[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 191758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI AUG 19 2011

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 FEATURE...

TROPICAL DEPRESSION EIGHT HAS NOW BEEN UPGRADED TO TROPICAL
STORM HARVERY AS OF 19/1800. HARVEY IS CENTERED NEAR 16.3N 84.2W
OR ABOUT 135 NM E OF ISLA ROATAN HONDURAS. HARVEY IS MOVING W
NEAR 9 KT. MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. FOR MORE
DETAILS REFER TO PUBLIC ADVISORIES ISSUED UNDER WMO HEADER
WTNT33 KNHC AND UNDER AWIPS HEADER MIATCPAT3.
FORECAST/ADVISORIES ARE ISSUED UNDER WMO HEADER WTNT22 KNHC AND
UNDER AWIPS HEADER MIATCMAT3. NUMEROUS MODERATE/SCATTERED STRONG
CONVECTION IS MAINLY N OF THE CENTER FROM 15N-18N BETWEEN
81W-88W IMPACTING EXTREME NRN HONDURAS. THE HEAVY RAINFALL
ACROSS NRN HONDURAS...GUATEMALA...AND BELIZE OVER THE NEXT
COUPLE OF DAYS COULD CAUSE POTENTIAL FLOODING AND MUDSLIDES.

A WELL-DEFINED TROPICAL WAVE IS JUST OFF THE WRN COAST OF AFRICA
ALONG 17N19W MOVING W AT 10-15 KT. LOW-LEVEL CYCLONIC FLOW IS
AROUND THE WAVE AXIS CONCENTRATED NEAR 13N AROUND A 1006 MB
SURFACE LOW. TOTAL PRECIPITABLE WATER IMAGERY INDICATES HIGH
MOISTURE VALUES SURROUND THE WAVE. SCATTERED MODERATE/STRONG
CONVECTION IS FROM 14N-16N BETWEEN 17W-23W....AND FROM 9N-12N
BETWEEN 24W-30W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS FROM 8N-12N BETWEEN 17W-24W. WHILE THE CONVECTION IS
DISORGANIZED AT THIS TIME...THE UPPER-LEVEL ENVIRONMENT IS
FAVORABLE FOR FURTHER DEVELOPMENT.

ANOTHER WELL-DEFINED WAVE IS IN THE CENTRAL TRPCL ATLC ALONG
17N48W TO 9N47W WITH CYCLONIC FLOW CONCENTRATED ALONG THE AXIS
AROUND A 1006 MB LOW NEAR 13N. THIS SYSTEM IS MOVING W NEAR 20
KT. CONVECTION NEAR THE WAVE HAS INCREASED OVER THE PAST 24
HOURS. CURRENTLY NUMEROUS MODERATE/SCATTERED STRONG CONVECTION
IS MAINLY W OF THE WAVE FROM 13N-17N BETWEEN 47W-53W...AND SE OF
THE AXIS  FROM 6N-9N BETWEEN 42W-47W. UPPER LEVEL CONDITIONS ARE
EXPECTED TO BECOME MORE CONDUCIVE FOR FURTHER DEVELOPMENT OVER
THE NEXT COUPLE OF DAYS.

...TROPICAL WAVES...

SEE SPECIAL FEATURES SECTION FOR DETAILS ON THE TROPICAL WAVES.

...THE ITCZ/THE MONSOON TROUGH...

THE ACTIVE TRPCL WAVE OVER THE FAR ERN TRPCL ATLC HAS SPLIT
THE MONSOON TROUGH. ONE SECTION REMAINS INLAND OVER
AFRICA...WHILE THE OTHER CONTINUES ON THE W SIDE OF THE TRPCL
WAVE ALONG 13N22W 11N35W TO THE TRPCL WAVE IN THE CENTRAL TRPCL
ATLC NEAR 13N48W. CONVECTION NEAR THE MONSOON TROUGH HAS BEEN
ASSOCIATED WITH THE TROPICAL WAVES AND IS DISCUSSED IN THE
SPECIAL FEATURES SECTION.

...DISCUSSION...

