[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121133
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE JUL 12 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1100 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS INTRODUCED IN THE ERN TRPCL ATLC ALONG 13N25W
TO 7N26W MOVING W 10-15 KT. WAVE IS LOW AMPLITUDE AND DIFFICULT
TO DISCERN AT THE SURFACE. HOWEVER...SATELLITE HOVMOLLER
DIAGRAMS INDICATE A TRACKABLE FEATURE BACK TO THE COAST OF
AFRICA. UPPER AIR DATA FROM DAKAR SENEGAL ALSO INDICATES A CLEAR
WAVE SIGNAL CROSSING THE STATION AROUND 10/1200 UTC. NO DEEP
CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE.

TROPICAL WAVE IN THE WRN TRPCL ATLC EXTENDS FROM NEAR 17N54W TO
8N59W MOVING WNW  10-15 KT. WAVE CONTINUES TO PRECEDE A SURGE OF
DEEP LAYER MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY.
SATELLITE IMAGERY ALSO INDICATES LOW LEVEL CYCLONIC FLOW IS
AROUND THE WAVE AXIS. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 11N-14N BETWEEN 55W-60W.

TROPICAL WAVE IN THE WRN CARIBBEAN EXTENDS ACROSS ERN
NICARAGUA/HONDURAS ALONG 84W FROM 13N-17N MOVING W 10-15 KT.
WAVE IS EMBEDDED WITHIN A BROAD AREA OF ENHANCED MOISTURE
ACROSS THE WRN CARIBBEAN. THE WAVE LIES UNDER DIFFLUENT FLOW
ALOFT WHICH IS HELPING ENHANCE CONVECTION. IT IS DIFFICULT TO
DETERMINE WHAT CONVECTION IS CAUSED BY THE WAVE...THE UPPER
LEVEL INFLUENCE...AND ALSO THE MONSOON TROUGH TO THE S OF THE
WAVE. NUMEROUS STRONG CONVECTION IS FROM 11N-13N BETWEEN
82W-84W. SCATTERED MODERATE/STRONG CONVECTION IS E OF THE WAVE
AXIS FROM 12N-17N BETWEEN 81W-83W. SIMILAR ACTIVITY IS ALSO
MOVING INTO THE YUCATAN PENINSULA AND BELIZE FROM 15N-20N
BETWEEN 87W-90W.

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

THE MONSOON TROUGH EXTENDS ACROSS AFRICA FROM THE PRIME MERIDIAN
AT 23N ALONG 22N12W 11N23W. THE ITCZ AXIS CONTINUES ON THE OTHER
SIDE OF A TROPICAL WAVE ALONG 8N31W 5N44W 6N55W. SCATTERED
MODERATE CONVECTION IS WITHIN 60 NM N...AND 75 NM S OF THE AXIS
BETWEEN 30W-37W.

...DISCUSSION...

GULF OF MEXICO...
WEAK SURFACE RIDGING COVERS THE GULF OF MEXICO THIS MORNING
CENTERED AROUND A 1018 MB HIGH OFF THE W CENTRAL COAST OF
FLORIDA NEAR 28N83W SUPPORTING FAIR WEATHER AND LIGHT
ANTI-CYCLONIC FLOW AROUND THE RIDGE. ALOFT...AN UPPER LEVEL
RIDGE COVERS THE NRN GULF CENTERED OVER NRN ALABAMA. AN UPPER
LEVEL TROUGH COVERS THE SW GULF EXTENDING FROM SRN MEXICO NEAR
18N95W TO 25N93W. A SHORTWAVE UPPER TROUGH IS ALONG IN THE N
CENTRAL GULF FROM SE LOUISIANA TO 25N89W SUPPORTING A FEW
ISOLATED SHOWERS/THUNDERSTORMS ALONG THE NRN GULF COAST BETWEEN
83W-89W. WATER VAPOR IMAGERY INDICATES DRY AIR IS WRAPPING
AROUND THE SRN EXTENT OF THE UPPER RIDGE WHICH IS FURTHER
SUPPORTING THE FAIR WEATHER. TOTAL PRECIPITABLE WATER IMAGERY
STILL INDICATES ENHANCED MOISTURE IS ACROSS THE NRN GULF. WITH
DAYTIME HEATING THIS WILL LIKELY MEAN SHOWERS/THUNDERSTORMS WILL
POP UP LATER IN THE AFTERNOON TODAY. SHOWER/THUNDERSTORM
ACTIVITY WILL ALSO LIKELY INCREASE OVER THE SE GULF AS MOISTURE
FROM A TROPICAL WAVE IN THE WRN CARIBBEAN FLOWS INTO THE BASIN
AS THE WAVE MOVES WWD. WEAK SURFACE RIDGING WILL CONTINUE OVER
THE NRN GULF.

