[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 182353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED AUG 18 2010

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 11N-25N ALONG 29W MOVING W AT 10-15
KT. LOW-LEVEL CYCLONIC FLOW IS NOTED IN GLOBAL MODEL GUIDANCE
AND SATELLITE IMAGERY IN THE VICINITY OF THE WAVE AXIS BETWEEN
25W-35W. THIS WAVE ALSO COINCIDES WITH MAXIMUM VALUES OF DEEP
LAYER MOISTURE INDICATED ON TOTAL PRECIPITABLE WATER IMAGERY
FROM 05N-27N E OF 34W. CONVECTION REMAINS EMBEDDED WITHIN THE
ITCZ REGION S OF 15N DUE TO THE SAHARAN AIR LAYER AND AFRICAN
DUST LOCATED N OF 15N. SCATTERED MODERATE AND ISOLATED STRONG
CONVECTION IS FROM 10N-13N BETWEEN 29W-35W.

TROPICAL WAVE EXTENDS FROM 11N-26N ALONG 40W MOVING W AT 15 KT.
OVERSHADOWED BY THE WAVE TO THE EAST...THE WAVE REMAINS SHROUDED
IN A SAHARAN AIR LAYER SUPPRESSING CONVECTIVE ACTIVITY. ANY
ASSOCIATED CONVECTION IS MORE RELATED TO THE ITCZ AND WILL BE
DISCUSSED IN THE ITCZ SECTION.

TROPICAL WAVE EXTENDS FROM NEAR 10N77W TO JAMAICA NEAR 18N78W
THEN TO THE CENTRAL BAHAMAS NEAR 24N76W MOVING W AT 15-20 KT.
BROAD LOW-LEVEL CYCLONIC FLOW IS NOTED IN THE VICINITY OF THE
WAVE AXIS FROM THE SW CARIBBEAN SEA NORTHWARD TO OVER CUBA AND
PORTIONS OF THE FLORIDA STRAITS. LOW-LEVEL MOISTURE IS MAXIMIZED
ACROSS THE CARIBBEAN BETWEEN 72W-82W AS DEPICTED ON TOTAL
PRECIPITABLE WATER IMAGERY THIS EVENING. SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION IS FROM 09N-24N BETWEEN 73W-84W.
MUCH OF THIS ACTIVITY IS FURTHER ENHANCED BY AN UPPER LEVEL
TROUGH AXIS EXTENDING FROM NORTHERN COLOMBIA NEAR 11N75W TO THE
YUCATAN CHANNEL NEAR 22N85W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N15W 13N27W 12N40W 08N53W 09N61W.
WITH A MONSOONAL TROUGH IMPACTING MUCH OF THE ITCZ REGION ACROSS
THE TROPICAL ATLC...SCATTERED MODERATE AND ISOLATED STRONG
CONVECTION IS FROM 09N-15N BETWEEN 16W-26W. ISOLATED MODERATE
CONVECTION IS ELSEWHERE FROM 04N-13N BETWEEN 09W-45W.

...DISCUSSION...

GULF OF MEXICO...
A PAIR OF UPPER LEVEL ANTICYCLONIC CIRCULATIONS...ONE CENTERED
OVER THE WESTERN ATLC NEAR 34N67W AND THE OTHER CENTERED OVER
NORTH TEXAS NEAR 32N98W ARE PROVIDING THE GULF AND FLORIDA
PENINSULA WITH EAST-NORTHEASTERLY UPPER LEVEL FLOW. WATER VAPOR
IMAGERY INDICATES DRY UPPER LEVEL AIR IS LOCATED E OF 89W...
HOWEVER...WARM AIR ADVECTION ON SOUTHWESTERLY LOW-LEVEL WINDS...
DAYTIME INSTABILITY AND SEABREEZE DYNAMICS OVER INTERIOR FLORIDA
ARE GENERATING ISOLATED SHOWERS AND TSTMS N OF 26N E OF 89W AND
AREAS E OF 84W S OF 26N...INCLUDING PORTIONS OF THE FAR SW
FLORIDA PENINSULA. THE INSTABILITY LOCATED OVER THE EASTERN GULF
IS LARGELY DUE TO THE WEAKNESS BETWEEN THE TWO UPPER LEVEL
ANTICYCLONES TO THE NORTH AND AN UPPER LEVEL TROUGH AXIS LOCATED
OVER THE NW CARIBBEAN SEA COUPLED WITH A TROPICAL WAVE
STRETCHING ITS IMPACTS FROM OVER CUBA INTO THE SE GULF WATERS.
FARTHER WEST...A MID-LEVEL CIRCULATION OVER LOUISIANA AND
STATIONARY FRONTAL BOUNDARY IS ANALYZED OVER THE LOWER
MISSISSIPPI RIVER VALLEY AND NORTH TEXAS PROVIDING FOR SCATTERED
SHOWERS AND ISOLATED TSTMS OVER THE NW GULF N OF 25N W OF 89W.
THE PREVIOUSLY MENTIONED UPPER LEVEL TROUGH AXIS OVER THE NW
CARIBBEAN IS ENHANCING ONGOING SCATTERED SHOWERS AND TSTMS OVER
THE WESTERN YUCATAN PENINSULA THAT STRETCH THEIR IMPACT WESTWARD
TO 92W THIS EVENING.

