[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231114
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU JUL 23 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 HAS BEEN ADDED TO THE 0600 UTC SURFACE ANALYSIS
ALONG 25W S OF 18N MOVING W NEAR 20 KT. THIS WAVE COINCIDES WITH
A DEEP MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER
IMAGERY. SATELLITE IMAGERY ALSO INDICATES LOW-LEVEL CYCLONIC
FLOW IN THE VICINITY OF THE WAVE AXIS. THIS WAVE IS SURROUNDED
BY A LOW/MID-LEVEL DRY SAHARAN AIR LAYER...WHICH IS SUPPRESSING
MOST DEEP CONVECTION EXCEPT FOR A SMALL PORTION EMBEDDED WITHIN
THE ITCZ FROM 11N-13N BETWEEN 26W-28W.

A TROPICAL WAVE IS ALONG 55W/56W S OF 17N MOVING W NEAR 25 KT.
THIS WAVE COINCIDES WITH A LOW AMPLITUDE DEEP LAYER MOISTURE
MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. THIS WAVE
IS FOLLOWED BY A DRY LOW/MID-LEVEL SAHARAN AIR LAYER...WHICH IS
INHIBITING DEEP CONVECTION IN THE VICINITY OF THE WAVE EXCEPT
FOR A SMALL PORTION OF SCATTERED MODERATE CONVECTION FROM
12N-14N BETWEEN 54W-56W.

A TROPICAL WAVE IS ALONG 71W S OF 18N MOVING W NEAR 20 KT. THE
POSITION OF THIS WAVE IS BASED MAINLY ON CONTINUITY. DEEP LAYER
DRY AIR AND SUBSIDENCE IN NELY FLOW ALOFT ARE INHIBITING DEEP
CONVECTION NEAR THIS WAVE. HOWEVER...SCATTERED MODERATE
CONVECTION IS INLAND OVER COLUMBIA FROM 2N-8N BETWEEN 69W-72W.

A TROPICAL WAVE EXTENDS FROM 19N83W TO 11N86W INTO THE E PACIFIC
TO NEAR 5N86W MOVING W NEAR 25 KT. THIS WAVE IS EMBEDDED WITHIN
A BROAD AREA OF DEEP LAYER MOISTURE OBSERVED IN TOTAL
PRECIPITABLE WATER IMAGERY. MOST OF THE DEEP CONVECTION
ASSOCIATED WITH THIS WAVE IS IN THE E PACIFIC DUE TO AN UPPER
LEVEL HIGH OVER THE N PORTION OF THE WAVE NEAR 18N84W.
HOWEVER...SCATTERED SHOWERS ARE WITHIN 100 NM EITHER SIDE OF THE
WAVE AXIS FROM 13N-18N. REFER TO THE TWDEP FOR MORE DETAILS
ABOUT THIS WAVE.

A TROPICAL WAVE IS ALONG 97W/98W S OF 16N MOVING W NEAR 18 KT.
WHILE THIS WAVE LIES MAINLY IN THE E PACIFIC...IT IS ENHANCING
AN AREA OF SCATTERED MODERATE CONVECTION OVER MEXICO FROM
14N-17N BETWEEN 93W-97W. REFER TO THE TWDEP FOR MORE DETAILS
ABOUT THIS WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N15W 12N27W 10N40W 11N54W
8N63W. SCATTERED MODERATE CONVECTION IS JUST OFF THE COAST OF
AFRICA FROM 5N-12N BETWEEN 15W-17W.

...DISCUSSION...

GULF OF MEXICO...
LOW-LEVEL CONVERGENCE NEAR A COLD FRONT N OF THE DISCUSSION AREA
ACROSS SE TEXAS...LOUISIANA...MISSISSIPPI...AND ALABAMA...ALONG
WITH UPPER LEVEL DIFFLUENCE ALOFT ARE SUPPORTING SCATTERED
SHOWERS OVER THE NW GULF OF MEXICO N OF 28N BETWEEN 88W-94W. THE
REMAINDER OF THE GULF IS UNDER A BROAD RIDGE ANCHORED BY A 1016
MB SURFACE HIGH NEAR 27N87W BRINGING GENERALLY FAIR WEATHER
ACROSS THE AREA. WEAK ANTICYCLONIC FLOW IS PRESENT NEAR THE
SURFACE HIGH SUPPORTING E WINDS UP TO 15 KT ACROSS THE S GULF
INCREASING UP TO 20 KT NEAR THE COAST OF THE YUCATAN PENINSULA.
DEEP LAYER DRY AIR AND SUBSIDENCE IS OVER THE MAJORITY OF THE
GULF S OF 27N SUPPORTING THE SURFACE RIDGE AND FAIR WEATHER.
EXPECT THE SURFACE RIDGE TO GRADUALLY SHIFT EWD WHILE THE WEAK
FRONTAL SYSTEM ACROSS SE TEXAS AND CENTRAL LOUISIANA SINKS SE
INTO THE N GULF AND DISSIPATES BY FRI. INCREASING E TO SE FLOW
WILL DEVELOP ACROSS THE W AND SW GULF BY LATE IN THE WEEKEND.

