[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUL 12 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1715 UTC.

...SPECIAL FEATURE....

A TROPICAL STORM WARNING IS IN EFFECT FOR BERMUDA. TROPICAL
STORM CONDITIONS ARE EXPECTED WITHIN THE NEXT 24 HOURS ACROSS
THE ISLAND. THE CENTER OF HURRICANE BERTHA AT 12/1800 UTC IS
NEAR 29.9N 62.5W. IT IS MOVING NORTH OR 360 DEGREES AT 2 KT.
PRELIMINARY DATA FROM AN AIR FORCE RECONNAISSANCE PLANE
ESTIMATES THE MINIMUM CENTRAL PRESSURE IS 983 MB. THE MAXIMUM
SUSTAINED WIND SPEEDS ARE 70 KT WITH GUSTS TO 85 KT. THIS
POSITION ALSO IS 185 NM/345 KM SOUTHEAST OF BERMUDA. THE CENTER
OF BERTHA IS EXPECTED TO PASS SLOWLY TO THE SOUTHEAST AND EAST
OF BERMUDA DURING THE NEXT COUPLE OF DAYS...BUT THE MOTION
OCCASIONALLY MAY BE ERRATIC AS MID LEVEL STEERING CURRENTS WILL
REMAIN WEAK OVER THE NEXT FEW DAYS. PLEASE READ THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
AND THE PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE
DETAILS. SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND
THUNDERSTORMS ARE FROM 28N TO 33N BETWEEN 58W AND 65W. THE
INTENSITY FORECAST WILL KEEP BERTHA AT 70 KT FOR THE FIRST 24
HOURS...WEAKENING GRADUALLY AND FALLING BELOW HURRICANE-FORCE
WINDS AFTER 72 HOURS.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 48W SOUTH OF 16N MOVING
WEST 20 KT. WAVE REMAINS WELL-DEFINED WITH LOW TO MIDDLE LEVEL
CYCLONIC CURVATURE ALONG THE WAVE AXIS NEAR 11N. SCATTERED
MODERATE CONVECTION TO ISOLATED STRONG CONVECTION IS FROM
10N-13N BETWEEN 44W-52W.

A CENTRAL CARIBBEAN SEA TROPICAL WAVE IS ALONG 75W SOUTH OF 18N
MOVING WEST 15-20 KT. WAVE STRETCHES FROM THE WINDWARD PASSAGE
TO THE NORTHERN COLOMBIA COAST AND IS MOVING INTO AN AREA OF
BROAD UPPER LEVEL ANTICYCLONIC FLOW. NEAR THE SURFACE...WEAK
CYCLONIC TURNING IN THE LOW-LEVEL CLOUDS IS EVIDENT ALONG THE
WAVE AXIS WITH NO DEEP CONVECTIVE PRECIPITATION OBSERVED.

...THE ITCZ...
13N16W 11N28W 8N35W 11N46W 11N50W AND INTO NORTHERN VENEZUELA
NEAR 9N61W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 90 NM
OF A LINE FROM 5N10W TO 9N18W. CLUSTERS OF SCATTERED MODERATE
CONVECTION ARE FROM THE EQUATOR TO 4N BETWEEN 31W-38W. SIMILAR
CONVECTION IS WITHIN 90 NM OF THE AXIS BETWEEN 35W-39W AND
BETWEEN 50W-58W.

...DISCUSSION...

THE GULF OF MEXICO...
BROAD MIDDLE TO UPPER LEVEL ANTICYCLONIC FLOW COVERS THE ENTIRE
AREA. MIDDLE TO UPPER LEVEL MOISTURE IS EAST OF 90W AND
COMPARATIVELY MUCH DRIER AIR ALOFT IS WEST OF 90W. AT THE
SURFACE...A RIDGE OF HIGH PRESSURE EXTENDS FROM THE W ATLC INTO
THE GULF WITH A 1021 MB HIGH CENTERED NEAR 28N86W. A SLIGHT
WEAKNESS IN THE SURFACE RIDGE ACROSS FLORIDA COUPLED WITH THE
BROAD UPPER LEVEL DIFFLUENT ENVIRONMENT IS PRODUCING SCATTERED
SHOWERS AND TSTMS ACROSS THE NERN GULF NE OF A LINE FROM BILOXI
MISSISSIPPI TO SARASOTA FLORIDA. SCATTERED SHOWERS AND ISOLATED
TSTMS ARE ALSO ACROSS SRN MEXICO AND WITHIN 60 NM OF THE MEXICO
COAST IN THE BAY OF CAMPECHE FROM 18N21N BETWEEN 95W-97W.
ELSEWHERE...THE GULF REMAINS RATHER TRANQUIL WITH LIGHT E-SE
WINDS ACROSS THE SRN AND WRN GULF WATERS.

