[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 130555
TWDAT

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

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 24W S OF 14N MOVING W NEAR 15 KT. THE
DAKAR SOUNDING SHOWED A CLEAR SIGNAL OF THIS WAVE CROSSING THE
STATION ON JUL 11 WITH 50 KT WINDS AT 650 MB. THE SATELLITE
APPEARANCE OF THE WAVE TONIGHT IS NOT AS IMPRESSIVE AS THE PAST
FEW WAVES IN THIS REGION. A BROAD AREA OF LOW-LEVEL CYCLONIC
TURNING IS APPARENT ESPECIALLY IN THE 600-800 MB LAYER ACCORDING
TO SATELLITE DERIVED WINDS. HOWEVER...ITS ENVELOPE OF MOISTURE
BASED ON TOTAL PRECIPITABLE WATER IS RATHER FLAT. CONVECTION IS
MINIMAL NEAR THE WAVE.

A TROPICAL WAVE EXTENDS ALONG 20N51W TO 03N44W MOVING W 20-25
KT. THIS WAVE HAS BECOME INCREASINGLY TILTED NW-SE BY THE NE
WIND SURGE E OF THE AXIS. A WELL DEFINED INVERTED V PATTERN IS
EVIDENT IN THE LOW-LEVEL CLOUDS AND A SMALL AREA OF CONVECTION
HAS RECENTLY DEVELOPED FROM 10N-12N BETWEEN 47W-50W ENHANCED BY
DIFFLUENCE ALOFT. GFS APPEARS TO HAVE A GOOD HANDLE ON THIS
FEATURE AND SHOWS IT MOVING INTO THE LESSER ANTILLES TUE WITH
THE N PART LIKELY FRACTURING.

A TROPICAL WAVE IS ALONG 85W MOVING W NEAR 20 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. EARLIER CONVECTION NEAR THE AXIS HAS
DIMINISHED.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 14N17W 7N28W 7N40W 6N57W.
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FROM 10N-16N E
OF 21W AND FROM 4N-9N BETWEEN 28W-35W.

...DISCUSSION...

GULF OF MEXICO...
EAST-NORTHEASTERLY UPPER FLOW COVERS MUCH OF THE GULF ON THE SE
SIDE OF AN UPPER RIDGE OVER THE SOUTHERN PLAINS...SUPPORTING A
SURFACE RIDGE ALONG 28N. GENERALLY FAIR WEATHER CONDITIONS ARE
PRESENT ACROSS THE GULF. ONLY EXCEPTION IS OVER THE BAY OF
CAMPECHE WHERE INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW
OVER SRN MEXICO IS PRODUCING SCATTERED SHOWERS AND TSTMS S OF
21N W OF 91W. 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
NEARLY STATIONARY.

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. ALOFT...INSTABILITY
ASSOCIATED WITH AN UPPER LEVEL TROUGH OVER THE N CENTRAL
CARIBBEAN IS RESULTING IN ISOLATED SHOWERS AND THUNDERSTORMS N
OF 19N BETWEEN 72W-78W INCLUDING PORTIONS OF E CUBA AND
HISPANIOLA. ACROSS THE SW CARIBBEAN...AN UPPER LEVEL HIGH IS
CENTERED NEAR 13N82W...WITH DIVERGENCE ALOFT PRODUCING
CLOUDINESS AND ISOLATED SHOWERS. DEEP LAYER DRY AIR AND
ATMOSPHERIC STABILITY ASSOCIATED WITH AN UPPER LEVEL HIGH OVER
THE WINDWARD ISLANDS ARE SUPPORTING GENERALLY FAIR WEATHER
ACROSS THE E CARIBBEAN.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH IS ACROSS THE SW NORTH ATLC WITH AN AXIS
EXTENDING FROM AN UPPER LOW OVER THE SE BAHAMAS TO 26N75W TO
32N61W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THE UPPER TROUGH
AND LOW-LEVEL CONVERGENCE NEAR A SFC TROUGH FROM 27N66W TO
23N68W IS SUPPORTING SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS WITHIN 90 NM OF THE SFC TROUGH. ANOTHER SURFACE
TROUGH EXTENDS FROM 26N59W TO 19N61W...BUT IS PRODUCING LITTLE
SENSIBLE WEATHER AT THE MOMENT. SCATTERED SHOWERS AND ISOLATED
TSTMS ARE FARTHER E FROM 20N-26N BETWEEN 48W-52W SUPPORTED BY
DIFFLUENCE ALOFT BETWEEN A TROUGH AND RIDGE WITH SOME INFLUENCE
FROM THE N PERIPHERY OF A TROPICAL WAVE. SUBSIDENCE AND
GENERALLY FAIR WEATHER ARE PRESENT ACROSS MUCH OF THE CENTRAL
AND E ATLC AROUND A BROAD SURFACE RIDGE WITH A 1030 MB HIGH NEAR
36N41W. A 1023 MB SFC LOW NEAR 32N35W IS PERTURBING THE RIDGE
BUT ITS CLOUDINESS/SHOWERS ARE SHALLOW IN NATURE. WINDS ARE
LIKELY 20-25 KT N AND W OF THE LOW...DUE TO THE TIGHTENED
PRESSURE GRADIENT.

$$
CANGIALOSI





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