[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 300006
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED AUG 29 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 28W S OF 21N IS MOVING W ABOUT 13 KT WITH
A 1011 MB LOW ON THE WAVE AXIS 14N28W. THIS WAVE APPEARS TO BE
EMBEDDED IN A BROAD MONSOON CYCLONIC GYRE THAT COVERS THE AREA
FROM THE COAST OF AFRICA WSW TO NEAR 31N AND FROM 9N-20N.
ISOLATED MODERATE CONVECTION IS NOTED FROM 12N-14.5N BETWEEN
26W-31W.

TROPICAL WAVE IS ALONG 46W S OF 18W IS MOVING W 10-15 KT WITH A
1010 MB LOW ON THE WAVE AXIS NEAR 11N46W. ALTHOUGH VOID OF
DEEP CONVECTION...THIS SYSTEM IS EXHIBITING SOME CYCLONIC
TURNING IN THE LOW AND MID CLOUD FIELD AS OBSERVED ON SATELLITE
IMAGERY. IN ADDITION...THIS WAVE HAS A GOOD TRACK RECORD EVER
SINCE IT MOVED OFF THE COAST OF AFRICA SEVERAL DAYS AGO. IN
ADDITION...THE CIMSS 850 MB WAVETRACKER CLEARLY REVEALS THE
WAVE SIGNATURE IN THE SAME AREA AS DEPICTED BY SATELLITE
IMAGERY. ONLY ISOLATED SHOWERS AND TSTMS ARE WITHIN 300 NM EITHER
SIDE OF THE WAVE FROM 7N-13N.

TROPICAL WAVE ALONG 72W S OF 25N IS MOVING WNW 15 KT. LOW-LEVEL
CLOUD MOTION BEING PREDOMINATELY SOUTHEASTWARD SUGGESTS THAT
THIS WAVE IS MORE DEFINED N OF 16N...HOWEVER IT THAN BECOMES
MASKED BY THE UPPER LEVEL TROUGH NNE OF HISPANIOLA. SCATTERED
MODERATE CONVECTION IS OVER MUCH OF HISPANIOLA. SCATTERED SHOWERS
AND AND ISOLATED TSTMS ARE SEEN WITHIN 120 NM EITHER SIDE OF
THE WAVE N OF 16N.

TROPICAL WAVE IS WELL INLAND THE YUCATAN PENINSULA ALONG 90W
REACHING NORTHWARD INTO THE GULF OF MEXICO TO 23N...AND MOVING
W 10 KT.  SCATTERED MODERATE TO STRONG CONVECTION IS OVER THE
YUCATAN PENINSULA FROM 16N-20N BETWEEN 87W-91W.  SIMILAR
CONVECTION IS OVER THE NW CARIBBEAN FROM 18N-21N BETWEEN
85W-87W.

...THE ITCZ...

ITCZ AXIS IS CENTERED ALONG 15N16W 13N27W 10N34W 10N40W 9N50W
TO INLAND S AMERICA NEAR 8N60W. IN ADDITION TO CONVECTION
ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE/ISOLATED
STRONG IS WITHIN 120 NM S OF THE AXIS BETWEEN 32W-35W. ISOLATED
SHOWERS AND TSTMS ARE WITHIN 60 NM EITHER SIDE OF THE AXIS
BETWEEN THE WAVE ALONG 28N AND 46W.

DISCUSSION...
GULF OF MEXICO...
WITH THE TROPICAL WAVE ALONG 90W EXTENDING NORTHWARD INTO THE
S CENTRAL GULF OF MEXICO...THE ENVIRONMENT IS PERTURBED OVER
MUCH OF THE CENTRAL AND WESTERN PORTIONS OF THE GULF AS ABUNDANT
CARIBBEAN MOISTURE IS ENTRAINED NORTHWEST AND NORTH INTO THE
WAVE...THEN IS EXPANDED NORTHEASTWARD IN A DIFFLUENT PATTERN
IN RESPONSE TO ANTICYCLONIC FLOW OVER THE NORTHWEST CARIBBEAN
SEA...AND MID/UPPER LEVEL TROUGHING ACROSS THE CENTRAL GULF
BETWEEN THE WAVE AND 95W. CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION RACING NORTHWESTWARD AHEAD OF THE WAVE ARE
WITHIN 30 NM EITHER SIDE OF LINE 20N93W 21N90W. SIMILAR
CONVECTION IS WITHIN 30 NM EITHER SIDE OF LINE 23N91W 24N96.5W.
A NARROW MID/UPPER LEVEL RIDGE EXTENDS NORTHEAST-SOUTHWEST ALONG
THE TEXAS COAST. AS A RESULT...LIGHT TO MODERATE WINDS WITH THE
RIDGE ARE SPREADING UPPER LEVEL DEBRIS CLOUDINESS FROM SCATTERED
MODERATE CONVECTION OCCURRING ALONG AND INLAND THE TEXAS COAST
SOUTHWARD INTO THE WESTERN BAY OF CAMPECHE. BROKEN TO SCATTERED
LOW AND MID LEVEL CLOUDS WITH SCATTERED SHOWERS AND ISOLATED
TSTMS ARE ELSEWHERE S OF 26N AND WEST OF 85W. SCATTERED LOW
CLOUDS WITH ISOLATED SHOWERS AND TSTMS ARE OVER THE REMAINDER
OF THE GULF W OF 84W. PRECIP POTENTIAL GUIDANCE INDICATES
THAT UNSETTLED WEATHER CAN BE EXPECTED FOR THE MUCH OF THE
WESTERN GULF DURING THE NEXT 3-4  DAYS AS TROPICAL MOISTURE
ATTENDING THE TROPICAL WAVE AND UPPER LEVEL DIFFLUENT FLOW TO
THE E OF THE WAVE CONTINUE TO PRODUCE SCATTERED SHOWERS AND
TSTMS OVER THIS PART OF THE GULF.

