[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 202348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT AUG 20 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
2315 UTC.

...TROPICAL WAVES...

FAR E ATLC WAVE ALONG 19W/20W S OF 23N MOVING W 10-15 KT.  A
1008 MB LOW IS ALONG THE WAVE NEAR 17.5N AND A 1009 MB LOW IS
ALSO ALONG THE WAVE AXIS NEAR 13N.  THE NORTHERN LOW IS EMBEDDED
WITHIN SOME DRY AIR N OF 17N E OF 28W SEEN ON VISIBLE SATELLITE
PICTURES AND WILL LIKELY DISSIPATE.  THIS IS NOT THE CASE FOR
THE SOUTHERN LOW WHICH IS FORMING SOME CURVED BANDS IN THE ITCZ
WITH PLENTY OF CONVECTION.  THERE IS LITTLE SHEAR NEAR THE
SYSTEM AND SLOW DEVELOPMENT SEEMS TO BE A GOOD BET.  COMPUTER
MODELS STRONGLY SUGGEST THAT THIS WAVE HAS A CHANCE OF TURNING
INTO A TROPICAL CYCLONE DURING THE NEXT FEW DAYS.  SCATTERED
MODERATE CONVECTION FROM 9N-12N BETWEEN 21W-29W WITH WIDELY
SCATTERED TSTMS FROM 13N-16N BETWEEN DAKAR AND 21W.

CENTRAL ATLC WAVE ALONG 42W S OF 22N MOVING W 15-20 KT.  THIS IS
A VERY BROAD WAVE WITH NO WELL-DEFINED AXIS AND AN AREA OF LIGHT
SURFACE WINDS WITHIN THE CIRCULATION ENVELOPE.  THE WAVE IS
POSITIONED BASED ON TURNING IN THE LOW/MID CLOUDS WHICH
ENCOMPASSES AN AREA FROM 35W-52W BETWEEN THE ITCZ AND AT LEAST
22N.  SURFACE OBSERVATIONS AND WATER VAPOR LOOPS SHOW THAT THE
WAVE HAS A DRIER THAN AVERAGE ENVIRONMENT WITH DEWPOINTS A
COUPLE DEGREES LESS THAN TYPICAL NEAR THE WAVE AND STRONG
SUBSIDENCE ALOFT DRYING OUT THE MID/UPPER LEVELS.  THE GFS
FORECASTS THE WAVE TO GRADUALLY DIMINISH WITH TIME WITH THE
LARGE WAVE IN THE E ATLC AND A SURFACE TROUGH TO ITS WEST
BECOMING THE MORE DOMINANT FEATURES.  NO SIGNIFICANT
CONVECTION.

CENTRAL CARIBBEAN WAVE ALONG 68W S OF 23N MOVING W 15 KT.  A
LARGE AREA OF DISORGANIZED WIDELY SCATTERED TSTMS IS NEAR AND
MOSTLY E OF THE WAVE AXIS FROM 16N-24N BETWEEN 63W-68W.  HOWEVER
PUERTO RICO RADAR IS SHOWING A MID-LEVEL ROTATION NEAR 20.5N67W
WITH BANDS OF SHOWERS AT LOWER-LEVELS CYCLONICALLY TURNING INTO
THE CENTER.  THIS IS CERTAINLY AN AREA TO WATCH FOR POTENTIAL
TROPICAL CYCLONE GENESIS DURING THE NEXT COUPLE OF DAYS WITH
LIGHT SHEAR FORECAST.

SW GULF WAVE IS ALONG 92W/93W S OF 21N THRU MEXICO MOVING W
10-15 KT.  WIDELY SCATTERED TSTMS ARE ENHANCED NEAR THE WAVE
AXIS WITHIN 60 NM IN THE BAY OF CAMPECHE.  THIS WAVE COULD
ENCOURAGE TSTM DEVELOPMENT IN SE MEXICO S OF TAMPICO TOMORROW.

...ITCZ...

ITCZ AXIS IS ALONG 16N17W 12N27W 9N36W 9N42W 6N54W. WIDELY
SCATTERED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 29W-38W.
ISOLATED MODERATE FROM 5N-9N BETWEEN 38W-49W.

