[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 012335
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON AUG 01 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 TROPICAL WAVE IS NEAR THE CAPE VERDES ALONG 24W/25W S
OF 17N MOVING W 10-15 KT.  THE SAL SOUNDING FROM THIS MORNING
SUGGESTED THE WAVE AXIS WAS NEARBY WITH VEERING WINDS IN THE
LOW-LEVELS AND STRONG ELYS OBSERVED IN THE MID-LEVELS.  ANOTHER
SURGE OF AFRICAN DUST IS NOTED ON SATELLITE BEHIND THE WAVE AXIS
S OF 22N THOUGH THE DUST MIGHT BE MOSTLY N OF 15N.  ISOLATED
TSTMS ARE NOTED FROM 9N-13N BETWEEN 22W-28W.

W-CENTRAL ATLC TROPICAL WAVE IS ALONG 57W S OF 19N MOVING W 15
KT.  AN EXACT WAVE AXIS IS HARD TO PINPOINT WITH SLY WINDS
DOMINATING THE LOW-LEVELS EVEN AHEAD OF THE WAVE.  THE EASIEST
PLACE TO PUT THE WAVE IS JUST AHEAD OF MORE AFRICAN DUST
ESPECIALLY E OF 56W.  WIDELY SCATTERED MODERATE CONVECTION IS
FROM 8N-12N BETWEEN 51W-57W.  MOISTURE FROM THIS WAVE SHOULD
OVERSPREAD THE LESSER ANTILLES OVERNIGHT BRINGING AN
ABOVE-AVERAGE CHANCE OF RAIN/TSTMS... MOVING INTO PUERTO RICO BY
LATE TOMORROW.

E CARIBBEAN TROPICAL WAVE IS ALONG 68W/69W S OF 17N MOVING W
15-20 KT.  SYSTEM HAS BECOME PROGRESSIVELY LESS WELL-DEFINED AS
CONVECTION HAS DIMINISHED SINCE YESTERDAY.  TURNING IN THE
LOW-CLOUDS IS THE BEST WAY TO POSITION THE WAVE ALONG WITH
ISOLATED TSTMS WITHIN 90 NM OF THE WAVE AXIS BETWEEN 67W-71W.

W CARIBBEAN TROPICAL WAVE IS ALONG 85W S OF 19N MOVING W 10-15
KT.  WEAK LOW-LEVEL SWIRL IS NOTED NEAR 17N85W.  A LARGE
EXPLOSION OF CONVECTION OVER CENTRAL AMERICA FROM SE HONDURAS
SOUTHWARD THRU NICARAGUA INTO COSTA RICA MAY BE RELATED TO THE
WAVE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 13N16W 8N30W 7N42W 11N56W.  ISOLATED
MODERATE CONVECTION WITHIN 45 NM OF AXIS BETWEEN 40W-56W AND
25W-31W.  WIDELY SCATTERED MODERATE FROM 4.5N-7N BETWEEN
35W-38W.  ISOLATED SHOWERS ARE BETWEEN 8N-15N E OF 20W WITH A
FEW TSTMS NEAR DAKAR.

...DISCUSSION...

GULF OF MEXICO...
AN OLD REMNANT FRONTAL TROUGH HAS MADE ITS WAY ALMOST TO THE
GULF COAST... STRETCHING FROM SE GEORGIA TO S-CENTRAL LOUISIANA.
 THIS SURFACE TROUGH HAS ENHANCED THE DAILY TSTM FORMATIONS
ALONG THE SEABREEZE WITH CONSIDERABLY MORE SURFACE CONVERGENCE
AND INSTABILITY THAN AVERAGE.  THE UPPER LEVELS ARE FAVORABLE
FOR TSTMS AS WELL WITH AN UPPER LOW OVER THE SW GULF AND AN
UPPER HIGH NEAR JACKSONVILLE.... LEAVING UPPER RIDGING AND A
LITTLE UPPER DIFFLUENCE OVER THE CENTRAL AND E GULF COAST.  A
WETTER-THAN-AVERAGE PERIOD FOR THE GULF COAST FOR THE NEXT
COUPLE OF DAYS THOUGH THE SURFACE TROUGH SHOULD WEAKEN... BUT
STILL LENDING A HAND WITH AFTERNOON TSTMS.  ACTIVE CONVECTION IS
POSSIBLE IN THE BAY OF CAMPECHE IN THE LATE AFTERNOON AS BIG
TSTMS FROM YUCATAN MOVE OFFSHORE INTO THE REGION.  OTHER
SIGNIFICANT TSTMS SHOULD BE N OF LAKE OKEECHOBEE IN FLORIDA.

