[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 191032
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU 19 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURE...

TROPICAL STORM DANIELLE CENTERED NEAR 30.0N 37.5W...OR ABOUT 815
MILES SW OF THE AZORES...AT 19/0900 UTC MOVING NE 5 KT. MAXIMUM
SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1007 MB. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE
DETAILS. WITH DANIELLE LOCATED ABOUT 420 NM ESE OF A MID/UPPER
LOW...THE SYSTEM REMAINS UNDER THE INFLUENCE OF BELLIGERENT SWLY
SHEAR. THE LOW LEVEL CENTER IS COMPLETELY EXPOSED...ABOUT 80
NM SW OF THE ASSOCIATED CONVECTION. CLOUD TOP TEMPERATURES HAVE
REMAINDER STEADY FOR THE PAST SEVERAL HOURS BUT THE COVERAGE OF
TSTMS HAS CONTINUED TO SHRINK. THERE ARE TWO SEPARATE CLUSTERS
OF TSTMS N OF THE CENTER WITH SCATTERED MODERATE CONVECTION FROM
30.5N-32.5N BETWEEN 35W-39W.

...TROPICAL WAVES...

TROPICAL WAVE BETWEEN THE CAPE VERDE ISLANDS AND THE COAST OF W
AFRICA ALONG 21W S OF 19N MOVING W 10-15 KT. HOVMOELLER
DIAGRAMS SHOW A DISTINCT CLUSTER OF TSTMS MOVING ACROSS W AFRICA
OVER THE PAST SEVERAL DAYS...AND THE TIMESECTIONS FROM BAMAKO
AND DAKAR SHOW A WAVE PASSAGE PRIMARILY BELOW 800 MB. THE WAVE
APPEARS TO BE TILTED TO THE EAST WITH HEIGHT...WITH THE
LOW-LEVEL CIRCULATION ABOUT 100 NM AHEAD OF THE CONVECTION...AND
THIS SEEMS TO AGREE WITH THE VERTICAL SOUNDINGS FROM W AFRICA.
VISIBLE IMAGERY FROM MET-8 ALSO SHOWS A WELL-DEFINED LOW-LEVEL
CIRCULATION APPROACHING THE CAPE VERDES. NUMEROUS
MODERATE/STRONG CONVECTION FROM 8N-11N BETWEEN 19W-23.5W.

TROPICAL WAVE ABOUT 925 NM E OF THE WINDWARD ISLANDS ALONG 45W
S OF 16N MOVING W 20-25 KT. THE WAVE HAS A POOR CONVECTIVE
PATTERN BUT HAS BEEN WELL-TRACKED ACROSS MUCH OF THE ATLC.
WIDELY SCATTERED SHOWERS WITH EMBEDDED ISOLATED MODERATE
CONVECTION FROM 6N-10N BETWEEN 43W-48W.

TROPICAL WAVE NEAR BARBADOS ALONG 59W S OF 17N MOVING W
15 KT. A MID-LEVEL FEATURE PASSED CAYENNE ALMOST 24 HOURS
AGO...AND NOW THE AXIS IS MOVING TOWARDS THE SOUTHERN WINDWARD
ISLANDS. ISOLATED SHOWERS ARE SPREADING ACROSS THE SOUTHERN
WINDWARD ISLANDS...FROM ST. VINCENT SWD TO TRINIDAD...FROM
10N-13N BETWEEN 58W-62W.

TROPICAL WAVE...REMNANTS OF T.S. EARL...LOCATED OVER THE SRN
MEXICO ALONG 92W S OF 21N MOVING W 15 KT. THE BULK OF THE STRONG
CONVECTION HAS ALREADY MOVED ACROSS CENTRAL AMERICA INTO THE E
PACIFIC.

...ITCZ...

ITCZ AXIS IS EMERGES OFF THE COAST OF SENEGAL ALONG 15N13W
15N19W...THEN ALONG 11N23W 5N48W 5N60W 9N70W 9N90W. ISOLATED
SHOWERS ABOUT 70 NM W OF DAKAR. SCATTERED MODERATE CONVECTION UP
TO 75 NM S OF THE AXIS BETWEEN 26W-35W. WIDELY SCATTERED
MODERATE 250 NM N OF THE AXIS BETWEEN 50W-54W. SCATTERED
MODERATE 275 NM S OF THE AXIS OVER SRN VENEZUELA...AND OVER LAKE
MARACAIBO. SCATTERED MODERATE/STRONG 150 NM N OF THE AXIS OVER
THE SW CARIBBEAN BETWEEN 76W-83W.

...DISCUSSION...