THE CARIBBEAN SEA...
BROAD UPPER LEVEL ANTICYCLONIC FLOW CUTS INTO THE NORTHWESTERN
CORNER ACROSS CUBA AND THE YUCATAN PENINSULA...FROM THE ATLANTIC
OCEAN AND THE EASTERN GULF OF MEXICO. A MIDDLE TO UPPER LEVEL
CYCLONIC CIRCULATION IS CENTERED OVER THE CENTRAL BAHAMAS NEAR
25N75W WHICH EXTENDS TROUGHING ACROSS EASTERN CUBA AND JAMAICA.
SHALLOW ISOLATED SHOWERS ARE ACROSS THE WINDWARD PASSAGE AREA
AND SOUTH OF EASTERN CUBA IN ASSOCIATION WITH UPPER LEVEL
DIFFLUENCE E OF THE TROUGH. AN UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTERED OVER THE SW CARIBBEAN SEA NEAR 12N76W IS
AIDING IN GENERATING SCATTERED MODERATE TO STRONG SHOWERS AND
TSTMS NORTH OF 9N BETWEEN 78W-85W. THIS AREA INCLUDES PORTIONS
OF COASTAL EASTERN NICARAGUA AND COSTA RICA. ELSEWHERE ACROSS
THE CARIBBEAN 10-20 KT TRADE WINDS ARE OBSERVED AND THESE ARE
EXPECTED TO PERSIST DURING THE NEXT 24 HOURS.

THE ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM 32N74W TO A CYCLONIC
CIRCULATION CENTER NEAR 25N75W ACROSS CUBA TO 18N79W SLIGHTLY
WEST OF JAMAICA. ISOLATED MODERATE SHOWERS AND TSTMS ARE ACROSS
FLORIDA...THE NW BAHAMAS AND THE ERN STRAITS OF FLORIDA ON THE
WRN SIDE OF THIS UPPER LOW. DRY AIR AND SUBSIDENCE COVERS MUCH
OF THE REST OF THE ATLANTIC WATERS NORTH OF THE ITCZ...HURRICANE
BERTHA BEING THE EXCEPTION. A DEEP LAYER TROUGH CONTINUES TO THE
EAST-NORTHEAST OF HURRICANE BERTHA...FROM A CYCLONIC CIRCULATION
CENTER NEAR 35N46W TO 25N51W. BROAD MIDDLE TO UPPER LEVEL
CYCLONIC FLOW COVERS THE AREA NORTH OF 25N BETWEEN 35W AND 55W.
MID-LEVEL GENERATED SCATTERED MODERATE TO STRONG SHOWERS ARE
WITHIN 120 NM E OF A LINE FROM 32N44W TO 29N47W. AT THE
SURFACE...A RIDGE EXTENDS FROM A 1022 MB HIGH PRESSURE CENTER
NEAR 28N72W TO THE CENTRAL FLORIDA COAST NEAR MELBOURNE AND INTO
THE NE GULF OF MEXICO. SURFACE RIDGE ALSO EXTENDS ACROSS THE
CENTRAL ATLC FROM NEAR 32N36W TO 24N45W ANCHORED BY A 1032 MB
HIGH PRESSURE CENTER NORTH OF THE AZORES. A COLD FRONT SKIRTS
THE NORTHERN FRINGE OF THE DISCUSSION AREA ACROSS THE EASTERN
ATLC ALONG 31N BETWEEN 10W-25W AND IS PRODUCING LITTLE SENSIBLE
WEATHER.

$$
HUFFMAN




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