CARIBBEAN SEA...
RATHER DRY AIR IN THE MID-LEVEL CONTROLS A GOOD PORTION OF THE
AREA.  INCREASING SHOWERS ARE FOUND AROUND THE TROPICAL WAVES
NEAR 68W AND 85W... OTHERWISE DIURNAL TSTMS ARE THE MAIN TSTMS
WITH ACTIVITY FLOURISHING OVER THE GREATER ANTILLES ESPECIALLY
IN HISPANIOLA.  TWO MAIN UPPER FEATURES ARE IN THE AREA... THE
FIRST BEING A LOW NEAR 16N79W SW OF JAMAICA... AND A MID/UPPER
HIGH NEAR THE US VIRGIN ISLANDS.  ELY WINDS CONTROL THE E
CARIBBEAN E OF 72W WITH MODERATE SUBSIDENCE OVER WATER.  CENTRAL
AMERICA LOOKS FAIRLY WET FOR THE NEXT COUPLE OF DAYS WITH
UPPER-LEVEL DIFFLUENCE PROGGED OVER THE REGION WITH OCCASIONAL
TROPICAL WAVES ENHANCING THE ACTIVITY EVEN MORE.  TRADEWINDS ARE
CONSIDERABLY REDUCED FROM LAST WEEK IN THE CENTRAL CARIBBEAN
WITH THE LOW PRESSURE AREA N OF THE BAHAMAS WEAKENING THE
PRESSURE GRADIENT... THOUGH SOME INCREASE IN SPEED TO 20 KT
SHOULD OCCUR BY THE MIDDLE PART OF THE WEEK.

ATLANTIC OCEAN...
MOST SIGNIFICANT FEATURE IS A 1013 MB LOW NEAR 23.5N69.5W MOVING
SLOWLY NNE.  CONVECTION HAS BEEN REDEVELOPING NEAR THE LOW
CENTER... THOUGH LAST VISIBLE IMAGES SUGGEST ANOTHER WEAK
LOW-LEVEL CIRCULATION MAY BE POPPING OUT OF DISTANT TSTMS NEAR
26N69W.  THIS AREA IS THE PRIMARY SYSTEM TO WATCH DURING THE
NEXT FEW DAYS AS UPPER-LEVEL WINDS COULD BECOME MORE FAVORABLE
FOR DEVELOPMENT.  FOR NOW A MID/UPPER LOW IS JUST NW OF THE
SURFACE LOW... WITH STRONG SW SHEAR PREVENTING ANY FURTHER
ORGANIZATION.  SCATTERED MODERATE CONVECTION IS MOSTLY E OF THE
LOW FROM 23.5N-27N BETWEEN 65W-68.5W.  MID/UPPER RIDGING COVERS
THE AREA BETWEEN 50W-70W WITH A DEEP MID-OCEANIC TROUGH
EXTENDING FROM A DEEP-LAYERED 1016 MB LOW NEAR 31N43W SSW TO
11N49W INTO THE TROPICAL ATLC.  A FEW TSTMS ARE FORMING IN
MID/UPPER DIVERGENCE E OF THE LOW WITHIN 60 NM OF 30N40W.  THIS
SYSTEM APPEARED TO BE GAINING SOME TROPICAL CHARACTERISTICS
YESTERDAY BUT HAS BECOME LESS ORGANIZED TODAY.  OTHERWISE A
SURFACE HIGH HAS BUILT INTO THE NE ATLC WITH VERY DRY AIR ALOFT
AND ENHANCED TRADES ESPECIALLY E OF 40W N OF 16N.  SURFACE RIDGE
RUNS FROM 31N31W TO 20N46W THOUGH IS WEAKENED BY THE LOW NEAR
31N43W.  ELSEWHERE IN THE DEEP TROPICS... MID/UPPER HIGH IS NEAR
16N18W RIDGING WSW TO 16N30W WHERE IT MEETS AN INVERTED TROUGH
ALONG 8N39W TO 21N31W.  W OF THE TROUGH VERTICAL WIND SHEAR
INCREASED ALONG WITH LARGE-SCALE SUBSIDENCE CREATING A RATHER
UNFAVORABLE ENVIRONMENT FOR TROPICAL CYCLONES TO FORM...
COINCIDENT WITH THE NEGATIVE PHASE OF THE MADDEN-JULIAN
OSCILLATION (MJO) BEING IN THE AREA.

$$
BLAKE


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