[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 270529
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED 27 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED ABOUT 950 NM E OF THE LESSER ANTILLES
ALONG 44W S OF 17N MOVING W NEAR 15 KT. A SHARP AND WELL-DEFINED
LOW-LEVEL CIRCULATION IS IDENTIFIED ALONG THE WAVE AXIS BUT MOST
OF THE ASSOCIATED SHOWERS/CLOUDINESS IS EAST AND SOUTH OF THE
STRONGEST ROTATION. SCATTERED MODERATE CONVECTION FROM 7N-12N
BETWEEN 42W-47W.

TROPICAL WAVE APPROACHING THE ABC ISLANDS ALONG 68W S OF 17N
MOVING W 15 KT. THE WAVE HAS A GENERALLY LOW AMPLITUDE WITH A
NARROW LINE OF SHOWERS EXTENDING E/W ACROSS THE E CARIBBEAN
WATERS. THIS LINE IS PARTIALLY DUE TO A DISSIPATING FRONTAL
BOUNDARY THAT EXTENDS ACROSS THE LEEWARD ISLANDS INTO THE CNTRL
ATLC. ISOLATED SHOWERS/TSTMS FROM 14N-16N BETWEEN THE LESSER
ANTILLES AND 72W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N12W 7N16W 10N37W 8N65W 9N84W. A
LARGE SQUALL LINE COMPLEX HAS MOVED OFF THE W AFRICAN
COAST...EXTENDING FROM LIBERIA TO GUINEA...WITH SCATTERED
MODERATE TO STRONG CONVECTION FROM 4N-11N BETWEEN 10W-15W.
WIDELY SCATTERED MODERATE WITHIN 30 NM OF LINE 4N13W 5N20W.
WIDELY SCATTERED MODERATE UP TO 180 NM N OF THE AXIS BETWEEN
22W-30W. ALTHOUGH NOT TOTALLY DUE TO THE ITCZ...A LARGE AREA OF
SCATTERED MODERATE EXTENDS FROM 8N-14N BETWEEN 30W-36W.
SCATTERED MODERATE ASSOCIATED WITH TROPICAL WAVE FROM 7N-12N
BETWEEN 42W-47W. ISOLATED MODERATE EXTENDING FROM NW COLOMBIA TO
COSTA RICA FROM 7N-11N BETWEEN 73W-86W.

...DISCUSSION...

GULF OF MEXICO...
AN ELONGATED SFC RIDGE EXTENDS DOWN THE EASTERN SEABOARD OF THE
UNITED STATES NUDGING SWD ACROSS FLORIDA AND THE E GULF OF
MEXICO. A WEAK 1022 MB HIGH IS CENTERED ALONG COASTAL SOUTH
CAROLINA WITH GENERALLY LIGHT E/SE FLOW CIRCULATING THROUGH THE
GULF. AN EXPANSIVE UPPER LEVEL HIGH IS CENTERED OVER THE CNTRL
GULF NEAR 25N90W AND MODERATE/STRONG SUBSIDENCE WITHIN 300/400
NM IS PRODUCING LIMITED CLOUDINESS AND FAIR WEATHER. A SMALL
MID/UPPER LOW IS CENTERED IN THE VICINITY OF MEXICO CITY AND IS
PRODUCING A FEW SHOWERS/TSTMS ACROSS SRN PARTS OF MEXICO.

