[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211151
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST MON 21 MAR 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1115 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N10W 4N17W 2N25W 2N41W ACROSS THE
EQUATOR AND INLAND OVER SOUTH AMERICA NEAR 50W. SCATTERED STRONG
CONVECTION IS WITHIN 90 NM 1N FROM 31W-34W. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM THE
EQUATOR TO INLAND OVER AFRICA E OF 10W AND FROM 5N TO S OF THE
EQUATOR W OF 21W TO INLAND OVER SOUTH AMERICA.

...DISCUSSION...

GULF OF MEXICO...
DEEP LAYERED TROUGH COVERS THE GULF WITH S STREAM SHORTWAVE
DISTURBANCE MOVING E FROM OVER THE SE UNITED STATES INTO THE W
ATLC. THE ATTENDANT COLD FRONT EXTENDS ACROSS S GEORGIA WHERE IT
PULLS UP STATIONARY MEANDER ALONG THE N GULF COAST THEN NW
OVER E TEXAS. SURFACE TROUGH EXTENDS ACROSS THE FLORIDA
PENINSULA ALONG 29N FROM 79W-86W. SCATTERED SHOWERS REMAIN OVER
THE E GULF WITHIN 60 NM OF 26N FROM 85W-90W. A SECOND S STREAM
SHORTWAVE TROUGH IS MOVING ACROSS TEXAS BRINGING ANOTHER CHANGE
FOR UNSETTLED WEATHER IN THE NEXT COUPLE OF DAYS. A WEAK 1020 MB
HIGH IS CENTERED OVER THE N BAHAMAS NEAR 25N78W. THE W ATLC
SHORTWAVE AND ANY SHOWER ACTIVITY SHOULD MOVE OUT OF FLORIDA AND
INTO THE W ATLC LATER THIS MORNING.

CARIBBEAN...
PERSISTENT MID/UPPER LEVEL RIDGE REMAINS ANCHORED FROM AN UPPER
HIGH IN THE W TROPICAL ATLC NEAR 17N50W WITH RIDGE AXIS
EXTENDING E/W. BROAD ANTICYCLONIC FLOW COVERS THE CARIBBEAN...
TROPICAL ATLC W OF THE CAPE VERDE ISLANDS...AND THE SUBTROPICAL
ATLC S OF 26N. SOME UPPER LEVEL MOISTURE CONTINUES TO MOVE
AROUND THE W PERIPHERY OF THE RIDGE FROM OVER CENTRAL AMERICA
AND E CUBA ADVECTING PACIFIC MOISTURE AS FAR N AS THE W ATLC.
HOWEVER...MOST OF THE AREA CONTINUES TO BE DOMINATED BY STRONG
SUBSIDENCE AND DRY/STABLE CONDITIONS. DRY CONDITIONS ALSO
PREVAIL IN THE LOWER LEVELS LIMITING SHOWER ACTIVITY SAVE SOME
ISOLATED ACTIVITY OVER THE LESSER ANTILLES.

ATLANTIC...
STRONG MID/UPPER LEVEL RIDGING OVER THE CARIBBEAN IS PRODUCING
MAINLY SW FLOW OVER THE W ATLC. A WEAK 1012 MB SURFACE LOW IS
JUST W OF BERMUDA NEAR 33N67W WITH A WEAK SURFACE TROUGH
EXTENDING SW TO 29N76W AND A WARM FRONT EXTENDING N AND E OF
BERMUDA TO 31N60W. THIS SYSTEM IS PRODUCING OVERCAST CLOUDINESS
WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 31N. A SECOND
SHORTWAVE TROUGH HAS MOVED NE OF THE E ATLC WITH ATTENDANT COLD
FRONT REMAINING THROUGH 32N20W SW ALONG 27N29W TO 25N39W THEN
STATIONARY TO 25N52W THEN AS A SURFACE TROUGH ALONG 24N64W TO
OVER E CUBA THUS SPLITTING THE SURFACE RIDGE. THE UPPER LEVEL
DYNAMICS/SUPPORT WITH THIS SYSTEM IS FOCUSED WELL N OF THE AREA
BUT LOW LEVEL MOISTURE POOLING IS PRODUCING A NARROW BAND OF LOW
CLOUDS AND ISOLATED SHOWERS EXTENDING UP TO 90/120 NM E OF FRONT
N OF 26N. BEHIND THESE FRONTS...BROKEN COLD AIR STRATOCUMULUS
CLOUDS ARE TO 50W. AN ELONGATED SURFACE RIDGE SPANS ACROSS THE
ATLC FROM THE CANARY ISLANDS SW TO A 1020 MB HIGH LOCATED NEAR
21N52W AND A 1020 MB HIGH N OF THE FRONT NEAR 28N53W. THIS
SCENARIO SUGGESTS THAT THE FRONTAL BOUNDARY IS NOT ALSO LOSING
THE UPPER SUPPORT BUT THE LOWER SUPPORT AS WELL. THERE IS NO
LARGE-SCALE PRECIPITATION OVER THE E HALF OF THE SUBTROPICAL
ATLC. FURTHER S...MODERATE/STRONG SUBSIDENCE IN THE UPPER LEVELS
AND DRY AIR IN THE LOWER LEVELS MOVING OFF W AFRICA ARE LARGELY
SUPPRESSING CLOUDS AND PRECIPITATION OVER THE AREA INCLUDING THE
N PORTION OF THE TROPICAL ATLC.

$$
WALLACE



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