[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 131722
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON JUL 13 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1645 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 27W S OF 16N MOVING W NEAR 15 KT. A
BROAD AREA OF LOW-LEVEL CYCLONIC TURNING IS APPARENT IN VISIBLE
SATELLITE IMAGERY AS WELL IN THE 600-800 MB LAYER ACCORDING TO
SATELLITE DERIVED WINDS. THE WAVE ALSO COINCIDES WITH A LOW
AMPLITUDE DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 7N-13N BETWEEN 24W-30W. DEEP CONVECTION NEAR
THE WAVE IS LIKELY BEING MAINLY SUPPORTED BY LOW LEVEL
CONVERGENCE NEAR THE ITCZ.

A TROPICAL WAVE IS E OF THE LESSER ANTILLES EXTENDING FROM
18N53W TO 5N49W MOVING W 15-20 KT. THIS WAVE HAS BECOME
INCREASINGLY TILTED NW-SE BY THE NE WIND SURGE E OF THE AXIS
OVER THE N PORTIONS OF THE WAVE AXIS. A WELL DEFINED INVERTED V
PATTERN IS EVIDENT IN THE LOW-LEVEL CLOUDS SEEN ON VISIBLE
SATELLITE IMAGERY. THE WAVE ALSO COINCIDES WITH A WELL AMPLIFIED
MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. A
SMALL AREA OF SCATTERED MODERATE CONVECTION IS FROM 9N-12N
BETWEEN 50W-53W. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE
ALSO N OF THE WAVE AXIS FROM 19N-26N BETWEEN 52W-55W. THIS
SHOWER ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE
NEAR A SHORTWAVE UPPER LEVEL TROUGH. GFS APPEARS TO HAVE A GOOD
HANDLE ON THIS FEATURE AND SHOWS IT MOVING INTO THE LESSER
ANTILLES TOMORROW WITH THE N PART LIKELY FRACTURING.

A TROPICAL WAVE IS ALONG 88W MOVING W NEAR 18 KT. THE WAVE
POSITION IS MAINLY BASED ON A MOISTURE MAXIMUM IN TOTAL
PRECIPITABLE WATER AS LITTLE SIGNATURE IS APPARENT IN SATELLITE
IMAGERY OR OBSERVATIONS. SCATTERED MODERATE CONVECTION IS IN THE
GULF OF HONDURAS AND INLAND OVER GUATEMALA FROM 16N-19N BETWEEN
87W-89W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 13N16W 11N25W 7N37W 9N48W TO THE
S AMERICA COAST NEAR 7N58W. SCATTERED MODERATE CONVECTION IS
FROM 10N-13N BETWEEN 15W-18W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 5N-12N BETWEEN 30W-39W.

...DISCUSSION...

GULF OF MEXICO...
A 1018 MB STATIONARY SURFACE HIGH NEAR 27N87N DOMINATES THE
MAJORITY OF THE GULF OF MEXICO BRINGING GENERALLY FAIR WEATHER
ACROSS THE AREA. E-NE FLOW ALOFT AROUND AN UPPER LEVEL HIGH OVER
NW MEXICO NEAR 29N108W IS SUPPORTING THE SURFACE RIDGE.
ATMOSPHERIC INSTABILITY NEAR AN UPPER LEVEL LOW S OF MEXICO NEAR
17N107W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OVER THE S
BAY CAMPECHE S OF 20N W OF 93W. WINDS ARE LIGHT
AND VARIABLE IN THE VICINITY OF THE SURFACE HIGH AND ACROSS THE
N GULF...WITH ANTICYCLONIC FLOW AROUND THE RIDGE SUPPORTING E-SE
WINDS OF 10-15 KT ACROSS THE S HALF OF THE GULF. EXPECT LITTLE
CHANGE OVER THE NEXT COUPLE DAYS.

CARIBBEAN SEA...
FRESH TO STRONG TRADE WINDS REMAIN ACROSS THE CARIBBEAN BETWEEN
THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH
OVER NRN S AMERICA. FLOW IS STRONGEST NEAR THE COAST OF
COLUMBIA. THESE WINDS WILL REMAIN IN THE AREA AS THE SUBTROPICAL
RIDGE PERSISTS AND AS A TROPICAL WAVE E OF THE LESSER ANTILLES
REACHES THE E CARIBBEAN LATE TONIGHT AND TOMORROW. A TROPICAL
WAVE ALONG 88W IS GENERATING SCATTERED SHOWERS/THUNDERSTORMS IN
THE GULF OF HONDURAS AND INLAND OVER GUATEMALA FROM 16N-19N
BETWEEN 87W-89W. ATMOSPHERIC INSTABILITY NEAR AN UPPER LEVEL LOW
OVER THE SE BAHAMAS NEAR 23N73W IS SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS N OF 18N BETWEEN 74W-80W INCLUDING
PORTIONS OF CUBA. IN THE SW CARIBBEAN...SURFACE CONVERGENCE NEAR
A 1009 MB SURFACE LOW OVER COLUMBIA NEAR 8N77W AND THE PROXIMITY
OF THE E PACIFIC ITCZ...AS WELL AS UPPER LEVEL DIFFLUENCE DUE TO
AN UPPER LEVEL HIGH NEAR 14N88W ARE SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS S OF 12N W OF 80W. DEEP LAYER DRY AIR AND
ATMOSPHERIC STABILITY ASSOCIATED WITH AN UPPER LEVEL HIGH OVER
THE WINDWARD ISLANDS NEAR 13N61W ARE SUPPORTING GENERALLY FAIR
WEATHER ACROSS THE E CARIBBEAN.

ATLANTIC OCEAN...
UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE
ERN CONUS AND THE AFOREMENTIONED UPPER LEVEL HIGH OVER NW MEXICO
IS SUPPORTING ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS N OF 28N
BETWEEN 76W-79W. AN UPPER LEVEL TROUGH IS ACROSS THE SW NORTH
ATLC EXTENDING FROM AN UPPER LEVEL LOW OVER THE SE BAHAMAS NEAR
23N73W TO 29N67W. THE UPPER LEVEL TROUGH IS SUPPORTING A SURFACE
TROUGH EXTENDING FROM 21N66W TO 28N62W. SCATTERED SHOWERS ARE
WITHIN 100 NM OF THE TROUGH AXIS BETWEEN 61W-67W. A SHORTWAVE
UPPER LEVEL TROUGH IS ALONG 51W SUPPORTING THE TROPICAL WAVE E
OF THE LESSER ANTILLES...SEE ABOVE. A BROAD SURFACE RIDGE
DOMINATES THE REMAINDER OF THE ATLC ANCHORED BY A 1029 MB
SURFACE HIGH N OF THE DISCUSSION AREA NEAR 34N43W...EXCEPT FOR A
1023 MB SURFACE LOW NEAR 34N31W WITH AN ASSOCIATED DYING COLD
FRONT THAT ENTERS THE AREA NEAR 32N32W EXTENDING TO 28N41W...AND
CONTINUING AS A STATIONARY FRONT TO 30N44W. NO SHOWER ACTIVITY
IS CURRENTLY ASSOCIATED WITH THE FRONTAL SYSTEM. A BROAD UPPER
LEVEL RIDGE DOMINATES THE E ATLC E OF 50W SUPPORTING CONVECTION
ALONG THE ITCZ.

$$
WALTON



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