[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 092342
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON JUL 09 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.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 20N27W TO 12N25W MOVING W NEAR 10 KT.
THE WAVE LIES WITHIN A LARGE SURGE OF DEEP LAYER MOISTURE
PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. THERE IS ALSO A
CLEARING IN THE LARGE AREA OF SAHARAN DUST AROUND THE WAVE
INDICATING ITS PRESENCE. ISOLATED MODERATE CONVECTION IS
EMBEDDED WITHIN THE MONSOON TROUGH FROM 10N-12N BETWEEN 24W-27W.

TROPICAL WAVE IS ALONG 25N63W TO 17N66W MOVING W NEAR 15 KT. THE
WAVE IS WITHIN AN AREA OF ENHANCED MOISTURE. THE WAVE ALSO LIES
ON THE LEADING EDGE OF A LARGE AREA OF SAHARAN DUST THAT EXTENDS
ACROSS MUCH OF THE TROPICAL ATLC. THE DUST IS SUPPRESSING MOST
CONVECTION NEAR THE WAVE. IT ALSO IS WITHIN AN UPPER LEVEL RIDGE
WITH UPPER TROUGHS/CUT-OFF LOWS ON EITHER SIDE. ISOLATED WEAK
CONVECTION IS IN THE VICINITY OF THE WAVE...BUT IS LIKELY DUE TO
THE UPPER TROUGHS/LOWS AND NOT THE WAVE ITSELF.

TROPICAL WAVE IS MOVING INLAND INTO ERN MEXICO ALONG 21N96W TO
15N97W MOVING W AT 12-15 KT. THERE ARE STILL ENHANCED MOISTURE
VALUES NEAR THE WAVE AND ACROSS THE WRN BAY OF CAMPECHE. A LARGE
BURST OF CONVECTION THAT FLARED UP EARLIER TODAY HAS MOSTLY
DISSIPATED WITH ONLY SCATTERED MODERATE CONVECTION FROM 19N-21N
BETWEEN 93W-97W. THERE IS ALSO ISOLATED MODERATE/STRONG
CONVECTION ELSEWHERE ACROSS SRN MEXICO AND THE YUCATAN
PENINSULA...BUT IT IS HARD TO SAY WHETHER IT CAN BE ATTRIBUTED
TO THE WAVE OR JUST TYPICALLY AFTERNOON CONVECTION. SIMILAR
ACTIVITY HAS BEEN PRESENT OVER THESE AREAS FOR SEVERAL DAYS...SO
IT SEEMS TO BE MOSTLY THE RESULT OF DAYTIME HEATING AND
INSTABILITY AND NOT THE WAVE. THERE IS ALSO THE INFLUENCE OF AN
UPPER LEVEL TROUGH THAT CAN ALSO BE ENHANCING SOME OF THE
ACTIVITY.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
GUINEA-BISSAU AT 12N17W TO 11N30W. THE ITCZ BEGINS AT 11N30W
CONTINUING ALONG 7N42W 4N52W. A CLUSTER OF STRONG CONVECTION IS
MOVING OFF THE COAST OF AFRICA FROM 9N-14N BETWEEN 13W-18W.
ISOLATED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 13W-22W...AND
WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 31W-52W.

...DISCUSSION...

GULF OF MEXICO...
WEAK SURFACE RIDGING IS ACROSS THE GULF OF MEXICO AROUND A 1018
MB HIGH CENTERED NEAR 26N88W. LIGHT ANTI-CYCLONIC FLOW IS AROUND
THE SURFACE RIDGE WITH STRONGER WINDS IN THE SW GULF NEAR A
TROPICAL WAVE MOVING INTO MEXICO. SEE TROPICAL WAVE SECTION
ABOVE FOR MORE DETAILS. DRY AIR ALOFT IS KEEPING A GOOD PORTION
OF THE BASIN UNDER MOSTLY FAIR CONDITIONS EXCEPT FOR AN AREA OF
SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE NRN GULF FROM 27N-29N
BETWEEN 88W-95W. SIMILAR ACTIVITY IS ACROSS INLAND PORTIONS OF
THE GULF COAST INCLUDING CENTRAL WRN FLORIDA....SRN ALABAMA AND
ERN TEXAS WITH ISOLATED ACTIVITY ACROSS MUCH OF THE OTHER
STATES. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO OVER THE
YUCATAN PENINSULA AND CUBA. THE ACTIVITY ACROSS THE NRN GULF CAN
BE TIED TO A MID-LEVEL TROUGH OVER LOUISIANA. THE ACTIVITY
ACROSS THE YUCATAN...CUBA AND FLORIDA IS ASSOCIATED WITH
DIFFLUENCE ALOFT AROUND AN UPPER LEVEL TROUGH/LOW EXTENDING FROM
THE FLORIDA PANHANDLE TO A CUT-OFF UPPER LOW AT 25N85W WHERE IT
THEN EXTENDS AN AXIS TO THE W TO THE BAY OF CAMPECHE NEAR
22N97W. ANOTHER UPPER TROUGH AXIS EXTENDS TOWARDS THE E TO
CONNECT WITH ANOTHER CUT-OFF LOW IN THE W ATLC. WEAK SURFACE
RIDGING WILL REMAIN ACROSS THE BASIN FOR THE NEXT 24 HOURS
BEFORE A SURFACE TROUGH FORMS NEAR THE YUCATAN PENINSULA AND
DRAWS MOISTURE ACROSS THE ERN GULF.

