[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 061804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT AUG 06 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 1200 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 1715 UTC.

...SPECIAL FEATURES..
THE CENTER OF TROPICAL STORM HARVEY AT 06/1500 UTC WAS NEAR
33.9N 56.5W MOVING NORTH 6 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 997 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 50 KT
WITH GUSTS TO 60 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC OR MIATCPAT3/WTNT33 KNHC
FOR MORE DETAILS. NUMEROUS STRONG SHOWERS AND THUNDERSTORMS FROM
33N TO 35N BETWEEN 55W AND 57W. MIDDLE TO UPPER LEVEL DRY AIR
SURROUNDS HARVEY FROM SOUTH TO WEST. MIDDLE TO UPPER LEVEL
WESTERLY SHEAR ALSO IS PRESENT.

THE CENTER OF TROPICAL DEPRESSION NINE AT 06/1500 UTC WAS NEAR
17.9N 42.3W MOVING WEST-NORTHWEST 10 KT. THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1008 MB. THE MAXIMUM SUSTAINED WIND SPEED IS
30 KT WITH GUSTS TO 40 KT. SEE THE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC OR MIATCPAT4/
WTNT34 KNHC FOR MORE DETAILS. NUMEROUS STRONG SHOWERS AND
THUNDERSTORMS FROM 17N TO 19N BETWEEN 39W AND 41W. ISOLATED TO
WIDELY SCATTERED MODERATE SHOWERS AND THUNDERSTORMS MORE TO THE
NORTH FROM 20N TO 26N BETWEEN 36W AND 41W. A MIDDLE TO UPPER
LEVEL TROUGH ORIGINATES TO THE NORTH OF T.D. NINE AND REACHES
ITS BASE NEAR 19N42W. SHOWERS AND THUNDERSTORMS NEAR THE CENTER
CURRENTLY ARE LIMITED DUE TO WESTERLY SHEAR...DRY AIR...AND
RELATIVELY COOL SEA SURFACE TEMPERATURES. NONE OF THESE
CONDITIONS IS EXPECTED TO CHANGE MUCH DURING THE NEXT DAY OR SO.
A SURFACE TROUGH TRAILS TO THE SOUTH AND SOUTHWEST OF HARVEY
STARTING NEAR 32N53W AND CONTINUING ALONG 28N57W 26N60W 27N67W
27N75W...TO A SOUTHWESTERN NORTH ATLANTIC OCEAN 1016 MB LOW
PRESSURE CENTER NEAR 31N80W IN THE GEORGIA COASTAL WATERS.
ISOLATED MODERATE SHOWERS WITHIN 30 TO 60 NM ON EITHER SIDE OF
THE TROUGH BETWEEN 54W AND 29N77W. SCATTERED STRONG SHOWERS
AND THUNDERSTORMS FROM 29N TO 31N BETWEEN 77W AND 78W.
CONVECTIVE DEBRIS CLOUDS AND POSSIBLE REMNANT PRECIPITATION
FROM 30N TO 33N BETWEEN 76W AND 80W.

...TROPICAL WAVES...

FAR EASTERN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 19W/20W SOUTH
OF 16N MOVING WEST 10 KT. WARMING CLOUD TOP TEMPERATURES AND
POSSIBLE REMNANT PRECIPITATION IN AN AREA OF EARLIER STRONG
SHOWERS AND THUNDERSTORMS FROM 12N TO 13N BETWEEN 18W AND 20W.

CENTRAL ATLANTIC TROPICAL WAVE IS ALONG 49W/50W SOUTH OF 17N
MOVING WEST 10-15 KT. THE CYCLONIC MOVEMENT OF THE LOW CLOUDS
IN VISIBLE IMAGERY SHOWS THIS WAVE. MOISTURE ASSOCIATED WITH
THIS WAVE SHOULD MOVE INTO THE WINDWARD ISLANDS LATE SUNDAY...
OVERSPREADING THE REST OF THE LESSER ANTILLES ON MONDAY.
ITCZ WIDELY SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND
THUNDERSTORMS WITHIN 100 NM ON EITHER SIDE OF 12N42W 10N46W
9N54W.

CENTRAL AMERICAN TROPICAL WAVE STRETCHES FROM THE WESTERN
CARIBBEAN SEA TO HONDURAS TO NICARAGUA INTO THE EASTERN PACIFIC
OCEAN...MOVING WEST 10-15 KT. SHOWERS AND THUNDERSTORMS IN THE
SOUTHWESTERN CORNER OF THE CARIBBEAN SEA MAY OR MAY NOT BE
ENHANCED BY THIS WAVE. THE ITCZ RUNS THROUGH THE SOUTHWESTERN
CARIBBEAN SEA. SOME OF THE WIDELY SCATTERED TO SCATTERED
MODERATE TO STRONG SHOWERS AND THUNDERSTORMS WEST-SOUTHWEST OF
10N76W 13N80W 14N84W MAY BE ENHANCED BY THE ITCZ.

