[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 211057
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT 21 AUG 2004

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1030 UTC.

...SPECIAL FEATURE...
TROPICAL DEPRESSION  DANIELLE IS LOCATED NEAR 30.6N 38.8W AT
21/0900 UTC. IT IS MOVING W 3 KT WITH MAXIMUM SUSTAINED WINDS OF
30 KT GUSTS 40 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS
1009 MB. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. CONVECTION
FALLING APART ONCE AGAIN AS WLY WIND SHEAR SHEAR QUICKLY PUSHES
TOPS NE AND E OF THE CIRCULATION CENTER.

...TROPICAL WAVES...
TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 28W/29W S OF
22N MOVING W 10 KT. DISSIPATING 1013 MB LOW PRESSURE CENTER IS
ALONG THE WAVE NEAR 16N...VERY DIFFICULT TO LOCATE IN INFRARED
IMAGERY AND JUST AS DIFFICULT TO FIND IN THE FIRST VISIBLE
IMAGES TODAY. ALTHOUGH LOW CENTER LIKELY TO BE REMOVED ON NEXT
ANALYSIS...THIS WAVE CONTINUES TO MOVE SLOWLY WESTWARD IN THE
WEAK STEERING FLOW OFF THE W AFRICAN COAST. FEATURE SHOULD BEGIN
TO ACCELERATE WESTWARD OVER THE NEXT DAY OF SO AS IT BECOMES
MORE INFLUENCED BY THE LOW TO MIDDLE LEVEL EASTERLIES ASSOCIATED
WITH THE AZORES HIGH. NO SIGNIFICANT CONVECTION.

TROPICAL WAVE IS ALONG 66W S OF 18N MOVING W AT 20-25 KT. BROAD
AREA OF LOCALLY STRONG CONVECTION IS PASSING N OF THE ABC
ISLANDS WITH LATEST IMAGERY INDICATING SOME CONVECTION BEGINNING
TO DEVELOP FURTHER SW...AND IS EXPECTED TO REACH BONAIRE AND
CURACAO IN A FEW HOURS. THIN BAND OF SCATTERED MODERATE
CONVECTION EXTENDS FURTHER E OF THE WAVE AXIS AND THROUGH THE
LESSER ANTILLES WITHIN 60 NM OF LINE 13N65W 11N57W...REMAINING
APPROXIMATELY 60 NM S OF BARBADOS.

TROPICAL WAVE IS ALONG 79W S OF 18N MOVING W 20-25 KT. WAVE ONCE
AGAIN REPOSITIONED FURTHER W BASED ON SOUNDING DATA FROM
KINGSTON JAMAICA WHICH INDICATED DEFINITE WIND SHIFT FROM 900 TO
700 MB BETWEEN 1200 UTC ON THE 19TH AND 1200 UTC ON THE 20TH.
ALTHOUGH THIS MAY STILL BE A BIT FURTHER E THAN ACTUAL WAVE
AXIS... POSITION IS A REASONABLE FIT 25 KT MOTION OVER THE LAST
24 HOURS. DISCONTINUITIES WITH SOUNDING DATA ACROSS PORTIONS OF
THE CARIBBEAN SEA HAVE MADE LOCATION OF THIS WAVE EVEN MORE
DIFFICULT.

ITCZ AXIS IS ALONG 11N13W 9N20W 11N28W 7N43W 12N65W 11N68W.
SCATTERED STRONG CONVECTION...TIED TO NEXT TROPICAL WAVE
EXPECTED TO MOVE OFF THE AFRICAN COAST LATER TODAY...IS FOUND
WITHIN 300 NM N OF THE AXIS E OF 20W TO THE COASTAL AREAS OF W
AFRICA. SCATTERED MODERATE CONVECTION WITHIN 60 NM EITHER SIDE
OF THE AXIS FROM 35W TO 41W.

