[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 100237 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU 09 SEP 2004

...CORRECTED FOR LATEST INFORMATION ON IVAN...

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...

THE CENTER OF HURRICANE IVAN...AT 10/0000 UTC...WAS NEAR 15.2N
72.8W OR ABOUT 325 MILES SE OF KINGSTON JAMAICA. IVAN IS MOVING
WNW AT 11 KT. MAXIMUM SUSTAINED WIND SPEED IS 130 KT WITH GUSTS
TO 160 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 923 MB. SEE LATEST
NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT4/WTNT34 KNHC OR MIATCMAT4/WTNT24 KNHC FOR MORE
DETAILS. IVAN CONTINUES TO DEMONSTRATE A VERY IMPRESSIVE
SATELLITE SIGNATURE WITH NUMEROUS STRONG CONVECTION WITHIN 60-90
NM RADIUS OF THE CENTER. ADDITIONALLY...OUTER RAINBANDS EXTEND
NWD TO HISPANIOLA AND SWD TO 12N.  GUSTY WINDS AND HEAVY RAINS
CAN BE EXPECTED WITHIN THESE OUTER BANDS ESPECIALLY ALONG THE S
COAST OF HISPANIOLA WHICH HAS BEEN EXPERIENCING RECURRING BANDS
DURING THE LAST FEW HOURS.  THE EYE REMAINS CLEAR AND WELL
DEFINED IN SATELLITE IMAGERY MEASURING APPROXIMATELY 15-20 NM.
IVAN IS WITHIN A VERY FAVORABLE UPPER LEVEL ENVIRONMENT
COMPRISED OF AN UPPER LEVEL LOW OVER THE W CARIBBEAN JUST E OF
NICARAGUA/ HONDURAS AND A WELL DEFINED UPPER LEVEL ANTICYCLONE
OVER THE E CARIBBEAN. THIS UPPER LEVEL REGIME IS PRODUCING
DIFFLUENT FLOW OVER IVAN WITH LOW VERTICAL SHEAR.
ADDITIONALLY...UPPER-LEVEL OUTFLOW IS IMPRESSIVE OVER ALL
QUADRANTS AND A WELL-ESTABLISHED OUTFLOW CHANNEL IS NOTED TO THE
NORTH ALONG 21N. BOTTOM LINE...IVAN IS EXPECTED TO REMAIN A VERY
DANGEROUS HURRICANE AS IT MOVES WNW THROUGH THE CENTRAL
CARIBBEAN TOWARD JAMAICA.

...TROPICAL WAVES...
TROPICAL WAVE OVER THE E ATLC ALONG 35N S OF 17N MOVING W NEAR
15 KT.  THE WAVE HAS NOT BECOME ANY BETTER ORGANIZED DURING THE
LAST SEVERAL HOURS BUT CONVECTION HAS INCREASED. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION FROM 4N-9N BETWEEN 36W-43W.

TROPICAL WAVE APPROXIMATELY 550 NM E OF BARBADOS ALONG 50W S OF
18N MOVING W 15 KT. CONVECTION ASSOCIATED WITH THIS WAVE HAS
BEEN WEAKENING AND THERE ARE NO SIGNS OF DEVELOPMENT. SMALL AREA
OF SCATTERED MODERATE CONVECTION W OF THE WAVE AXIS FROM 13N-17N
BETWEEN 51W-53W.

TROPICAL WAVE OVER S MEXICO ALONG 97W S OF 19N MOVING W 15 KT.
WIDELY SCATTERED MODERATE CONVECTION OVER THE BAY OF CAMPECHE
AND THE ISTHMUS OF TEHUANTEPEC FROM 15N-21N BETWEEN 93W-97W.

...ITCZ...
ITCZ 10N20W 6N35W 11N50W 12N70W 8N80W.  ASIDE FROM TROPICAL WAVE
ACTIVITY DISCUSSED ABOVE...AREA OF SCATTERED MODERATE CONVECTION
MOVING OFF THE W COAST OF AFRICA FROM 7N-14N BETWEEN 11W-22W.

...DISCUSSION...

GULF OF MEXICO...
THERE HAS BEEN LITTLE CHANGE OVER THE GLFMEX DURING THE LAST
SEVERAL DAYS WITH A NEARLY STATIONARY MID/UPPER LEVEL TROUGH
LEFT BEHIND BY FRANCES EXTENDING SWD FROM THE E UNITED STATES
OVER LOUISIANA TO THE BAY OF CAMPECHE. STRONG SUBSIDENCE AND DRY
AIR CONTINUES TO COVER THE AREA W OF THE TROUGH SUPPRESSING
CONVECTIVE ACTIVITY ALONG THE NW GULF COAST. FURTHER
E...MID/UPPER LEVEL RIDGE EXTENDS FROM CENTRAL FLORIDA SW TO
JUST N OF THE YUCATAN PENINSULA.  DIFFLUENT UPPER LEVEL FLOW
ALONG THE RIDGE AXIS IS PRODUCING SCATTERED SHOWERS/
THUNDERSTORMS WITHIN 150 NM EITHER SIDE OF A SURFACE TROUGH
EXTENDING FROM N FLORIDA NEAR THE BIG BEND AREA TO THE W YUCATAN
PENINSULA.  BOTH THE SURFACE TROUGH AND UPPER LEVEL RIDGE HAVE
BEEN SLOWLY DRIFTING WESTWARD DURING THE LAST 24 HOURS AND THIS
TREND IS EXPECTED TO CONTINUE.  ACCORDINGLY...SHOWERS/
THUNDERSTORMS WILL CONTINUE TO AFFECT THE GLFMEX WITHIN 100-200
NM EITHER SIDE OF A LINE FROM CENTRAL FLORIDA TO THE COAST OF
MEXICO NEAR TAMPICO DURING THE NEXT DAY OR SO.

