[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 072332
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU 07 OCT 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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...

A 1007 MB LOW PRES IS CENTERED ABOUT 80 NM ENE OF TAMPICO MEXICO
NEAR 23N96.5W. THE LOW IS LOCATED ALONG A SFC TROF WHICH EXTENDS
NWD TO THE TEXAS COAST THEN NEWD TO NEAR HOUSTON/BEAUMONT TEXAS.
A TROF ALSO EXTENDS S OF THE LOW TO NEAR COATZACOALCOS MEXICO
ALONG THE MEXICAN COAST. AN AIR FORCE RESERVE AIRCRAFT FLEW INTO
THE STORM EARLIER THIS AFTERNOON AND FOUND THAT THE CENTRAL
PRESSURE OF THE LOW HAS DROPPED...BUT THE WINDS ARE CURRENTLY
NOT STRONG ENOUGH NEAR THE LOW TO WARRANT THE FORMATION OF A
TROPICAL CYCLONE. HOWEVER...STRONG 20-25 KT SE GRADIENT FLOW IS
LOCATED OVER THE NW GULF AND TEXAS COAST. TROPICAL CYCLONE
DEVELOPMENT IS POSSIBLE WITHIN THE NEXT 36 HOURS AS THE LOW
TRACKS NWD TOWARDS THE TEXAS COAST. SCATTERED MODERATE
CONVECTION CURRENTLY EXTENDS E AND NE OF THE LOW/TROF N OF 21N
BETWEEN 89W-97W. RADAR IMAGERY SHOWS A LARGE AREA OF HEAVY RAIN
AND EMBEDDED TSTMS ALONG THE TEXAS AND LOUISIANA COAST BETWEEN
THE MISSISSIPPI DELTA AND BROWNSVILLE TEXAS...AND THERE IS THE
POTENTIAL FOR FLOODING ALONG THE N GULF COAST AS THIS RAIN
CONTINUES THROUGH THE WEEKEND.

...TROPICAL WAVES...

TROPICAL WAVE IS LOCATED JUST E OF THE CAPE VERDE ISLANDS ALONG
22W S OF 17N MOVING W 10-15 KT. THE DAKAR SOUNDING INDICATES
THAT THE WAVE HAS A STRONG BACKWARD TILT WITH HEIGHT...WITH A
WELL-DEFINED LOW-LEVEL PASSAGE AROUND 00Z ON 10/6...AND THE
MID-LEVEL PASSAGE AROUND 18Z ON 10/6. SATELLITE IMAGERY SUGGESTS
THAT THE MAIN PART OF THE CIRCULATION IS NOW JUST SE OF THE CAPE
VERDE ISLANDS. WIDELY SCATTERED MODERATE CONVECTION IS FROM
10N-15N BETWEEN 20W-26W.

TROPICAL WAVE IS LOCATED OVER THE E ATLC ALONG 35W/36W S OF 14N
MOVING W 10-15 KT. STRONG NELY AND SELY LOW-LEVEL FLOW IS
CONVERGING ALONG THE ITCZ OVER THE CNTRL ATLC AND THIS HAS GIVEN
THE WAVE A VERY FLAT APPEARANCE. THE WAVE MAY BECOME MORE
APPARENT OVER THE NEXT 2-3 DAYS AS IT HEADS INTO THE WEAKER FLOW
REGIME NEAR THE LESSER ANTILLES. RIGHT NOW...CONVECTION IS
ALIGNED LINEARLY ALONG THE ITCZ AXIS.

WEAKENING TROPICAL WAVE IS LOCATED ABOUT 440 NM E OF BARBADOS
ALONG 52W S OF 15N MOVING W 10-15 KT. THE WAVE IS BEING DRAGGED
INTO THE MUCH LARGER CIRCULATION ASSOCIATED WITH ANOTHER
TROPICAL WAVE/SFC TROF EXTENDING FROM THE LESSER ANTILLES
NWD...AND SO ITS SIGNATURE HAS BECOME LESS DISTINCT. HOWEVER...A
CONVERGENCE LINE HAS SET UP TO THE N OF THE WAVE AND SCATTERED
MODERATE/STRONG CONVECTION HAS DEVELOPED FROM 11N-20N BETWEEN
47W-55W.

TROPICAL WAVE IS SITUATED OVER THE LEEWARD/WINDWARD ISLAND CHAIN
ALONG 61W S OF 19N MOVING W 5-10 KT. SURFACE OBSERVATIONS FROM
THE ISLANDS AND RADAR IMAGERY FROM GUADELOUPE INDICATE THAT A
WEAK 1010 MB LOW HAS FORMED ALONG THE WAVE BETWEEN DOMINICA AND
MARTINIQUE NEAR 15N61W. A SMALL CLUSTER OF MODERATE CONVECTION
IS LOCATED E OF THE LOW FROM 13N-17N BETWEEN 56W-60W. A SFC TROF
ALSO EXTENDS N OF THE WAVE INTO THE SUBTROPICS ALONG 20N62W
29N57W WITH WIDELY SCATTERED SHOWERS AND EMBEDDED TSTMS UP TO
450 NM SE OF THE AXIS. W/SW SHEAR IS CURRENTLY OVER THE
WAVE...AND THIS SHOULD KEEP THE BULK OF THE HEAVIEST RAIN E OF
THE LESSER ANTILLES OVER THE NEXT SEVERAL DAYS BUT OCCASIONAL
SHOWERS/TSTMS COULD STILL MOVE ACROSS THE ISLANDS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 15N12W 10N22W...THEN ALONG 7N23W
9N34W...THEN ALONG 7N37W 6N47W 7N50W...THEN ALONG 6N62W 7N80W.
SCATTERED MODERATE CONVECTION OVER FAR NW GUINEA AND GUINEA-
BISSAU. WIDELY SCATTERED MODERATE WITHIN 100 NM OF THE AXIS
BETWEEN 24W-33W. SCATTERED MODERATE WITHIN 140 NM OF THE AXIS
BETWEEN 37W-48W. SCATTERED MODERATE/ISOLATED STRONG OVER THE E
HALF OF VENEZUELA AND N PART OF COLOMBIA.

