[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251051
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT JUL 25 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 21N41W TO 14N38W TO 8N34W MOVING W
NEAR 18 KT. THIS WAVE IS JUST W OF A DEEP LAYER MOISTURE MAXIMUM
OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE IMAGERY
INDICATES LOW-LEVEL CYCLONIC FLOW AROUND THE VICINITY OF THIS
WAVE. SATELLITE DERIVED WINDS ALSO INDICATE CYCLONIC TURNING IN
THE LOW/MID-LEVELS OF THE ATMOSPHERE. THE PRESENCE OF
LOW/MID-LEVEL DRY SAHARAN AIR IS LIMITING DEEP CONVECTION NEAR
THE WAVE. HOWEVER...SCATTERED MODERATE CONVECTION IS EMBEDDED
WITHIN THE ITCZ FROM 7N-9N BETWEEN 34W-37W.

A TROPICAL WAVE IS ALONG 78W/79W S OF 21N MOVING W 20 KT. THIS
WAVE COINCIDES WITH A BROAD AREA OF DEEP LAYER MOISTURE OBSERVED
IN TOTAL PRECIPITABLE WATER IMAGERY. SUBSIDENCE AND DRY AIR IN
NELY FLOW ALOFT ARE INHIBITING DEEP CONVECTION NEAR THE WAVE.
HOWEVER...NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS OVER
COLUMBIA FROM 7N-11N BETWEEN 76W-80W. THIS CONVECTION IS
ENHANCED BY LOW-LEVEL CONVERGENCE NEAR A PERSISTENT SURFACE LOW
CENTERED NEAR 8N76W AND THE PROXIMITY OF THE E PACIFIC ITCZ.

A TROPICAL WAVE IS ALONG 92W S OF 21N MOVING W 20-25 KT. THIS
WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN
TOTAL PRECIPITABLE WATER IMAGERY. A CLUSTER OF NUMEROUS
MODERATE/SCATTERED STRONG CONVECTION IS E OF THE WAVE AXIS FROM
11N-14N BETWEEN 88W-91W. THIS CONVECTION IS ENHANCED BY UPPER
LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE OVER MEXICO AND AN
UPPER LEVEL TROUGH IN THE E PACIFIC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N15W 9N25W 10N43W 10N53W
8N61W. SCATTERED MODERATE CONVECTION IS FROM 6N-10N BETWEEN
21W-29W. SIMILAR CONVECTION IS FROM 8N-12N BETWEEN 48W-53W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER LEVEL TROUGH EXTENDS DOWN THE ERN CONUS TO
LOUISIANA EXTENDING OVER THE GULF OF MEXICO TO 25N97W. THIS
UPPER LEVEL TROUGH SUPPORTS A STATIONARY FRONT EXTENDING ALONG
31N BETWEEN 85W-92W. LOW-LEVEL CONVERGENCE AHEAD OF THIS FRONT
IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ALONG THE NW GULF
N OF 27N BETWEEN 85W-92W. UPPER LEVEL DIFFLUENCE BETWEEN THE
UPPER LEVEL TROUGH AND AN UPPER LEVEL RIDGE OVER MEXICO IS
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE SW GULF S
OF 21N BETWEEN 94W-97W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER
LEVEL TROUGH OVER THE GULF AND AN UPPER LEVEL HIGH N OF THE
BAHAMAS NEAR 23N71W IS SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS ACROSS THE SE GULF S OF 25N E OF 88W
INCLUDING THE STRAITS OF FLORIDA. THE REMAINDER OF THE GULF IS
DOMINATED BY DRY AIR AND SUBSIDENCE ALOFT ASSOCIATED WITH A 1017
MB SURFACE HIGH NEAR 27N84W...RESULTING IN GENERALLY FAIR
WEATHER. E TO SE SURFACE WINDS UP TO 15 KT ARE ACROSS THE SW
GULF...REACHING 20 KT NEAR THE YUCATAN PENINSULA COAST. EXPECT
SE FLOW TO INCREASE ACROSS THE W GULF EARLY NEXT WEEK.

CARIBBEAN SEA...
UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER THE
GULF OF MEXICO AND AN UPPER LEVEL HIGH N OF THE BAHAMAS NEAR
23N71W IS SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE
NW CARIBBEAN N OF 16N W OF 83W. SCATTERED SHOWERS/THUNDERSTORMS
ARE ACROSS THE SW CARIBBEAN S OF 14N W OF 76W INCLUDING
NICARAGUA...COSTA RICA...AND PANAMA. THIS ACTIVITY IS SUPPORTED
BY UPPER LEVEL DIFFLUENCE...THE PROXIMITY OF THE E PACIFIC
ITCZ...AND A TROPICAL WAVE ALONG 78W/79W. ELSEWHERE...DRY AIR
AND SUBSIDENCE IN NELY FLOW ALOFT ARE SUPPORTING GENERALLY FAIR
WEATHER ACROSS THE CENTRAL AND E CARIBBEAN. FRESH TO STRONG
TRADE WINDS ARE OCCURRING ACROSS THE E AND CENTRAL CARIBBEAN
WITH THE STRONGEST WINDS UP TO 30 KT OCCURRING NEAR THE COAST OF
COLUMBIA.

ATLANTIC OCEAN...
THE BROAD UPPER LEVEL TROUGH OVER THE ERN CONUS EXTENDS OVER THE
FAR W ATLC SUPPORTING A SURFACE TROUGH OVER THE FLORIDA
PENINSULA EXTENDING FROM 27N81W TO 30N79W. LOW-LEVEL CONVERGENCE
NEAR THE SURFACE TROUGH ALONG WITH UPPER LEVEL DIFFLUENCE
BETWEEN THE UPPER LEVEL TROUGH AND AN UPPER LEVEL RIDGE TO THE E
CENTERED N OF THE BAHAMAS NEAR 23N71W ARE SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS N OF 23N BETWEEN 71W-80W. A SECOND SURFACE
TROUGH IS ANALYZED N OF THE BAHAMAS FROM 22N73N TO 27N67W.
LOW-LEVEL CONVERGENCE NEAR THIS TROUGH MAY BE ENHANCING THE
SHOWER ACTIVITY TO THE W. UPPER LEVEL DIFFLUENCE BETWEEN AN
UPPER LEVEL TROUGH CENTERED NEAR 28N56W AND AN UPPER LEVEL RIDGE
CENTERED NEAR 21N41N IS SUPPORTING AN AREA OF SHOWERS/POSSIBLE
THUNDERSTORMS FROM 25N-29N BETWEEN 56W-58W. THE REMAINDER OF THE
ATLC IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A 1028 MB
HIGH N OF THE DISCUSSION AREA CENTERED NEAR 34N34W BRINGING
GENERALLY FAIR WEATHER ACROSS THE AREA. AN UPPER LEVEL HIGH OVER
THE CENTRAL ATLC CENTERED NEAR 21N41W IS SUPPORTING CONVECTION
ALONG THE ITCZ.

$$
WALTON






This weather bulletin was brought to you by:
www.nashvilleweather.net