[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 250537
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT AUG 25 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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
0515 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 23W S OF 16N MOVING W 10 KT. WHILE
SATELLITE IMAGERY DOES NOT SHOW MUCH ORGANIZATION OR STRUCTURE
TO THIS FEATURE THE UW-CIMSS TPW PRODUCT DEPICTS A PRONOUNCED
AREA OF MOIST AIR...COMPARED TO THE SURROUNDINGS...ASSOCIATED
WITH THIS WAVE. AN EARLIER QSCAT PASS AND OBS FROM THE CAPE
VERDE ISLANDS INDICATE LITTLE ASSOCIATION AT THE SFC BUT...THE
LOW TO MID LEVEL SATELLITE WINDS SHOW AN ELONGATED GYRE TYPE
FEATURE. SHOWER ACTIVITY IS ISOLATED IN NATURE FROM 9N-13N E OF
25W.

TROPICAL WAVE IS ALONG 49W/50W S OF 15N MOVING W 10 KT. THIS
WAVE APPEARS TO HAVE BECOME A LITTLE BETTER ORGANIZED WITH LOW
LEVEL TURNING APPARENT ON NIGHT CHANNEL VIS IMAGES...THOUGH
STILL WELL EMBEDDED IN THE ITCZ. SCATTERED SHOWERS AND TSTMS ARE
CONFINED TO THE INTERSECTION OF THE ITCZ FROM 8N-11N WITHIN 180
NM EITHER SIDE OF THE WAVE AXIS.

TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 80W S OF 18N MOVING W
20 KT OVER THE PAST 24 HRS. IR IMAGES SHOWS A BIT OF CURVATURE
TO THE TSTM ACTIVITY NEAR THE BASE OF THE WAVE EMBEDDED WITHIN
THE ITCZ S OF 11N BETWEEN 77W-83W. OTHERWISE...LITTLE SIGNATURE
OR SHOWER ACTIVITY IS APPARENT IN THE AVAILABLE DATA ACROSS THE
REMAINDER OF THE AXIS.

THE NRN PORTION OF A HIGH AMPLITUDE TROPICAL WAVE EXTENDS INTO
THE S GULF ALONG 88W/89W S OF 24N MOVING W 15 KT. LOW-LEVEL LIFT
ASSOCIATED WITH THIS WAVE AND DIFFLUENCE ALOFT IS GENERATING
SCATTERED TSTM ACTIVITY OVER THE YUCATAN PENINSULA AND WEAKENING
SHOWERS ACROSS THE SE GULF. SHIP/BUOY DATA INDICATE SOME SFC
TURNING AND SLIGHTLY LOWER PRESSURES NEAR THIS WAVE. FOR MORE
DETAILS REFER TO THE GULF OF MEXICO SECTION BELOW.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 8N28W 9N46W 10N62W. BESIDES
FOR THE ACTIVITY DISCUSSED ABOVE...THE ITCZ IS RATHER LINEAR
WITH NO SIGNIFICANT CONVECTION.

DISCUSSION...

GULF OF MEXICO...
A WELL DEFINED UPPER LOW IS CENTERED ACROSS THE MID GULF NEAR
26N88W. INSTABILITY ASSOCIATED WITH THIS UPPER CIRCULATION AND
S-SWLY FLOW ALOFT E OF THE CENTER IS ADVECTING MOISTURE ACROSS
THE E GULF AND FLORIDA. CURRENTLY...LIGHTNING DATA SHOWS MOST OF
THE TSTM ACTIVITY OVER THE E GULF WATERS FROM 26N-30N BETWEEN
84W-86W. SHOWERS/TSTMS ARE MORE ISOLATED IN NATURE IN THE S
CENTRAL GULF LIKELY ENHANCED SOME BY A TROPICAL WAVE IN THE
REGION. CONVECTION HAS REALLY FIRED UP OVER THE WRN HALF OF THE
YUCATAN AND IN THE S BAY OF CAMPECHE. DIFFLUENCE ALOFT APPEARS
TO BE THE PRIMARY TRIGGER THOUGH NO DOUBT THERE IS INFLUENCE
FROM THE NEARBY TROPICAL WAVE AND SMALLER SCALE FLOWS. THE SFC
PATTERN IS VERY TRANQUIL WITH WEAK RIDGING FROM THE ATLC
STRETCHING JUST N OF THE AREA. THIS IS KEEPING E TO SELY SFC
FLOW ON THE LIGHT SIDE.

