[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 071026
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON JUL 07 2008

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0945 UTC.

...SPECIAL FEATURE....

TROPICAL STORM BERTHA WAS UPGRADED TO HURRICANE AT 07/0900 UTC.
HURRICANE BERTHA IS CENTERED NEAR 19.3N 50.2W AT 07/0900 UTC OR
ABOUT 730 NM E OF THE NORTHERN LEEWARD ISLANDS MOVING WNW AT 15
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB. MAXIMUM
SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SEE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT42
KNHC FOR MORE DETAILS. BERTHA HAS DEVELOPED AN EYE ROUGHLY 15-20
NM IN DIAMETER. WHILE A HURRICANE DOES NOT FORM EVERY YEAR IN
JULY IN THE ATLANTIC BASIN...IT HAS CERTAINLY HAPPENED BEFORE...
INCLUDING IN 1996 WHEN ANOTHER HURRICANE BERTHA FORMED...
COINCIDENTALLY ALSO ON JULY 7. DEEP CONVECTION NOW SURROUNDS THE
EYE BUT THE LARGEST AREA REMAINS TO THE NW. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS WITHIN 75 NM OF LINE FROM 18N51W
TO 22N49W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 34W/35W S OF 13N MOVING W NEAR 20 KT. LOW
AMPLITUDE WAVE MOSTLY EMBEDDED WITHIN THE ITCZ. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 8N-13N
BETWEEN 31W-40W.

TROPICAL WAVE IS ALONG 26N74W 19N76W TO 8N76W MOVING WNW NEAR 20
KT. WAVE REMAINS HIGHLY AMPLIFIED AND EXTENDS FROM N COLOMBIA
ACROSS THE BAHAMAS. SATELLITE IMAGERY CLEARLY INDICATES AN
INVERTED-V CURVATURE AND IS MOVING OUT OF THE AREA OF SOMEWHAT
DRY AIR INTO MOISTER CONDITIONS. ANY ACTIVITY/CONVECTION IN THE
VICINITY IS ASSOCIATED WITH AN UPPER LEVEL FEATURE.

TROPICAL WAVE IS ALONG 92W S OF 25N MOVING W 15-20 KT. WAVE
REMAINS BENEATH A BROAD UPPER RIDGE MASKING ANY SATELLITE
SIGNATURE WITH ANY ACTIVITY/CONVECTION ASSOCIATED WITH THAT
UPPER LEVEL RIDGE.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N12W 6N21W 6N32W 8N44W 7N60W.
SMALL CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN 120
NM OF THE ITCZ BETWEEN 19W-25W AND FROM THE EQUATOR TO 9N
BETWEEN 35W-47W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LOW IS INLAND OVER N/CENTRAL MEXICO WITH A BROAD UPPER
RIDGE ANCHORED OVER S/CENTRAL MEXICO AND A RIDGE AXIS EXTENDING
INTO THE GULF NEAR TUXPAN MEXICO TO THE LOUISIANA/TEXAS BORDER
COVERING THE GULF SW OF A LINE FROM TEXAS/LOUISIANA BORDER TO
THE W TIP OF CUBA. THE DIFFLUENCE ALOFT BETWEEN THIS UPPER
FEATURES COUPLED WITH THE ABUNDANCE OF UPPER LEVEL MOISTURE IS
GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS SW OF A LINE
FROM BROWNSVILLE TEXAS TO INTO THE BAY OF CAMPECHE NEAR 18N92W.
A SHARP UPPER TROUGH OVER THE E US DIPS S OVER THE FLORIDA
PANHANDLE WITH A WEAK SHORTWAVE CONTINUING S TO W CUBA ENHANCING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OVER THE NE GULF N OF
27N E OF 86W. AT THE SURFACE IS A WEAK RIDGE EXTENDING FROM THE
W ATLC ACROSS FLORIDA ALONG THE N GULF COAST TO TEXAS.

CARIBBEAN SEA...
WEAK UPPER LOW IS IN THE CENTRAL CARIBBEAN JUST S OF JAMAICA
WITH STRONG N FLOW OVER THE W CARIBBEAN DUE TO THE BROAD UPPER
RIDGE OVER THE W GULF OF MEXICO AND WEAKER E TO SE UPPER FLOW
OVER THE E CARIBBEAN DUE TO AN UPPER RIDGE EXTENDING FROM NEAR
BERTHA ACROSS THE LEEWARD ISLANDS. ABUNDANCE OF UPPER LEVEL
MOISTURE COUPLED WITH DIFFLUENCE ALOFT IS GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 120 NM OF LINE FROM THE
GULF OF URABA ALONG 18N80W ACROSS CUBA NEAR 22N80W INTO THE
FLORIDA STRAITS. THIS ACTIVITY IS FURTHER ENHANCED BY THE
TROPICAL WAVE. ISOLATED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS ARE IN THE GULF OF HONDURAS S OF 18N W OF 85W OT
INLAND OVER CENTRAL AMERICA AND THE YUCATAN. STRONG SUBSIDENCE
AND DRY STABLE AIR CURRENTLY DOMINATE THE E CARIBBEAN WITH
MODERATE/STRONG EASTERLY TRADE WINDS USHERING IN SOME ISOLATED
BUT FAST MOVING SHOWERS ACROSS THE AREA E OF 73W.

ATLANTIC OCEAN...
THE MAIN FOCUS TONIGHT IS HURRICANE BERTHA. OTHERWISE...AN UPPER
TROUGH COVERS THE W ATLC WITH A WEAK UPPER LOW NE OF THE BAHAMAS
NEAR 28N75W. THIS IS GENERATING CLUSTERS OF SCATTERED
SHOWERS/THUNDERSTORMS WITHIN 90/120 NM OF LINE FROM 27N75W TO
31N65W...IN THE FLORIDA STRAITS WITHIN FROM CUBA TO S FLORIDA
BETWEEN 79W-81W...AND OFF THE E US COAST WITHIN 45/60 NM OF LINE
FROM 28N80W TO 32N79W. STRONG SUBSIDENCE AND DRY STABLE AIR ARE
S OF 24N INTO THE TROPICS AND THE E CARIBBEAN W OF BERTHA TO
65W. WEAK UPPER RIDGE COVERS THE W TROPICAL ATLC INTO THE E
CARIBBEAN. WEAK UPPER TROUGH EXTENDS INTO THE N/CENTRAL ATLC
JUST N OF BERTHA WITH A SECOND STRONG UPPER TROUGH EXTENDING
INTO THE E ATLC OVER THE MADEIRA ISLANDS TO JUST W OF THE CANARY
ISLANDS. IN ALL THESE ARE RATHER BENIGN UPPER LEVEL FEATURES AS
A BROAD SURFACE RIDGE DOMINATES THE ATLC ANCHORED BY A PAIR 1028
MB HIGHS JUST N OF THE REGION NEAR 24N37W AND 33N59W.

$$
WALLACE


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