CARIBBEAN SEA...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS MUCH OF CUBA ALONG
WITH PORTIONS OF JAMAICA...THE CAYMAN ISLANDS...AND HISPANIOLA.
THIS ACTIVITY IS DUE TO THE COMBINATION OF DAYTIME HEATING AS
WELL AS THE INFLUENCE OF AN ELONGATED UPPER TROUGH WITH A SERIES
OF CUT-OFF UPPER LOWS THAT EXTENDS FROM THE CENTRAL ATLC INTO
THE W ATLC CONTINUING N OF CUBA INTO THE ERN GULF. A TROPICAL
WAVE MOVING THROUGH PUERTO RICO IS ONLY CAUSING A FEW
SHOWERS/THUNDERSTORMS OVER THE ISLAND. A WEAK UPPER TROUGH HAS
ALSO FORMED ACROSS THE CENTRAL CARIBBEAN BETWEEN TWO UPPER LEVEL
RIDGES TO EITHER SIDE ACROSS BOTH THE WRN AND ERN CARIBBEAN.
STRONG AND NUMEROUS SHOWERS/THUNDERSTORMS COVER MOST OF PANAMA
AND PORTIONS OF NRN COLOMBIA ASSOCIATED WITH THE E PACIFIC
MONSOON TROUGH EXTENDING S OF PANAMA TO A 1007 MB LOW OVER NRN
COLOMBIA. THE CENTRAL AND ERN CARIBBEAN ARE EXPERIENCING MOSTLY
FAIR CONDITIONS DUE TO DRY AIR ALOFT AROUND THE UPPER RIDGE IN
THE ERN CARIBBEAN. TRADEWIND FLOW OF 15-20 KT IS PRESENT ACROSS
MUCH OF THE BASIN REACHING UP TO 25 KT NEAR THE COAST OF
COLOMBIA. EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS.

ATLANTIC OCEAN...
A BROAD UPPER LEVEL RIDGE IS COVERING A PORTION OF THE W ATLC
NEAR THE NRN EXTENT OF THE DISCUSSION AREA SUPPORTING WEAK
SURFACE RIDGING EXTENDING FROM THE CENTRAL ATLC. AN ELONGATED
UPPER TROUGH WITH SEVERAL CUT-OFF LOWS EXTENDS S OF THE RIDGE
BEGINNING IN THE CENTRAL ATLC NEAR 31N33W TO AN UPPER LOW AT
29N47W TO A SECOND UPPER LOW NEAR 26N68W AND TO A THIRD UPPER
LOW IN THE SE GULF OF MEXICO. THIS SERIES OF LOWS IS PRODUCING
ISOLATED SHOWER/THUNDERSTORM ACTIVITY ACROSS THE WRN
BAHAMAS...NEAR THE TROPICAL WAVE FROM 21N-26N BETWEEN
64W-69W...AND FROM 24N-26N BETWEEN 53W-59W. UPPER LEVEL RIDGING
COVERS THE REMAINDER OF THE BASIN FROM THE TROPICAL ATLC NEAR
10N45W TO NW AFRICA. AT THE SURFACE....BROAD SURFACE RIDGING
DOMINATES ANCHORED BY A 1030 MB AZORES HIGH. SATELLITE IMAGERY
CONTINUES TO SHOW A LARGE AREA OF AFRICAN DUST COVERING MUCH OF
THE TROPICAL ATLC BETWEEN THE TROPICAL WAVES.

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

$$
WALTON





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