[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 241138
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI JUL 24 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1000 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 19N33W TO 9N29W MOVING W 10-15 KT.
THIS WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED
IN TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE IMAGES INDICATE
BROAD LOW-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS.
SATELLITE DERIVED WINDS ALSO INDICATE GOOD CYCLONIC TURNING IN
THE LOW-MID LEVELS. CONVECTION IS LIMITED DUE TO THE THE
PRESENCE OF A DRY SAHARAN AIR LAYER EXCEPT FOR A SMALL PORTION
OF SCATTERED MODERATE CONVECTION EMBEDDED IN THE ITCZ FROM
8N-10N BETWEEN 29W-33W.

A TROPICAL WAVE IS ALONG 71W S OF 20N MOVING W NEAR 25 KT. THIS
WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN
TOTAL PRECIPITABLE WATER IMAGERY. NO DEEP CONVECTION IS
CURRENTLY ASSOCIATED WITH THIS WAVE DUE TO DRY AIR AND
SUBSIDENCE IN NELY FLOW ALOFT.

A TROPICAL WAVE IS ALONG 83W S OF 22N MOVING W NEAR 25 KT.
CURRENT POSITION IS BASED MAINLY ON CONTINUITY DUE TO THE LACK
OF GOOD PRESENCE IN SATELLITE IMAGERY. LITTLE DEEP CONVECTION IS
CURRENTLY ASSOCIATED WITH THE WAVE DUE TO DRY SAHARAN AIR
DIRECTLY TO THE E OF THE WAVE AXIS. HOWEVER...SCATTERED SHOWERS
ARE WITHIN 100 NM EITHER SIDE OF THE WAVE AXIS FROM 17N-22N.

A TROPICAL WAVE IS ALONG 97W S OF 21N MOVING W NEAR 25 KT. THIS
WAVE IS EMBEDDED IN A BROAD AREA OF DEEP LAYER MOISTURE OBSERVED
IN TOTAL PRECIPITABLE WATER IMAGERY. WHILE THE MAJORITY OF THE
WAVE AXIS IS IN THE E PACIFIC...SCATTERED MODERATE/STRONG
CONVECTION IS OVER MEXICO AND THE BAY OF CAMPECHE FROM 18N-20N
BETWEEN 94W-96W. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION
IS FROM 14N-17N BETWEEN 93W-96W. THIS CONVECTION IS BEING
ENHANCED BY UPPER LEVEL DIFFLUENCE. REFER TO THE TWDEP FOR MORE
DETAILS ABOUT THE SRN PORTION OF THIS WAVE IN THE E PACIFIC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N13W 10N22W 9N37W 8N60W.
SCATTERED MODERATE/STRONG CONVECTION IS FROM 7N-12N BETWEEN
20W-23W. SCATTERED MODERATE CONVECTION IS FROM 9N-11N BETWEEN
40W-45W.

...DISCUSSION...

GULF OF MEXICO...
LOW-LEVEL CONVERGENCE AHEAD OF A COLD FRONT ACROSS SRN
ALABAMA...MISSISSIPPI...AND LOUISIANA ALONG WITH UPPER LEVEL
DIFFLUENCE AND MOIST WLY FLOW ALOFT ARE SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS OVER THE NRN GULF OF MEXICO N OF 27N
BETWEEN 83W-92W. UPPER LEVEL DIFFLUENCE NEAR AN UPPER LEVEL HIGH
OVER THE YUCATAN PENINSULA NEAR 18N95W AND LOW-LEVEL CONVERGENCE
NEAR A TROPICAL WAVE ALONG 97W ARE SUPPORTING SCATTERED SHOWERS/
THUNDERSTORMS FROM 18N-20N BETWEEN 94W-96W. ELSEWHERE ACROSS THE
GULF...A BROAD SURFACE RIDGE ANCHORED BY A 1016 MB HIGH NEAR
27N85W DOMINATES BRINGING GENERALLY FAIR WEATHER...AND IS
SUPPORTED BY DRY AIR AND SUBSIDENCE ALOFT. WEAK ANTICYCLONIC
FLOW IS PRESENT AROUND THE RIDGE WITH STRONGER WINDS IN THE SW
GULF ESPECIALLY NEAR THE YUCATAN PENINSULA COAST. EXPECT THE
SURFACE RIDGE TO GRADUALLY SHIFT SE AND EASTWARD THROUGH THE
WEEKEND. E TO SE FLOW WILL INCREASE ACROSS THE W GULF BY LATE IN
THE WEEKEND.

