[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 180540
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON 18 APR 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0345 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N10W 3N27W 4N35W 4N52W. SCATTERED
MODERATE/STRONG CONVECTION IS WITHIN 125 NM OF THE AXIS FROM
25W-29W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
75/90 NM OF THE AXIS FROM 29W-36W AND WITHIN 90/120 NM S OF THE
AXIS FROM 20W-25W. CLUSTERS OF SIMILAR CONVECTION ARE FROM THE
EQUATOR TO 4N E OF 6W TO ACROSS THE PRIME MERIDIAN.

...DISCUSSION...

GULF OF MEXICO INTO THE FAR W ATLANTIC...
WEAKENING 1026 MB HIGH IS CENTERED OVER SE ALABAMA WITH A BROAD
RIDGE EXTENDING S INTO THE GULF OF MEXICO. UPPER LEVEL RIDGING
EXTENDS FROM THE E PACIFIC ACROSS MEXICO INTO TEXAS TO JUST W OF
THE UPPER MISSISSIPPI VALLEY. THIS IS ADVECTING PACIFIC MOISTURE
OVER MEXICO BUT WITH WEAK UPPER FLOW IS NOT MAKING IT TO THE W
GULF. OVER THE E GULF...A MID/UPPER TROUGH EXTENDS FROM THE
CANADIAN MARITIMES SW ALONG THE EASTERN SEABOARD OF THE U.S.
THROUGH 32N74W TO CENTRAL CUBA NEAR 23N80W. SERIES OF UPPER LOWS
ARE ROTATING THROUGH THE TROUGH MOSTLY N OF THE REGION WITH ONE
NEAR 33N75W. THIS SYSTEM IS RESPONSIBLE FOR THE STORM AND GALE
CONDITIONS OVER THE W ATLC DURING THE PAST WEEKEND. MODERATE/
STRONG SUBSIDENCE REMAINS OVER THE E GULF TO ACROSS FLORIDA AND
70W. AT THE SURFACE...EASTERLY WINDS PREVAIL ACROSS THE GULF
EXCEPT IN THE AREA WEAK SURFACE TROUGH THAT EXTENDS IS FROM
APALACHEE BAY TO THE FLORIDA KEYS. OVERALL SKIES ACROSS THE GULF
ARE FAIR WITH ISOLATED PATCHES OF LOW LEVEL CLOUDS DOTING THE W
GULF.

CARIBBEAN...
A NEAR STATIONARY FRONTAL SURFACE TROUGH REMAINS OVER THE W PART
OF THE CARIBBEAN STRETCHING FROM HISPANIOLA SW ALONG 16N76W TO
COSTA RICA. ENOUGH LOW-LEVEL CONVERGENCE AND MOISTURE REMAIN TO
PRODUCE SCATTERED SHOWERS/THUNDERSTORMS WITHIN 150 NM NW OF THE
AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS INLAND
AND WITHIN 60 NM ALONG THE COAST OF COSTA RICA. A HIGH AMPLIFIED
UPPER RIDGE STRETCHES FROM THE W TROPICAL ATLC...E OF THE LESSER
ANTILLES ALONG 10N60W N TO 26N60W THEN NE OVER THE CENTRAL ATLC.
THIS IS ALLOWING DEEP TROPICAL MOISTURE TO BE ADVECTED N OVER
THE CENTRAL CARIBBEAN. ELSEWHERE...THE ISLANDS OF PUERTO RICO
THROUGH THE LESSER ANTILLES ARE UNDER THE INFLUENCE OF FAIR
SKIES AND LIGHT EASTERLY TRADES.

WEST ATLANTIC...
HIGH PRESSURE OVER THE SE U.S. HAS WEAKENED THEREFORE THE
PRESSURE GRADIENT HAS RELAXED OVER THE W ATLC. THE MID/UPPER
TROUGH OVER THE FAR W ATLC THAT GENERATED STORM AND GALE
CONDITIONS OVER THE AREA DURING THE PAST WEEKEND HAS WEAKENED
WITH THE ASSOCIATED OCCLUDED FRONT NOW BEING WELL N OF THE
REGION. A 1009 MB SURFACE LOW REMAINS NEAR 33N64W AND THE
ASSOCIATED STATIONARY FRONT HAS ALSO BEGUN TO WEAKEN AND EXTENDS
THROUGH 32N55W SW 26N59W TO OVER HISPANIOLA NEAR 19N68W.
OVERCAST LOW/MID CLOUDS WITH SCATTERED SHOWERS ARE WITHIN 200 TO
300 NM W OF THE FRONTAL BOUNDARY.

CENTRAL/EAST ATLANTIC...
SUBTROPICAL 1027 MB HIGH DOMINATES THE REMAINDER OF THE ATLC AND
IS CENTERED ABOUT NEAR 34N34W AND IS PRODUCING CONSISTENT NE/E
TRADE WINDS ACROSS MOST OF THE ATLC E OF 55W. A HIGH AMPLIFIED
UPPER RIDGE STRETCHES FROM THE W TROPICAL ATLC...E OF THE LESSER
ANTILLES ALONG 10N60W N TO 26N60W THEN NE ACROSS THE CENTRAL
ATLC TO BEYOND 32N47W. THIS RIDGE IS AMPLIFYING IN RESPONSE TO
THE CUT-OFF LOW/TROUGH OVER THE E ATLC. A TROUGH AXIS OVER
THE E ATLC EXTENDS FROM 28N28W THROUGH A CUT-OFF UPPER LOW
CENTERED NEAR 22N33W INTO THE TROPICAL ATLC NEAR 10N46W.
CYCLONIC FLOW AND STRONG SUBSIDENCE EXTEND OUT UP TO 500 NM FROM
THE AXIS. MUCH DRIER UPPER LEVEL AIR IS FROM 20N-30N E OF 25W TO
WELL INLAND OVER AFRICA. WEAK SUBTROPICAL JET REMAINS IN PLACE
SE OF THIS LOW/TROUGH EXTENDING FROM 12N30W OVER THE CAPE VERDE
ISLANDS TO INLAND OVER AFRICA NEAR 19N16W WITH THE FASTEST WINDS
REMAINING OVER N MAURITANIA.

$$
WALLACE


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