[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 072348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU SEP 07 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
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...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC.

...SPECIAL FEATURE...
THE CENTER OF TROPICAL STORM FLORENCE AT 07/2100 UTC IS NEAR
19.8N 54.9W MOVING WEST-NORTHWEST AT 12 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1000 MB. THE MAXIMUM SUSTAINED WIND
SPEED IS 45 KT WITH GUSTS TO 55 KT. PLEASE READ THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
AND THE PUBLIC ADVISORY UNDER MIATCPAT1/WTNT31 KNHC FOR MORE
DETAILS. FLORENCE IS A VERY LARGE TROPICAL CYCLONE WITH TROPICAL
STORM FORCE WINDS EXTENDING OUTWARD 350 NM IN THE NE QUADRANT
AND 250 NM IN THE NW AND SE QUADRANTS. HOWEVER THE SYSTEM IS
VERY ASYMMETRIC WITH LESS THAN T.S. WINDS FOUND IN THE SW QUAD.
THIS ASYMMETRIC STRUCTURE IS CAUSED BY A WELL-DEFINED UPPER
LEVEL LOW CENTERED TO ITS WEST WHICH IS IMPARTING S-SW VERTICAL
WIND SHEAR AND DRY AIR ACROSS PART OF THE CIRCULATION. THE MOST
ORGANIZED WEATHER LIES IN A LARGE BAND FEATURE IN THE
N-SEMICIRCLE FROM 20N-23N BETWEEN 50W-58W. OUTER BANDS EXTEND
SEVERAL HUNDRED NM TO THE N AND E OF THE CENTER. INNER-CORE
CONVECTION HAS BEGUN DEVELOPING AND STEADY STRENGTHENING IS
FORECAST AS FLORENCE TRACKS WNW-NW OVER THE NEXT COUPLE OF DAYS.


...TROPICAL WAVES...
AN E ATLC TROPICAL WAVE IS ALONG 27W S OF 13N MOVING W 10 TO 15
KT. THIS WAVE IS LOW AMPLITUDE AND HAS LITTLE WAVE SIGNATURE ON
SATELLITE IMAGES. SHOWER ACTIVITY IS DISORGANIZED AND MINIMAL.

A TROPICAL WAVE IS ALONG 44W S OF 20N MOVING W NEAR 10 KT. AT
ONE POINT THIS WAVE WAS WELL-DEFINED AND ORGANIZED WITH A SFC
LOW ALONG THE WAVE AXIS. HOWEVER...THIS ENERGY IS NOW BECOMING
ABSORBED BY THE ABNORMALLY LARGE AND CONTINUOUSLY EXPANDING
CIRCULATION OF TROPICAL STORM FLORENCE CENTERED ABOUT 600-700 NM
TO THE WNW.

A TROPICAL WAVE IS ADJUSTED SLIGHTLY AHEAD IN THE CARIBBEAN
ALONG 76W S OF 21N MOVING W 10 TO 15 KT. THIS SLIGHT ADJUSTMENT
WAS BASED A WEAK INVERTED V-PATTERN SEEN ON VIS PICTURES AND SFC
OBSERVATIONS WHICH DISPLAYED A WAVE STRUCTURE. THIS WAVE ALONG
WITH UPPER DIFFLUENCE BETWEEN AN UPPER LOW N OF THE LEEWARD
ISLANDS AND UPPER RIDGING IN THE CARIBBEAN IS GENERATING
SCATTERED SHOWERS AND TSTMS BETWEEN 67W-77W FROM 16N-20N. THE
STRONGEST ACTIVITY IS OVER HISPANIOLA WHERE CONVECTION HAS
INTENSIFIED AND EXPANDED OVER THE LAST FEW HOURS. SIMILAR
WEATHER IS ALONG THE BASE OF THE WAVE ENHANCED BY THE ITCZ FROM
8N-11N BETWEEN 72W AND 78W.

A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 86/87W SOUTH OF
21N MOVING WEST 10 TO 15 KT. SLIGHT LOW-MID LEVEL CYCLONIC
TURNING IS NOTED ABOUT THE AXIS. SCATTERED SHOWERS AND TSTMS ARE
WITHIN 180 NM EITHER SIDE OF THE AXIS...MOST ORGANIZED OVER
NICARAGUA AND HONDURAS.

...THE ITCZ...
ITCZ IS CENTERED ALONG 11N15W 8N42W 15N54W 10N63W TO N PANAMA
NEAR 9N83W. BESIDES FOR THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVES...SCATTERED MODERATE IS MOVING OFF THE COAST OF
AFRICA E OF 18W FROM 11N-16N. SCATTERED SHOWERS AND ISOLATED
TSTMS ARE WITHIN 240 NM S OF THE AXIS BETWEEN 30W-40W. SCATTERED
MODERATE LIES ACROSS N VENEZUELA FROM 6N-11N BETWEEN 63W-69W.

...DISCUSSION...

