[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 302330
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI SEP 30 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.

...SPECIAL FEATURES...

TROPICAL DEPRESSION NINETEEN HAS DEVELOPED NEAR 11.8N 32.9W...OR
580 NM WSW OF THE CAPE VERDE ISLANDS...AT 30/2100 UTC MOVING W 2
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM
SUSTAINED WIND SPEED IS 25 KT WITH GUSTS TO 35 KT. SEE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24
KNHC FOR MORE DETAILS. T.D. NINETEEN HAS PRODUCED A LARGE
MUSHROOM OF CONVECTION OVER THE PAST FEW HOURS WITH NUMEROUS
STRONG FROM 9N-12.5N BETWEEN 31W-34.5W. THE DEPRESSION IS
CREEPING TO THE W WITH THERE ESSENTIALLY BEING NO SUBTROPICAL
RIDGE OVER THE ATLC AT THE MOMENT...BUT IT HAS BEEN ABLE TO
SITUATE ITSELF BENEATH RELATIVELY WEAK WINDS ALOFT THUS ALLOWING
THE INCREASED CONVECTION. WIDELY SCATTERED MODERATE CONVECTION
IS LOCATED ELSEWHERE FROM THE BURST NEAR THE CENTER FROM 7N-15N
BETWEEN 27W-37W...POSSIBLY THE FIRST STAGES OF BANDING FEATURES
TO THE NE AND SW.

A 1006 MB LOW IS LOCATED OVER THE NW CARIBBEAN NEAR 19N84W...OR
ABOUT 180 NM SE OF COZUMEL MEXICO...MOVING WNW ABOUT 5 KT. THIS
LOW HAS BEEN TRACKED FOR THE PAST SEVERAL DAYS BUT HAS NOT BEEN
ABLE TO CONSOLIDATE AN AREA OF DEEP CONVECTION NEAR THE CENTER.
THE SYSTEM CURRENTLY LIES JUST W OF AN UPPER HIGH AND WITHIN A
RIDGE AXIS...SO UPPER LEVEL WINDS HAVE BECOME FAVORABLE RIGHT
NEAR THE CENTER. THE LOW-LEVEL CIRCULATION APPEARS SOMEWHAT
ELONGATED AND A SURFACE TROUGH EXTENDS NWD ACROSS THE W TIP OF
CUBA TO NEAR FT. MYERS FLORIDA. CONVECTION REMAINS DISORGANIZED
FOR NOW WITH WIDELY SCATTERED MODERATE OVER WATER FROM 15N-22N
BETWEEN 79W-85W BUT CONDITIONS ARE FAVORABLE FOR TROPICAL
DEVELOPMENT WITHIN THE NEXT 24-36 HRS BEFORE THE SYSTEM MOVES
INLAND OVER THE YUCATAN PENINSULA.

...TROPICAL WAVES...

CENTRAL CARIBBEAN TROPICAL WAVE ALONG 70W S OF 23N MOVING W
15-20 KT. VISIBLE SATELLITE IMAGERY INDICATES THAT STRONG UPPER
LEVEL WESTERLY FLOW AND AN UPPER TROUGH OVER THE W ATLC WATERS
MAY BE CAUSING THE WAVE TO SPLIT...WITH THE SRN PORTION RACING
QUICKLY WWD S OF HISPANIOLA AND THE NRN PORTION BENDING SW/NE
NEAR THE TURKS AND CAICOS ISLANDS. MOST OF THE CONVECTION IN THE
VICINITY APPEARS TO BE BEING CAUSED BY AN ASSORTMENT OF
LOW-LEVEL CONVERGENCE LINES...TERRAIN EFFECTS...AND UPPER LEVEL
FEATURES BUT THE WAVE IS LIKELY ENHANCING THE WIDELY SCATTERED
MODERATE CONVECTION OCCURRING FROM 13N-22N BETWEEN 67W-77W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 15N10W 7N20W 16N30W...THEN ALONG
9N31W 14N56W...THEN ALONG 10N71W 13N86W. IT APPEARS AS THOUGH A
NEW TROPICAL WAVE IS JUST EMERGING OFF THE AFRICAN COAST AND
SCATTERED MODERATE/STRONG TSTMS ARE ALIGNED ALONG THE COAST FROM
7N-17N BETWEEN 11W-19W. SCATTERED MODERATE FROM 3N-9N BETWEEN
22W-27W. AN ELONGATED 1009 MB LOW IS EMBEDDED ALONG THE ITCZ
NEAR 12N50W WITH SCATTERED/NUMEROUS MODERATE WITHIN 90 NM OF THE
AXIS BETWEEN 41W-51W. SCATTERED MODERATE ALONG COASTAL AREAS OF
COLOMBIA.

...DISCUSSION...

GULF OF MEXICO...
DRY AIR ALOFT HAS OVERSPREAD ALMOST THE ENTIRE GULF REGION AND
THE CLOSEST DEEP-LAYERED MOISTURE IS BEING KEPT AT BAY OVER THE
CARIBBEAN SEA AT THE MOMENT. A WEAK UPPER LOW SITS JUST N OF THE
YUCATAN CHANNEL NEAR 22N86W DRIFTING SLOWLY W AND HAS ALLOWED
SOME OF THIS CARIBBEAN MOISTURE TO BE TAPPED...BRINGING IT JUST
OVER CUBA TOWARDS THE STRAITS OF FLORIDA AND INSTIGATING A FEW
SHOWERS NEAR THE FLORIDA KEYS. ELSEWHERE...A FRONTAL BOUNDARY
WHICH HAD MADE ITS WAY OVER THE N GULF WATERS IS BEGINNING TO
SURGE BACK TO THE N A BIT AND EXTENDS FROM THE FLORIDA PANHANDLE
WWD TO SRN LOUISIANA AND SE TEXAS. WSR-88D IMAGERY SHOWS A
SPECKLING OF SHOWERS/TSTMS FROM VALDOSTA GEORGIA SW TO MOBILE
ALABAMA ALONG THE BOUNDARY. A 1010 MB LOW MOVING SW 10-15 KT
OVER THE W GULF WATERS NEAR 25N93W BUT THE DRY AIR HAS PREVENTED
ANY CONVECTIVE DEVELOPMENT. ISOLATED SHOWERS HAVE BEEN FORMING
ABOUT 250 NM SW OF THE LOW MOST LIKELY DUE TO AN UPPER TROUGH
WHICH IS SITTING ALONG THE MEXICAN COAST.

