[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 230557
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 53W/54W S OF 16N 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.
HOWEVER...SCATTERED SHOWERS ARE FROM 11N-14N BETWEEN 51W-58W.

A TROPICAL WAVE IS ALONG 69W S OF 20N 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/ISOLATED
STRONG CONVECTION IS INLAND OVER VENEZUELA FROM 4N-10N BETWEEN
67W-70W.

A TROPICAL WAVE IS ALONG 83W/84W S OF 22N MOVING W NEAR 25 KT.
THIS WAVE IS EMBEDDED WITHIN A BROAD AREA OF DEEP LAYER MOISTURE
OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. CONVECTION
ASSOCIATED WITH THIS WAVE HAS DIMINISHED OVER THE PAST FEW HOURS
DUE TO THE PRESENCE OF AN UPPER LEVEL HIGH DIRECTLY ABOVE THIS
WAVE NEAR 17N83W. HOWEVER...SCATTERED MODERATE CONVECTION E OF
THE WAVE AXIS FROM 10N-16N BETWEEN 85W-89W OVER NICARAGUA AND
HONDURAS MAY BE ENHANCED BY THIS WAVE.

A TROPICAL WAVE IS ALONG 95W/96W S OF 17N MOVING W NEAR 18 KT.
WHILE THIS WAVE LIES MAINLY IN THE E PACIFIC...IT IS ENHANCING A
CLUSTER OF NUMEROUS MODERATE/SCATTERED STRONG CONVECTION OVER
MEXICO FROM 15N-17N BETWEEN 93W-96W. REFER TO THE TWDEP FOR MORE
DETAILS ABOUT THIS WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N14W 12N25W 10N36W 10N52W
9N63W. ISOLATED MODERATE CONVECTION IS WITHIN 75 NM EITHER SIDE
OF THE AXIS BETWEEN 23W-28W. SIMILAR CONVECTION IS AFFECTING THE
LESSER ANTILLES FROM 10N-15N BETWEEN 61W-63W.

...DISCUSSION...

GULF OF MEXICO...
LOW-LEVEL CONVERGENCE NEAR A STATIONARY FRONT N OF THE
DISCUSSION AREA ACROSS TEXAS...LOUISIANA...AND
MISSISSIPPI...ALONG WITH UPPER LEVEL DIFFLUENCE ALOFT ARE
SUPPORTING SCATTERED SHOWERS OVER THE NW GULF OF MEXICO N OF 28N
W OF 89W.B THE REMAINDER OF THE GULF IS UNDER A BROAD RIDGE
ANCHORED BY A 1016 MB SURFACE HIGH NEAR 28N85W 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 28N SUPPORTING THE SURFACE RIDGE AND
FAIR WEATHER. EXPECT THE SURFACE RIDGE TO GRADUALLY SHIFT
EWD THROUGH THE WEEKEND.

CARIBBEAN SEA...
A BROAD UPPER LEVEL HIGH IS OVER THE W CARIBBEAN CENTERED NEAR
17N83W. THIS UPPER LEVEL HIGH LIES DIRECTLY OVER A TROPICAL WAVE
SUPPRESSING 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 NICARAGUA AND
HONDURAS FROM 10N-16N BETWEEN 85W-89W...AND OVER CUBA AND THE
ADJACENT WATERS N OF 19N BETWEEN 75W-79W. THE E CARIBBEAN IS
EXPERIENCING GENERALLY FAIR WEATHER DESPITE THE PRESENCE OF A
TROPICAL WAVE ALONG 69W. DEEP LAYER DRY AIR AND SUBSIDENCE IN
NELY FLOW ALOFT ARE INHIBITING DEEP CONVECTION NEAR THE WAVE AND
ACROSS THE E CARIBBEAN. HOWEVER...SCATTERED SHOWERS ARE ACROSS
THE LESSER ANTILLES FROM 10N-15N BETWEEN 61W-63W. THIS SHOWER
ACTIVITY IS ENHANCED BY THE PROXIMITY OF THE ITCZ...UPPER LEVEL
DIFFLUENCE...AND THE APPROACH OF A TROPICAL WAVE. EXPECT THIS
TROPICAL WAVE 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 22N BETWEEN 74W-78W. THIS
UPPER TROUGH IS SUPPORTING A SURFACE TROUGH EXTENDING FROM
22N78W TO 30N77W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL
TROUGH AND THE UPPER LEVEL HIGH OVER THE W CARIBBEAN ALONG WITH
SURFACE CONVERGENCE NEAR THE SURFACE TROUGH ARE SUPPORTING
SCATTERED SHOWERS/THUNDERSTORMS ACROSS E CUBA AND THE NRN
ADJACENT WATERS S OF 24N BETWEEN 75W-79W. STRONG UPPER LEVEL
DIFFLUENCE AND MOIST SWLY FLOW ALOFT BETWEEN THE UPPER LEVEL
TROUGH AND ANOTHER UPPER LEVEL RIDGE DIRECTLY TO THE E OF THE
TROUGH ANCHORED BY AN UPPER LEVEL HIGH NEAR 28N69W IS SUPPORTING
NUMEROUS SHOWERS/ THUNDERSTORMS N OF 23N BETWEEN 69W-77W. 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 28N58W AND AN UPPER
LEVEL HIGH DOMINATING THE REMAINDER OF THE E ATLC CENTERED NEAR
21N33W IS SUPPORTING AN AREA OF ISOLATED SHOWERS FROM 23N-30N
BETWEEN 56W-61W. THE REMAINDER OF THE CENTRAL AND E ATLC IS
DOMINATED BY A 1027 MB SURFACE HIGH CENTERED N OF THE DISCUSSION
AREA NEAR 38N49W RESULTING IN GENERALLY FAIR WEATHER.
HOWEVER...A STATIONARY FRONT INTRUDES THE SURFACE RIDGE CLIPPING
THE AREA ALONG 32N BETWEEN 23W-48W. A PRE-FRONTAL TROUGH IS
AHEAD OF THE FRONT FROM 30N26W TO 29N42W. NO SHOWER ACTIVITY IS
CURRENTLY ASSOCIATED WITH THE FRONTAL SYSTEM BESIDES A SMALL
CLUSTER OF SHOWERS N OF THE DISCUSSION AREA FROM 32N-34N BETWEEN
53W-56W.

$$
WALTON





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