CARIBBEAN SEA...
UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL HIGH OVER THE
YUCATAN PENINSULA NEAR 18N95W AND A SHORTWAVE UPPER LEVEL TROUGH
OVER W CUBA IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS
THE NW CARIBBEAN N OF 16N W OF 81W. THIS SHOWER ACTIVITY IS
ENHANCED BY THE TROPICAL WAVE ALONG 83W. THE TROPICAL WAVE MAY
ALSO BE ENHANCING A FEW ISOLATED SHOWERS IN THE SW CARIBBEAN S
OF 14N BETWEEN 78W-82W. A FEW ISOLATED SHOWERS ARE OVER THE E
CARIBBEAN S OF 15N BETWEEN 64W-67W ENHANCED BY UPPER LEVEL
DIFFLUENCE. ELSEWHERE ACROSS THE CARIBBEAN...FAIR WEATHER
PREVAILS UNDER THE PRESENCE OF A DRY SAHARAN AIR LAYER BETWEEN
70W-80W ALONG WITH SUBSIDENCE IN NELY FLOW ALOFT. FRESH TO
STRONG TRADE WINDS ARE PRESENCE ACROSS THE MAJORITY OF THE
CARIBBEAN. EXPECT THE TRADE WINDS TO INCREASE EARLY NEXT WEEK.

ATLANTIC OCEAN...
A MID-UPPER LEVEL TROUGH IS OVER THE W ATLC SUPPORTING A SURFACE
TROUGH EXTENDING FROM 27N77W TO 32N71W CONTINUING N OF THE
DISCUSSION AREA. LOW-LEVEL CONVERGENCE NEAR THE SURFACE TROUGH
IS SUPPORTING SCATTERED SHOWERS OVER THE BAHAMAS FROM 23N-27N
BETWEEN 75W-79W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL
TROUGH OVER THE W ATLC AND AN UPPER LEVEL HIGH CENTERED N OF THE
BAHAMAS NEAR 24N72W IS SUPPORTING AN AREA OF NUMEROUS SHOWERS/
THUNDERSTORMS FROM 24N-28N BETWEEN 69W-73W. UPPER LEVEL
DIFFLUENCE ASSOCIATED WITH AN UPPER LEVEL LOW CENTERED NEAR
27N57W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM
23N-25N BETWEEN 57W-62W. A SURFACE TROUGH IS ANALYZED IN THE
CENTRAL ATLC EXTENDING FROM 27N41W TO 30N48W. NO SHOWER ACTIVITY
IS CURRENTLY ASSOCIATED WITH THIS SURFACE TROUGH. THE REMAINDER
OF THE ATLC IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A
1026 MB HIGH N OF THE DISCUSSION AREA NEAR 37N35W BRINGING
GENERALLY FAIR WEATHER ACROSS THE MAJORITY OF THE BASIN. AN
UPPER LEVEL HIGH DOMINATES THE UPPER LEVELS IN THE CENTRAL AND E
ATLC CENTERED NEAR 21N36W. IN THE TROPICAL ATLC...AN UPPER LEVEL
LOW CENTERED NEAR 10N26N IS ENHANCING CONVECTION ALONG THE ITCZ
BETWEEN 20W-24W.

$$
WALTON





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