[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 111800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUNE 11 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.

...SPECIAL FEATURE...
TROPICAL STORM ARLENE IS CENTERED NEAR 30.0N 87.5W AT 11/1800
UTC...OR ABOUT 20 MILES SOUTH-SOUTHEAST OF GULF SHORES
ALABAMA...MOVING NNW AT 12 KT. MAXIMUM SUSTAINED WIND SPEED HAS
DECREASED TO 50 KT GUSTING TO 65 KT WITH MINIMUM CENTRAL
PRESSURE UP SLIGHTLY TO 991 MB. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND/OR
MIATCPAT1/WTNT31 FOR MORE DETAILS.  LATEST SATELLITE IMAGERY
SHOWS NO MAJOR CHANGES TO THE STRUCTURE OR APPEARANCE OF ARLENE
WITHIN THE LAST FEW HOURS. THE DEEPEST CONVECTION REMAINS
FOCUSED OVER THE W PERIPHERY WITHIN 75 NM OF THE CENTER
SPREADING NWD OVER E MISSISSIPPI...ALABAMA...AND S GEORGIA.
OUTER RAINBANDS CONTINUE TO AFFECT PORTIONS OF FLORIDA
ESPECIALLY N OF A LOW LEVEL TROUGH EXTENDING FROM ARLENE TO LAKE
OKEECHOBEE.  ARLENE IS FORECAST TO CONTINUE ON A GENERAL NNW
MOTION TAKING THE SYSTEM INLAND LATER THIS AFTERNOON.  ONCE
INLAND...ARLENE SHOULD BEGIN WEAKENING BUT WILL PRODUCE HEAVY
RAINFALL FROM THE EASTERN AND CENTRAL GULF COAST NORTHWARD
THROUGH THE TENNESSEE VALLEY AND INTO THE LOWER TO MIDDLE OHIO
VALLEY OVER THE NEXT TWO DAYS.

...TROPICAL WAVES...

CENTRAL ATLC TROPICAL WAVE ALONG 40W S OF 16N MOVING W 10 TO 15
KT OR 4-5 DEG/DAY.  SATELLITE IMAGERY INDICATES THAT THE WAVE
REMAINS ALONG THE LEADING EDGE OF AN AFRICAN DUST SURGE WHICH IS
SUPPRESSING DEEP CONVECTIVE ACTIVITY.  VERY DRY/STABLE
CONDITIONS E OF THE AFRICAN SURGE WILL LIKELY LIMIT SIGNIFICANT
CONVECTION DURING THE NEXT FEW DAYS AS THE SURGE OVERTAKES THE
WAVE.

W ATLC TROPICAL WAVE IS ALONG 58W/59W S OF 16N MOVING W 10 TO 15
KT.  ANALYSIS OF SATELLITE IMAGERY SUGGEST A LOCATION FURTHER E
BUT THE PRESENT POSITION MAINTAINS CONTINUITY AND APPEARS TO BE
CONSISTENT WITH NEARBY SURFACE OBSERVATIONS.  THE WAVE IS
LOCATED WITHIN A COL BETWEEN AN UPPER LEVEL RIDGE OVER THE
TROPICAL ATLC AND UPPER RIDGE OVER THE CARIBBEAN.
ADDITIONALLY...AN UPPER LEVEL LOW IS LOCATED TO THE NW. THIS
PATTERN IS PRODUCING DIFFLUENT FLOW ALOFT AND PROVIDING AN
OPTIMAL ENVIRONMENT FOR THE DEVELOPMENT OF SHOWERS/TSTMS.
CURRENTLY...A LARGE AREA OF SCATTERED MODERATE CONVECTION IS
LOCATED FROM 15N-20N BETWEEN 50W-60W WITH WIDELY SCATTERED
SHOWERS AND ISOLATED MODERATE CONVECTION ELSEWHERE S OF 15N
BETWEEN 45W-55W.  THE UPPER LOW IS EXPECTED TO RETROGRADE TOWARD
THE BAHAMAS OVER NEXT FEW DAYS WHICH SHOULD MAINTAIN A GOOD
UPPER LEVEL ENVIRONMENT FOR SHOWERS/TSTMS...ESPECIALLY N OF
15N...AS THE WAVE MOVES INTO THE E CARIBBEAN.

CARIBBEAN TROPICAL WAVE IS ALONG 80W S OF 18N MOVING W 10 KT.
THE WAVE SIGNATURE IN SATELLITE IMAGERY REMAINS WEAK AND THE
CURRENT POSITION IS BASED ON CONTINUITY.  A SMALL AREA OF
SCATTERED MODERATE CONVECTION IS NOTED OVER COSTA RICA BUT IS
THE ONLY NEARBY CONVECTIVE ACTIVITY.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N10W 6N40W 10N60W...THEN DIFFUSE
ACROSS N VENEZUELA AND COLOMBIA.  WIDELY SCATTERED MODERATE
CONVECTION FROM 4N-11N BETWEEN 45W-55W INCLUDING N PORTIONS OF
FRENCH GUIANA AND SURINAME.

...DISCUSSION...

