[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 210548
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT 21 AUG 2004

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC.

...SPECIAL FEATURE...
TROPICAL DEPRESSION  DANIELLE IS LOCATED NEAR 31.2N 38.3W AT
21/0300 UTC. IT IS MOVING NW 4 KT WITH MAXIMUM SUSTAINED WINDS
OF 30 KT GUSTS 40 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS
1009 MB. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. PERSISTENT NWLY
TO WLY WIND SHEAR SHEAR CONTINUES WITH BRIEF PULSES OF DEEP
CONVECTION DEVELOPING AND RAPIDLY SHEARING OFF N AND NE OF THE
CIRCULATION CENTER.

...TROPICAL WAVES...
TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 27W/28W S OF
22N MOVING W 10 KT. 1013 MB LOW PRESSURE CENTER IS ALONG THE
WAVE NEAR 16N AND IS VERY DIFFICULT TO LOCATE IN INFRARED
IMAGERY ALONE TONIGHT. THIS WAVE CONTINUES CREEPING WESTWARD...
EMBEDDED IN THE SW MONSOON FLOW OFF W AFRICA.  FEATURE SHOULD
BEGIN TO ACCELERATE WESTWARD OVER THE NEXT DAY OF SO AS IT
BECOMES STEERED VIA THE LOW TO MIDDLE LEVEL EASTERLIES
ASSOCIATED WITH THE AZORES HIGH. NO SIGNIFICANT CONVECTION.

TROPICAL WAVE PREVIOUSLY RELOCATED INTO THE SE CARIBBEAN SEA IS
NOW ALONG 63W/64W S OF 17N MOVING W 20-25 KT. RECENT FLARE-UP IN
WAVE RELATED MODERATE TO STRONG CONVECTION IS FOUND FROM 12N TO
15N BETWEEN 62W AND 67W...MAINLY E OF THE WAVE AXIS. THIN BAND
OF SCATTERED MODERATE CONVECTION EXTENDS E OF THE LESSER
ANTILLES WITHIN 60 NM OF LINE 13N62W 11N57W...PASSING
APPROXIMATELY 60 NM S OF BARBADOS.

TROPICAL WAVE IS ALONG 75W S OF 18N MOVING W 20 KT. POSITION
BEST FITS EXTRAPOLATED MOTION AND CLOUD STREAMERS IN THE CENTRAL
CARIBBEAN. ONLY CLUSTERS OF SCATTERED MODERATE CONVECTION FOUND
S OF 12N E OF 80W TO THE COAST OF COLOMBIA SEEM TO BE RELATED TO
THIS WAVE.

...ITCZ...
ITCZ AXIS IS ALONG 11N15W 8N20W 12N27W 8N38W 9N62W. SCATTERED
MODERATE TO STRONG CONVECTION...TIED TO NEXT TROPICAL WAVE
EXPECTED TO MOVE OFF THE AFRICAN COAST...IS FOUND WITHIN 300 NM
N OF THE AXIS...MAINLY INLAND AND ALONG THE WEST AFRICAN COAST.
SCATTERED MODERATE CONVECTION WITHIN 60 NM RADIUS OF 39W ON THE
AXIS. DISSIPATING SCATTERED MODERATE CONVECTION WITHIN 60 NM
RADIUS OF 45W ON THE AXIS.

...DISCUSSION...
GULF OF MEXICO AND SUBTROPICAL ATLC W OF 75W...
W GULF DOMINATED BY UPPER RIDGING WITH MODERATE SUBSIDENCE.
SHORTWAVE RIDING NE OUT OF EASTERN OKLAHOMA/ARKANSAS ALONG THE
WESTERN PERIPHERY OF THE RIDGE HAS HELPED TO IGNITE A FAIRLY
LARGE AREA OF INLAND TSTMS OVER THE FLORIDA PANHANDLE...AS WELL
AS COASTAL ALABAMA/MISSISSIPPI/LOUISIANA. DOWNSTREAM OF THIS
RIDGE...UPPER TROUGH RUNS FROM THE OUTER BANKS OF N CAROLINA SSW
ACROSS LAKE OKEECHOBEE THROUGH THE FLORIDA KEYS AND INTO NW
CUBA. THIN WEDGE OF DRIER MIDDLE LEVEL AIR NOTED IN WATER VAPOR
IMAGERY EXTENDS WITHIN 200 NM EITHER SIDE OF TROUGH AXIS INTO
CENTRAL FLORIDA. E OF THIS TROUGH AXIS...BROAD AREA OF SCATTERED
SHOWERS AND ISOLATED TSTMS AREA FOUND IN AN AREA OF WEAK
DIFFLUENCE ALOFT.

