[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 212323
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN AUG 21 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2300 UTC.

...SPECIAL FEATURE...

A 1008 MB LOW IS CENTERED ABOUT 100 NM SW OF THE SOUTHERNMOST
CAPE VERDE ISLANDS NEAR 14N26W...ALONG A TROPICAL WAVE THAT
EXTENDS S OF 20N AND IS MOVING W 10-15 KT. SEVERAL LOW AND
MID-LEVEL LAYERS OF CLOUDS ARE MAKING THE EXACT CENTER OF THE
LOW A LITTLE DIFFICULT TO LOCATE...BUT THE BEST ESTIMATE PUTS IT
ABOUT A DEGREE OR TWO N OF THE DEEPEST CONVECTION. THE
CONVECTIVE INTENSITY AND COVERAGE IS NOT AS GREAT AS IT WAS
YESTERDAY...AND SCATTERED MODERATE CONVECTION IS NOW FROM 9N-13N
BETWEEN 25W-32W. LOW-LEVEL MOISTURE IS ALSO BEING PULLED UP
BEHIND THE WAVE AXIS AND MAY PRODUCE A FEW SHOWERS OVER THE CAPE
VERDES TONIGHT. THE LOW IS CURRENTLY ON THE CUSP OF A SHEAR
GRADIENT...IS ENTRAINING DRY DUSTY AIR TO ITS N...AND IS
HOVERING JUST S OF THE 26C OCEANIC ISOTHERM...BUT GIVEN THE
LARGE CIRCULATION AND LOW PRES NEAR THE CENTER TROPICAL CYCLONE
DEVELOPMENT IS POSSIBLE WITHIN THE NEXT 36 HRS.

...TROPICAL WAVES...

SEE SPECIAL FEATURES FOR TROPICAL WAVE/LOW ALONG 25W/26W.

WEAK TROPICAL WAVE ALONG 49W S OF 21N MOVING W 15-20 KT. THE
WAVE HAS AN EXTREMELY POOR SIGNATURE AND IS ONLY ASSOCIATED WITH
A SLIGHT CYCLONIC TURNING IN THE CLOUD FIELD. NO ASSOCIATED DEEP
CONVECTION.

CENTRAL CARIBBEAN TROPICAL WAVE ALONG 73W EXTENDS ACROSS
HISPANIOLA TO NEAR 25N68W OVER THE SW N ATLC...MOVING W 10-15
KT. EXTREMELY CLEAR WEATHER IS OVER THE CENTRAL CARIBBEAN S OF
17N NEAR THE WAVE AXIS...BUT THE NRN PART OF THE AXIS HAS MERGED
WITH A SFC TROUGH WHICH WAS OVER THE SRN BAHAMAS AND IS
INTERACTING WITH AN UPPER LOW NEAR 26N66W. THIS IS PRODUCING A
CONSIDERABLE AREA OF SCATTERED MODERATE CONVECTION FROM 17N-25N
BETWEEN 65W-72W...PRIMARILY OVER HISPANIOLA AND 200 NM TO THE N
OF THE ISLAND. THE N PART OF THE WAVE IS EXPECTED TO SPLIT OFF
AND MOVE SLOWLY NW ACROSS THE BAHAMAS OVER THE NEXT SEVERAL DAYS
WITH THE POTENTIAL FOR SCATTERED SHOWERS/TSTMS FOR MUCH OF THE
UPCOMING WEEK.

TROPICAL WAVE OVER MEXICO ALONG 99W HAS SHIFTED SW OF THE AREA.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 13N10W 13N15W 17N24W...THEN ALONG
10N26W 9N30W 11N39W 10N47W...THEN ALONG 11N51W 6N61W. NUMEROUS
STRONG CONVECTION OVER W AFRICA FROM 9N-17N BETWEEN 6W-18W.
WIDELY SCATTERED MODERATE 220 NM S OF THE AXIS BETWEEN 30W-42W.

...DISCUSSION...

GULF OF MEXICO...
PRIMARY FOCUS FOR THE EVENING IS OVER NRN GUATEMALA AND SRN
MEXICO WITH A 1008 MB LOW WHICH HAS DEVELOPED NEAR 17N91W MOVING
W TOWARDS CIUDAD DEL CARMEN MEXICO. THE LOW IS AMAZINGLY
WELL-DEFINED FOR BEING INLAND...AND THE OBS OVER SRN MEXICO SHOW
A GOOD CYCLONIC CIRCULATION. SCATTERED MODERATE CONVECTION IS
DEVELOPING NEAR THIS FEATURE FROM 17N-21N BETWEEN 91W-96W. THE
EXACT TRACK OF THE LOW WILL BE EXTREMELY IMPORTANT IN DICTATING
WHETHER IT STAYS OVER LAND OR EMERGES INTO THE BAY OF
CAMPECHE...AND IF THE LATTER SHOULD OCCUR THEN IT WILL NEED TO
BE WATCHED FOR SIGNS OF TROPICAL DEVELOPMENT. THE LOW IS
SANDWICHED BETWEEN AN INVERTED UPPER TROUGH OVER THE WRN BAY OF
CAMPECHE AND AN UPPER HIGH OVER THE YUCATAN...AND CONDITIONS
WILL BECOME EVEN MORE FAVORABLE IF THE TROUGH CONTINUES TO
WEAKEN. ELSEWHERE...A MUCH LARGER UPPER HIGH IS CENTERED OVER SE
ALABAMA WITH A LARGE AREA OF EASTERLIES FLOWING ACROSS FLORIDA
AND THE GULF N OF 22N. ISOLATED SHOWERS/TSTMS ARE MOVING WWD IN
THIS FLOW FROM 22N-26N BETWEEN 85W-95W. OTHER HEAVY TSTMS ARE
LOCATED OVER LOUISIANA...BUT ONLY A FEW OF THESE MAY BRUSH THE
COASTAL WATERS TONIGHT.

