[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 232340
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU JUN 23 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...

E ATLC TROPICAL WAVE ALONG 28W S OF 13N MOVING W 15 KT.  THE
WAVE IS NOT WELL-DEFINED ON SATELLITE PICTURES BUT A BURST OF
CONVECTION NEAR THE MODEL CONSENSUS POSITION LEND SOME
CONFIDENCE TO THE WAVE'S LOCATION.  WIDELY SCATTERED MODERATE
CONVECTION IS FROM 7N-10N BETWEEN 26W-31W.

CENTRAL ATLANTIC TROPICAL WAVE ALONG 50W S OF 13N MOVING W 15
KT. THE WAVE IS AT THE EDGE OF A MOISTURE SURGE WITHIN THE ITCZ
WITH RELATIVELY DRIER AIR W OF THE WAVE AXIS TO THE LESSER
ANTILLES.  SHOWERS/TSTMS ASSOCIATED WITH THE WAVE SHOULD
INCREASE AS THE WAVE ENCOUNTERS A MID/UPPER TROF TO ITS W AND
MORE UNSTABLE AIR DUE TO THE VERY WARM SSTS.  THE WAVE IS
FORECAST TO ENTER THE CARIBBEAN ON SAT WITH ENHANCED RAIN
ACTIVITY FOCUSED IN THE WINDWARD ISLANDS.

E CARIBBEAN TROPICAL WAVE ALONG 66W S OF 19N MOVING W 20 KT. NW
SHEAR COUPLED WITH DEEP-LEVEL MOISTURE HAS CAUSED SCATTERED
TSTMS MOSTLY S OF PUERTO RICO TO 15N BETWEEN 66W-70W.  VERY
HEAVY RAINS SHOULD CONTINUE OVERNIGHT IN HISPANIOLA AS ENERGY
FROM THIS WAVE HEADS OVER THE HIGH TERRAIN OF THAT ISLAND.

HIGH-AMPLITUDE TROPICAL WAVE IS FROM THE CENTRAL CARIBBEAN NEAR
10N77W TILTED NNE THRU E CUBA INTO THE SE BAHAMAS NEAR 22N74W.
THE WAVE IS MOVING W 15-20 KT AND INTERACTING WITH A LARGE
MID/UPPER LOW OVER THE FLORIDA KEYS.. PRODUCING AN AREA OF
WIDELY SCATTERED TSTMS FROM S OF 26N BETWEEN 70W-77W IN THE ATLC
OCEAN.  PIECE OF THE WAVE SHOULD BREAK OFF AND HEAD MORE TO THE
NW OVERNIGHT WITH HEAVY RAINS POSSIBLE THROUGHOUT THE BAHAMAS
TOMORROW INTO JAMAICA.  THE MAIN PART OF THE WAVE WILL CONTINUE
MOVING W AND POTENTIALLY INCREASE CONVECTION OVER THE W
CARIBBEAN FRI AND SAT.

TROPICAL WAVE OVER CENTRAL AMERICA ALONG 86W S OF 18N MOVING W
15 KT. THE NRN PART OF THE WAVE IS UNDER THE INFLUENCE OF STRONG
WESTERLY SHEAR RESULTING FROM A CUT-OFF LOW OVER THE FLORIDA
STRAITS...WHICH HAS DISPLACED ALL OF THE CONVECTION TO THE E OF
THE AXIS. THE WAVE HAS ALSO SPAWNED A 1010 MB LOW BETWEEN SAN
ANDRES ISLAND AND THE EASTERN TIP OF HONDURAS WITH WIDELY
SCATTERED MODERATE CONVECTION FROM 13N-17N BETWEEN 78W-83W.  THE
CONVECTION IS DIMINISHING SOMEWHAT WITH A MESOSCALE CONVECTIVE
VORTEX NOTED NEAR 15N81.5W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N14W 9N27W 6N44W 9N54W.   THE ITCZ
IS ILL-DEFINED W OF 50W.  WIDELY SCATTERED MODERATE CONVECTION
IS BETWEEN 8N-10N FROM 25W-33W AND WITHIN 75 NM OF 9N19.5W.

...DISCUSSION...