...THE ITCZ...

ITCZ 11N16W 9N25W 10N38W 9N47W 7N58W. THE ITCZ IS NOT
WELL-DEFINED WEST OF 46W. ISOLATED MODERATE SHOWERS AND
THUNDERSTORMS ELSEWHERE FROM 7N TO 11N BETWEEN 20W AND 40W.

...DISCUSSION...

THE GULF OF MEXICO...
WEAK 1015 MB LOW SITS SOUTH OF THE ALABAMA/WESTERN FLORIDA
PANHANDLE BORDER NEAR 29.5N88W. THIS AREA IS NOT REALLY
CONSIDERED A SUSPECT AREA DUE TO A MID/UPPER LOW  NEAR
BIRMINGHAM WITH PLENTY OF WLY SHEAR. WHAT THE LOW COMBINATION
WILL DO IS HELP FIRE DAILY TSTMS FROM THE SE LOUISIANA THRU SE
GEORGIA. COMPUTER MODELS SUGGEST THE LOW WILL REMAIN NEAR THE
COAST OR DRIFT NORTHWARD FOR THE NEXT SEVERAL DAYS...ADDING TO
DIURNAL CONVECTION NEAR AND E OF THE LOW. OTHERWISE A WEAK
INVERTED MID/UPPER TROUGH IS OVER THE SE GULF AND STRONG NW
WINDS ALOFT ARE OVER THE SW GULF WITH UPPER TROUGHING EXTENDING
FROM THE YUCATAN CHANNEL TO SE TEXAS. WESTERN AND SOUTHWESTERN
GULF OF MEXICO THUNDERSTORMS HAVE DEVELOPED FROM PART OF A
TROPICAL WAVE THAT HAS LEFT THE AREA.

THE CARIBBEAN SEA...
THE CYCLONIC CIRCULATION CENTER FROM 24 HOURS AGO HAS MOVED
NORTHWESTWARD NOW REACHING 20N68W...WITH A TROUGH EXTENDING
WEST-NORTHWESTWARD INTO THE YUCATAN CHANNEL. THIS TROUGH IS
LEADING TO WNW TO NW WINDS ALOFT IN THE W CARIBBEAN WITH SOME
UPPER DIFFLUENCE IN THE EXTREME SW CARIBBEAN PRODUCING STRONG
TSTMS SOUTH OF 14N WEST OF 77W. HIGH PRESSURE ALOFT SHOULD
REBUILD INTO THE E CARIBBEAN BY MON BUT THE W CARIBBEAN LOOKS TO
BE UNDER THE INFLUENCE OF UPPER TROUGHING FOR THE FORESEEABLE
FUTURE.

THE ATLANTIC OCEAN...
MID/UPPER RIDGING COVERS THE NW PART OF THE AREA.... FROM 30N64W
S OF BERMUDA TO NE FLORIDA. RELATIVELY DRY ELY FLOW IS S OF THE
RIDGE AXIS E OF THE CENTRAL BAHAMAS AROUND THE NORTHERN SIDE OF
THE COLD LOW IN THE CARIBBEAN.  FARTHER E... MID/UPPER HIGH IS
NEAR 25N53W WITH LOTS OF SUBSIDENCE N OF 12N BETWEEN 48W-60W.  A
CUT-OFF LOW CONTINUES TO SPIN NEAR 26N42W WITH A FEW TSTMS NEAR
THE COLD AIR INSTABILITY IN THE CENTER WITHIN 60 NM OF THE LOW.
THIS LOW IS THE SYSTEM THAT IS SHEARING TD #9 FOR AT LEAST THE
NEXT DAY OR TWO.  VERY DRY AIR ALOFT CONTROLS THE REST OF THE
AREA E OF 35W N OF 20N WITH SUBSIDENCE BETWEEN AN UPPER TROUGH
NW OF THE CANARY ISLANDS AND UPPER RIDGING IN THE DEEP TROPICS.
ELY UPPER WINDS DOMINATE MOST OF THE DEEP TROPICS... SAVE AN
INVERTED TROUGH PASSING W OF THE CAPE VERDES ISLANDS ALONG 27W
AND THE SOUTHERN EXTENT OF THE COLD LOW IN THE CENTRAL ATLC WITH
A TROUGH S TO 18N44W.  THE UPPER RIDGE AXIS LIES AT ABOUT 16.5N
NEAR THE DEPRESSION... WHICH IS N OF THE RIDGE AND IS
EXPERIENCING WLY SHEAR ALONG WITH LOTS OF DRY AIR IN THE
MID/UPPER LEVELS.

$$
MT


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