CARIBBEAN...
AN UPPER LEVEL INVERTED TROUGH EXTENDS OVER THE NW CARIBBEAN
FROM 14N80W TO THE W TIP OF CUBA AND HAS SPARKED AN AREA OF
SCATTERED MODERATE CONVECTION FROM 17N-23N BETWEEN 76W-85W...
MUCH OF WHICH HAS SPREAD ACROSS JAMAICA...CUBA...AND THE CAYMAN
ISLANDS. ELSEWHERE...AN UPPER HIGH HAS SET UP NEAR HAITI AND IS
REINFORCING DEEP EASTERLY FLOW ACROSS THE E/CENTRAL CARIBBEAN.
HOWEVER...THIS FLOW IS ABNORMALLY DRY SO THERE IS LITTLE IF ANY
IN THE WAY OF TRADE SHOWERS BETWEEN THE LESSER ANTILLES AND 77W.
SOME OF THIS DRY AIR IS BEING DRAGGED SWD BY ANOTHER UPPER TROF
FROM 15N78W TO THE NICARAGUA/COSTA RICA BORDER...AND ALL THE
UPPER MOISTURE IS LIMITED TO S OF 11.5N WHERE THE FLOW IS
WESTERLY. ELSEWHERE...AN INVERTED UPPER TROF IS MOVING INTO THE
E CARIBBEAN ALONG 12N65W 18N60W AND IS COLLOCATED WITH A SFC
TROF APPROACHING THE LEEWARD ISLANDS. THESE FEATURES ARE
PRODUCING SCATTERED SHOWERS/TSTMS FROM 13N-18N BETWEEN 58W-62W.
SOME OF THE HEAVIER SHOWERS MAY SPREAD ACROSS THE ISLANDS OF
GUADELOUPE...DOMINICA...MARTINIQUE...AND ST. LUCIA TONIGHT.

WEST ATLANTIC...
AN UPPER RIDGE AXIS EXTENDS NEWD OFF THE COAST OF GEORGIA AND IS
PRODUCING MODERATE NELY FLOW OVER THE W ATLC WATERS AND ACROSS
THE NRN BAHAMAS AND FLORIDA. THIS FLOW LIES ON THE W SIDE OF AN
UPPER LOW LOCATED BETWEEN PUERTO RICO AND BERMUDA NEAR
26N66W...WITH A TROF EXTENDING SW ACROSS THE SRN BAHAMAS TO ERN
CUBA. STRONG UPPER DIFFLUENCE E OF THE TROF IS HELPING TO
PRODUCE SCATTERED MODERATE CONVECTION N OF HISPANIOLA ASSOCIATED
WITH A TROPICAL WAVE.

EAST/CENTRAL ATLANTIC...
A CUT-OFF MID/UPPER LOW IS CENTERED NEAR THE NRN BOUNDARY OF THE
DISCUSSION AREA NEAR 31.5N47W AND IS MOVING SLOWLY WWD ABOUT 5
KT. THE LOW IS PRODUCING EXTREMELY ISOLATED SHOWERS N OF 29N
BETWEEN 46W-50W. THE UPPER LEVEL ENVIRONMENT IS PARTICULARLY DRY
OVER THE CNTRL ATLC AT THE MOMENT...WITH THE AREA OF STRONG
SUBSIDENCE LOCATED WITHIN 100 NM OF A LINE FROM 28N35W 20N45W
10N50W. AN UPPER RIDGE AXIS LIES FROM THE MAURITANIA/WESTERN
SAHARA BORDER SW ACROSS THE TROPICAL ATLC TO 14N55W WITH THE
MOST ABUNDANT TROPICAL MOISTURE LIMITED S OF THAT LINE. THE
ASSOCIATED SUBSIDENCE N OF THE RIDGE IS PLACING A CAPPING
INVERSION OVER THE E ATLC...WHICH IS KEEPING A LARGE PLUME OF
DUST QUITE CONCENTRATED N OF 14N E OF 35W. ANOTHER MID/UPPER LOW
IS LOCATED W OF THE CANARY ISLANDS NEAR 30N22W AND IS PRODUCING
WIDELY SCATTERED MODERATE CONVECTION TO ITS S FROM 25N-28N
BETWEEN 19W-24W. THE LOW IS EXPECTED TO MEANDER JUST W AND N OF
THE CANARY ISLANDS FOR THE NEXT WEEK...AND MAY HAVE JUST ENOUGH
MOISTURE TO SUPPORT ISOLATED SHOWERS/TSTMS.

$$
BERG


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