[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 182338
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

EASTERN ATLC TROPICAL WAVE IS ALONG 41W SOUTH OF 16N MOVING WEST
NEAR 20 KT.  THE WAVE DISPLAYS A LARGE ELONGATED 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.  BESIDES THE CONVECTION ALONG THE
ITCZ...ISOLATED MODERATE CONVECTION IS FROM 10N-12N BETWEEN
38W-45W.

CENTRAL ATLC TROPICAL WAVE IS ALONG 54W/55W 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
CONVECTION IS E OF THE WAVE AXIS FROM 11N-13N BETWEEN 57W-59W.
SHOWERS/TSTMS ALONG THE WAVE SHOULD GRADUALLY BECOME LESS
NUMEROUS AS DRY AIR BEHIND THE AFRICAN SURGE OVERTAKES THE WAVE.

E CARIBBEAN TROPICAL WAVE IS ALONG 64W 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 OF THE WAVE
AXIS.

W CARIBBEAN TROPICAL WAVE IS ALONG ALONG 84W S OF 16N 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 W OF THE WAVE AXIS.  SCATTERED MODERATE
TO STRONG CONVECTION IS INLAND OVER NICARAGUA AND HONDURAS FROM
9N-16N BETWEEN 84W-88W.

...THE ITCZ...

ITCZ IS CENTERED ALONG 9N13W 6N20W 8N40W 9N65W.  SCATTERED
MODERATE CONVECTION IS WITHIN 30 NM OF THE AXIS BETWEEN
13W-24W...AND BETWEEN 37W-43W.

...DISCUSSION...

GULF OF MEXICO...
1009 MB LOW IS CENTERED OFF THE COAST OF GEORGIA NEAR 31N80W.  A
STATIONARY FRONT EXTENDS W OVER N FLORIDA AND CONTINUES W TO E
TEXAS ALONG 30N83W 30N94W.  SCATTERED MODERATE CONVECTION IS
OVER N FLORIDA FROM 30N-32N BETWEEN 79W-83W.  SIMILAR CONVECTION
IS OVER S LOUISIANA FROM 29N-31N BETWEEN 91W-94W.  A WEAK 1013
MB HIGH IS OVER THE N GULF OF MEXICO NEAR 27N89W.  WINDS ARE
RELATIVELY LIGHT OVER THE GULF ESPECIALLY IN VICINITY OF THE
HIGH.  IN THE UPPER LEVELS...LARGE AND UNUSUALLY HIGH AMPLITUDE
MIDDLE TO UPPER LEVEL TROUGH LIES OVER THE E UNITED STATES AND N
GULF OF MEXICO N OF 25N WITH ATTENDANT WEAK STATIONARY FRONT.
FURTHER S...A WELL-DEFINED UPPER LEVEL ANTICYCLONE IS
LOCATED OVER S PORTIONS OF MEXICO AND THE SOUTHERN GULF OF
MEXICO S OF 25N.  AS A RESULT A 60-80 KT UPPER LEVEL JET AND
STRONG SUBSIDENCE IS OVER THE CENTRAL GULF BETWEEN S TEXAS AND S
FLORIDA.  EXPECT IN 24 HOURS FOR THE SURFACE LOW TO MOVE E AND
THE STATIONARY FRONT TO DISSIPATE.

CARIBBEAN SEA...
SEE TROPICAL WAVE SECTION ABOVE.  IN ADDITION...SCATTERED
MODERATE TO STRONG CONVECTION IS OVER THE NORTHERN YUCATAN
PENINSULA FROM 19N-22N BETWEEN 85W-90W.  SIMILAR CONVECTION IS
OVER W CUBA FROM 21N-24N BETWEEN 80W-84W.  SCATTERED MODERATE
CONVECTION IS OVER HISPANIOLA FROM 18N-21N BETWEEN 71W-73W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS OVER N
COLOMBIA FROM 10N-12N BETWEEN 72W-74W.  IN THE UPPER LEVELS...
MIDDLE TO UPPER LEVEL ANTICYCLONE OVER S MEXICO NEAR 16N93W
EXTENDS A RIDGE AXIS E 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 NEAR 15N61W.  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.

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.

$$
FORMOSA




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