[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 051745
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 05 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1715 UTC.

...SPECIAL FEATURE...
TROPICAL DEPRESSION SIX HAS BEEN UPGRADED TO TROPICAL STORM
FLORENCE. AS OF 05/1500 UTC FLORENCE IS CENTERED NEAR 17.3N
47.3W OR ABOUT 935 MILES...1510 KM...EAST OF THE LESSER
ANTILLES. IT IS MOVING WEST AT 11 KT. THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1005 MB. THE MAXIMUM SUSTAINED WIND SPEED IS
35 KT WITH GUSTS TO 45 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 CONTINUES TO SLOWLY ORGANIZE WITH A CURVED
BAND FEATURE BECOMING MORE CONVECTIVE IN THE NORTHERN
SEMI-CIRCLE FROM 17N-22N BETWEEN 44W-49W. THE CYCLONE'S WIND
FIELD IS RATHER LARGE WITH TROPICAL STORM FORCE WINDS EXTENDING
WITHIN 100 NM IN THE NE AND 90 NM IN THE NW QUADRANT. MODERATE
SOUTHWESTERLY SHEAR ASSOCIATED WITH A LARGE MID-UPPER LEVEL
TROUGH IN THE CENTRAL ATLANTIC CONTINUES TO AFFECT THE
CIRCULATION SHEARING THE HIGH CLOUDS TOWARDS THE NE AND SOME OF
THE CONVECTION TO THE N OF THE CENTER OR DOWN-SHEAR. SCATTERED
SHOWERS AND TSTMS ARE ALSO BECOMING BETTER ORGANIZED IN A BAND
OR TRAILING TROF FEATURE TO THE S AND SE OF THE CENTER FROM
9N-14N BETWEEN 45W-49W. BECAUSE OF THE MODERATE WIND SHEAR AND
LARGE WIND FIELD ONLY SLOW STRENGTHENING IS FORECAST OVER THE
NEXT COUPLE OF DAYS AS IT TRACKS TOWARDS THE WEST-NORTHWEST.

...TROPICAL WAVES...
AN E ATLC TROPICAL WAVE IS ALONG 32W FROM 8N-21N MOVING W NEAR
10 KT OVER THE PAST 24 HOURS. THIS SYSTEM REMAINS WELL-DEFINED
WITH A 1010 MB LOW ANALYZED ALONG THE WAVE NEAR 14.5N. A 36 HOUR
INFRARED SATELLITE LOOPS SHOWS THAT CONVECTION HAS BEEN PULSING
DURING THIS TIME BUT IN GENERAL HAS DECREASED SOMEWHAT...HOWEVER
THERE IS SLIGHTLY BETTER ORGANIZATION TO THE SHOWER ACTIVITY.
SCATTERED SHOWERS AND TSTMS ARE MOST ORGANIZED IN A BROKEN
CURVED BAND ON THE N AND W SIDE OF THE SFC LOW...NAMELY FROM
13N-18N BETWEEN 33W-37W. THIS BROAD AREA IS BEING MONITORED AS
THERE IS SOME POTENTIAL FOR DEVELOPMENT OVER THE NEXT COUPLE OF
DAYS.

