[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI JUL 17 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
1715 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 35W S OF 17N MOVING W NEAR 10 KT. THIS
WAVE COINCIDES WITH A LOW TO MIDDLE LEVEL CYCLONIC CIRCULATION
ALONG THE WAVE AXIS NEAR 11N. SCATTERED MODERATE CONVECTION IS
FROM 7N-10N BETWEEN 34W-37W AND FROM 11N-15N BETWEEN 33W-38W.

A TROPICAL WAVE IS ALONG 53W S OF 21N MOVING W NEAR 18 KT. THIS
WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON
THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SATELLITE
IMAGERY INDICATES THE WAVE EXHIBITS AN INVERTED-V PATTERN IN THE
COVERAGE OF LOW LEVEL CLOUDS. THE PRESENCE OF DRY LOW/MID-LEVEL
SAHARAN AIR SURROUNDS THE WAVE WITH SCATTERED MODERATE
CONVECTION LIMITED TO WITHIN 100 NM EITHER SIDE OF THE WAVE AXIS
FROM 11N-17N.

A TROPICAL WAVE EXTENDS ALONG 93W S OF 17N ACROSS SRN MEXICO AND
INTO THE E PACIFIC REGION. SCATTERED SHOWERS ACCOMPANY THE WAVE
ACROSS BELIZE...GUATEMALA...AND SERN MEXICO. FOR MORE
INFORMATION AS THIS WAVE TRACKS WWD PLEASE REFER TO THE E
PACIFIC TROPICAL WEATHER DISCUSSION...TWDEP...OR WMO HEADER
AXPZ20 KNHC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 12N33W 9N37W 13N51W
12N56W 10N63W. SCATTERED MODERATE CONVECTION IS FROM 11N-14N
BETWEEN 24W-28W...WHICH IS BEING SUPPORTED BY LOW LEVEL
CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM THE CAPE VERDE
ISLANDS NEAR 15N24W TO 8N26W. ELSEWHERE...SCATTERED MODERATE
CONVECTION IS FROM 7N-10N BETWEEN 38W-43W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE IS PRESENT ACROSS NRN FLORIDA AND THE NRN
GULF TO 93W...WITH A SURFACE RIDGE ACROSS THE CENTRAL GULF AND A
1019 MB HIGH NEAR 27N83W. STABLE ATMOSPHERIC CONDITIONS AND
SUBSIDENCE ASSOCIATED WITH THE SURFACE HIGH AND SURFACE RIDGE
ARE RESULTING IN GENERALLY FAIR WEATHER ACROSS THE GULF.
HOWEVER...ACROSS THE NRN GULF COAST...UPPER LEVEL MOISTURE IS
INTERACTING WITH ATMOSPHERIC LIFT ASSOCIATED WITH A WEAK
SHORTWAVE TROUGH OVER ERN TEXAS TO RESULT IN SCATTERED SHOWERS
AND TSTMS N OF 27N BETWEEN 84W-95W. ANTICYCLONIC FLOW AROUND THE
SURFACE RIDGE IS SUPPORTING GENERALLY E TO SE WINDS OF 10-15 KT
ACROSS A LARGE PART OF S GULF. A WEAK FRONTAL BOUNDARY IS
FORECAST TO MOVE INTO THE FAR NE GULF DURING THE WEEKEND...
BEFORE BECOMING DIFFUSE ON MONDAY.

CARIBBEAN SEA...
FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE
SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER
NRN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST OF
COLOMBIA. AN EARLIER SCATTEROMETER PASS AROUND 1100 UTC
INDICATES A LARGE AREA OF NE TO E WINDS OF 20 TO 30 KT IS
PRESENT ACROSS THE CENTRAL AND SW CARIBBEAN. THESE TRADE WINDS
ARE FORECAST TO REMAIN FRESH TO STRONG INTO THIS WEEKEND AS THE
SUBTROPICAL RIDGE REMAINS IN PLACE. COMPUTER MODEL GUIDANCE
INDICATES THAT STRONGER WINDS TO GALE FORCE ARE OCCURRING NEAR
THE COAST OF COLOMBIA...WHERE WINDS ARE BEING ENHANCED DUE TO
LOCAL TOPOGRAPHICAL VARIATIONS NEAR THE COAST OF COLOMBIA.
ALSO...AN UPPER LEVEL DIFFLUENT PATTERN IS OVER THE SW
CARIBBEAN...COSTA RICA AND PANAMA GENERATING SCATTERED SHOWERS
AND TSTMS S OF A LINE FROM 9N76W TO 13N84W. ACROSS MUCH OF
THE CENTRAL AND ERN CARIBBEAN...DEEP LAYER DRY AIR AND STABLE
ATMOSPHERIC CONDITIONS ARE RESULTING IN GENERALLY FAIR WEATHER.

ATLANTIC OCEAN...
DEEP LAYER MOISTURE IS COMBINING WITH UPPER LEVEL DIFFLUENCE TO
RESULT IN SCATTERED SHOWERS AND TSTMS N OF 31N BETWEEN 73W-77W.
FARTHER TO THE E...ISOLATED SHOWERS ARE BEING ENHANCED BY AN
UPPER LEVEL DIFFLUENT PATTERN N OF 29N BETWEEN 53W-62W.
SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT ACROSS MUCH OF
THE CENTRAL AND E ATLC AROUND A BROAD SURFACE RIDGE ASSOCIATED
WITH A 1037 MB HIGH CENTERED NE OF THE AZORES NEAR 40N25W.
ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE EXTENDS FROM
17N27W TO AN UPPER LEVEL HIGH NEAR 17N46W TO 12N60W. UPPER LEVEL
DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL RIDGE IS SUPPORTING
THE CONVECTION ALONG THE ITCZ AND IN THE VICINITY OF THE
TROPICAL WAVES MOVING WWD.

$$
HUFFMAN





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