[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 250608
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON JUL 25 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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
0515 UTC.

...SPECIAL FEATURES...

TROPICAL STORM GERT IS CENTERED NEAR 22.3N 98.6W AT 25/0600 UTC
MOVING WNW AT 10 KT. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH
GUSTS TO 50 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. GERT MADE
LANDFALL A FEW HOURS AGO. MOST OF THE DEEP CONVECTION IS NOW
INLAND OVER MEXICO BANKED AGAINST THE E SLOPES OF THE SIERRA
MADRE MOUNTAINS. A MID/UPPER LEVEL RIDGE WILL KEEP GERT OVER
MEXICO AND FINALLY DISSIPATE IT IN 24 TO 36 HOURS. IN THE
MEANTIME...HEAVY RAINS WILL CONTINUE OVER THE AREA FROM 21N-25N
BETWEEN THE MOUNTAINS AND THE COAST. THIS AREA WAS HIT
PREVIOUSLY BY EMILY...THUS COULD PRODUCE FLOODING OVER THE
MOUNTAINOUS TERRAIN.

TROPICAL STORM FRANKLIN IS CENTERED NEAR 30.9N 71.6W AT 25/0300
UTC MOVING SSW AT 3 KT. MAXIMUM SUSTAINED WIND SPEED IS 40 KT
WITH GUSTS TO 50 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005
MB. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. FRANKLIN IS UNDERGOING
STRONG NW SHEAR WHICH HAS COMPLETELY EXPOSED THE LOW LEVEL
CENTER. AFTER STALLING AROUND 24/1800 UTC...FRANKLIN IS NOW
DRIFTING SSW DUE TO A SURFACE RIDGE N OF FRANKLIN THAT IS
BUILDING BEHIND A COLD FRONT THAT IS TO THE NE THAT ENDS NEAR
BERMUDA. FRANKLIN IS ALSO AT THE BASE OF AN UPPER LEVEL TROUGH
THAT EXTENDS FROM THE NORTH CENTRAL ATLC. ALL THIS COMBINES TO
PRODUCE A RATHER UNFAVORABLE ENVIRONMENT FOR INTENSIFICATION.
CURRENTLY SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN 90/120 NM OF LINE FROM 28N69W-33N66W.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS ALONG 27W/28W S OF 20N MOVING W 10-15
KT. A 1014 MB LOW HAS DEVELOPED ALONG THE WAVE NEAR 13N.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS N OF THE LOW
WITHIN A 60 NM RADIUS OF 14N28.5W. REMAINDER OF THE CONVECTION
IS CONFINED TO WITHIN THE ITCZ.

CENTRAL ATLC TROPICAL WAVE IS FROM 21N52W ALONG 13N57W TO 6N60W
MOVING W 15-20 KT. WELL-DEFINED...PERSISTENT BROAD CURVATURE IS
OBSERVED ON INFRARED SATELLITE IMAGERY. WAVE IS TILTED SW TO NE
WITH THE MID LEVEL CURVATURE LAGGING THE LOW LEVEL. WITH THE
HIGH AMPLITUDE OF THIS WAVE...THE N PORTION COULD SPLIT OFF OVER
THE NEXT DAY OR TWO. WAVE REMAINS EMBEDDED BROAD AREA OF AFRICAN
DUST COUPLED WITH DRY AIR ARE LIMITING DEEP CONVECTION...THUS
ONLY LOW LEVEL ISOLATED SHOWERS HAVE FORMED FROM 14N-22N BETWEEN
50W-55W.

W CARIBBEAN TROPICAL WAVE IS ALONG 83W S OF 20N MOVING W 15-20
KT. WAVE CONTINUES AT THE LEADING EDGE OF THE AFRICAN DUST
SURGE...THUS ONLY SCATTERED LOW LEVEL SHOWERS/ISOLATED
THUNDERSTORMS ARE S OF 20N FROM 80W-85W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 14N16W 14N25W...THEN ALONG 10N29W
8N36W 12N54W. SCATTERED/NUMEROUS STRONG CONVECTION IS INLAND
OVER A LARGE PORTION OF W AFRICA AND IS STARTING TO EMERGE ALONG
THE COAST FROM 10N-17N. SCATTERED MODERATE/STRONG CONVECTION IS
WITHIN 60 NM OF THE AXIS FROM 17W-20W. CLUSTERS OF SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION ARE S OF 12N TO THE
EQUATOR FROM 29W-44W.

...DISCUSSION...