...DISCUSSION...

GULF OF MEXICO AND W ATLANTIC...
SEE SPECIAL FEATURES FOR DISCUSSION ON LOW NE OF TAMPICO.
ELSEWHERE...STRONG HIGH PRES HAS BUILT IN OVER THE MID-ATLC
STATES WITH A TIGHTENING GRADIENT NOW ACROSS FLORIDA AND THE
GULF OF MEXICO. A WEAKENING STATIONARY FRONT...MARKED MORE OR
LESS BY A MOISTURE GRADIENT ALONG THE LEADING EDGE OF THE HIGH
PRES SYSTEM...EXTENDS FROM NEAR BERMUDA SWWD TO THE NRN BAHAMAS
AND S FLORIDA. ISOLATED SHOWERS WITH BRIEF PERIODS OF HEAVY
RAINFALL HAVE DEVELOPED ALONG THIS BOUNDARY AND ARE NOW MOVING
WWD ACROSS EXTREME S FLORIDA AND THE FLORIDA KEYS. BROAD
ANTICYCLONIC FLOW DOMINATES THE UPPER LEVELS OVER THE GULF OF
MEXICO WITH BROAD DIFFLUENT FLOW FOSTERING CONVECTION OVER THE W
GULF WATERS. A VIGOROUS SHORTWAVE IS MOVING E ACROSS NEW MEXICO
AND W TEXAS...AND MAY INDUCE SOME SORT OF TROPICAL/NON-TROPICAL
DEVELOPMENT AS THE LOW NEAR THE MEXICAN COAST TRACKS N. FARTHER
E...A MID/UPPER LEVEL TROF HAS DROPPED DOWN OVER THE W ATLC WITH
MUCH DRIER AIR E OF FLORIDA TO 70W...AND TRIGGERING SCATTERED
MODERATE CONVECTION AHEAD OF THE STATIONARY FRONT OVER THE
WATERS OF THE W ATLC FROM 25N-29N BETWEEN 61W-67W.

CARIBBEAN...
A LARGE AREA OF DRY MID/UPPER LEVEL AIR CONTINUES TO BE PUMPED
SWD OVER THE CNTRL/W PARTS OF THE CARIBBEAN...SANDWICHED BETWEEN
AN UPPER LEVEL HIGH NEAR GUATEMALA AND A DEEP-LAYERED TROF
STRETCHING FROM PUERTO RICO TO LAKE MARACAIBO. ISOLATED TSTMS
HAVE POPPED OVER PARTS OF HISPANIOLA...CUBA...AND JAMAICA BUT
OTHERWISE THE AREA IS GENERALLY UNDER THE INFLUENCE OF EASTERLY
TRADES WITH LIGHT PASSING SHOWERS. HOWEVER...THE TRADES HAVE
BEEN INTERRUPTED A BIT OVER THE E CARIBBEAN DUE TO A SLOW-MOVING
TROPICAL WAVE/TROF OVER THE LESSER ANTILLES. THE UPPER TROF
CONTINUES TO DRAG A LOT OF MOISTURE NEWD FROM S AMERICA INTO THE
ATLC BUT FORTUNATELY THE HEAVIEST RAINFALL HAS STAYED TO THE E
OVER OPEN WATERS.

REMAINDER OF SUBTROPICS...
A BROAD UPPER LEVEL RIDGE EXTENDS NWD ACROSS THE CNTRL ATLC FROM
20N49W TO 32N49W...WITH UPPER DIFFLUENCE PRODUCING WIDELY
SCATTERED SHOWERS AND EMBEDDED TSTMS BETWEEN 50W-58W. FARTHER
E...A SFC RIDGE EXTENDS ACROSS THE E ATLC FROM 30N41W 25N30W TO
THE CANARY ISLANDS WITH A BROAD UPPER LEVEL TROF SPANNING
BETWEEN THE AFRICAN COAST AND 40W. A MID-LEVEL SHORTWAVE IS
EMBEDDED WITHIN THE TROF NEAR 23N30W BUT THE ATMOSPHERE IS TOO
DRY FOR SIGNIFICANT WEATHER.

TROPICAL ATLANTIC...
THE TROPICS ARE REALLY JUST AN EXTENSION OF THE SUBTROPICAL
FEATURES WITH STRONG UPPER LEVEL RIDGING ALONG 8N50W 20N51W AND
BROAD UPPER LEVEL TROUGHING EXTENDING AS FAR S AS 12N BETWEEN
20W-40W. CONVECTION NEAR THE ITCZ HAS BEEN FAIRLY LINEAR AND
COMPACT OVER THE PAST FEW DAYS...BUT DIFFLUENCE AHEAD OF THE
TROF IS BEGINNING TO MAKE THE TSTM ACTIVITY A LITTLE MORE
WIDESPREAD IN COVERAGE ESPECIALLY S OF THE CAPE VERDE ISLANDS.

$$
BERG


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