THE GULF OF MEXICO...
UPPER LEVEL RIDGING COVERS MUCH OF THE GULF OF MEXICO CENTERED
OVER WRN TEXAS. WATER VAPOR IMAGERY ALSO INDICATES MOSTLY DRY
AIR ALOFT COVERING THE AREA. THIS IS MAINTAINING MOSTLY FAIR
WEATHER AND LIGHT SURFACE FLOW. WEAK HIGH PRESSURE IS CENTERED
OVER ERN MEXICO NEAR 21N98W. A FEW ISOLATED
SHOWERS/THUNDERSTORMS ARE NOTED OVER THE SE GULF S OF 27N E OF
83W ASSOCIATED WITH AN AREA OF DEEP LAYER MOISTURE EVIDENT IN
TOTAL PRECIPITABLE WATER IMAGERY. EXPECT WEAK RIDGING TO FORM
OVER THE NE GULF WITH RELATIVELY LIGHT ANTI-CYCLONIC FLOW AROUND
IT.

THE CARIBBEAN SEA...
T.S. HARVERY IS CURRENTLY IMPACTING NRN HONDURAS AND HEADING WWD
TOWARDS THE BAY ISLANDS OF HONDURAS AND BELIZE. SEE SPECIAL
FEATURES SECTION FOR MORE DETAILS. SCATTERED
SHOWERS/THUNDERSTORMS ARE ACROSS THE SW CARIBBEAN FROM 10N-12N
BETWEEN 81W-83W...AND S OF 12N TO PANAMA BETWEEN 75W-80W
ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS FROM THE E
PACIFIC ACROSS COSTA RICA AND PANAMA TO NRN COLOMBIA. ALOFT...AN
UPPER LEVEL RIDGE IS CENTERED OVER THE FAR NW CARIBBEAN NEAR
20N85W. UPPER LEVEL TROUGHING COVERS THE ERN ATLC EXTENDING FROM
THE ATLC ACCOMPANIED BY MODERATE DRY AIR ALOFT. THIS IS
MAINTAINING MOSTLY FAIR CONDITIONS ACROSS THE ERN CARIBBEAN WITH
AREAS OF ISOLATED SHOWERS EMBEDDED WITHIN THE TRADEWIND FLOW.
EXPECT T.S. HARVEY TO CONTINUE TO IMPACT PORTIONS OF THE NW
CARIBBEAN. AN ACTIVE TROPICAL WAVE STILL E OF THE LESSER
ANTILLES MAY BEGIN IMPACTING THE ERN ISLANDS WITHIN THE NEXT
24-36 HOURS. SEE SPECIAL FEATURES FOR MORE DETAILS ON THIS WAVE.

THE ATLANTIC OCEAN...
A LARGE AREA OF SCATTERED SHOWERS/THUNDERSTORMS IS OVER THE WRN
ATLC W OF 73W ACROSS THE NW BAHAMAS AND REACHING S FLORIDA
ASSOCIATED WITH A SHORTWAVE UPPER TROUGH EXTENDING FROM 35N74W
TO 28N80W. A WEAK UPPER RIDGE IS TO THE E ACROSS THE CENTRAL
BAHAMAS TO 31N65W. ANOTHER UPPER LEVEL TROUGH IS FROM 31N57W TO
THE ERN CARIBBEAN. THIS UPPER TROUGH IS SUPPORTING A WEAK
SURFACE TROUGH ALONG 32N54W TO 28N57W WITH ISOLATED SHOWERS
WITHIN 90 NM EITHER SIDE THE AXIS. THE REMAINDER OF THE BASIN IS
DOMINATED BY SURFACE RIDGING AROUND A 1026 MB HIGH NEAR 39N29W
PROVIDING MOSTLY FAIR WEATHER. ALOFT...A PAIR OF UPPER RIDGES
ARE CENTERED NEAR 25N48W...AND 34N33W SUPPORTING THE SURFACE
RIDGE. AN UPPER LEVEL TROUGH IS TO THE E ALONG 15W N OF 25N.
VISIBLE SATELLITE IMAGERY CONTINUES TO SHOW AN AREA OF DUST E OF
50W TO THE N OF THE TROPICAL WAVES.

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

$$
WALTON




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