GULF OF MEXICO...
THE SUBTROPICAL SFC RIDGE EXTENDS FROM THE W ATLC WWD ALONG THE
N GULF COAST TO THE NEW ORLEANS VICINITY...WITH MOIST SE/S FLOW
ROUNDING THE RIDGE AXIS INLAND INTO SE TEXAS AND THE SOUTHERN
PLAINS. THE UPPER LEVEL FLOW IS PREDOMINANTLY FROM THE
WEST...WHICH HAS BEEN ADVECTING HIGH LEVEL MOISTURE FROM TSTMS
OVER MEXICO ACROSS THE GULF TO FLORIDA...AND KEEPING THE
ATMOSPHERE QUITE MOIST. A WEAK SHORTWAVE TROF IS EMBEDDED IN THE
FLOW ACROSS THE NE GULF...WHICH IS HELPING TO PRODUCE WIDELY
SCATTERED SHOWERS OVER THE GULF FROM 23N-27N BETWEEN 84W-94W.
THE GFS AMPLIFIES THE SHORTWAVE AND PUTS IT IN PHASE WITH
ANOTHER SHORTWAVE NEAR THE W TIP OF CUBA...AND THIS MAY BRING
MORE WIDESPREAD TSTM ACTIVITY TO PARTS OF FLORIDA LATER THIS
AFTERNOON.

CARIBBEAN...
MUCH OF THE CARIBBEAN IS BEGINNING TO CLEAR OUT AS THE REMNANTS
OF T.S. EARL CROSS CENTRAL AMERICA INTO THE EPAC. IN THE UPPER
LEVELS...THE RIDGE WHICH HAD EXTENDED FROM THE BAY OF CAMPECHE
TO W CUBA IS BEGINNING TO SPLIT IN TWO...WITH A RIDGE NOW FROM
THE COAST OF HONDURAS TO THE FLORIDA STRAITS. THE REMAINDER OF
THE AREA IS UNDER THE INFLUENCE OF A BROAD UPPER TROF WHICH
EXTENDS FROM PUERTO RICO SWWD TO 15N70W 14N80W. MODERATE/STRONG
SUBSIDENCE 200 NM EITHER SIDE OF THE TROF CONTINUES TO PRODUCE A
VERY DRY ATMOSPHERE...WITH SSM/I AND AMSU INDICATING PWAT VALUES
AS LOW AS 1.2"...HARDLY ENOUGH TO SUPPORT MUCH IF ANY TSTM
ACTIVITY.

WEST ATLANTIC...
A BROAD UPPER RIDGE EXTENDS FROM THE NW CARIBBEAN ACROSS THE NW
BAHAMAS WITH WLY FLOW BRINGING MOISTURE ACROSS FLORIDA INTO THE
W ATLC. SPOTTY SHOWERS/TSTMS HAVE BEEN RANDOMLY FORMING ACROSS
THE AREA...GENERALLY N OF 28N BETWEEN 68W-80W. DRIER CONDITIONS
TO THE E ARE DUE TO A LARGE MID/UPPER LOW CENTERED N OF PUERTO
RICO NEAR 22N66W. NONETHELESS...WIDELY SCATTERED SHOWERS/TSTMS
HAVE BEEN TRIGGERED WITHIN 30 NM OF A LINE 21N66W 24N62W IN THE
FAVORABLY DIVERGENT AREA EAST OF THE LOW.

REMAINDER OF SUBTROPICS...
THE MAIN STEERING FEATURE OVER THE AREA IS A MID/UPPER LEVEL
ANTICYCLONE CENTERED NEAR 24N35W WITH RIDGE SAGGING SWWD TO THE
NORTHERN LEEWARD ISLANDS. BROAD SWLY FLOW IS LOCATED N OF THE
RIDGE AXIS...WITH A SECOND MID/UPPER LOW NEAR 33N44W. THE LOW IS
SERVING TO PUSH T.S. DANIELLE OUT OF THE AREA TOWARDS THE AZORES
WHILE ALSO PRODUCING UP TO 30 KT OF SWLY SHEAR AND HASTENING THE
STORM'S WEAKENING. WATER VAPOR IMAGERY SHOWS THE RIDGE BUILDING
QUICKLY TO THE EAST...WITH A LEFTOVER MID/UPPER LEVEL TROF
EXTENDING FROM MADEIRA ISLAND SWD ACROSS THE CANARY ISLANDS TO
NEAR 20N23W.

TROPICAL ATLANTIC...
BROAD UPPER LEVEL RIDGE EXTENDS FROM THE SUBTROPICS INTO THE
AREA ALONG 20N44W 16N60W NEAR THE LEEWARD ISLANDS...WITH DEEP
EASTERLY FLOW ACROSS THE ATLC BETWEEN 30W AND 50W. THE STRONGEST
UPPER DIVERGENCE IS LOCATED S OF THE RIDGE AXIS WITH A LARGE
AREA OF UPPER LEVEL MOISTURE AND EMBEDDED SHOWERS/TSTMS MOVING
SWWD TOWARDS THE BRAZILIAN COAST. AN INVERTED UPPER TROF IS
LOCATED JUST UPSTREAM ALONG 8N35W 13N40W...WHICH IS ENHANCING
THIS DIVERGENCE. ELSEWHERE...A SECOND AREA OF DIVERGENCE LIES
JUST OFF THE COAST OF SENEGAL/GUINEA-BISSAU AND CONVECTION HAS
BEEN PERSISTING WITH THE TROPICAL WAVE THAT MOVED OFF AFRICA
DURING THE PAST 24 HOURS.

$$
BERG



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