CARIBBEAN SEA...
MOIST DIFFLUENT FLOW ALOFT COVERS THE NW CARIBBEAN AROUND THE
ERN SIDE OF AN INVERTED UPPER TROUGH OVER THE SRN GULF OF
MEXICO...AND A NARROW UPPER RIDGE EXTENDING FROM NRN COLOMBIA
TO NEAR 19N83W. THIS AREA OF DIFFLUENCE LIES OVER A TROPICAL
WAVE ALONG 84W. THIS COMBINATION IS PRODUCING SHOWERS/
THUNDERSTORMS ACROSS THE WRN CARIBBEAN S OF 20N BETWEEN 80W-90W
WITH THE STRONGEST ACTIVITY E OF THE WAVE AXIS...AND ACROSS SRN
NICARAGUA. STRONG SHOWERS/THUNDERSTORMS ARE ALSO FROM 9N-12N
BETWEEN 74W-86W INFLUENCED BY THE MONSOON TROUGH EXTENDING FROM
THE ERN PACIFIC ACROSS NRN COSTA RICA TO NRN COLOMBIA. THE
REMAINDER OF THE BASIN IS UNDER MOSTLY FAIR CONDITIONS WITH
15-20 KT ELY TRADEWIND FLOW. A FEW ISOLATED SHOWERS ARE NOTED IN
THE NE CARIBBEAN N OF 15N E OF 71W. THIS AREA IS ALSO IN AN AREA
OF MODERATE MOISTURE INDICATED BY TOTAL PRECIPITABLE WATER
IMAGERY. A FEW ISOLATED SHOWERS ARE ALSO MOVING ACROSS THE SRN
WINDWARD ISLANDS DUE TO MOISTURE ASSOCIATED WITH A TROPICAL WAVE
E OF THE ISLANDS. SHOWER ACTIVITY IN THIS AREA WILL INCREASE AS
THE WAVE MOVES WWD TOWARDS THE BASIN. ALOFT...A HORIZONTALLY
ALIGNED UPPER LEVEL TROUGH IS ACROSS THE NRN CARIBBEAN WITH
AXIS ALONG 18N. AN UPPER RIDGE IS TO THE S OF THE UPPER TROUGH
CENTERED OVER THE WINDWARD ISLANDS NEAR 13N62W. EXPECT
SHOWER/THUNDERSTORM ACTIVITY TO PERSIST ACROSS THE WRN CARIBBEAN
AS MOISTURE ASSOCIATED WITH THE TROPICAL WAVE REMAINS.
ALSO...MUCH OF CENTRAL AMERICA AND SRN MEXICO IS AT THREAT FOR
PROLONGED HEAVY RAINFALL THROUGHOUT THE END OF THE WEEK WHICH
WILL INCREASE THE CHANCE FOR DEADLY FLOODING AND MUDSLIDES.
MODEL GUIDANCE INDICATES THE MONSOON TROUGH WILL STRENGTHEN AND
LIFT FARTHER N PLACING ABNORMALLY STRONG WLY FLOW AGAINST
CENTRAL AMERICA AND SRN MEXICO. THIS W-SW FLOW WILL DRAW
SIGNIFICANT TROPICAL MOISTURE ACROSS THESE AREAS. COMBINED WITH
OROGRAPHIC LIFT DUE TO MOUNTAINS THIS CREATES A FORMULA TO EQUAL
HEAVY PRECIPITATION. THESE AREAS SHOULD MONITOR THE SITUATION
OVER THE NEXT FEW DAYS AND STAY TUNED FOR UPDATES ON THIS
POSSIBLY DANGEROUS SCENARIO.

ATLANTIC OCEAN...
SURFACE RIDGING DOMINATES THE MAJORITY OF THE ATLC THIS MORNING
ANCHORED BY A 1028 MB HIGH NEAR 33N47W PROVIDING FAIR CONDITIONS
BASIN-WIDE. ALOFT...AN UPPER LEVEL RIDGE COVERS THE WRN ATLC
CENTERED OVER NRN ALABAMA. AN UPPER LEVEL TROUGH IS TO THE E
ALONG 52W. A SHORTWAVE UPPER TROUGH EXTENDS OFF THE MAIN TROUGH
EXTENDING TO THE NW BAHAMAS ALONG 25N. THIS IS PRODUCING SOME
UPPER LEVEL CLOUDS AND POSSIBLE ISOLATED SHOWERS FROM 24N-32N
BETWEEN 51W-74W. UPPER LEVEL RIDGING COVERS MUCH OF THE ERN ATLC
CENTERED NEAR 36N33W. AN UPPER LEVEL TROUGH COVERS THE FAR ERN
ATLC EXTENDING ACROSS SPAIN TO E OF THE CANARY ISLANDS. ACROSS
THE TROPICAL ATLC S OF 26N...AN UPPER LEVEL RIDGE IS CENTERED
OVER THE SRN WINDWARD ISLANDS NEAR 13N62W. AN UPPER LEVEL LOW IS
CENTERED NEAR 23N35W...AND AN UPPER LEVEL RIDGE IS CENTERED OFF
THE W COAST OF AFRICA NEAR 19N18W.\

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

$$
WALTON






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