A TROPICAL WAVE IS ALONG 59W FROM 8N-22N MOVING W NEAR 10 KT.
THIS WAVE CONTINUES TO BE EASY TO TRACK AS AN INVERTED V-PATTERN
IS EASILY SEEN IN THE LOW CLOUD STRUCTURE. DESPITE THE CLEAR
WAVE SIGNATURE...NEARLY ALL OF THE ASSOCIATED CONVECTION HAS
BEEN SHEARED WELL AHEAD OF THE WAVE AXIS FROM 13N-17N BETWEEN
64W-73W. SCATTERED SHOWERS AND TSTMS HAVE FORMED NEAR THE BASE
OF THE WAVE...ENHANCED BY THE ITCZ AND SOME LAND INFLUENCE FROM
6N-9N BETWEEN 57W-60W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 76W SOUTH OF 20N MOVING
WEST 5-10 KT. AN UPPER TROUGH IN THE AREA IS MASKING THE
LOW-LEVEL SIGNATURE...HOWEVER SOME SLIGHT LOW-MID LEVEL CYCLONIC
TURNING IS STILL NOTICEABLE ON VIS IMAGES AND SFC OBSERVATIONS.
SOME POSSIBLE INTERACTION FROM THIS WAVE AND THE UPPER TROUGH IS
TRIGGERING SCATTERED SHOWERS AND TSTMS FROM 11N-15N BETWEEN
82W-86W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 7N10W 10N31W 14N41W TO THE COAST OF
VENEZUELA NEAR 9N61W. BESIDES FOR CONVECTION ASSOCIATED WITH
TROPICAL STORM FLORENCE AND THE TROPICAL WAVES...SCATTERED
SHOWERS AND TSTMS EXIST FROM 3N-8N BETWEEN 19W-23W.

...DISCUSSION...

THE GULF OF MEXICO...
MID-UPPER LEVEL TROUGHING LIES ACROSS THE E GULF WITH A PAIR OF
UPPER LOWS EMBEDDED. ONE UPPER LOW CENTER IS NEARLY STATIONARY
OR DRIFTING SW NEAR 24N89W AND THE OTHER CONTINUES TO PULL NE IN
THE W ATLC OFF THE CAROLINA COASTLINE. AN UPPER HIGH IS ANCHORED
JUST W OF THE BAJA WITH RIDGING EXTENDING ACROSS THE S U.S. AND
N GULF ALONG 30N OUT TO 85W. THIS COMPLEX PATTERN IS PRODUCING A
CONSIDERABLE AMOUNT OF MOISTURE IN THE E GULF. THE DEEPEST
MOISTURE IS IN THE SE GULF WHERE NUMEROUS SHOWERS AND TSTMS
EXIST ACROSS THE SOUTHERN PORTION OF FLORIDA AND THE STRAITS
FROM 24N-26N BETWEEN 78W-82W. THIS MOISTURE IS ENHANCED BY A
POSSIBLE SFC TROUGH OR LOW-MID LEVEL LOW PRES AREA OFF THE SW
COAST OF FLORIDA. A SLOW MOVING WEAKENING FRONTAL BOUNDARY IS
ALONG OR JUST OFF THE GULF COAST FROM S MS TO 28N92W TO THE S
TEXAS COAST NEAR 27N97W. A PRE-FRONTAL SFC TROUGH LIES ABOUT
50-100 NM SE OF THE FRONT FROM THE FL PANHANDLE TO THE
TEXAS/MEXICO BORDER. A LINE OF CLOUDS AND SCATTERED SHOWERS ARE
WITHIN 100 NM MAINLY AHEAD OF THESE SFC BOUNDARIES.
OVERALL...DEEP MOISTURE IS SOMEWHAT LIMITED IN THE NW GULF AS
MODERATE SUBSIDENCE COVERS THE MAJORITY OF THE REGION UNDER
UPPER RIDGING. SCATTERED SHOWERS AND TSTMS ARE ALSO IN THE W BAY
OF CAMPECHE IN A SFC CONVERGENCE ZONE. THIS MOIST PATTERN IN THE
E GULF AND FLORIDA IS EXPECTED TO PERSIST TONIGHT AND TOMORROW.
THEREAFTER... GFS TAKES THE BULK OF THE MOISTURE TO THE NE OF
THE AREA.

