[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON AUG 11 2008

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
1715 UTC.

...SPECIAL FEATURES...
A TROPICAL WAVE LOCATED OVER THE CENTRAL ATLANTIC ALONG 47W/48
OR ABOUT 720 NM EAST OF THE WINDWARD ISLANDS IS SUPPORTING AN
AREA OF DISORGANIZED SCATTERED SHOWERS AND THUNDERSTORMS FROM
12N-15N BETWEEN 47W-51W. A BROAD AREA OF LOW PRES IS ASSOCIATED
WITH THIS WAVE CENTERED NEAR 12N47W.
ALTHOUGH ASSOCIATED SHOWER AND THUNDERSTORM ACTIVITY REMAINS
LIMITED AT THIS TIME...ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE
FOR GRADUAL DEVELOPMENT...AND THIS SYSTEM HAS THE POTENTIAL TO
BECOME A TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS AS
IT MOVES WESTWARD AT 15 TO 20 MPH.

A 1011 MB BROAD LOW PRES AREA IS LOCATED OVER THE EASTERN
ATLANTIC NEAR 11N29W. VIS SAT IMAGERY SHOWS SOME SIGNS OF
BANDING...INDICATING THAT THE SYSTEM HAS BECOME A LITTLE BETTER
ORGANIZED TODAY. A LARGE AREA OF SHOWERS AND THUNDERSTORMS
ACCOMPANIES THIS LOW...AND A TROPICAL DEPRESSION COULD FORM
DURING THE NEXT DAY OR TWO AS IT MOVES WESTWARD AT ABOUT 10
MPH.

...TROPICAL WAVES...
A TROPICAL WAVE IS APPROACHING THE CAPE VERDE ISLANDS. ITS AXIS
IS ALONG 22W/23W S OF 17N MOVING W AT 10-15 KT. SOME CYCLONIC
TURNING IS SEEN ALONG THE WAVE AXIS NEAR 13N. SCATTERED MODERATE
CONVECTION IS NOTED MAINLY AHEAD OF THE WAVE LINE FROM 11N-14N
BETWEEN 23W-26W. SIMILAR CONVECTION IS WITHIN 60 NM BEHIND THE
WAVE APEX FROM 13N-14N.

A TROPICAL WAVE IS ALONG 70W S OF 20N MOVING W 15-20 KT. A WEAK
INVERTED-V PATTERN IS SEEN ON VIS SAT IMAGERY. THE MIMIC-TPW
INDICATES THAT MOISTURE ASSOCIATED WITH THIS FEATURE HAS SPLIT
IN TWO PIECES. ONE REMAINS OVER THE CARIBBEAN SEA SOUTH OF
HISPANIOLA WHILE THE SECOND ONE IS MOVING NWD OVER THE W ATLC. A
SURGE OF AFRICAN DUST CONTINUES TO FOLLOWS THIS WAVE AS SEEN ON
VIS SAT IMAGERY AND THE SAHARAN AIR LAYER FROM CIMSS.

AN ACTIVE TROPICAL WAVE EXTENDS FROM THE CAYMAN ISLANDS TO
PANAMA ALONG 80W. A LARGE AREA OF MODERATE TO ISOLATED STRONG
CONVECTION IS RELATED TO THE WAVE AND COVERS THE SW CARIBBEAN S
OF 15N W OF 75W. MOISTURE ASSOCIATED WITH THIS TROPICAL WAVE
WILL GRADUALLY SPREAD OVER CENTRAL AMERICA LATE TODAY THROUGH
WED INCREASING THE CHANCE OF RAIN PARTICULARLY IN NICARAGUA AND
HONDURAS. A DIFFLUENT PATTERN ALOFT IS HELPING TO INDUCE THIS
CONVECTIVE ACTIVITY.

