[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 190005
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT AUG 18 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION HELENE IS INLAND CENTERED NEAR 22.6N 98.8W
AT 18/2100 UTC...OR ABOUT 65 MI WNW OF TAMPICO MEXICO... MOVING
WNW AT 4 KT. MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH GUSTS TO
35 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB. THE BROAD
CYCLONIC CIRCULATION ASSOCIATED WITH HELENE CONTINUES TO
DOMINATE MUCH OF THE SW GULF S OF 25N AND W OF 94W...WITH WIDELY
SCATTERED MODERATE CONVECTION. SEE LATEST NHC INTERMEDIATE
PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC
AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. THE CIRCULATION
ASSOCIATED WITH HELENE IS EXPECTED TO DRIFT WNW OVER THE NEXT 24
HOURS AND WEAKEN...AND INTERACT WITH SIERRA MADRE ORIENTALES OF
MEXICO TO PRODUCE SIGNIFICANT RAINFALL... WITH THE POTENTIAL FOR
WIDESPREAD HEAVY RAINS...LEADING TO AREAS OF FLASH FLOODING AND
MUDSLIDES.

HURRICANE GORDON IS LOCATED NEAR 34.3N 35.2W AT 19/0000...OR
ABOUT 525 NM WSW OF THE AZORES...MOVING E AT 18 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 965 MB. MAXIMUM SUSTAINED WIND SPEED
IS 90 KT WITH GUSTS TO 110 KT. SATELLITE IMAGERY SHOWS A 20 NM
WELL DEFINED EYE. SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION IS FROM 33N-36N BETWEEN 33W-37W. THE GOVERNMENT OF
PORTUGAL HAS ISSUED A HURRICANE WARNING FOR THE CENTRAL AND
EASTERN AZORES. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT3/WTNT33 AND THE FULL FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE
DETAILS.

A VIGOROUS TROPICAL WAVE IS LOCATED IN THE ERN ATLC ALONG
30W...WITH A ASSOCIATED 1008 MB LOW NEAR 14N30W EMBEDDED WITHIN
THE MONSOON TROUGH. THIS WAVE IS MOVING WESTWARD AROUND 20 KT.
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 14N-17N BETWEEN
30W-33W. CONDITIONS APPEAR CONDUCIVE FOR GRADUAL DEVELOPMENT
DURING THE NEXT FEW DAYS...AND THIS SYSTEM HAS A HIGH CHANCE
OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. GLOBAL
MODELS HAS A WWD TRAJECTORY TOWARDS THE CARIBBEAN. INTERESTS
ACROSS THE E AND NE CARIBBEAN SHOULD MONITOR THE PROGRESS OF
THIS SYSTEM AS IT TREKS ACROSS THE ATLC.

...TROPICAL WAVES...

A TROPICAL WAVE IS LOCATED ACROSS THE CENTRAL TROPICAL ATLC
ALONG 42W...WITH AN ASSOCIATED 1010 MB LOW NEAR 11N42W
EMBEDDED WITHIN THE MONSOON TROUGH. THIS WAVE IS MOVING W AT
15-20 KT. SAHARAN AIR CONTINUES TO DOMINATE THIS WAVE AND LIMIT
CONVECTION. SCATTERED SHOWERS ARE WITHIN 90 NM OF THE WAVE AXIS.

A CARIBBEAN TROPICAL WAVE IS ALONG ABOUT 73W S OF 20N MOVING WWD
NEAR 20 KT. THIS WAVE HAS BEEN ACCOMPANIED BY A LARGE AREA OF
SAL. SCATTERED MODERATE TO STRONG CONVECTION IS PRESENTLY OVER
HISPANIOLA FROM 18N-20N BETWEEN 70W-73W. SIMILAR CONVECTION IS
OVER N VENEZUELA AND N COLOMBIA FROM 7N-12N BETWEEN 70W-74W. THE
CARIBBEAN ALSO HAS SCATTERED SHOWERS WITHIN 120 NM OF THE WAVE
AXIS FROM 12N-18N.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXITS THE W AFRICAN COAST NEAR 14N17W...AND
CONTINUES WWD TO A LOW PRES 1008 MB NEAR 14N30W...THEN CONTINUES
WSW TO A LOW PRES NEAR 11N42W...THEN CONTINUES ON TO 7N47W...
WHERE IT TRANSITIONS TO AN ITCZ...CONTINUING ON TO 5N52W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 9N-12N
BETWEEN 18W-24W...FROM 10N-13N BETWEEN 30W-36W...AND FROM 7N-10N
BETWEEN 38W-43W.

...DISCUSSION...

GULF OF MEXICO...
WEAK SURFACE RIDGING EXTENDS FROM THE W ATLC ACROSS SRN FLORIDA
AND INTO THE CENTRAL GULF...THEN NW INTO THE NW GULF. HELENE IS
DRIFTING FURTHER INLAND ACROSS MEXICO. A WEAK SURFACE TROUGH IS
OVER N CENTRAL FLORIDA...YIELDING ISOLATED MODERATE CONVECTION.
A WEAK COLD FRONT IS SINKING SWD ACROSS THE N GULF STATES WITH
NUMEROUS MODERATE TO STRONG CONVECTION ERUPTING ACROSS S
LOUISIANA AND THE NEARSHORE COASTAL WATERS...AND IS EXPECTED TO
SHIFT SLOWLY ESE TONIGHT. BROAD UPPER TROUGHING ACROSS THE E
TWO-THIRDS OF THE US.S WILL MAINTAIN MILD W TO NW FLOW ALOFT
ACROSS THE N AND NE GULF AND YIELD UNSTABLE CONDITIONS...AND
THUS ACTIVE CONVECTION IS EXPECTED THERE THROUGH TONIGHT. ACROSS
THE SW AND S CENTRAL GULF...MOIST AND UNSTABLE SELY SURFACE FLOW
CONTINUES TO SPREAD MOISTURE TOWARDS TEXAS AND THE MEXICAN
OFFSHORE WATERS. SE WINDS 15-20 KT WITH SEAS 6-7 FT ARE LIKELY
TO CONTINUE ACROSS THIS REGION.

CARIBBEAN SEA...
A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN. SEE ABOVE.
ELSEWHERE...SCATTERED MODERATE TO STRONG CONVECTION IS ALONG THE
COAST OF NICARAGUA FROM 10N-15N BETWEEN 81W-86W. SIMILAR
CONVECTION IS OVER CUBA BETWEEN 75W-83W. 10-20 KT TRADEWINDS ARE
OVER THE CARIBBEAN SEA WITH STRONGEST WINDS ALONG THE COAST OF N
COLOMBIA. SCATTERED SHOWERS ARE OVER THE SW CARIBBEAN S OF 14N.
EXPECT THE TROPICAL WAVE TO CONTINUE TO MOVE W AT 20 KT WITH
SHOWERS OVER THE NEXT 24 HOURS. ALSO EXPECT MORE CONVECTION OVER
THE SW CARIBBEAN.

ATLANTIC OCEAN...
A 1022 MB HIGH IS CENTERED OVER THE CENTRAL ATLANTIC NEAR
27N57W. A LARGE AREA OF AFRICAN DUST EXTENDS FROM 15N-30N E OF
60W. IN THE UPPER LEVELS...DIFFLUENCE FROM THE UPPER TROUGH OVER
THE SE UNITED STATES IS PRODUCING WIDELY SCATTERED MODERATE
CONVECTION OVER THE W ATLANTIC FROM 27N-32N BETWEEN 72W-80W.

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

$$
FORMOSA




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