THE GULF OF MEXICO...
AN UPPER LEVEL TROUGH HAS BECOME ESTABLISHED ACROSS THE N
PORTIONS OF THE GULF WITH A WEAK SQUASHED RIDGE LYING TO THE S
OF THE TROUGH STRETCHING FROM S MEXICO TO THE CARIBBEAN. A
CONSIDERABLE AMOUNT OF MOISTURE EXISTS TO THE E OF THE TROUGH
AXIS WHICH IS ALONG 92W. THE DEEPEST MOISTURE IS IN THE NE GULF
WHERE SCATTERED TO NUMEROUS SHOWERS AND TSTMS ARE FOUND...N OF
26N E OF 87W ACROSS N CNTRL FLORIDA. THIS ACTIVITY IS BEING
ENHANCED BY AN ASSOCIATED STATIONARY FRONT WHICH EXTENDS FROM
THE FLORIDA PANHANDLE SW ALONG 26N92W THEN SURGING SOUTHWARD TO
19N96W THEN AS A DISSIPATING STATIONARY FRONT ALONG THE E SLOPES
OF THE SIERRA MADRE MOUNTAINS. SCATTERED SHOWERS AND ISOLATED
TSTMS ARE WITHIN 120 NM EITHER SIDE OF THE SFC BOUNDARY. THERE
IS SOME DRY SLOTS NEAR THE CORNERS OF THE GULF WITH MODERATE TO
STRONG SUBSIDENCE NOTED IN THE NW GULF N OF 28N W OF 88W AND
SOME DRY AIR ALOFT OVER S FLORIDA. SFC WINDS ARE GENERALLY LIGHT
AND VARIABLE DUE TO A WEAK PRES GRAD. GFS DOES NOT ANTICIPATE
THE MID-UPPER TROUGH TO DIG MUCH FURTHER SOUTHWARD BEFORE
LIFTING NE AND THE SOUTHERN PORTION OF THE STATIONARY FRONT WILL
LIKELY BEGIN TO LIFT N AND DISSIPATE...SO THE GREATEST CHANCE OF
PRECIP WILL CONTINUE TO BE IN THE NE GULF TOMORROW.

THE CARIBBEAN SEA...
WEAK MID-UPPER LEVEL RIDGING STRETCHES ACROSS THE AREA W OF 70W
WITH AN UPPER ANTICYCLONE CENTERED NEAR 17N85W. AN UPPER LEVEL
LOW IS LOCATED ABOUT 300 NM TO THE NE OF THE LEEWARD ISLANDS.
UPPER DIFFLUENCE BETWEEN THESE FEATURES IN ADDITION TO SOME
INFLUENCE FROM A NEARBY WEAK TROPICAL WAVE AND UPSLOPE FLOW OVER
MOUNTAINOUS TERRAIN IS PRODUCING SCATTERED SHOWERS AND TSTMS
ACROSS THE GREATER ANTILLES FROM 16N-20N BETWEEN 67W-77W. THE
STRONGEST ACTIVITY IS OVER HISPANIOLA WHERE CONVECTION HAS
INTENSIFIED AND EXPANDED OVER THE LAST FEW HOURS. SCATTERED
MODERATE CONVECTION EXISTS S OF 13N BETWEEN 70W-84W HIGHLY
CONTRIBUTED TO THE ITCZ. SCATTERED TSTMS ARE ALSO OVER NICARAGUA
AND HONDURAS LIKELY ENHANCED BY ANOTHER TROPICAL WAVE. ISOLATED
SHOWERS COVER THE REMAINDER OF THE AREA NOT OUTLINED. TRADE
WINDS ARE MAINLY IN THE 10-15 KT RANGE. THESE WINDS WILL LIKELY
REMAIN FAIRLY LIGHT OVER THE NEXT DAY OR TWO.

THE ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH IS TRACKING EASTWARD ACROSS THE CENTRAL
U.S. AND N GULF WITH THE AXIS ALONG 92W. AN ASSOCIATED
STATIONARY FRONT LIES JUST N OF THE DISCUSSION AREA IN THE ATLC
THEN ACROSS THE SE U.S. AND GULF. UPPER DIFFLUENCE BETWEEN THIS
TROUGH AND AN UPPER HIGH N OF THE BAHAMAS AND SFC
CONVERGENCE NEAR THE BOUNDARY IS GENERATING SCATTERED SHOWERS
AND TSTMS N OF 26N W OF 74W. AN UPPER LEVEL LOW IS CENTERED NEAR
22N63W. THIS LOW FORMED EARLIER THIS WEEK AT THE TAIL END OF A
LARGE UPPER TROUGH AND CONTINUES TO IMPART VERTICAL WIND SHEAR
ACROSS THE CIRCULATION OF TROPICAL STORM FLORENCE. UPPER LEVEL
RIDGING LIES ABOVE PART OF FLORENCE AND STRETCHES EASTWARD TO
20W WITH THE RIDGE AXIS ALONG 19N. A LARGE UPPER LEVEL TROUGH
LIES TO THE N OF THE RIDGE AND COVERS THE REGION E OF 40W N OF
25N. SCATTERED SHOWERS AND TSTMS ASSOCIATED WITH FLORENCE COVERS
A LARGE AREA FROM 14N-27N BETWEEN 44W-63W. DEBRIS MOISTURE FROM
FLORENCE CARRIED EASTWARD BY THE UPPER RIDGE AND ENHANCED BY
DIFFLUENCE NEAR THE BASE OF THE E ATLC TROUGH HAS PRODUCED
SCATTERED SHOWERS WITHIN 120 NM OF A LINE ALONG 21N39W 26N25W
32N17W. ACCORDING TO THE CIMSS SAL TRACKING PRODUCT AND THE
MILKY LOOK ON THE EARLIER VIS IMAGES THE SAHARAN DUST HAS SPREAD
TO NEAR 40W FROM 12N-24N. AT THE SFC...A 1025 MB HIGH PRES
SYSTEM IS LOCATED NEAR 35N46W. THE TIGHTEST PRES GRAD IS IN THE
CENTRAL ATLC NEAR T.S. FLORENCE WHICH IS PRODUCING A LARGE AREA
OF TROPICAL STORM FORCE WINDS TO THE N OF THE CYCLONE.

$$
CANGIALOSI


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