[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181801
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUN 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

EASTERN ATLC TROPICAL WAVE ALONG 38W/39W SOUTH OF 16N MOVING
WEST NEAR 20 KT.  THE WAVE DISPLAYS A LARGE SW/NE ELONGATE
CYCLONIC ENVELOPE IN SATELLITE IMAGERY AND THE PRESENT POSITION
IS BASED ON THE MEAN CENTER.  DESPITE THE LARGE AMPLITUDE...THE
WAVE APPEARS TO BE EMBEDDED WITHIN A LARGE AREA OF DRY/STABLE
AIR ASSOCIATED WITH AN AFRICAN DUST OUTBREAK WHICH STRETCHES
ACROSS MOST OF THE TROPICAL ATLC.  AS A RESULT...ASSOCIATED
CONVECTION IS MAINLY CONFINED WITHIN THE ITCZ.

CENTRAL ATLC TROPICAL WAVE ALONG 53W/54W S OF 13N MOVING
WEST 20 KT.  SATELLITE IMAGERY INDICATES THAT THE WAVE IS
QUICKLY BEING OVERTAKEN BY AN AFRICAN DUST SURGE.
TYPICALLY...THE ENVIRONMENT IS CONDUCIVE FOR SHOWERS/TSTMS RIGHT
ALONG THE LEADING EDGE OF THESE AFRICAN SURGES AND CONVECTION
ALONG THE WAVE HAS INCREASED TODAY.  CURRENTLY...SCATTERED
MODERATE ACTIVITY IS LOCATED WITHIN 75 NM EITHER SIDE A LINE
FROM 4N51W-12N57W.  SHOWERS/TSTMS ALONG THE WAVE SHOULD
GRADUALLY BECOME LESS NUMEROUS AS DRY AIR BEHIND THE AFRICAN
SURGE OVERTAKES THE WAVE.

E CARIBBEAN TROPICAL WAVE ALONG 63W S OF 16N MOVING WEST
NEAR 15 KT. THIS WAVE IS LOCATED NEAR THE BASE OF A MIDDLE TO
UPPER LEVEL TROUGH/LOW WITH ASSOCIATED SUBSIDENCE AND DRY AIR
SUPPRESSING CONVECTIVE ACTIVITY.  ONLY WIDELY SCATTERED SHALLOW
TOPPED SHOWERS ACCOMPANY THE WAVE MAINLY TO THE EAST.

W CARIBBEAN TROPICAL WAVE ALONG ALONG 83W S OF 17N MOVING WEST
10-15 KT. THIS WAVE IS NEAR THE E EXTENT OF A MIDDLE TO UPPER
LEVEL ANTICYCLONE OVER S MEXICO. RESULTING UPPER LEVEL FLOW IS
NLY ACROSS THE WAVE WITH SOME DRY AIR NOTED IN WATER VAPOR
IMAGERY.  AS A RESULT...NEARLY ALL OF THE SIGNIFICANT CONVECTION
IS CONFINED OVER THE E PACIFIC S OF COSTA RICA AND PANAMA.
THERE IS AN AREA OF SHOWERS/TSTMS N OF JAMAICA BUT THIS ACTIVITY
APPEARS MORE DIRECTLY RELATED TO THE S EXTENT OF A TROUGH OVER
THE ATLC.

...THE ITCZ...

ITCZ 12N16W 9N31W IS CENTERED ALONG 13N10W 7N20W 7N50W 9N60W
THEN ACROSS N PORTIONS OF VENEZUELA AND COLOMBIA. WIDELY
SCATTERED MODERATE CONVECTION WITHIN 120 NM EITHER SIDE OF ITCZ
BETWEEN 20W-35W.  SCATTERED MODERATE CONVECTION WITHIN 120 NM N
OF ITCZ BETWEEN 35W-40W.

...DISCUSSION...

GULF OF MEXICO...
LARGE AND UNUSUALLY HIGH AMPLITUDE MIDDLE TO UPPER LEVEL TROUGH
LIES OVER THE E UNITED STATES AND N GLFMEX WITH ATTENDANT WEAK
STATIONARY FRONT ALONG THE NE GULF COAST FROM FLORIDA TO
LOUISIANA. A SHORTWAVE DISTURBANCE CURRENTLY ROUNDING THE BASE
OF THE LONGWAVE TROUGH IS PRODUCING A DEVELOPING LINE OF
SCATTERED SHOWERS AND STRONG THUNDERSTORMS AHEAD OF THE FRONT
STRETCHING FROM N CENTRAL FLORIDA TO THE S COAST OF LOUISIANA.
THIS ACTIVITY IS MOVING SWD AND WILL BE AFFECTING THE NE GLFMEX
AND FLORIDA N OF LAKE OKEECHOBEE THROUGH THE REMAINDER OF
TODAY.  ADDITIONALLY...THE SHORTWAVE WILL CONTINUE TO AMPLIFY
THE LONGWAVE TROUGH SWD THROUGH THE WEEKEND WHICH WILL PRODUCE
AN INCREASINGLY DIFFLUENT FLOW ALOFT TO THE E OF THE AXIS. AS A
RESULT...EXPECT UNSTABLE CONDITIONS WITH ABOVE AVERAGE COVERAGE
OF SHOWERS/TSTMS ACROSS THE E GLFMEX AND FLORIDA TODAY AND
TOMORROW. FURTHER S...A WELL-DEFINED UPPER LEVEL ANTICYCLONE IS
LOCATED OVER S PORTIONS OF MEXICO.  THIS UPPER LEVEL ANTICYCLONE
IS PRODUCING A FAVORABLE REGIME FOR THE DEVELOPMENT OF
SHOWERS/TSTMS ALONG THE N EXTENT OF A TROPICAL WAVE OVER THE
PACIFIC WHICH EXTENDS NWD ACROSS S MEXICO NEAR THE ISTHMUS OF
TEHUANTEPEC TO THE YUCATAN PENINSULA.  CURRENTLY...SCATTERED
SHOWERS/TSTMS FROM GUATEMALA NWD OVER THE YUCATAN PENINSULA.
THIS ACTIVITY IS EXPECTED TO GRADUALLY SPREAD INTO THE BAY OF
CAMPECHE DURING THE NEXT 2 DAYS AS THE WAVE MOVES SLOWLY WEST.

