[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 291756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED APR 29 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...THE ITCZ...

THE ITCZ AXIS EXTENDS FROM 07N11W TO THE EQUATOR AT 23W THEN
CONTINUES S OF THE EQUATOR TO 03S38W. SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 120 NM OF A LINE
FROM 02N07W TO 02N19W...WITHIN 120 NM OF THE ITCZ AXIS BETWEEN
20W AND 35W...AND ALSO IN A CLUSTER WITHIN 90 NM OF 02N40W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH DISSECTS THE GULF FROM CENTRAL FLORIDA TO
THE SW BAY OF CAMPECHE. AN UPPER RIDGE IS COLLAPSING SE OVER THE
NW GULF ACCOMPANIED BY DEBRIS CIRRUS COVERING THE AREA N OF 24NW
OF 92W. THERE IS STILL SOME EVIDENCE OF A MID LEVEL TROUGH OVER
THE CENTRAL WATERS WITH PATCHES OF LOW CLOUDS AND WEAK SHOWERS
NOW SPREADING WNW NEAR 25N88W...WITH ANOTHER SMALL CLUSTER OVER
THE EXTREME NE YUCATAN PENINSULA. OTHERWISE THE UPPER LEVELS
APPEAR QUITE DRY. ELSEWHERE AT THE SURFACE...HIGH PRES LOCATED
OVER THE W ATLC HAS A RIDGE EXTENDING W AND DISSECTING THE GULF
OF MEXICO FROM NW FLORIDA TO THE BAY OF CAMPECHE. THE ASSOCIATED
GRADIENT IS MAINTAINING FRESH E TO SE LOW LEVEL FLOW ACROSS GULF
WATERS.

CARIBBEAN SEA...
AN QUASI STATIONARY UPPER LEVEL ANTICYCLONE OVER S AMERICA IS
CURRENTLY ESTIMATED NEAR 08N62W. AN ASSOCIATED UPPER RIDGE
EXTENDS NW ACROSS COLOMBIA CRESTING ALONG POINTS 14N91W TO
20N84W TO BEYOND 21N75W. UPPER DEBRIS MOISTURE FROM CONVECTION
FLARING ALONG THE E PACIFIC ITCZ...BETWEEN 76W AND 98W...IS
STREAMING NE ACROSS THE UPPER RIDGE AND TURNING ENE ACROSS ALL
THE E CARIBBEAN ISLANDS BECOMING A NARROW BAND OF MOISTURE ALONG
21N OVER THE CENTRAL N ATLC. AT THE LOW LEVELS...ATLC HIGH
PRESSURE N OF AREA IS MAINTAINING FRESH EASTERLY TRADES ACROSS
THE CARIBBEAN. TYPICAL OROGRAPHIC SHOWERS ARE NOTED OVER THE
LARGER ISLANDS WITH ELEVATED TERRAIN. STREAKS OF TRADE WINDS
CUMULUS ACCOMPANIED BY BRIEF SHOWERS ARE NOTED ELSEWHERE.

ATLANTIC OCEAN...
THE UPPER LEVELS ARE QUITE COMPLICATED BUT BASICALLY AN UPPER
TROUGH DOMINATES THE SUBTROPICAL ATLC BETWEEN 80W AND 68W...AND
ANOTHER UPPER TROUGH LIES BETWEEN 48W AND 27W. DRY UPPER AIR IS
INDICATED OVER THE DISCUSSION AREA W OF 69W AND ALSO ALONG A 240
NM WIDE BAND CENTERED ALONG 32N58W TO 24N41W TO 28N30W. DRY
UPPER AIR IS ALSO NOTED S OF 18N BETWEEN 55W AND 25W WITH THE
DRY AIR CONTINUING NE WITHIN 300 NM EITHER SIDE OF LINE FROM
12N30W TO OVER INTERIOR AFRICA AT 28N03W. BETWEEN THESE DRY
AREAS IS A BAND OF DENSE CIRRUS ADVECTED E ALONG WITHIN AN UPPER
WIND MAXIMUM AND CURRENTLY DISPLAYING TRANSVERSE UPPER
BANDING...WITH POSSIBLE TURBULENCE...ALL WITHIN 90 NM EITHER
SIDE OF LINE 21N55W TO 21N32W TO NEAR 29N11W. SURFACE HIGH
PRESSURE CENTERS ALONG 31N ARE MAINTAINING A FAIRLY TIGHT
PRESSURE GRADIENT ACROSS MOST OF THE ATLC S OF 32N. A WEAK
FRONTAL TROUGH IS SPLITTING THE RIDGE ALONG 33N52W TO 29N68W AND
IS ACCOMPANIED BY TOWERING CUMULUS AND LIGHT SHOWERS. SOME
SHOWERS HAVE FORMED NEAR 24N67W AND ARE SPREADING W IN THE FRESH
NE FLOW. LOCALLY OVERCAST STRATOCUMULUS CLOUDS ARE SPREADING SW
OVER THE E ATLC WATERS FROM 19N TO 29N BETWEEN 35W AND 19W.
OTHERWISE LOCALLY BROKEN CUMULUS IS OBSERVED RACING ACROSS THE
ATLC WATERS IN STRONG TRADES.

$$
NELSON





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