GULF OF MEXICO...
ARLENE CONTINUES TO DOMINATES THE WEATHER OVER THE GLFMEX
AFFECTING MUCH OF THE AREA E OF 90W.  THE CENTER OF CIRCULATION
IS NEARING THE NE GULF COAST WITH THE STRONGEST AND MOST
NUMEROUS SHOWERS/TSTMS FOCUSED TO THE NORTH OF THE SYSTEM NOW
AFFECTING AN AREA FROM THE GULF COAST NWD INTO THE TENNESSEE
VALLEY.  A LOW LEVEL TROUGH TRAILS SEWD ACROSS CENTRAL FLORIDA
NEAR LAKE OKEECHOBEE AND IS PRODUCING WIDELY SCATTERED
SHOWERS/TSTMS TO IT NORTH.  OTHERWISE...ONLY A FEW WIDELY
SCATTERED BANDS OF SHOWERS/ISOLATED TSTMS REMAIN S OF ARLENE
WITH THE SE GLFMEX AND S FLORIDA EXPERIENCING RAPIDLY IMPROVING
CONDITIONS.  HOWEVER...WITH RESIDUAL TROPICAL MOISTURE REMAINING
LARGELY IN PLACE...DAYTIME HEATING MAY TRIGGER THE USUAL
AFTERNOON VARIETY SHOWERS/TSTMS.  OVER THE W GLFMEX...BROAD
MID/UPPER TROUGH EXTENDS FROM THE CENTRAL UNITED STATES INTO N
MEXICAN WITH ASSOCIATED SW FLOW AND STRONG SUBSIDENCE SPREADING
RAPIDLY FROM W TO E IN THE WAKE OF ARLENE.  CURRENTLY THIS DRY
AIR WRAPS AROUND THE SOUTH SIDE OF ARLENE TO THE W COAST OF
FLORIDA.  HOWEVER...THIS AIRMASS IS FORECAST TO BEGIN RETREATING
WESTWARD LATER TONIGHT OR SUNDAY AS A LARGE RETROGRADING UPPER
LOW APPROACHES FLORIDA FROM THE EAST.  THIS UPPER LOW IS
EXPECTED TO SPREAD RELATIVELY DRIER AIR OVER THE SUNSHINE STATE
ON MONDAY POSSIBLY REDUCING THE COVERAGE OF AFTERNOON
SHOWERS/TSTMS.

CARIBBEAN SEA...
A UNSETTLED WEATHER PATTERN CONTINUES OVER THE N HALF OF THE
CARIBBEAN TODAY.  THE UPPER LEVEL PATTERN IS COMPRISED OF A
WELL-DEFINED ANTICYCLONE NEAR THE CAYMAN ISLANDS WITH ASSOCIATED
RIDGE EXTENDING SEWD ACROSS THE WINDWARD ISLANDS.  FURTHER N...A
MID/UPPER RETROGRADING ACROSS THE CENTRAL ATLC CLIPS THE NE
PORTION OF THE AREA.  THE PATTERN IS CREATING A LARGE AREA OF
DIFFLUENCE PRIMARILY POLEWARD OF THE RIDGE AXIS.  THE DIFFLUENT
PATTERN ALOFT COUPLED WITH AMPLE DEEP-LAYERED TROPICAL MOISTURE
IS SUPPORTING WIDESPREAD CLOUDINESS AND SCATTERED MODERATE TO
STRONG CONVECTION N OF 15N E OF 70W.  WIDELY SCATTERED MODERATE
CONVECTION IS ALSO NOTED N OF A LINE FROM 15N70W TO THE CAYMAN
ISLANDS.  THIS OVERALL WET PATTERN IS LIKELY TO CONTINUE ACROSS
MUCH OF THE CENTRAL TO E CARIBBEAN THROUGH THE WEEKEND AS UPPER
LOW RETROGRADES SLOWLY WEST AND A TROPICAL WAVE MOVES INTO THE E
CARIBBEAN.

ATLANTIC OCEAN...
A SHARP MID/UPPER LEVEL RIDGE EXIST OVER THE FAR W ATLC
EXTENDING FROM W CUBA NWD INTO THE SE UNITED STATES.  A NARROW
SWATH OF DEEP-LAYERED MOISTURE LIES WITHIN 100-200 NM EITHER
SIDE OF THE RIDGE PRODUCING WIDESPREAD CLOUDINESS AND AREAS OF
SHOWERS/TSTMS FROM THE BAHAMAS WESTWARD OVER FLORIDA.  THIS
RIDGE AND ASSOCIATED MOISTURE IS FORECASTED TO BE ERODED BY A
RETROGRADING UPPER LOW N OF PUERTO RICO NEAR 26N62W.  THE UPPER
LOW WILL APPROACH THE S BAHAMAS ON SUNDAY WITH ASSOCIATED DRY
AIR TO ITS WEST REACHING THE FLORIDA E COAST SUN AFTERNOON.  E
OF THE UPPER LOW...A STRONGLY DIFFLUENT PATTERN COUPLED WITH
AMPLE DEEP-LAYERED MOISTURE CONTINUES TO GENERATE WIDESPREAD
CLOUDINESS AND SCATTERED SHOWERS/TSTMS S OF 25N BETWEEN 50W-60W
WITH WIDELY SCATTERED SHOWERS/TSTMS BETWEEN 60W-65W. THIS
ACTIVITY WILL GRADUALLY SPREAD WESTWARD WITH THE UPPER LOW OVER
THE NEXT TWO DAYS. BROAD UPPER TROUGH COVERS THE REMAINDER OF
THE ATLC E OF 40W...THUS RESULTING IN NO SIGNIFICANT WEATHER. AT
THE SURFACE...THE SUBTROPICAL RIDGE AXIS IS N OF THE AREA WITH A
WEAK LOW LEVEL TROUGH OVER THE CENTRAL TO W ATLC ALONG 31N55W SW
TO HISPANIOLA.  OVER THE E ATLC...AREA OF AFRICAN DUST CAN BE
SEEN IN VISIBLE SATELLITE IMAGERY E OF 40W FROM THE ITCZ NWD TO
ROUGHLY 20N.

$$
RHOME




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