GULF OF MEXICO...
MID/UPPER HIGH IS LOCATED ALONG THE COAST OF MEXICO JUST NE OF
T.S. GERT NEAR 24N98W WITH A RIDGE EXTENDING N OVER TEXAS. THIS
IS LEAVING THE W GULF WITH HIGH LEVEL DEBRIS CLOUDS W OF 94W. AN
INVERTED UPPER TROUGH EXTENDS FROM THE NW CARIBBEAN THROUGH THE
YUCATAN CHANNEL TO THE N GULF COAST NEAR ALABAMA. DIFFLUENCE ON
THE S SIDE OVER THE UPPER HIGH FLOW IS GENERATING SCATTERED
MODERATE/ISOLATED STRONG CONVECTION INLAND OVER S MEXICO AND
ALONG THE COAST IN THE BAY OF CAMPECHE. A SECOND MID/UPPER RIDGE
AXIS EXTENDS FROM A BROAD UPPER HIGH OVER THE MOUNTAINS OF NORTH
CAROLINA S OVER FLORIDA ACROSS CUBA INTO THE CARIBBEAN. A
SURFACE TROUGH EXTENDING FROM NEAR T.S. FRANKLIN TO OVER CENTRAL
FLORIDA IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
MOVING OFF THE FLORIDA PENINSULA INTO THE NE GULF N OF 26N E OF
86W. ALSO AT THE SURFACE...A WEAK 1018 MB HIGH IS OVER THE NW
GULF NEAR 28N92W.

CARIBBEAN...
WATER VAPOR IMAGERY SHOWS VERY LITTLE DEEP MOISTURE OVER THE
CARIBBEAN AT THE MOMENT WITH ONLY SHOWERS/THUNDERSTORMS
ASSOCIATED WITH THE TROPICAL WAVE. DRY AIR WITH SUSPENDED
AFRICAN DUST HAS MOVED INTO THE W CARIBBEAN ESSENTIALLY
PRECLUDING THE DEVELOPMENT OF DEEP CONVECTION. THE DUST CAN
PRODUCE HAZY SKIES OVER THE AREA AS IT CONTINUES MARCH WEST.
AT THE UPPER LEVELS...A MID/UPPER LEVEL TROUGH SPLITS THE
CARIBBEAN FROM A WEAK UPPER LOW OVER E HISPANIOLA SW TO THE
COAST OF CENTRAL AMERICA NEAR THE NICARAGUA/COSTA RICA BORDER.
MID/UPPER HIGH E OF THE LESSER ANTILLES NEAR 13N59W IS GIVING
THE E CARIBBEAN S FLOW AND ADVECTING TROPICAL MOISTURE OVER THE
SE CARIBBEAN...PRODUCING SCATTERED SHOWERS S OF 13N FROM 62W-68W
APPROACHING THE ABC ISLANDS.

ATLANTIC...
THE W ATLC IS DOMINATED BY SHARP UPPER LEVEL FEATURES WHILE THE
REMAINDER OF THE ATLC WATERS REMAIN RATHER BENIGN. MID/UPPER
TROUGH EXTENDS ACROSS BERMUDA SW ALONG 26N72W TO THE COAST OF
CUBA NEAR 23N78W. A MID/UPPER LEVEL RIDGE N OF THE REGION IS
PRODUCING NW SHEAR OVER T.S. FRANKLIN AND PUSHING THE UPPER
TROUGH FURTHER S. NARROW MID/UPPER LEVEL RIDGE EXTENDS FROM THE
CENTRAL BAHAMAS NE JUST SW OF FRANKLIN TO BEYOND 32N57W.
DIFFLUENCE TO THE NW OF THE UPPER RIDGE IS AIDING IN THE
CONVECTION ASSOCIATED WITH THE STORM. MID/UPPER LEVEL TROUGH
EXTENDS FROM THE W ATLC NEAR 24N65W THROUGH THE UPPER LOW OVER E
HISPANIOLA INTO THE CARIBBEAN. A SECOND WEAK MID/UPPER LOW IS
CENTERED TO THE E NEAR 25N54W PRODUCING SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS N OF 25N FROM 55W-62W. MID/UPPER LEVEL
HIGH IS IN THE NORTH CENTRAL ATLC NEAR 31N41W WITH A BROAD UPPER
RIDGE AXIS EXTENDING FROM OFF THE COAST OF AFRICA NEAR 17N WNW
TO 20N40W. AT THE SURFACE...SUBTROPICAL RIDGE EXTENDS ACROSS THE
ATLC FROM MADEIRA ISLANDS WSW THROUGH A 1023 MB HIGH LOCATED
NEAR 30N37W TO A WEAK 1020 MB HIGH LOCATED NEAR 26N60W. THIS
SCENARIO COUPLED WITH THE AFRICAN DUST/DRY AIR IS GIVING THE
ATLC WATERS E OF 55W FAIR WEATHER.

$$
WALLACE


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