CARIBBEAN SEA...
MID-OCEANIC TROUGH REMAINS IN PLACE FROM E HISPANIOLA WSW TO E
NICARAGUA.  MODERATE/STRONG SUBSIDENCE WITHIN 90 NM OF THE
TROUGH AXIS IS LIMITING SIGNIFICANT CONVECTION OVER MUCH OF THE
AREA. COMBINATION OF A TROPICAL WAVE WITH UPPER DIFFLUENCE S OF
THE TROUGH AXIS IS AIDING CONVECTION S OF 12N E OF 80W TO THE
COAST OF COLOMBIA. SIMILARLY...DIFFLUENCE S OF THE TROUGH OVER
THE EASTERN CARIBBEAN SEA IS HELPING TO SUPPORT THE FAIRLY BROAD
AREA OF CONVECTION N OF VENEZUELA AND W OF THE LESSER ANTILLES.
GIVEN LOCATION OF THE UPPER TROUGH AND THE WESTWARD MOTION OF
THE E CARIBBEAN TROPICAL WAVE...WOULD EXPECT CONTINUED
CONVECTION WITH THIS WAVE AT LEAST THROUGH TODAY AS THE SOUTHERN
PORTION OF IT REMAINS IN A SOMEWHAT FAVORABLE POSITION.

SUBTROPICAL ATLANTIC E OF 75W...
SURFACE TROUGH IS ALONG 31N63W 27N74W. ONLY ISOLATED SHOWERS
PRESENT FROM 25N-30N BETWEEN 60W-70W APPEAR TO INDICATE THE
LOCATION OF THIS FEATURE. UPPER HIGH NEAR 24N71W APPEARS TO BE
BUILDING RIDGE AXIS N ALONG 71W TO NEAR 33N IN THE W ATLC.
DOWNSTREAM REACTION TO THIS IS THE SE PROGRESSION OF MIDDLE ATLC
TROUGH  WITH A SMALL LOW CENTER NOTED NEAR 28N61W. SECOND UPPER
HIGH NEAR 21N53W APPEARS TO BE RETROGRADING VERY SLOWLY TO THE W
BENEATH THE SE MOVING TROUGH AND WEAKENING. TROUGH ACROSS THE
CENTRAL ATLC ALONG 33N38W 20N44W IS THE CULPRIT CREATING
WESTERLY SHEAR OVER DANIELLE. ALTHOUGH STRONGEST WESTERLIES LIES
ROUGHLY 300 NM N OF DANIELLE...A DIGGING NE ATLC TROUGH COULD
HELP TO PUSH THOSE STRONGER WESTERLIES A BIT FURTHER S OVER THE
NEXT FEW DAYS CAUSING THE FINAL DECAY OF AN ALREADY DETERIORATED
TROPICAL CYCLONE.

TROPICAL ATLANTIC...
STRONG MID/UPPER SUBSIDENCE IS CAPPING CONVECTION OUTSIDE OF THE
ITCZ TONIGHT.  DRY AIR STRETCHES ACROSS THE ENTIRE AREA WITH
STRONGEST SUBSIDENCE FOUND FROM 14N TO 25N BETWEEN 30W AND 40W
IN ASSOCIATION WITH A WESTWARD MOVING MIDDLE TO UPPER LEVEL
CIRCULATION CENTERED NEAR 16N35W. LINE OF STRONG TSTMS
ASSOCIATED WITH NEXT TROPICAL WAVE INLAND OVER AFRICA ARE ABOUT
TO EMERGE IN THE E ATLC OFF W AFRICA BETWEEN 10N AND DAKAR.

$$
HOLWEG

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