[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 061043
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES..
THE CENTER OF TROPICAL STORM HARVEY AT 06/0900 UTC WAS NEAR
33.3N 56.6W MOVING NNE 6 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1000 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 45 KT
WITH GUSTS TO 55 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC OR MIATCPAT3/WTNT33 KNHC
FOR MORE DETAILS.  A LARGE BURST OF CONVECTION HAS GONE UP NEAR
THE CENTER OF HARVEY WITH THE CENTER NO LONGER EXPOSED.
SIGNIFICANT INTENSIFICATION MAY BE PREVENTING BY WLY SHEAR AND
DRY AIR IN THE MID/UPPER LEVELS  AND LITTLE CHANGE IS EXPECTED
BEFORE HARVEY IS PICKED UP BY A MID-LATITUDE TROUGH IN A COUPLE
DAYS.  SCATTERED MODERATE CONVECTION WITHIN 75 NM OF 34N56W.

THE CENTER OF TROPICAL DEPRESSION NINE AT 06/0900 UTC WAS NEAR
17.7N 41.7W MOVING WNW 13 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.  ALTHOUGH THE LOW-LEVEL CENTER IS STILL
WITHOUT ANY DEEP CONVECTION... TSTMS HAVE COME A LITTLE CLOSER
TO THE CENTER TONIGHT AND ARE SIGNIFICANTLY STRONGER THAN
EARLIER... SUGGESTING THE ENVIRONMENT MIGHT BE LESS STABLE.
WIDELY SCATTERED MODERATE CONVECTION IS FROM 14.5N-17.5N BETWEEN
39W-41W WITH A FEW TSTMS WITHIN 60 NM OF 19.5N40.5W.  CIRRUS
CLOUDS CAN STILL BE SEEN ON SATELLITE MOVING W TO E... A SIGN
THAT WLY SHEAR REMAINS.  COMPUTER MODELS SUGGEST THAT CONDITIONS
WILL REMAIN HOSTILE FOR SIGNIFICANT DEVELOPMENT FOR THE NEXT
COUPLE OF DAYS.. WHEN THEREAFTER SLIGHTLY LOWER SHEAR AND WARMER
WATER COULD AID IN THE ORGANIZATION OF THE DEPRESSION.

...TROPICAL WAVES...

FAR E ATLC WAVE W OF DAKAR ALONG 18W/19W S OF 17N MOVING W 10
KT.  A BURST OF CONVECTION IS NEAR THE WAVE AXIS THOUGH IT IS
DIFFICULT TO DISCERN FROM THE ITCZ.  A LOW-LEVEL CIRCULATION IS
W OF THE WAVE AXIS NEAR 10N21W DRIFTING NORTHEASTWARD WITHIN THE
ITCZ.  WIDELY SCATTERED MODERATE CONVECTION IS FROM 8.5N-12.5N
BETWEEN 17.5W-20W.

CENTRAL ATLC TROPICAL WAVE IS ALONG 48W/49W S OF 17N MOVING W
10-15 KT.  CURVATURE NOTED IN THE LOW/MID-LEVEL CLOUD FIELD IS
USED TO POSITION THE WAVE ALONG WITH TSTMS IN THE ITCZ.
MOISTURE ASSOCIATED WITH THIS WAVE SHOULD MOVE INTO THE WINDWARD
ISLANDS LATE SUN...OVERSPREADING THE REST OF THE LESSER ANTILLES
ON MON.  WIDELY SCATTERED MODERATE CONVECTION IS FROM 8N-10.5N
BETWEEN 45W-50W.

CENTRAL AMERICAN TROPICAL WAVE IS ALONG 85W/86W S OF 19N MOVING
W 10-15 KT.  SCATTERED MODERATE CONVECTION IS OVER HONDURAS E OF
86W PROBABLY ASSOCIATED WITH THE WAVE.  IN ADDITION ISOLATED
SHOWERS ARE OVER THE NW CARIBBEAN N OF 15N W OF 82W.

...ITCZ...

ITCZ IS CENTERED ALONG 11N16W 9N25W 11N38W 9N46W 5N52W.   THE
ITCZ IS NOT WELL-DEFINED W OF 46W.  ISOLATED MODERATE WITHIN 60
NM OF AXIS BETWEEN 18W-30W AND W OF 45W AND FROM 9N-11N BETWEEN
30W-40W.

...DISCUSSION...

GULF OF MEXICO...
WEAK 1015 MB LOW SITS S OF MOBILE NEAR 29.5N87W.  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.  THE
NORTHERN PORTION OF A TROPICAL WAVE THAT HAS LEFT THE AREA TSTMS
ARE IN THE BAY OF CAMPECHE... LEFTOVERS FROM DIURNAL ACTIVITY
OVER YUCATAN ALONG WITH ISOLATED MODERATE CONVECTION WITHIN 90
NM OF 21N95W.

CARIBBEAN SEA...
FOR THE FIRST TIME IN RECENT MEMORY... CYCLONIC WINDS ALOFT
COVER THE CARIBBEAN.  GONE ARE THE ELY WINDS THAT HELPED PRODUCE
MAJOR HURRICANES IN THE CARIBBEAN IN JULY... REPLACED WITH A
MID/UPPER LOW IN THE MONA PASSAGE AND A TROUGH EXTENDING WNW TO
THE YUCATAN CHANNEL.  THIS TROUGH IS LEADING TO WNW TO NW WINDS
ALOFT IN THE W CARIBBEAN WITH SOME UPPER DIVERGENCE IN THE
EXTREME SW CARIBBEAN PRODUCING STRONG TSTMS S OF 11N W OF 78W.
MODERATE/STRONG SUBSIDENCE COVERS THE CARIBBEAN WATERS.  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.

ATLANTIC OCEAN...
MID/UPPER RIDGING COVERS THE NW PART OF THE AREA.... FROM 30N64W
S OF BERMUDA TO NE FLORIDA.  A WEAK SURFACE TROUGH EXTENDS FROM
27N72W TO 30N80W WITH A WEAK LOW PERHAPS FORMING ON THE NW EDGE
OF THE TROUGH.  ISOLATED TSTMS WITHIN 90 NM OF 31N78W.
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.

$$
BLAKE



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