[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 140532
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE JUL 14 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 31W S OF 16N MOVING W 15-20 KT. THIS
WAVE COINCIDES WITH A LOW AMPLITUDE MAXIMUM IN DEEP LAYER
MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. SATELLITE-DERIVED WINDS INDICATE CYCLONIC CURVATURE IN
THE FLOW WITHIN THE 800-600 MB LAYER. THE QUIKSCAT PASS AROUND
13/2015 UTC INDICATED E WINDS AT 10-15 KT AHEAD OF THE WAVE
FOLLOWED BY E TO SE WINDS AT 15-20 KT BEHIND THE WAVE. THIS WAVE
IS ASSOCIATED WITH SCATTERED MODERATE CONVECTION FROM 8N-15N
BETWEEN 29W-32W.

A TROPICAL WAVE IS E OF THE LESSER ANTILLES AND EXTENDS FROM
19N57W TO 5N53W MOVING W 15-20 KT. THE STRONG LOW LEVEL EASTERLY
JET FOLLOWING THE N PORTION OF THE WAVE IS CONTRIBUTING TO THE
NW-SE TILT OF THE WAVE. A WELL-DEFINED INVERTED V PATTERN IS
EVIDENT IN THE COVERAGE OF LOW-LEVEL CLOUDS BASED ON RECENT
SATELLITE IMAGERY. THE RELATIVELY SHORT WAVELENGTH OF THE
TROPICAL WAVE IS CURRENTLY PRECLUDING AN EVEN FASTER WESTWARD
WAVE MOTION. THE WAVE ALSO COINCIDES WITH A WELL-AMPLIFIED
MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY.
THE WAVE IS LEADING ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR THAT
IS INHIBITING DEEP CONVECTION NEAR THE WAVE. NEVERTHELESS...
SCATTERED SHOWERS ARE OCCURRING FROM 8N-12N BETWEEN
54W-56W...AND THE DRY AIR IS LIKELY CONTRIBUTING TO STRONG
DOWNDRAFTS AND GUSTY OUTFLOW WINDS WITH THESE SHOWERS. THE GFS
APPEARS TO HAVE A GOOD HANDLE ON THIS FEATURE AND SHOWS IT
MOVING INTO THE LESSER ANTILLES DURING THE NEXT DAY.

A TROPICAL WAVE IS ALONG 92W MOVING W NEAR 15-20 KT. THE WAVE
POSITION IS MAINLY BASED ON A MOISTURE MAXIMUM IN TOTAL
PRECIPITABLE WATER AS FEW ADDITIONAL SIGNATURES ARE APPARENT IN
SATELLITE IMAGERY OR OBSERVATIONS. SCATTERED MODERATE
CONVECTION IS FROM 17N-20N BETWEEN 91W AND 95W INCLUDING
PORTIONS OF THE BAY OF CAMPECHE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 14N17W 11N28W 9N38W 8N47W 8N60W.
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 8N-13N BETWEEN
17W-23W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
6N-12N BETWEEN 25W-28W. SCATTERED MODERATE CONVECTION IS FROM
8N-12N BETWEEN 34W-44W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE EXTENDS SOUTHEASTWARD INTO THE GULF OF
MEXICO AND IS ASSOCIATED WITH A SURFACE RIDGE ALONG 26N AND A
1016 MB SURFACE HIGH NEAR 26N91W. GENERALLY FAIR WEATHER IS
PRESENT ACROSS THE GULF. ONE EXCEPTION IS OVER THE BAY OF
CAMPECHE...WHERE SCATTERED MODERATE CONVECTION IS OCCURRING NEAR
THE TROPICAL WAVE ALONG 92W S OF 20N. THIS ACTIVITY IS BEING
ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE AFOREMENTIONED
UPPER LEVEL RIDGE AND AN UPPER LEVEL LOW OVER THE N CARIBBEAN
SEA. ALSO...WEAKENING SCATTERED SHOWERS AND THUNDERSTORMS...
WHICH DEVELOPED EARLIER OVER THE SE UNITED STATES NEAR A SURFACE
TROUGH...ARE IMPACTING LOCATIONS IN THE GULF OF MEXICO N OF 28N
E OF 87W. WINDS ARE LIGHT AND VARIABLE IN THE VICINITY OF THE
SURFACE RIDGE ACROSS THE N GULF...WITH ANTICYCLONIC FLOW AROUND
THE RIDGE SUPPORTING A BROAD SWATH OF E WINDS OF 10-15 KT ACROSS
THE S HALF OF THE GULF. LITTLE CHANGE IS EXPECTED OVER THE NEXT
DAY OR TWO AS BOTH THE UPPER AND SFC RIDGE REMAIN IN PLACE.

CARIBBEAN SEA...
FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE
SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER
NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST
OF COLOMBIA. THESE WINDS WILL REMAIN STRONG OVER THE NEXT
SEVERAL DAYS AS THE SUBTROPICAL RIDGE REMAINS IN PLACE AND A
TROPICAL WAVE MOVES INTO THE AREA. IN FACT...GALE CONDITIONS ARE
FORECAST FOR THE LATTER HALF OF THE WEEK...AS THE LOW LEVEL FLOW
STRENGTHENS ACROSS THE CARIBBEAN. ALOFT...INSTABILITY ASSOCIATED
WITH AN UPPER LEVEL LOW OVER THE N CENTRAL CARIBBEAN CENTERED
NEAR 19N79W IS RESULTING IN SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS N OF 18N BETWEEN 78W-82W INCLUDING PORTIONS OF
JAMAICA AND CUBA. DEEP LAYER DRY AIR IS RESULTING IN GENERALLY
FAIR WEATHER ACROSS THE E CARIBBEAN.

ATLANTIC OCEAN...
DEEP LAYER MOISTURE IS COMBINING WITH UPPER LEVEL DIFFLUENCE IN
NORTHWESTERLY FLOW ALOFT TO RESULT IN SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF 28N W OF 77W.
ALSO...SCATTERED SHOWERS AND ISOLATED TSTMS ARE FARTHER E WITHIN
90 NM EITHER SIDE OF A SURFACE TROUGH EXTENDING FROM 28N65W TO E
PORTIONS OF THE DOMINICAN REPUBLIC NEAR 19N69W. THIS ACTIVITY IS
ALSO SUPPORTED BY DIFFLUENCE ALOFT BETWEEN AN UPPER TROUGH OVER
THE SW NORTH ATLC AND AN UPPER RIDGE FARTHER TO THE E.
SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT ACROSS MUCH OF
THE CENTRAL AND E ATLC AROUND A BROAD SURFACE RIDGE WITH A 1031
MB HIGH NEAR 34N44W. A SURFACE TROUGH FROM 31N34W TO 28N35W TO
26N39W IS PERTURBING THE RIDGE...THOUGH ASSOCIATED CLOUDINESS
AND SHOWERS ARE SHALLOW IN NATURE AND LIMITED TO LOCATIONS
WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH. ACROSS THE
TROPICAL N ATLC...AN UPPER LEVEL RIDGE IS ALONG 14N E OF 37W
WITH ASSOCIATED UPPER LEVEL DIVERGENCE ENHANCING THE CONVECTION
NEAR THE ITCZ.

$$
COHEN



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