CARIBBEAN SEA...
A TROPICAL WAVE EXTENDS FROM NORTHERN COLOMBIA TO THE CENTRAL
BAHAMAS AND CONTINUES IMPACTING MUCH OF THE WESTERN CARIBBEAN
WITH SCATTERED SHOWERS AND TSTMS. MOST OF THE STRONGEST
CONVECTION IS LOCATED BETWEEN 73W-84W...INCLUDING HAITI...
JAMAICA...AND CUBA. WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS
ARE OCCURRING ACROSS THE REMAINDER OF THE WESTERN CARIBBEAN...
INCLUDING INTERIOR PORTIONS OF CENTRAL AMERICA. THIS LARGE AREA
OF SHOWER ACTIVITY IS FURTHER SUPPORTED BY A NARROW UPPER LEVEL
TROUGH WITH AXIS EXTENDING FROM NORTHERN COLOMBIA NEAR 11N75W TO
THE YUCATAN CHANNEL NEAR 22N85W. CONVECTION LOCATED IN THE SW
CARIBBEAN AS SCATTERED SHOWERS AND ISOLATED TSTMS ARE PRIMARILY
DUE TO SURFACE CONVERGENCE NEAR A PORTION OF THE ITCZ EXTENDING
ACROSS SOUTHERN COSTA RICA ALONG 10N TO NEAR 10N78W. FARTHER
EAST...AN UPPER LEVEL LOW IS CENTERED IN THE TROPICAL N ATLC
NEAR 18N58W AND EXTENDS AN UPPER LEVEL TROUGH AXIS FROM THE
UPPER LEVEL LOW TO 12N61W THEN WESTWARD TO 13N69W. MOSTLY DRY
NORTHERLY UPPER LEVEL FLOW COVERS THE BASIN E OF 70W DUE TO THIS
FEATURE AND IS MAINTAINING OVERALL FAIR WEATHER AT THE SURFACE.

ATLANTIC OCEAN...
AN UPPER LEVEL ANTICYCLONE IS CENTERED NORTH OF THE DISCUSSION
AREA NEAR 34N67W AND IS PROVIDING MUCH OF THE W ATLC N OF 24N W
OF 55W WITH NE TO E UPPER LEVEL FLOW AND OVERALL DRY CONDITIONS
ALOFT. THIS UPPER LEVEL PATTERN CONTINUES TO SUPPORT A 1021 MB
HIGH CENTERED NEAR 27N67W AND A 1022 MB HIGH CENTERED NW OF
BERMUDA NEAR 35N66W. WEDGED IN BETWEEN THESE HIGH CENTERS IS A
SURFACE TROUGH ANALYZED ALONG 30N BETWEEN 60W-67W. ISOLATED
SHOWERS ARE OCCURRING FROM 28N-30N BETWEEN 57W-70W. FARTHER
WEST...A FEW ISOLATED SHOWERS ARE FROM 29N-32N BETWEEN 74W-79W.
A COLD FRONT EXTENDS FROM 33N48W TO 31N55W ACROSS THE CENTRAL
ATLC WITH ISOLATED SHOWERS LOCATED WITHIN 90 NM EITHER SIDE OF
THE FRONT. MIDDLE TO UPPER LEVEL MOISTURE CONTINUES TO ADVECT SW
FROM THE FRONTAL BOUNDARY GENERATING WIDELY SCATTERED SHOWERS
FROM 20N-28N BETWEEN 55W-62W. THIS MOISTURE IS LOCATED NW OF AN
UPPER LEVEL LOW CENTERED OVER THE TROPICAL NORTH ATLC NEAR
18N58W. EAST OF A LINE FROM 32N49W TO THE UPPER LEVEL LOW...
WATER VAPOR IMAGERY INDICATES A VERY DRY AND SUBSIDENT
ENVIRONMENT DUE TO A VERY BROAD UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTERED NEAR 25N38W. THIS UPPER LEVEL ANTICYCLONE
SUPPORTS A 1023 SURFACE HIGH CENTERED SOUTH OF THE AZORES NEAR
35N27W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
HUFFMAN



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