CARIBBEAN SEA...
A BROAD UPPER LEVEL HIGH IS OVER THE W CARIBBEAN CENTERED NEAR
18N84W. THIS UPPER LEVEL HIGH LIES DIRECTLY OVER A TROPICAL WAVE
SUPPRESSING DEEP CONVECTION NEAR THE WAVE AXIS. HOWEVER...UPPER
LEVEL DIFFLUENCE TO THE SW AND NE OF THE UPPER LEVEL HIGH IS
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OVER GUATEMALA AND
BELIZE FROM 15N-17N BETWEEN 87W-90W...AND NEAR CUBA AND JAMAICA
FROM 17N-21N BETWEEN 77W-80W. THE E CARIBBEAN IS EXPERIENCING
GENERALLY FAIR WEATHER DESPITE THE PRESENCE OF A TROPICAL WAVE
ALONG 71W. DEEP LAYER DRY AIR AND SUBSIDENCE IN NELY FLOW ALOFT
ARE INHIBITING DEEP CONVECTION NEAR THE WAVE AND ACROSS THE E
CARIBBEAN. HOWEVER...ISOLATED SHOWERS ARE ACROSS THE LESSER
ANTILLES FROM 10N-13N BETWEEN 63W-69W. THIS SHOWER ACTIVITY IS
ENHANCED BY THE PROXIMITY OF THE ITCZ AND UPPER LEVEL
DIFFLUENCE. EXPECT A TROPICAL WAVE CURRENTLY ALONG 55W/56W TO
REACH THE E CARIBBEAN LATER TODAY. FRESH TO STRONG WINDS WILL
CONTINUE ACROSS THE E AND CENTRAL CARIBBEAN THROUGH THE
REMAINDER OF THIS WEEK.

ATLANTIC OCEAN...
A SHORTWAVE UPPER LEVEL TROUGH IS N OF 24N BETWEEN 74W-79W. THIS
UPPER TROUGH IS SUPPORTING A SURFACE TROUGH EXTENDING FROM
23N78W TO 31N78W. STRONG UPPER LEVEL DIFFLUENCE AND MOIST SWLY
FLOW ALOFT BETWEEN THE UPPER LEVEL TROUGH AND AN UPPER
LEVEL RIDGE DIRECTLY TO THE E OF THE TROUGH ANCHORED BY AN UPPER
LEVEL HIGH NEAR 29N69W IS SUPPORTING SCATTERED SHOWERS/TSTMS N
OF 22N BETWEEN 70W-76W. THIS ACTIVITY IS ALSO BEING ENHANCED BY
LOW LEVEL CONVERGENCE NEAR THE SURFACE TROUGH. FARTHER TO THE
E...UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH
CENTERED NEAR 27N57W AND AN UPPER LEVEL HIGH DOMINATING THE
REMAINDER OF THE E ATLC CENTERED NEAR 21N33W IS SUPPORTING AN
AREA OF SCATTERED SHOWERS/THUNDERSTORMS FROM 23N-30N BETWEEN
55W-60W...AND JUST N OF THE DISCUSSION AREA FROM 32N-34W BETWEEN
54W-56W. THE REMAINDER OF THE CENTRAL AND E ATLC IS DOMINATED BY
A 1026 MB SURFACE HIGH CENTERED N OF THE DISCUSSION AREA NEAR
37N48W RESULTING IN GENERALLY FAIR WEATHER. HOWEVER...A
STATIONARY FRONT INTRUDES THE SURFACE RIDGE CLIPPING THE AREA
ALONG 32N BETWEEN 23W-46W. A PRE-FRONTAL TROUGH IS AHEAD OF THE
FRONT FROM 30N27W TO 29N44W. NO SHOWER ACTIVITY IS CURRENTLY
ASSOCIATED WITH THE FRONTAL SYSTEM.

$$
WALTON





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