CARIBBEAN SEA...
BROAD MID/UPPER LEVEL RIDGING COVERS THE NORTHWEST PORTION
OF THE CARIBBEAN WITH AN ANTICYCLONE NEAR 21N86W. A RIDGE
EXTENDS SOUTHEASTWARD FROM THE ANTICYCLONE TO NEAR 14N81W.
THE TAIL END OF THE ATLANTIC MID/UPPER LEVEL TROUGH STRETCHES
SOUTHWESTWARD ACROSS HISPANIOLA TO 16N74W. BROAD CYCLONIC FLOW
IS PRESENT N OF 16N BETWEEN 67W-76W. THE MID/UPPER FLOW IS
GENERALLY CONFLUENT BETWEEN THE ANTICYCLONE AND THE TROUGH
ADVECTING A NLY SURGE OF SOMEWHAT DRIER AIR OVER MUCH OF
CUBA AND JAMAICA. SATELLITE-DERIVED WINDS INDICATE THAT
UPPER LEVEL NLY WINDS ARE PRETTY LIGHT OVER THE NORTHERN
AND WESTERN PORTION OF THE CARIBBEAN. UPPER LEVEL EASTERLY
FLOW INCREASES TO THE BASE OF THE MID/UPPER LEVEL RIDGE
OVER THE SW PART OF THE SEA. HERE IS WHERE SCATTERED TO
MODERATE CONVECTION OCCURRED EARLIER IN CLUSTERS...AND
HAS JUST RECENTLY DIMINISHED TO ISOLATED. THE UPPER EASTERLY
FLOW IS PUSHING REMNANT UPPER DEBRIS CLOUDINESS WESTWARD
TOWARDS HONDURAS AND NICARAGUA. MOST OF THE EASTERN AND
REMAINDER OF THE CENTRAL CARIBBEAN ARE UNDER RATHER DRY
AIR AS AMPLE MODERATE TO STRONG SUBSIDENCE MOVES INTO
THE AREA FROM THE ATLANTIC. ONLY SCATTERED LOW CLOUDS
MOVING WESTWARD ABOUT 15 KT WITH ISOLATED SHOWERS ARE
FOUND THROUGHOUT THIS PART OF THE CARIBBEAN N OF MAINLY
13N.

ATLANTIC OCEAN...
MID/UPPER LEVEL TROUGH EXTENDS THROUGH 32N60W 26N64W TO
HISPANIOLA FOLLOWED BY MID/UPPER LEVEL ANTICYCLONIC FLOW
THAT COVERS THE BAHAMAS W TO 80W. A WEAK 1015 MB SURFACE
LOW MOVING S 10-15 KT IS NEAR 30N76W. ONLY ISOLATED WEAK
MODERATE CONVECTION IS NOTED WITHIN 120 NM TO THE NE OF
THE LOW. THE LOW IS FORECAST TO CONTINUE TO MOVE IN A SLY
DIRECTION OVER THE NEXT FEW DAYS. THE MID/UPPER LEVEL FLOW
BECOMES ANTICYCLONIC TO THE EAST OF THE TROUGH N OF 15N
BETWEEN THE TROUGH AND 49W. AN UPPER LEVEL HIGH IS NOTED
NEAR 24N54W. MODERATE SUBSIDENCE AND ASSOCIATED DRY AIR
IS FOUND HERE WITH A 1021 MB HIGH ANALYZED NEAR 31N56.5W.
A WEAK UPPER LEVEL TROUGH EXTENDS SSW FROM AN UPPER LEVEL
LOW NEAR 30N37W SSW THROUGH 32N40W TO 24N42W. ITS ASSOCIATED
WEAKENING SURFACE TROUGH EXTENDS FROM 32N35W TO 28N42W. PATCHES
OF LOW AND MID LEVEL CLOUDS WITH EMBEDDED ISOLATED SHOWERS ARE
WITHIN 60 NM EITHER SIDE OF THE TROUGH. BROAD MID/UPPER LEVEL
RIDGING COVERS THE FAR EASTERN PORTION OF THE ATLANTIC EAST OF
ABOUT 37W. AN UPPER LEVEL HIGH IS NEAR 13N41W. A WEAK PRESSURE
GRADIENT IS EVIDENT ON THE SURFACE OVER THE AREA WITH SCATTERED
PATCHES OF LOW CLOUDS AND ISOLATED SHOWERS...EXCEPT BETWEEN
63W-71W WHERE SCATTERED SHOWERS AND TSTMS ARE SEEN NEAR THE
TAIL END OF THE MID/UPPER LEVEL TROUGH.

$$
AGUIRRE



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