[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 281804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE AUG 28 2012

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

RECENTLY UPGRADED HURRICANE ISAAC CENTERED NEAR 28.4N 88.7W AT
15/1800 UTC OR ABOUT 55 MILES S-SE OF THE MOUTH OF THE
MISSISSIPPI RIVER...OR ABOUT 135 MILES SE OF NEW ORLEANS
LOUISIANA MOVING NW AT 9 KT. MINIMUM CENTRAL PRESSURE IS 975 MB.
MAXIMUM SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SEE
THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SCATTERED TO NUMEROUS
MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 120 NM OF THE
CENTER OF ISAAC. ISAAC IS FORECAST TO REMAIN A HURRICANE PRIOR
TO LANDFALL BEFORE GRADUALLY WEAKENING AS IT MOVES INLAND. THE
MAIN THREATS ASSOCIATED WITH ISAAC WILL BE VERY HEAVY RAINFALL
OVER THE N GULF COAST STATES...DANGEROUS STORM SURGE AND SURF
CONDITIONS...AND STRONG WINDS WELL AWAY FROM THE CENTER AS THE
OVERALL CIRCULATION OF ISAAC IS QUITE LARGE. FOR MORE DETAILED
INFORMATION REFER TO HURRICANE LOCAL STATEMENTS ISSUED BY YOUR
LOCAL NATIONAL WEATHER SERVICE OFFICE.

1011 MB LOW PRES IS POSITIONED NEAR 23N43W WITH A SURFACE TROUGH
EXTENDING FROM 31N34W THROUGH THE LOW CENTER TO 15N47W.
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS BETWEEN 45
NM AND 240 NM IN THE NE SEMICIRCLE OF THE LOW. A RECENT ASCAT
PASS SHOWED 20-25 KT WINDS WITHIN 240 NM IN THE N AND NE
QUADRANTS OF THE LOW AND 8-10 FT SEAS ARE ACCOMPANYING THESE
WINDS. THIS LOW IS MOVING TO THE NW AT 10 KT AND ENVIRONMENTAL
CONDITIONS APPEAR TO BE CONDUCIVE FOR SLOW DEVELOPMENT DURING
THE NEXT COUPLE OF DAYS. THIS LOW HAS A MEDIUM CHANCE OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 21N24W TO LOW PRES NEAR 13N27.5W
1011 MB. SCATTERED MODERATE CONVECTION IS WITHIN 180-240 NM IN
THE NW QUADRANT OF THE LOW. FRESH TO STRONG WINDS AND 8-10 FT
SEAS ACCOMPANY THIS LOW AND THESE CONDITIONS WILL PERSIST
THROUGH THE NEXT 48 HOURS AS THE LOW AND TROPICAL WAVE CONTINUE
WESTWARD AT 15-20 KT.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH IS ALONG THE COAST OF MAURITANIA NEAR 18N16W
TO NEAR 16N19W WHERE IT ENDS...THEN RESUMES FROM 9N29W TO
8N40W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
13N50W TO THE COAST OF VENEZUELA NEAR 9N61W. SCATTERED MODERATE
AND ISOLATED STRONG CONVECTION IS FROM 15N TO 17N BETWEEN 21W
AND 24W...AND ALSO WITHIN 60 NM EITHER SIDE OF A LINE FROM
14N55W TO 13N59W TO 15N63W.

...DISCUSSION...

GULF OF MEXICO...
THE DOMINATE FEATURE IN THE GULF OF MEXICO IS HURRICANE ISAAC
WITH THE LARGE AND VAST CIRCULATION COVERING ALMOST THE ENTIRE
GULF...EXCEPT FOR THE SW PORTION AND BAY OF CAMPECHE. PLEASE
REFER TO THE SPECIAL FEATURES SECTION ABOVE FOR MORE DETAILS
ABOUT ISAAC. LIGHT TO MODERATE SW-W WINDS ARE IN THE SW GULF
WITH 4-7 FT NW SWELL ASSOCIATED WITH ISAAC PROPAGATING INTO THE
AREA. ATLC HIGH PRES WILL BUILD INTO THE AREA FROM THE W IN THE
WAKE OF ISAAC LATE WED THROUGH THE END OF THE WEEK WITH MODERATE
TO FRESH SE-S RETURN FLOW BECOMING ESTABLISHED ACROSS THE GULF
BY FRI.