...DISCUSSION...

GULF OF MEXICO...
THE GULF IS DOMINATED BY A LARGE HIGH CENTERED OVER GEORGIA WITH
MID/UPPER ELY FLOW CONTROLLING THE REGION.  DIURNAL TSTMS WERE
CONCENTRATED OVER N FLORIDA WNW TO S MS WITH SOME TRAPPED
MOISTURE BENEATH THE RIDGE.  THIS AREA OF MOISTURE SHOULD MOVE
SLIGHTLY WEST AND SOUTH TOMORROW... BRINGING BETTER CHANCES OF
TSTMS AS FAR W AS SE LOUISIANA AND IN FLORIDA NEAR LAKE
OKEECHOBEE.  OTHERWISE MODERATE/STRONG SUBSIDENCE IS LIMITING
MOST TSTMS TO BE ISOLATED IN NATURE EXCEPT OVER LAND.  THIS HIGH
SHOULD BE THE CONTROLLING FORCE FOR THE NEXT SEVERAL DAYS WITH
GENERAL ELY FLOW AND FEW MARITIME TSTMS SAVE NEAR THE COAST IN
THE NRN GULF.  THE SW GULF IS THE ONLY PART OF THE AREA NOT
INFLUENCED BY THE HIGH WITH A WEAK SHEAR AXIS FROM YUCATAN NEAR
19N91W TO 24N97W IN NE MEXICO.  CONDITIONS ARE VERY DRY NEAR THE
TROUGH AXIS HOWEVER A SIGNIFICANT INCREASE OF MOISTURE IS FOUND
E OF THE TROUGH... WHICH IS SHIFTING EWD.  THE BAY OF CAMPECHE
SHOULD BE STORMY TOMORROW FROM A COMBINATION OF THE UPPER TROUGH
AND A WEAK SURFACE TROUGH OVER THE NW CARIBBEAN.  IN ADDITION
THERE IS PLENTY OF MOISTURE S OF 23N...KEEPING A HIGHER CHANCE
OF RAIN THAN AVERAGE OVER THE SRN GULF.

CARIBBEAN SEA...
A SMALL UPPER HIGH IS NEAR THE GULF OF HONDURAS WITH AN INVERTED
UPPER TROUGH FROM THE CAYMANS TO 15N75W AND A SMALL UPPER TROUGH
NEAR E CUBA.  CONVERGENCE S OF THESE FEATURES IS CAUSING
SUBSIDENCE ALOFT OVER THE SRN CARIBBEAN AND VERY LITTLE
CONVECTION S OF 15N W OF 70W.  WEAK SURFACE TROUGH IS NEAR THE
BELIZE COAST WITH HINTS OF A MID-LEVEL LOW JUST OFFSHORE OF
BELIZE.  COMPUTER MODELS SUGGEST THIS TROUGH COULD OVER THE BAY
OF CAMPECHE LATE TOMORROW INTO MON AND HAVE SOME CHANCE OF
TROPICAL CYCLONE FORMATION.  THE NW CARIBBEAN WILL REMAIN A BIT
UNSETTLED AS PLENTIFUL DEEP-LAYERED MOISTURE CONTINUES TO BE
FUNNELED FROM THE E TO PRODUCE TSTMS OVER CUBA AND SPOTTY TSTMS
ELSEWHERE.  FARTHER E...ELY WINDS IN DEEP LEVELS DOMINATES FROM
A WEAK UPPER HIGH N OF PUERTO RICO.  TRADES ARE LIGHT E OF 65W
BUT INCREASE TO 20-25 KT IN THE TYPICAL ENHANCED REGION NW OF
COLOMBIA.  MOST OF THE WEATHER IS CENTERED AROUND THE TROPICAL
WAVE CLOSE TO PUERTO RICO WITH A FEW TSTMS IN THE LEEWARD
ISLANDS AND VERY LITTLE ACTIVITY AT ALL IN THE WINDWARDS.
HOWEVER INCREASING MOISTURE IS LIKELY STARTING LATE TOMORROW FOR
THE LESSER ANTILLES FROM A WEAK SURFACE TROUGH FROM 12N54W TO
21N56W SLOWLY MOVING WESTWARD.  SCATTERED SHOWERS AND A FEW
TSTMS LOOK LIKELY FOR MON WITH THE BEST CHANCE OF TSTMS N OF
BARBADOS.  PERHAPS THE DRIEST DAY OF THE NEXT FEW DAYS WILL BE
MON ON PUERTO RICO IN BETWEEN THE TWO SYSTEMS.  WET CONDITIONS
SHOULD PERSIST FOR HISPANIOLA INTO CUBA THRU THE BEGINNING OF
THE WEEK.