...THE ITCZ...
THE ITCZ IS CENTERED ALONG 12N17W 12N25W 10N34W 13N45W 7N58W.
OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TWO TROPICAL WAVES
AND THE LOW NEAR 11N29W...ISOLATED MODERATE CONVECTION IS FROM
8N-12N E OF 21W TO THE AFRICAN COAST...AND FROM 6N-10N BETWEEN
34W-40W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER-LEVEL HIGH CENTERED OVER THE BIG BEND REGION OF TEXAS
EXTENDS RIDGING OVER THE GULF WATERS NORTH OF 20N. AN UPPER
LEVEL TROUGH LIES SOUTH OF THE RIDGE AND EXTENDS FROM THE W ATLC
THROUGH THE STRAITS OF FLORIDA AND YUCATAN CHANNEL ALONG 19N TO
THE MEXICO COASTLINE NEAR 19N96W. UPPER DIFFLUENCE BETWEEN THE
RIDGE AND AN UPPER LOW OVER THE CARIBBEAN SEA IS ENHANCING
SCATTERED SHOWERS AND TSTMS OVER SOUTH FLORIDA...THE KEYS AND
THE E PORTION OF THE GULF. MOSAIC DOPPLER RADAR FROM THE SE U.S.
ALSO SHOWS SCATTERED SHOWERS AND TSTMS OVER THE N GULF WATERS N
OF 28N BETWEEN 85W-90W INCLUDING THE FLORIDA PANHANDLE AND PARTS
OF SE LOUISIANA. THIS CONVECTIVE ACTIVITY IS RELATED TO A
DISSIPATING FRONTAL BOUNDARY. AT THE SURFACE...A RIDGE ANCHORED
ON A 1017 MB HIGH OVER THE SE GULF NEAR 25N85W AT 1500 UTC
DOMINATES THE REMAINDER OF THE GULF. THE SURFACE CIRCULATION
AROUND THIS HIGH IS PROVIDING THE WRN AND CENTRAL GULF WITH
LIGHT TO MODERATE SOUTHERLY RETURN FLOW. THESE WINDS ARE
EXPECTED TO GRADUALLY INCREASE THROUGH TUE AS A LOW PRESSURE
SYSTEM DEVELOPS OVER TEXAS AND NE MEXICO.

CARIBBEAN SEA...
AN UPPER-LEVEL LOW IS CENTERED BETWEEN THE CAYMAN ISLANDS AND
JAMAICA WITH A TROUGH EXTENDING EWD ACROSS HISPANIOLA INTO THE
CENTRAL ATLC TO ANOTHER UPPER-LEVEL LOW LOCATED NEAR 27N51W.
SOUTH OF THIS UPPER LOW THERE IS AN UPPER-LEVEL HIGH SITUATED
OVER THE SW CARIBBEAN WITH THE RIDGE AXIS EXTENDING TO THE E
OVER NORTHERN SOUTH AMERICA...AND TO THE W OVER CENTRAL AMERICA.
THIS SYSTEM IS ENHANCING CONVECTION OVER THE SW CARIBBEAN.
MODERATE TO STRONG SUBSIDENCE AND DRY AIR IS OVER THE ERN
CARIBBEAN WITH PATCHES OF SHALLOW MOISTURE CROSSING THE
WINDWARD ISLANDS. MODERATE TO STRONG EASTERLY TRADE WINDS ARE
BLOWING ACROSS THE BASIN WITH THE STRONGEST WINDS OFFSHORE OF
THE NRN COLOMBIAN COAST. TWO TROPICAL WAVES ARE MOVING WWD
ACROSS THE BASIN...SEE TROPICAL WAVE SECTION FOR MORE DETAILS.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH IS LOCATED OVER THE ERN U.S. INTO THE FAR
W ATLC WITH THE ASSOCIATED FRONTAL BOUNDARY OVER THE CAROLINAS
AND THE SE U.S.. AN UPPER-LEVEL RIDGE IS TO THE SE CENTERED NEAR
27N69. UPPER DIFFLUENCE BETWEEN THIS HIGH AND THE UPPER-LEVEL
LOW SPINNING BETWEEN THE CAYMAN ISLANDS AND JAMAICA IS PRODUCING
A 140 NM BAND OF SHOWERS AND TSTMS FROM THE NW BAHAMAS ALL THE
WAY NE TO BEYOND 31N70W. THIS ACTIVITY IS ALSO ASSOCIATED WITH
THE REMNANTS OF A FRONTAL BOUNDARY. ELSEWHERE AN UPPER LOW IS
OVER THE CENTRAL ATLC NEAR 27N51W WITH ANOTHER WEAK UPPER-LEVEL
LOW OVER THE ERN ATLC NEAR 29N28W. AN UPPER-LEVEL HIGH IS
LOCATED NEAR 22N19W...AND A SECOND ONE IS NEAR 17N42W WITH THE
RIDGE COVERING THE DEEP TROPICS. THESE UPPER SYSTEMS ARE
ENHANCING CONVECTION ALONG THE ITCZ. OTHERWISE...THE ATLANTIC
FORECAST AREA IS DOMINATED BY A 1025 MB SURFACE HIGH CENTERED
NEAR 34N46W. THIS HIGH EXTENDS A RIDGE SW INTO THE E GULF AND IS
FORECAST TO MOVE NEWD DURING THE NEXT 24 HOURS OR SO.

$$
GR


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