED NEAR THE ISLE OF YOUTH HAS A RIDGE AXIS
EXTENDING NNE ACROSS CENTRAL FLORIDA INTO THE W ATLC AND IS
ENHANCING THE SHOWERS ASSOCIATED WITH THE SURFACE TROUGH JUST
TO ITS W.

CARIBBEAN...
THE MAJOR FEATURE OVER THE CARIBBEAN IS HURRICANE IVAN WHICH IS
NOW JUST S OF JAMAICA. ASSOCIATED RAINBANDS AND CONTINUE TO
AFFECT HAITI...SE CUBA AND MOVING OVER THE CAYMAN ISLANDS. THE E
CARIBBEAN IS UNDER MODERATE/STRONG SUBSIDENCE IN THE MID-UPPER
LEVELS EFFECTIVELY CAPPING SIGNIFICANT CLOUDS/CONVECTION AND A
STRONG MID/UPPER LEVEL HIGH E OF IVAN.

SUBTROPICAL ATLANTIC...
THE BIG FEATURE OVER THE SUBTROPICAL ATLC IS THE MID-OCEANIC
UPPER TROUGH ACROSS THE ATLC FROM THE NE ATLC 550 NM WNW OF THE
CANARY ISLANDS NEAR 32N26W W TO A SMALL UPPER LOW NEAR 32N47W TO
A VERY LARGE UPPER LOW NEAR 29N63W THEN SW TO A SMALLER
MID/UPPER LOW NEAR 26N73W. THE LARGE UPPER LOW NEAR 63W IS
RETROGRADING 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 AND IS PUSHING SW TO THE COAST OF CUBA. AT THE SURFACE...
SUBTROPICAL RIDGE REMAINS DISRUPTED OVER THE CENTRAL ATLC BY THE
REMNANTS OF A SURFACE TROUGH THAT WAS ALONG 55W. A WEAK RIDGE
EXISTS ACROSS THE W ATLC FROM BERMUDA W TO CENTRAL FLORIDA.

TROPICAL ATLANTIC...
TROPICS ARE DOMINATED BY A PAIR OF UPPER LEVEL HIGHS...ONE OFF
THE COAST OF AFRICA NEAR 15N14W AND A SECOND NEAR 16N41W.
MODERATE SUBSIDENCE AND DRY AIR IS SUPPRESSING SHOWER ACTIVITY
ACROSS THE ENTIRE E ATLC.

$$
WALLACE


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