THE CARIBBEAN SEA...
THE UPPER TROUGH THAT COVERS THE E GULF DIGS INTO THE W
CARIBBEAN WITH THE AXIS EXTENDING FROM THE UPPER LOW NEAR 24N89W
ACROSS CENTRAL AMERICA. A FAIR AMOUNT OF MOISTURE IS EMBEDDED IN
THIS TROUGH W OF 82W. UPPER DIFFLUENCE NEAR THE BASE OF THE
TROUGH AND ON THE SE SIDE AIDED BY MOUNTAINOUS TERRAIN IS
GENERATING SCATTERED SHOWERS AND TSTMS OVER COSTA RICA AND
NICARAGUA FROM 11N-15N BETWEEN 81W-85W. THE MOST ORGANIZED AREA
OF DISTURBED WEATHER IN THE REGION IS IN THE E AND CENTRAL
CARIBBEAN AHEAD OF A TROPICAL WAVE ALONG 59W. SCATTERED SHOWERS
AND TSTMS EXIST FROM 13N-17N BETWEEN 64W-73W. A NARROW AREA OF
DRY STABLE AIR LIES BETWEEN 73W AND 79W GENERATED BY AN UPPER
HIGH OVER PUERTO RICO. TRADE WINDS ARE GENERALLY IN THE 15-20 KT
RANGE E OF 80W...LIGHTER WINDS W OF THERE. GFS HAS THE OVERALL
MOISTURE PATTERN INITIALIZED WELL AND KEEPS A FAIR AMOUNT OF
MOISTURE IN THE S CARIBBEAN TOMORROW.

THE ATLANTIC OCEAN...
AN UPPER TROUGH COVERS THE ATLC AND MUCH OF THE CARIBBEAN W OF
70W. CONSIDERABLE MOISTURE LIES UNDER THE INFLUENCE OF THE
TROUGH...HOWEVER THE MOST ORGANIZED PRECIP IS IN THE W BAHAMAS
AND S FLORIDA WHERE UPPER DIFFLUENCE IS STRONGEST AND A POSSIBLE
SFC TROUGH OR LOW-MID LEVEL LOW MAY HAVE FORMED. AN UPPER LEVEL
HIGH IS CENTERED TO THE NE OF THE TROUGH NEAR 32N65W. ANOTHER
UPPER HIGH IS CENTERED TO THE S OF THE AREA NEAR PUERTO RICO.
ESSENTIALLY...A NARROW AREA OF UPPER RIDGING AND DRY AIR EXISTS
BETWEEN 58W-70W. A DEEP LAYER TROUGH COVERS THE REGION BETWEEN
39W AND 57W N OF 20N. MODERATE SWLY VERTICAL WIND SHEAR
ASSOCIATED WITH THIS TROUGH IS AFFECTING T.S. FLORENCE. THIS
SHEAR AND BECAUSE OF IT'S LARGE WIND FIELD WILL LIKELY ONLY
ALLOW FLORENCE TO SLOWLY STRENGTHEN OVER THE NEXT DAY OR TWO. AN
ASSOCIATED SFC FRONT ENTERS THE AREA NEAR 32N33W AND EXTENDS SW
TO 27N41W THEN STATIONARY TO 25N59W. SCATTERED SHOWERS ARE
WITHIN 180 NM OF THE BOUNDARY. A CUT-OFF UPPER LEVEL LOW
APPEARS TO BE DEVELOPING NEAR THE TAIL END OF THE SFC FRONT
ENHANCING SOME ACTIVITY FROM 24N-28N BETWEEN 50W-59W. FARTHER
EAST...A BROAD MID-UPPER LEVEL RIDGE COVERS THE REMAINDER OF THE
REGION WITH THE MAIN HIGH CENTER NEAR 21N31W. ACCORDING TO VIS
IMAGES AND THE CIMSS SAL TRACKING PRODUCT...THE SAHARAN DUST IS
FAIRLY SPARSE NEAR FLORENCE AND THE E ATLC TROPICAL
WAVE...HOWEVER A NEW SURGE OF DUST HAS PUSHED OFF THE COAST
SPREADING TO ABOUT 28W. AT THE SFC...THE FRONTAL BOUNDARY
DRAPED ACROSS THE CENTRAL ATLC MENTIONED EARLIER HAS WEAKENED
THE SUBTROPICAL RIDGE.

$$
CANGIALOSI


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