...DISCUSSION...
GULF OF MEXICO AND SUBTROPICAL ATLC W OF 75W...
WESTERN AND CENTRAL GULF DOMINATED BY UPPER RIDGING WITH
MODERATE SUBSIDENCE. EARLIER COASTAL TSTMS OVER PORTIONS OF THE
FLORIDA PANHANDLE...COASTAL ALABAMA/MISSISSIPPI/LOUISIANA HAVE
BEGUN TO RAPIDLY WEAKEN AS CULPRIT SHORTWAVE CONTINUES TO RIDE
NE OUT OF NORTHERN MISSISSIPPI...NORTHERN ALABAMA AND SOUTHERN
TENNESSEE ALONG THE WESTERN PERIPHERY OF THE RIDGE. SECOND
OUTBREAK OF STRONG TSTMS ARE MOVING SE ACROSS EASTERN TEXAS
TOWARD THE NW GULF COAST EXTENDING FROM CENTRAL LOUISIANA TO
CENTRAL TEXAS AND WILL REACH GULF WATERS IN THE NEXT HOUR.
DOWNSTREAM OF THIS RIDGE...UPPER TROUGH RUNS FROM CAPE HATTERAS
SW ACROSS LAKE OKEECHOBEE THROUGH THE FLORIDA KEYS AND INTO NW
CUBA. THIN WEDGE OF DRIER MIDDLE LEVEL AIR NOTED IN WATER VAPOR
IMAGERY EXTENDS WITHIN 180 NM EITHER SIDE OF TROUGH AXIS INTO
CENTRAL FLORIDA. E OF THIS TROUGH AXIS...BROAD AREA OF SCATTERED
SHOWERS AND ISOLATED TSTMS AREA FOUND IN AN AREA OF WEAK
DIFFLUENCE ALOFT.

CARIBBEAN SEA...
TROUGH REMAINS IN PLACE FROM E HISPANIOLA WSW TO E NICARAGUA.
MODERATE/STRONG SUBSIDENCE WITHIN 90 NM OF THE TROUGH AXIS IS
LIMITING SIGNIFICANT CONVECTION OVER MUCH OF THE AREA. EXCEPTION
BEING THE COMBINATION OF A TROPICAL WAVE WITH UPPER DIFFLUENCE S
OF THE TROUGH AXIS WHICH IS AIDING CONVECTION OVER A BROAD AREA
S OF 16N E OF 70W TO THE LESSER ANTILLES. GIVEN LOCATION OF THE
UPPER TROUGH AND THE WESTWARD MOTION OF THE E CARIBBEAN TROPICAL
WAVE...WOULD EXPECT CONTINUED CONVECTION...OCCASIONALLY
STRONG...THROUGH TODAY ACROSS PORTIONS OF THE SE AND S CENTRAL
CARIBBEAN SEA TO INCLUDE THE ABC ISLANDS AS THE SOUTHERN PORTION
OF THE TROPICAL WAVE CONTINUES TO PASS THROUGH A WEAKLY
FAVORABLE ENVIRONMENT ALOFT FOR CONVECTION.

SUBTROPICAL ATLANTIC E OF 75W...
CLUSTERS OF SCATTERED SHOWERS AND TSTMS ARE DEVELOPING BENEATH
AN UPPER HIGH NEAR 24N71W. THIS HIGH CONTINUES TO BUILD RIDGE
AXIS N ALONG 71W TO NEAR 34N IN THE W ATLC. DOWNSTREAM REACTION
TO THIS IS THE SE PROGRESSION OF MIDDLE ATLC TROUGH WITH A SMALL
LOW CENTER NOTED NEAR 28N61W. SECOND UPPER HIGH NEAR 21N53W
APPEARS TO BE RETROGRADING VERY SLOWLY TO THE W BENEATH THE SE
MOVING TROUGH AND WEAKENING QUITE RAPIDLY. TROUGH ACROSS THE
CENTRAL ATLC ALONG 33N38W 20N44W IS THE FEATURE TO BLAME IN
CREATING WESTERLY SHEAR OVER DANIELLE. ALTHOUGH STRONGEST
WESTERLIES LIES ROUGHLY 300 NM N OF DANIELLE...A DIGGING NE ATLC
TROUGH COULD HELP TO PUSH THOSE STRONGER WESTERLIES FURTHER S
OVER THE NEXT FEW DAYS CAUSING THE FINAL DECAY OF AN ALREADY
DETERIORATED TROPICAL CYCLONE.

TROPICAL ATLANTIC...
STRONG MID/UPPER SUBSIDENCE IS CAPPING CONVECTION ASIDE FROM
ITCZ AND W AFRICAN TROPICAL SQUALL. DRY AIR STRETCHES ACROSS THE
ENTIRE AREA WITH STRONGEST SUBSIDENCE FOUND FROM 14N TO 25N
BETWEEN 30W AND 40W IN ASSOCIATION WITH A WESTWARD MOVING MIDDLE
TO UPPER LEVEL CIRCULATION CENTERED NEAR 16N35W. THE LINE OF
STRONG TSTMS...W AFRICAN TROPICAL SQUALL...ASSOCIATED WITH NEXT
TROPICAL WAVE INLAND OVER AFRICA HAVE EMERGED FROM THE COAST
WITH CLOUD TOP TEMPERATURES HAVING WARMED DRAMATICALLY OVER THE
LAST 2 HOURS.

$$
HOLWEG

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