[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202314
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2215 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 6N10W 1N35W 4N60W. SCATTERED TO
LOCALLY NUMEROUS STRONG CONVECTION OVER SW AFRICA FROM 5N-10N
BETWEEN 7W-13W.  WIDELY SCATTERED MODERATE/ISOLATED STRONG
ELSEWHERE WITHIN 90 NM EITHER SIDE OF ITCZ E OF 20W.  WIDELY
SCATTERED MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF ITCZ W
OF 40W.

...DISCUSSION...

GULF OF MEXICO...
A MOISTURE STARVED MID-UPPER LEVEL SHORTWAVE CURRENTLY MOVING
ACROSS FLORIDA IS PROVIDING JUST ENOUGH LIFT FOR SCATTERED/
BROKEN CLOUDINESS OVER THE S HALF OF FLORIDA INTO THE SW ATLC.
OTHERWISE...DRY/TRANQUIL CONDITIONS PREVAIL IN THE WAKE OF THE
SHORTWAVE AS A MIDDLE TO UPPER LEVEL RIDGE BUILDS NWD FROM
MEXICO THROUGH THE CENTRAL UNITED STATES. AT THE
SFC...SUBTROPICAL RIDGE IS ALIGNED E/W ALONG THE N GULF
COAST...ANCHORED BY A HIGH TO THE E OVER THE W ATLC.  THIS
PATTERN IS PRODUCING LIGHT E/SE FLOW ACROSS THE GLFMEX. THE
PATTERN WILL BECOME INCREASINGLY AMPLIFIED DURING THE NEXT 2
DAYS AS A LONG-WAVE TROUGH SETS UP E OF FLORIDA.  AT THE SAME
TIME...RIDGE WILL CONTINUE TO BUILD NWD OVER MEXICO AND THE
CENTRAL UNITED STATES EFFECTIVELY BLOCKING UPSTREAM DISTURBANCES
THROUGH THE END OF THE WEEK.  THE RIDGE-TROUGH COMBO WILL CREATE
AN HIGHLY CONFLUENT PATTERN ALOFT OVER THE AREA WHICH SHOULD
LIMIT SIGNIFICANT CLOUDS/CONVECTION UNTIL THE NEXT COLD FRONT
WHICH IS CURRENTLY FORECAST TO MOVE OFF THE SE COAST OF TEXAS
SAT.

CARIBBEAN...
THE SHARP UPPER LEVEL TROUGH WHICH HAS BEEN OVER THE W CARIBBEAN
FOR THE PAST SEVERAL DAYS IS BEGINNING TO FILL AS THE SHORTWAVE
TROUGH OVER THE W ATLC E OF BERMUDA LIFTS NEWD.  AT THE SAME
TIME...RIDGE OVER N PORTIONS OF SOUTH AMERICA HAS LIFTED SLOWLY
NWD.  RESULTING PATTERN ALOFT HAS BECOME MORE ZONAL DURING THE
LAST 24 HOURS BUT THIS WILL BE A TEMPORARY SETUP AS A SHORTWAVE
TROUGH CURRENTLY MOVING ACROSS FLORIDA RE-AMPLIFIES THE W ATLC
TROUGH SWD INTO THE W CARIBBEAN BY THE END OF THE WEEK.  THIS
EVOLUTION WILL LIKELY CREATE DIFFLUENT FLOW ALOFT OVER THE E
CARIBBEAN...E OF 70W...PRODUCING A FAVORABLE ENVIRONMENT FOR THE
DEVELOPMENT OF SHOWERS/THUNDERSTORMS.  AT THE SURFACE...TAIL END
OF AN ATLC DISSIPATING STATIONARY FRONT TRAILS INTO THE AREA
NEAR THE MONA PASSAGE.  THE FRONT HAS MOVED LITTLE DURING THE
LAST 24 HOURS AND CONTINUES TO PRODUCE SCATTERED
SHOWERS/THUNDERSTORMS OVER PUERTO RICO AND HISPANIOLA. THE
WEAKENING FRONT WILL LIKELY REMAIN QUASI-STATIONARY DURING THE
NEXT SEVERAL DAYS PROVIDING THE FOCUS FOR SHOWERS/THUNDERSTORMS
OVER THE NE CARIBBEAN ISLANDS.  IN FACT...ACTIVITY MAY BECOME
MORE NUMEROUS BY THE END OF THE WEEK AS MIDDLE TO UPPER LEVEL
CONDITIONS BECOME MORE DIVERGENT AND LOW LEVEL MOISTURE SURGES
NWD FROM S AMERICA.  EXPECT LOCALLY HEAVY RAINFALL AND POSSIBLE
FLOODING...ESPECIALLY ALONG AND NEAR THE FRONTAL
BOUNDARY...DURING THE NEXT FEW DAYS.  OTHERWISE...THE REMAINDER
OF THE AREA IS UNDER FAIR SKIES AND EASTERLY TRADES.