CARIBBEAN...
THE SOUTHERN PERIPHERY OF A BROAD SFC RIDGE OVER THE GULF OF
MEXICO BARELY POKES INTO THE NW PART OF THE CARIBBEAN BASIN
WHILE TROUGHING EXTENDS TO THE E OF HISPANIOLA. IN THE UPPER
LEVELS...A TROF IS SINKING INTO THE AREA FROM THE DOMINICAN
REPUBLIC SWWD TO 13N80W THEN AS A SHEAR LINE ACROSS NICARAGUA.
BROAD N FLOW BEHIND THIS TROF IS USHERING IN DRY MID/UPPER LEVEL
AIR OVER THE W/CNTRL CARIBBEAN AND KEEPING THE AREA SHOWER-FREE
DOWN TO ABOUT 12N. FARTHER E...MOISTURE IS BEING PULLED NWD
AHEAD OF THE TROF AND STREAMS ACROSS MOST OF THE E CARIBBEAN
WATERS AND LESSER ANTILLES. A FEW ISOLATED SHOWERS/TSTMS ARE
OVER THE E CARIBBEAN NEAR A TROPICAL WAVE BUT THE MOST
WIDESPREAD CONVECTIVE ACTIVITY EXTENDS FROM ABOUT DOMINICA AND
MARTINIQUE NEWD OVER THE ATLC WATERS.

ATLANTIC WEST OF 50W...
THE SAME UPPER TROF WHICH IS DRAPED ACROSS THE CARIBBEAN IS
STATIONED OVER THE W ATLC ALONG 32N60W 20N71W WITH DRY AND
STABLE AIR FEEDING SWD JUST TO THE E OF THE BAHAMAS. THE AIR IS
COOL AND MOIST ENOUGH IN THE LOWER LEVELS TO PRODUCE A LAYER OF
STRATOCUMULUS EXTENDING S OF THE GULF STREAM BETWEEN 70W-78W TO
THE N BAHAMAS. FARTHER E...A COMPLEX MULTI-LOW SYSTEM IS
CENTERED NE OF BERMUDA WITH SEVERAL REMNANT SFC TROFS DRAGGING
SWD INTO THE SUBTROPICAL WATERS. ONE TROF DEMARCATES A LINE
ALONG 32N53W 25N60W 23N70W WITH TWO LOW-LEVEL SWIRLS TO THE W
NEAR 30N57W AND 30N62W. WIDELY SCATTERED SHOWERS/TSTMS ARE
WITHIN 60 NM OF THE TROF N OF 29N. A SECOND TROF...OR MORE OF A
CONVERGENCE LINE...EXTENDS NE OF THE NRN LEEWARD ISLANDS ALONG
18N62W 30N49W WITH SCATTERED MODERATE CONVECTION UP TO 200 NM SE
OF THE AXIS BETWEEN 51W-61W.

ATLANTIC EAST OF 50W...
EXTENSIVE SFC HIGH PRES EXTENDS ACROSS THE SUBTROPICAL/TROPICAL
ATLC BETWEEN AFRICA AND 55W WITH A 1020 MB HIGH CENTERED NEAR
25N33W. IN ADDITION...AN ELONGATED UPPER RIDGE IS LOCATED E/NE
OF THE LESSER ANTILLES ALONG 12N57W 28N41W. FARTHER E...A POTENT
MID/UPPER LOW IS TUMBLING WWD OVER THE TROPICAL ATLC NEAR 13N39W
AND IS UNDERCUTTING THE RIDGE...AND A TROF/SHEAR AXIS EXTENDS
NEWD TO 22N30W 26N20W 24N10W. MODERATE/STRONG SUBSIDENCE EXTENDS
UP TO 400 NM W OF THE LOW/TROF AND HAS PRODUCED FAIR WEATHER
JUST TO THE E OF THE ISLANDS. AMPLIFYING RIDGING TO THE E OF THE
LOW IS ENHANCING UPPER DIFFLUENCE TO THE SW OF THE CAPE VERDE
ISLANDS WITH A LARGE AREA OF SCATTERED MODERATE CONVECTION FROM
8N-16N BETWEEN 30W-36W. ELSEWHERE...MOSTLY DRY WEATHER COVERS
THE E ATLC EXCEPT FOR AN AREA OF WIDELY SCATTERED MODERATE
CONVECTION TO THE N OF THE SUBTROPICAL RIDGE FROM 28N-31N
BETWEEN 27W-40W.

$$
BERG







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