CARIBBEAN SEA...
MIDDLE TO UPPER LEVEL ANTICYCLONE OVER S MEXICO EXTENDS A RIDGE
AXIS ESE INTO THE CENTRAL CARIBBEAN NEAR 15N75W. FURTHER
E...MID-OCEANIC TROUGH IS BEGINNING TO SPLIT WITH A RETROGRADING
UPPER LOW NOW ENTERING THE E CARIBBEAN OVER THE LESSER
ANTILLES.  THIS FEATURE IS PRODUCING SUBSIDENCE AND DRYING ALOFT
TO ITS WEST OVER THE CENTRAL AND E CARIBBEAN WHICH IS
SUPPRESSING TYPICAL SHOWERS/TSTM ACTIVITY.  HOWEVER...THE UPPER
LOW WILL CONTINUE TO MOVE ACROSS THE E CARIBBEAN REACHING 70W BY
MONDAY.  THIS EVOLUTION WILL PRODUCE AN INCREASINGLY DIVERGENT
PATTERN TO ITS EAST. IN THE LOWER LEVELS...THE S EXTENT OF A
TROUGH OVER THE E ATLC EXTENDS ACROSS CENTRAL CUBA TO THE CAYMAN
ISLANDS.  SCATTERED SHOWERS/TSTMS ARE OBSERVED ALONG THE TROUGH
FROM JAMAICA NWD OVER THE E HALF OF CUBA. THIS OVERALL AREA OF
ACTIVITY IS EXPECTED TO MOVE SLOWLY TOWARD THE NW DURING THE
NEXT 12-24 HOURS.  A TROPICAL WAVE ENTERING THE E CARIBBEAN
ALONG 63W IS CURRENTLY VOID OF DEEP CONVECTION AND IS EXPECTED
TO STAY SO AS IT ENCOUNTERS AN UNFAVORABLE ENVIRONMENT
ASSOCIATED WITH THE AFOREMENTIONED UPPER LOW.  FINALLY...
SHOWERS/TSTMS ASSOCIATED WITH A TROPICAL WAVE OVER GUATEMALA AND
THE YUCATAN PENINSULA SHOULD SLOWLY MOVE AWAY FROM THE AREA OVER
THE NEXT DAY OR SO.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH-RIDGE-TROUGH PATTERN PREVAILS OVER THE W
TWO-THIRDS OF THE ATLC WATERS WITH A HIGH AMPLITUDE TROUGH OVER
THE E UNITED STATES AND W ATLC WATERS W OF BERMUDA...SHARP RIDGE
OVER THE CENTRAL ATLC EXTENDING FROM PUERTO RICO NEWD BEYOND
34N50W...AND THE MID-OCEANIC TROUGH EXTENDING FROM THE AZORES SW
TO THE LESSER ANTILLES.  OVER THE FAR E ATLC...A PAIR OF
ANTICYCLONES NEAR 22N30W AND 12N45W CHARACTERIZE A LARGE SCALE
RIDGE EXTENDING FROM THE CANARY ISLANDS SW TO THE N COAST OF S
AMERICA NEAR SURINAME/GUYANA.  RESULTING DEEP-LAYERED ELY FLOW
DOMINATES MUCH OF THE TROPICAL ATLC.  THE BULK OF THE ACTIVE
WEATHER IS FOCUSED OVER THE W ATLC AHEAD OF THE PERSISTENT
TROUGH OVER THE E UNITED STATES.  ONE AREA OF SHOWERS/TSTMS LIES
ALONG A WEAK STATIONARY FRONT OFF THE SE COAST...MAINLY N OF 30N
W OF 70W.  A SECOND AREA OF SCATTERED SHOWERS/TSTMS LIES ALONG
THE S EXTENT...S OF 26N...OF A TROUGH EXTENDING FROM 32N60W TO
HISPANIOLA.  THE UPPER TROUGH IS EXPECTED TO FURTHER AMPLIFY
OVER THE WEEKEND WHICH WILL LIKELY PRODUCE INCREASING CLOUDINESS
AND SHOWERS/TSTMS OVER THE W ATLC.  ELSEWHERE...THE SUBTROPICAL
RIDGE CONTINUES TO STRENGTHEN OVER THE CENTRAL AND E ATLC
RESULTING IN INCREASING TRADES S OF 20N.  THIS IS ALLOWING A
LARGE OUTBREAK OF AFRICAN DUST TO PROPAGATE WESTWARD ACROSS THE
TROPICAL ATLC WATERS NOW SPANNING FROM THE LESSER ANTILLES TO
AFRICA.

$$
RHOME



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