CARIBBEAN...
AN UPPER LEVEL HIGH CENTERED NEAR THE CAYMAN ISLANDS AND AN
UPPER LOW NE OF THE LEEWARD ISLANDS ARE PRODUCING STRONG 30-40
KT NORTHERLY SHEAR OVER A GOOD CHUNK OF THE AREA. A LARGE AREA
OF TSTMS EXTENDS FROM THE YUCATAN PENINSULA EWD TO HISPANIOLA
AND PUERTO RICO AND ALL THE CIRRUS OUTFLOW IS BEING BLOWN SWD
TOWARDS SOUTH AMERICA. SOME OF THIS ACTIVITY EXTENDS ACROSS THE
WATERS OF THE W/CENTRAL CARIBBEAN ALTHOUGH THE HEAVIEST
CONVECTION IS CURRENTLY OVER LAND AREAS OF HISPANIOLA...CUBA...
AND FROM NICARAGUA TO BELIZE. A 1006 MB LOW...AS DESCRIBED IN
SPECIAL FEATURES...IS CENTERED 180 NM SE OF COZUMEL MEXICO NEAR
19N84W AND LIES WITHIN THE AREA OF LOWEST SHEAR BUT HAS BEEN
UNABLE TO MUSTER ENOUGH ORGANIZATION TO DEVELOP INTO A
DEPRESSION. THE E CARIBBEAN AND LESSER ANTILLES...E OF ABOUT
67W...ARE UNDER THE SUBSIDENT REGIME OF THE UPPER LOW NE OF THE
AREA AND ITS TRAILING TROUGH AXIS THAT EXTENDS TO ISLA
MARGARITA...SO SKIES ARE MAINLY CLEAR AND WINDS ARE GENERALLY
LIGHT.

ATLANTIC WEST OF 50W...
AN UPPER LEVEL TROUGH AXIS IS LOCATED OVER THE W ATLC WATERS
FROM 31N71W TO 25N66W AND THE ASSOCIATED UPPER DIFFLUENCE HAS
BEEN PRODUCING SCATTERED SHOWERS/TSTMS E OF THE BAHAMAS FROM
23N-28N BETWEEN 66W-71W. PLENTIFUL MOISTURE IS ALSO BEING
ADVECTED ACROSS CUBA TO THE BAHAMAS AND BAHAMA BANKS...WHICH IS
FOSTERING WIDELY SCATTERED SHOWERS/TSTMS PRIMARILY FROM THE
BAHAMA ISLANDS S AND SWWD. A TIGHTLY-WOUND UPPER LOW IS LOCATED
ABOUT 250 NM NE OF THE NORTHERN LEEWARD ISLANDS NEAR 21N61W AND
HAS BEEN QUITE CONVECTIVE WITH SCATTERED MODERATE FROM 18N-27N
BETWEEN 55W-62W. THE UPPER LOW/TROUGH HAS CREATED LIGHT AND
VARIABLE WINDS E OF THE LESSER ANTILLES AND AN EXTREMELY DIFFUSE
ITCZ.

ATLANTIC EAST OF 50W...
A STRONG UPPER HIGH IS PLASTERED IN THE MIDDLE OF THE ATLC NEAR
16N45W AND CONNECTS TO A RIDGE WHICH EXTENDS TO T.D. NINETEEN
THEN EWD TO THE COAST OF AFRICA NEAR GUINEA. UPPER DIFFLUENCE
JUST S OF THE RIDGE AXIS IS ALLOWING A LINEAR AREA OF CONVECTION
TO DEVELOP ALONG THE ITCZ...AND FAIR OUTFLOW TO THE S OF THE
T.D. NINETEEN. A VIGOROUS UPPER LOW IS CENTERED WSW OF THE
CANARY ISLANDS NEAR 26N28W AND HAS PRODUCED A 1011 MB LOW AT THE
SURFACE NEAR 22N27W. SCATTERED MODERATE CONVECTION HAS FORMED
NEAR THE SFC LOW FROM 23N-26N BETWEEN 26W-29W ALTHOUGH ISOLATED
SHOWERS ARE ALSO EMBEDDED WITHIN THE CIRCULATION OF THE UPPER
LOW ANYWHERE FROM 23N-32N BETWEEN 22W-32W. FARTHER E...A SHARP
UPPER RIDGE AXIS LIES ACROSS W AFRICA FROM MAURITANIA TO MADEIRA
ISLAND AND THE UPPER DIFFLUENCE NEAR THE APEX HAS PHASED WITH A
DEEP POOL OF MOISTURE TO PRODUCE SCATTERED MODERATE CONVECTION
FROM 24N-28N BETWEEN 11W-19W...MOVING ACROSS PORTIONS OF WESTERN
SAHARA AND TOWARDS THE CANARY ISLANDS. THIS ACTIVITY MAY PERSIST
FOR ANOTHER 24 HRS OR SO BUT THEN NELY FLOW WILL REDEVELOP AND
BRING BACK DRIER AIR.

$$
BERG




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