AT THE UPPER LEVELS...A MID TO UPPER LOW IS NEAR THE NE MEXICAN
COAST AT 24N98W AND IT IS MOVING WESTWARD TOWARD CENTRAL MEXICO.
DRY AND STABLE AIR EXTENDS FROM THIS LOW TO THE SW GULF. A
NEARLY STATIONARY UPPER LEVEL RIDGE IS N OF ISSAC ALONG THE N
GULF COAST STATES FROM TEXAS NEAR 31N99W TO SOUTHERN ALABAMA
NEAR 32N87W TO CENTRAL FLORIDA NEAR 27N81W. DRY AIR ALONG THE
SOUTHERN PERIPHERY OF THE RIDGE IS ADVECTING INTO THE
CIRCULATION OF ISAAC HELPING TO LIMIT ADDITIONAL DEVELOPMENT AND
INTENSIFICATION.

CARIBBEAN SEA...
A RIDGE AXIS EXTENDS FROM HIGH PRES N OF THE AREA IN THE ATLC SW
THROUGH THE WINDWARD PASSAGE TO ACROSS JAMAICA TO THE EASTERN
COAST OF HONDURAS NEAR 15.5N83W. MEANWHILE NEARLY STATIONARY
1009 MB SURFACE LOW PRES IS JUST W OF THE COAST OF COLOMBIA NEAR
10N76W. THE PRES GRADIENT BETWEEN THE TWO FEATURES IS RESULTING
IN FRESH TO STRONG NE-E TRADES ACROSS THE CENTRAL CARIBBEAN WITH
MODERATE ANTICYCLONIC WINDS ELSEWHERE ACROSS THE BASIN. SEAS OF
8-10 FT ACCOMPANY THESE STRONGER WINDS WITH THE HIGHEST SEAS NW
OF THE COAST OF COLOMBIA AT THE TAIL END OF THE EASTERLY FETCH.
THESE CONDITIONS ARE FORECAST TO NOT CHANGE MUCH THROUGH THE
NEXT 48 HOURS.

ALOFT...A MID TO UPPER LEVEL LOW IS CENTERED SW OF THE COAST OF
HAITI NEAR 17N74W WITH AN ATTENDANT TROUGH STRETCHING N-NE OF
HAITI AND S-SW TO EASTERN PANAMA. SCATTERED SHOWERS AND ISOLATED
TSTMS ARE PRESENT OVER THE NW CARIBBEAN AS WELL AS OVER THE E
CARIBBEAN ISLANDS. AN UPPER LEVEL RIDGE EXTENDS FROM THE ATLC TO
ACROSS THE E CENTRAL CARIBBEAN ISLANDS TO N CENTRAL VENEZUELA.

ATLANTIC OCEAN...
1022 MB SURFACE HIGH PRES IS SE OF BERMUDA NEAR 25N61W WITH A
RIDGE AXIS REACHING TO THE W-NW TO SE GEORGIA. LIGHT TO MODERATE
WINDS DOMINATE THE WATERS W OF 50W WITH A CLUSTER OF SCATTERED
SHOWERS AND TSTMS N OF HISPANIOLA TO ACROSS THE TURKS AND
CAICOS...WITH ADDITIONAL CONVECTION E OF FLORIDA TO 77W. THE
OTHER MAIN FEATURES IN THE ATLC ARE THE AREA OF LOW PRES AND
ASSOCIATED TROUGH DISCUSSED IN THE SPECIAL FEATURES SECTION...
AND THE TROPICAL WAVE AND ASSOCIATED LOW DISCUSSED IN THE
TROPICAL WAVES SECTION ABOVE.

AN UPPER LEVEL ANTICYCLONE IS NEAR 22N31W WITH AN UPPER RIDGE
REACHING FROM 23N25W THROUGH THE ANTICYCLONE TO 21N67W. UPPER
LEVEL EASTERLIES DOMINATE THE REGION S OF 20N ON THE SOUTHERN
PERIPHERY OF THE ANTICYCLONE/RIDGE. OTHERWISE...AN UPPER LEVEL
LOW IS E OF THE RIDGE NEAR 24N20W. DRY AIR COVERS THE WATERS N
OF 24N E OF 25W. AN UPPER LEVEL TROUGH EXTENDS FROM 32N42W TO
27N50W AND THIS FEATURE IS SUPPORTING A SURFACE COLD FRONT N OF
32N...AS WELL AS A SURFACE TROUGH THAT REACHES NE FROM THE LOW
IN THE SPECIAL FEATURES SECTION.

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

$$
LEWITSKY




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