CARIBBEAN SEA...
SEE SPECIAL FEATURES FOR DISCUSSION OF HURRICANE IVAN
ELSEWHERE...AN UPPER LEVEL LOW LIES OVER THE W CARIBBEAN JUST E
OF NICARAGUA/HONDURAS WITH A MID/UPPER LEVEL RIDGE OVER THE E
CARIBBEAN.  MIDDLE TO UPPER LEVEL SUBSIDENCE AND DRY AIR COVERS
MOST OF THE CARIBBEAN OUTSIDE OF IVAN PRODUCING GENERALLY
TRANQUIL WEATHER.  INCREASED INSTABILITY ASSOCIATED WITH THE W
CARIBBEAN UPPER LOW IS PRODUCING ENHANCED AFTERNOON CONVECTION
OVER A GOOD PORTION OF CUBA AND PORTIONS OF CENTRAL AMERICA FROM
NICARAGUA SWD TO PANAMA.

SUBTROPICAL ATLANTIC...
A LARGE SCALE RIDGE-TROUGH-RIDGE PATTERN DOMINATES MOST OF THE
SUBTROPICAL ATLC. THE PATTERN IS COMPRISED OF A HIGH AMPLITUDE
MID-UPPER LEVEL RIDGE OVER THE WESTERN ATLC EXTENDING FROM
FLORIDA NEWD OVER BERMUDA. MOST OF THE UPSTREAM MOISTURE IS
RIDING UP AND OVER THE RIDGE LEAVING A LARGE AREA OF SUBSIDENCE
AND DRY AIR N OF 25N W OF 60W. SHIFTING EWD...MID-OCEANIC TROUGH
EXTENDS FROM A FORMING UPPER LOW NEAR 31N50W SWWD TO THE
BAHAMAS. THE TROUGH IS UNDERCUTTING THE AFOREMENTIONED W ATLC
RIDGE AND THIS INTERACTION WILL LIKELY AFFECT THE EVENTUAL TRACK
OF HURRICANE FRANCES. CURRENTLY...WATER VAPOR IMAGERY INDICATES
THAT THE UPPER LOW IS BECOMING CUTOFF AND BEGINNING TO DRIFT
WESTWARD.  ENHANCED INSTABILITY ASSOCIATED WITH THE FORMING COLD
CORE LOW IS PRODUCING A LARGE AREA OF CLOUDINESS AND SHOWERS/
THUNDERSTORMS OVER THE CENTRAL ATLC FROM 23N-30N BETWEEN
40W-55W. OVER THE E ATLC MIDDLE TO UPPER LEVEL ANTICYCLONE HAS
FORMED NEAR 17N40W WITH RIDGING EXTENDING E/W ALONG 17N/18N FROM
50W TO THE COAST OF AFRICA. WEAK UPPER LEVEL TROUGH LIES ALONG
THE W COAST OF AFRICA FROM THE CANARY ISLANDS SWD TO JUST NW OF
THE CAPE VERDE ISLANDS.  SUBSIDENCE AND DRY AIR WITH THIS
FEATURE BLANKETS THE AREA E OF 30W. AT THE SURFACE...THE
SUBTROPICAL RIDGE CONTINUES TO BE WEAKENED OVER THE CENTRAL ATLC
BY THE AFOREMENTIONED MID-OCEANIC TROUGH AND FORMING UPPER LOW.
HOWEVER...A WELL-ESTABLISHED RIDGE AXIS REMAINS OVER THE W ATLC
FROM BERMUDA TO CENTRAL FLORIDA.

TROPICAL ATLANTIC...
MID-UPPER LEVEL RIDGE IS SLOWLY BECOMING MORE ESTABLISHED ALONG
17N/18N AS A WEAK UPPER TROUGH NEAR THE LESSER ANTILLES DRIFTS
WEST.  THE STRENGTHENING RIDGE IS PRODUCING DEEP EASTERLY FLOW
OVER A GOOD PORTION OF THE TROPICAL ATLC SAVE THE FAR E ATLC
NEAR THE CAPE VERDE ISLANDS.

$$
RHOME



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