[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121727
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN JUL 12 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 HAS BEEN ADDED TO THE SURFACE ANALYSIS ALONG 21W
S OF 15N MOVG W 15-20 KT. UPPER-AIR TIME SECTION ANALYSIS FROM
DAKAR INDICATED THE WAVE PASSING DAKAR BETWEEN 1200 UTC ON 07/11
AND 0000 UTC ON 07/12. THE WAVE ALSO COINCIDES WITH AN 850 MB
RELATIVE VORTICITY MAXIMUM SEEN ON THE CIMSS WAVETRAK PRODUCT AS
WELL AS A DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS
FROM 8N-13N BETWEEN 19W-23W.

A TROPICAL WAVE EXTENDS FROM 18N45W TO 3N41W MOVING W 15-20 KT.
SATELLITE IMAGERY INDICATES BROAD CYCLONIC FLOW AROUND THE
VICINITY OF THE WAVE. THIS WAVE ALSO COINCIDES WITH A DEEP LAYER
MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY.
DEEP CONVECTION IS LIMITED DUE TO THE VICINITY OF A MID-LEVEL
LAYER OF SAHARAN DRY AIR. SCATTERED MODERATE CONVECTION IS FROM
4N-5N BETWEEN 41W-42W.

A TROPICAL WAVE EXTENDS FROM 20N79W TO 7N81W MOVING W 20-25 KT.
THE WAVE POSITION IS MAINLY BASED ON A MOISTURE MAXIMUM IN TOTAL
PRECIPITABLE WATER IMAGERY AS LITTLE SIGNATURE IS APPARENT IN
SATELLITE IMAGERY OR OBSERVATIONS. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS W OF THE WAVE AXIS FROM 11N-17N BETWEEN
82W-86W AND S OF PANAMA IN THE E PACIFIC. THIS CONVECTION IS
BEING ENHANCED BY UPPER LEVEL DIFFLUENCE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N13W 9N23W 6N33W 6N48W AND
INTO S AMERICA NEAR 6N60W. SCATTERED MODERATE/STRONG CONVECTION
IS INLAND OVER AFRICA APPROACHING THE COAST 11N-15N BETWEEN
11W-13W. SCATTERED MODERATE CONVECTION IS FROM 4N-10N BETWEEN
24W-28W. SIMILAR CONVECTION IS FROM 2N-7N BETWEEN 44W-49W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD SURFACE RIDGE DOMINATES THE MAJORITY OF THE GULF OF
MEXICO PROVIDING GENERALLY FAIR WEATHER. AN UPPER LEVEL HIGH
OVER CENTRAL TEXAS IS PROVIDING SUBSIDENCE AND DRY AIR
SUPPORTING THE SURFACE RIDGE. ANTICYCLONIC FLOW AROUND THE
SURFACE RIDGE IS PRESENT WITH E-SE WINDS OF 10-15 KT DOMINATING
THE S PORTION OF THE GULF S OF 26N. THE N GULF IS EXPERIENCING
LIGHT AND VARIABLE WIND. AN UPPER LEVEL LOW IS OVER THE BAY OF
CAMPECHE NEAR 19N95W SUPPORTING A SURFACE TROUGH EXTENDING FROM
21N96W TO 19N95W. SURFACE CONVERGENCE NEAR THE TROUGH IS
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 18N-21N BETWEEN
94W-97W. UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL LOW S OF
CUBA NEAR 21N81W AND THE UPPER LEVEL RIDGE OVER THE GULF OF
MEXICO IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE
STRAITS OF FLORIDA FROM 22N-25N E OF 86W. EXPECT THE SURFACE
RIDGE TO REMAIN OVER THE GULF OF MEXICO FOR THE NEXT SEVERAL
DAYS.

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 STRENGTHENS.
IN THE UPPER LEVELS...AN UPPER LEVEL LOW IS S OF CUBA NEAR
21N81W...WHILE A BROAD UPPER LEVEL RIDGE DOMINATES THE E
CARIBBEAN CENTERED AROUND AN UPPER LEVEL HIGH NEAR 15N63W. A
TROPICAL WAVE IS IN THE W CARIBBEAN SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS FROM 11N-17N BETWEEN 82W-86W AND S OF
PANAMA IN THE E PACIFIC. THIS CONVECTION IS BEING ENHANCED BY
ATMOSPHERIC INSTABILITY NEAR THE UPPER LEVEL LOW. THE REMAINDER
OF THE CARIBBEAN IS UNDER A MID-LEVEL LAYER OF DRY SAHARAN AIR
PROVIDING GENERALLY FAIR WEATHER E OF 77W.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH IS ACROSS THE SW NORTH ATLC WITH AN AXIS
EXTENDING FROM THE UPPER LEVEL LOW S OF CUBA NEAR 21N81W TO
32N72W TO NE OF THE DISCUSSION AREA SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS N OF 28N BETWEEN 77W-80W. UPPER LEVEL
DIFFLUENCE BETWEEN THE UPPER LEVEL LOW S OF CUBA AND THE UPPER
LEVEL RIDGE OVER THE GULF OF MEXICO IS SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS N OF CUBA INCLUDING THE STRAITS OF FLORIDA
AND THE BAHAMAS FROM 22N-26N W OF 76W. A SERIES OF SURFACE
TROUGHS ARE IN THE W ATLC. THE FIRST IS N OF THE BAHAMAS FROM
24N74W TO 26N71W SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS
WITHIN 100 NM E OF THE TROUGH AXIS BETWEEN 69W-74W. A SECOND
SURFACE TROUGH IS FROM 23N67W TO 27N65W. SCATTERED
SHOWERS/POSSIBLE THUNDERSTORMS ARE FROM 22N-28N BETWEEN 63W-67W.
A THIRD SURFACE TROUGH IS FROM 18N61W TO 25N56W. ISOLATED
SHOWERS ARE WITHIN 60 NM EITHER SIDE OF THE TROUGH AXIS. ALL
THREE SURFACE TROUGHS ARE SUPPORTED BY UPPER LEVEL DIFFLUENCE
BETWEEN THE UPPER LEVEL TROUGH OVER THE SW NORTH ATLC AND AN
UPPER LEVEL RIDGE THAT EXTENDS NWD FROM THE E CARIBBEAN ALONG
63W. MOIST SWLY FLOW ALOFT BETWEEN THE UPPER LEVEL FEATURES IS
ALSO SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 21W-23W
BETWEEN 71W-75W OVER THE ERN BAHAMAS. A BROAD SURFACE RIDGE
DOMINATES THE REMAINDER OF THE ATLC ANCHORED BY A 1026 MB HIGH
NEAR 31N54W. HOWEVER...FARTHER E...A COLD FRONT DIPS INTO THE
DISCUSSION AREA NEAR 32N35W EXTENDING TO 30N41W AND CONTINUING
AS A DYING STATIONARY FRONT TO 32N44W. NO SHOWERS ARE CURRENTLY
ASSOCIATED WITH THE FRONT.

$$
WALTON



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