ATLANTIC...
PERSISTENT UPPER LEVEL CUTOFF LOW AND ASSOCIATED TROUGH E OF
BERMUDA IS BEGINNING TO LIFT AWAY FROM THE W ATLC WATERS AS A
SECOND SHORTWAVE DROPS SEWD ACROSS FLORIDA. THIS EVOLUTION HAS
CREATED A TEMPORARY RELAXATION OF THE W ATLC TROUGH PATTERN BUT
THE SHORTWAVE OVER FLORIDA WILL ONCE AGAIN CARVE OUT A STRONG
TROUGH DURING THE NEXT 24-36 HOURS.  CURRENTLY...ONLY PATCHY
CLOUDINESS AND A FEW ISOLATED SHOWERS ACCOMPANY THE SHORTWAVE
MOVING OVER FLORIDA.  HOWEVER...EXPECT A HIGHLY AMPLIFIED AND
DIFFLUENT PATTERN ALOFT TO EVOLVE BY THE END OF THE WEEK.  THIS
PATTERN WILL INVIGORATE AN ALREADY ACTIVE AREA OF SCATTERED
SHOWERS/THUNDERSTORMS OCCURRING WITHIN 100 NM EITHER SIDE OF A
STATIONARY FRONT OVER THE CENTRAL ATLC FROM 31N37W SW THROUGH
25N55W THEN WEAKENING TO THE MONA PASSAGE.  CLOUD TOP
TEMPERATURES INDICATE THAT DEEP CONVECTION IS INCREASING AND THE
OVERALL CLOUD SIGNATURE RESEMBLES THAT OF A LEAF TYPE PATTERN.
THIS WOULD IMPLY A LOW OR FRONTAL WAVE IS FORMING ALONG THE
FRONT AND THE LATEST GFS MODEL ALONG WITH ABOUT HALF OF THE GFS
ENSEMBLE MEMBERS DEVELOP A SFC LOW N OF PUERTO RICO WITHIN 12-24
HOURS.  REGARDLESS OF WHETHER A FRONTAL WAVE/LOW FORMS...EXPECT
STRONG SHOWERS/THUNDERSTORMS TO CONTINUE ALONG THE STATIONARY
FRONT DURING THE NEXT SEVERAL DAYS. FARTHER E...STRONG
SUBTROPICAL RIDGE PREVAILS EXTENDING FROM A 1023 MB HIGH NEAR
THE CANARY ISLANDS SW TO 20N50W. IN THE UPPER LEVELS...A
PERSISTENT MID/UPPER LEVEL CUT-OFF LOW IS LOCATED ABOUT 350 NM
NW OF THE CAPE VERDE ISLANDS NEAR 21N30W. THIS SYSTEM CONTINUES
TO DRAW TROPICAL MOISTURE NWD INTO SW AFRICA PRODUCING
WIDESPREAD HIGH CLOUDINESS AND ENHANCED ITCZ ACTIVITY E OF ABOUT
20W. DRY AIR ON THE BACK OR CONFLUENT SIDE OF THE LOW HAS
PENETRATED WELL INTO THE TROPICAL WATERS SUPPRESSING ITCZ
CONVECTION BETWEEN 25W-40W.

$$
RHOME



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