[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 190527
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC.

...SPECIAL FEATURE...

TROPICAL STORM DANIELLE CENTERED NEAR 29.6N 37.5W...OR ABOUT 835
MILES SW OF THE AZORES...AT 19/0300 UTC MOVING NE 9 KT. MAXIMUM
SUSTAINED WIND SPEED HAS DECREASED TO 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 500 NM ESE OF A
MID/UPPER LOW...THE SYSTEM REMAINS UNDER THE INFLUENCE OF
BELLIGERENT SWLY SHEAR. THE LOW LEVEL CENTER IS NOW COMPLETELY
EXPOSED...ALMOST 40 NM S OF THE ASSOCIATED CONVECTION. CLOUD TOP
TEMPERATURES HAVE WARMED BY ABOUT 10C OVER THE PAST SEVERAL
HOURS AS THE TSTMS CONTINUE TO WEAKEN. SCATTERED MODERATE
CONVECTION FROM 30N-32N BETWEEN 35W-38W.

...TROPICAL WAVES...

TROPICAL WAVE INTRODUCED OFF THE COAST OF W AFRICA ALONG 18W/19W
S OF 17N 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. SCATTERED MODERATE/STRONG
CONVECTION FROM 8N-10N BETWEEN 19W-21W. WIDELY SCATTERED
SHOWERS/TSTMS OVER SENEGAL AND JUST OFFSHORE FROM 13N-16N
BETWEEN 14W-19W.

TROPICAL WAVE ABOUT 1000 NM E OF THE WINDWARD ISLANDS ALONG 44W
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 5N-10N BETWEEN 41W-50W.

TROPICAL WAVE APPROACHING BARBADOS ALONG 58W 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 WITH ISOLATED SHOWERS/TSTMS FROM 10N-13N BETWEEN 57W-61W.

TROPICAL WAVE...REMNANTS OF T.S. EARL...LOCATED OVER THE YUCATAN
PENINSULA ALONG 90W S OF 21N MOVING W 15 KT. THE BULK OF THE
STRONG CONVECTION HAS ALREADY MOVED ACROSS CENTRAL AMERICA INTO
THE E PACIFIC...AND LEFTOVER DIURNAL CONVECTION OVER LAND
CONTINUES TO DISSIPATE.

...ITCZ...

ITCZ AXIS IS ALONG 11N15W 10N20W 10N30W 9N44W 9N85W. SEE
TROPICAL WAVES FOR RELATED CONVECTION. ELSEWHERE...ISOLATED
MODERATE CONVECTION 160 NM S OF THE AXIS BETWEEN 29W-32W AND 100
NM N OF THE AXIS BETWEEN 49W-52W. WIDELY SCATTERED MODERATE OVER
CENTRAL VENEZUELA AND MUCH OF COLOMBIA.

...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 N/CNTRL GULF...WHICH IS HELPING TO PRODUCE
ISOLATED SHOWERS OVER THE SE GULF FROM 23N-28N BETWEEN 82W-89W.
THE GFS AMPLIFIES THE SHORTWAVE AND PUTS IT IN PHASE WITH
ANOTHER SHORTWAVE OVER THE YUCATAN CHANNEL...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 CAYMAN ISLANDS 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 15N80W. 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. TSTMS OVER FLORIDA HAVE MOSTLY DIED OFF BUT WIDELY
SCATTERED MODERATE CONVECTION HAS BEEN FLARING UP FROM NASSAU
BAHAMAS NEWD FROM 25N-29N BETWEEN 72W-78W. DRIER CONDITIONS TO
THE E ARE DUE TO A LARGE MID/UPPER LOW CENTERED N OF PUERTO RICO
NEAR 22N66W. NONETHELESS...ISOLATED SHOWERS/TSTMS HAVE BEEN
TRIGGERED WITHIN 30 NM OF A LINE 20N65W 24N60W 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 32N45W. 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 20N48W 15N60W 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 8N34W 16N42W...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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