ATLANTIC OCEAN...
AN UPPER HIGH CENTERED OVER THE SE USA CONTROLS THE WEATHER W OF
75W N OF 25.. GENERALLY DRIER THAN AVERAGE.  HOWEVER A FEW
SHOWERS ARE N OF 28N W OF 70W ASSOCIATED WITH A WEAK SURFACE
TROUGH N OF THE AREA.   THE REMNANTS OF TD 10 ARE WEAK SURFACE
TROUGH NEAR TURKS/CAICOS ISLAND TO THE WINDWARD PASSAGE BUT ARE
WEAKENING WITH TIME.  A MORE SIGNIFICANT FEATURE APPEARS TO BE
THE LOW/MID-LEVEL ROTATION N OF PUERTO RICO NEAR A TROPICAL
WAVE.  THIS DISTURBED AREA OF WEATHER HAS AN UPPER ANTICYCLONE
OVER IT WITH SCATTERED TSTMS.  A FEW OF THE COMPUTER MODELS TRY
TO DEVELOPMENT THIS AREA.. BRINGING IT TOWARD THE NW BAHAMAS IN
THE NEXT FEW DAYS.  THIS SOLUTION HAS TO BE CONSIDERED HIGHLY
UNCERTAIN THOUGH.  FARTHER N.. AN UPPER TROUGH LIES FROM 30N56W
TO 24N68W.  A FEW SHOWERS ARE BENEATH THE TROUGH AXIS THOUGH
THEY ARE QUITE ISOLATED.  IN THE CENTRAL ATLC..  A MID/UPPER LOW
IS NEAR 28N45W AND IS MOVING SLOWLY NNW WITH TROUGH AXIS SSW TO
20N51W.  THE GFS SUGGEST THE FEATURE WILL MOVE OUT OF THE AREA
WITH THE TROUGH RETREATING FROM THE DEEP TROPICS. VERY DRY AIR
ALOFT CONTINUES S OF THE LOW N OF 10N BETWEEN 40W-60W AND E OF
THE LOW N OF 15N W OF 30W.

OTHERWISE IN THE ATLC...  UPPER TROUGH EXTENDS FROM MADEIRA
ISLANDS TO 25N30W...BRINGING MID/UPPER MOISTURE TO WESTERN
SAHARA AND ASSISTING RARE TSTMS DEVELOPMENT.  UPPER HIGH IS JUST
N OF THE CAPE VERDES RIDGING WSW TO 15N55W WHERE IT MEETS A WEAK
INVERTED TROUGH SLIGHTLY E OF THE LESSER ANTILLES S OF 17N.  S
OF THE RIDGE AXIS... FAIRLY MOIST AIR IS PRESENT ALOFT WITH
STRONG SUBSIDENCE DRYING N OF THE AXIS.  AT THE SURFACE... RIDGE
IS N OF THE AREA WITH SOME ENHANCED TRADES N OF 22N ALONG THE
NORTHERN PERIPHERY OF THE TROPICAL WAVES E OF 40W.  EARLIER
TROUGH ALONG 30W/31W HAS DISSIPATED.  THE LARGE BROAD TROPICAL
WAVE IN THE CENTRAL ATLC HAS WEAKENED THE TRADES WITH MOST WINDS
BELOW 15 KT N OF THE ITCZ W OF THE CAPE VERDES S OF 20N.  THE
NEXT SIGNIFICANT INCREASE IN TRADES SHOULD COME IN ASSOCIATION
WITH THE E ATLC WAVE.

$$
BLAKE

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