CARIBBEAN SEA...
MOST OF THE CARIB IS FAIRLY QUIET THIS EARLY MORNING THOUGH
THERE ARE A FEW AREAS EXPERIENCING SOME UNSETTLED WEATHER. THE
MOST ACTIVE IS IN THE SW CARIB WHERE A TROPICAL WAVE IS ENHANING
ITCZ RELATED CONVECTION...SEE ABOVE FOR DETAILS. ELSEWHERE MUCH
OF THE SENSIBLE WEATHER/MOISTURE APPEARS RELATED TO FEATURES
ALOFT. THE MID AND UPPER PATTERN CONSISTS OF A N-S STRETCHED
HIGH PRES RIDGE CENTERED OVER CENTRAL CUBA AND ELONGATED TROUGH
EXTENDING FROM THE ATLC ACROSS THE NRN LEEWARDS TOWARD THE COAST
OF COLOMBIA. STRONG N TO NELY FLOW BETWEEN THESE FEATURES HAS
BLOWN OFF EVENING TSTM ACTIVITY OVER E CUBA AND HISPANIOLA INTO
THE COASTAL WATERS TO NEAR JAMAICA. LIGHTNING DATA IS DETECTING
SOME FLASHES ESPECIALLY IN THE CLUSTER S OF HISPANIOLA. MUCH OF
THE REMAINDER OF THE CENTRAL CARIB LIES IN AN UPPER CONFLUENT
ZONE HELPING TO SINK AND SUPPRESS DEEP CLOUD COVER. HIGH LEVEL
CLOUDINESS LIES OVER THE E CARIB ON THE RETURN SIDE OF THE
TROUGH AND OVER THE W CARIB LOCKED WITHIN THE RIDGE.

ATLANTIC OCEAN...
THE SFC PATTERN ACROSS THE ATLC DISCUSSION AREA REMAINS WEAK
THIS EVENING. THIS WEAK PATTERN IS MAINLY DUE TO AN UNUSUAL (FOR
AUGUST) COLD FRONT DEEP INTO THE SUBTROPICS ENTERING THE AREA
NEAR 32N41W TO A 1012 MB LOW NEAR 28N52W CONTINUING ALONG
25N58W 32N66W. A RECENT QSCAT PASS DEPICTED THIS BOUNDARY
WELL...MARKING IT AS A PRONOUNCED NLY WIND SHIFT AND INCREASE TO
20 KT N OF IT NEAR THE LOW. SATELLITE IMAGERY ALSO SHOWS
SCATTERED SHOWERS WITHIN 60 NM AHEAD OF THE BOUNDARY AND A
SCATTERED STABLE STRATOCUMULUS DECK BEHIND IT. THIS LOW-LATITUDE
FRONT HAS GREATLY BROKEN UP THE TYPICAL SUBTROPICAL RIDGING
ALLOWING TRADES TO BE FAIRLY LIGHT ACROSS THE BULK OF THE
AREA.

IN THE MID AND UPPER LEVELS...A RIDGE IS OVER THE W ATLC
CENTERED VERY NEAR BERMUDA. A DIFFLUENT PATTERN LIES AT THE
W EDGE OF THE RIDGE ASSOCIATED WITH SOME TROUGHING OVER THE
BAHAMAS AND IN THE GULF OF MEX. THIS DIFFLUENCE IS PRODUCING A
FAIR AMOUNT OF CLOUDINESS ACROSS THE AREA W OF 76W. A LARGER
SCALE TROUGH...THE SUPPORT FOR THE FRONT DISCUSSED ABOVE...IS
OVER THE CENTRAL ATLC  EXTENDING FROM 32N46W TO AN UPPER LOW
NEAR 22N57W CONTINUING INTO THE E CARIB. A DOMINATING WELL
DEFINED RIDGE TAKES OVER IN THE E ATLC WITH THE MAIN ANTICYCLONE
CENTERED NEAR 18N35W. OUTSIDE OF THE AREAS OUTLINED IN THE ABOVE
PARAGRAPH...DRY AIR ALOFT IS WIDESPREAD ON WATER VAPOR IMAGERY.

$$
CANGIALOSI




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