GULF OF MEXICO...
UNSEASONABLE DRY WEATHER CONTINUES FOR THE NRN GULF COAST WITH
NLY SURFACE WINDS BRINGING DOWN DEWPOINTS IN THE 60S ALL THE WAY
TO THE COAST FROM NE FLORIDA TO SE TEXAS.  ONLY AN ISOLATED TSTM
IS POSSIBLE...THOUGH TEMPERATURES ARE A BIT WARMER THAN AVERAGE
DUE TO THE DRY AIR AND THE SEA-BREEZE BEING HELD CLOSER TO THE
COAST.  FARTHER E... SCATTERED TSTMS HAVE DEVELOPED OVER FLORIDA
IN THE COOL AIR ALOFT AND DEEP-LAYERED MOISTURE NEAR A CUT-OFF
MID/UPPER LOW OVER THE FLORIDA STRAITS.  A RELATIVELY LARGE AREA
OF DRY AIR AND SUBSIDENCE IS BEHIND THE LOW OVER THE ERN AND NW
GULF... KEEPING THINGS MOSTLY DRY.  HOWEVER THE REMNANTS OF A
COLD FRONT ARE STICKING AROUND AS A TROUGH FROM THE CENTRAL GULF
27N88W TO 22N97W... PROVIDING A FOCUSING MECHANISM FOR ISOLATED
TSTMS WITHIN 60 NM OF THE AXIS W OF 90W.  INCREASING MOISTURE
FROM MEXICO IN THE MID/UPPER LEVELS IS ALSO INCREASING THE
INSTABILITY IN THAT AREA.  LITTLE CHANGE IS LIKELY OVER MOST OF
THE GULF COAST TOMORROW WITH RAIN CHANCES ON THE RISE OVER THE
WEEKEND AS A MORE TYPICAL HUMID AIRMASS COMES IN FROM THE GULF
BECAUSE OF THE RETURN OF SLY WINDS.

CARIBBEAN...
TWO MAIN AREAS OF CONVECTION ARE AFFECTING THE CARIBBEAN
COURTESY OF THE PARADE OF TROPICAL WAVES THAT ARE MARCHING
ACROSS THE BASIN. THESE AREAS ARE MAINLY OVER OPEN WATERS S OF
HISPANIOLA...AND E OF HONDURAS AND NICARAGUA. THE WESTERN AREA
OF TSTMS IS ALSO BEING ENHANCED BY A SHORTWAVE TROF SWINGING
DOWN ACROSS THE NW CARIBBEAN...WHICH ALSO HAPPENS TO BE
SPREADING DRY AIR AND CLEAR SKIES N OF A CAYMAN ISLANDS-BELIZE
LINE.  UPPER RIDGING IS BUILDING IN THE CENTRAL AND SW CARIBBEAN
S OF THE SHORTWAVE WITH ANOTHER HIGH CENTER FORMING CLOSE TO
PUERTO RICO.  THE AREA OF TSTMS HAS NEAR THE DOMINICAN REPUBLIC
LIES BENEATH THIS HIGH.  HOWEVER... FARTHER TO THE E MOST OF THE
LEEWARD/WINDWARD ISLANDS ARE EXPERIENCING EXCELLENT WEATHER DUE
TO DRY MID-LEVEL AIR SPREADING OVER THE AREA NOSING IN FROM THE
ATLC DUE TO THE WESTERN SUBSIDENCE REGION OF A MID/UPPER TROUGH.

ATLANTIC...
THE CUT-OFF MID/UPPER LOW OVER THE FLORIDA STRAITS CONTINUES TO
MOVE SLOWLY E AND SHOULD BE NEAR THE NW BAHAMAS BY TOMORROW.
DIFFLUENCE ALOFT E OF THE LOW SHOULD PERSIST...PRODUCING WAVES
OF CONVECTION THROUGHOUT THE BAHAMAS ON FRI ALONG/AHEAD OF THE
NRN END OF A TROPICAL WAVE.  THE AREA WILL ALSO BE WATCHED FOR
TROPICAL DEVELOPMENT THOUGH THE PROXIMITY OF THE UPPER LOW WITH
THE TROPICAL WAVE WILL PROBABLY INHIBIT SIGNIFICANT DEVELOPMENT
FOR THE NEXT COUPLE OF DAYS.   FARTHER E...AN AMPLIFIED UPPER
RIDGE EXTENDS FROM THE PUERTO RICO NE TO 31N54W...AND ONLY A FEW
HIGH CLOUDS ARE MAKING IT E OF THE RIDGE AXIS.  SUBSIDENCE
BETWEEN THE HIGH AND A DEEP-LAYERED CENTRAL ATLC TROUGH FROM
30N44W TO 14N60W IS CAUSING THE EVAPORATION OF THOSE CLOUDS AND
ANY SIGNIFICANT CONVECTION WITH ONLY TROPICAL TRADEWIND CUMULUS
BENEATH THE TROUGH.  THIS SITUATION CHANGES A BIT N OF 25N
BETWEEN 40W-50W AS COLDER AIR ALOFT IS OVERCOMING THE SUBSIDENCE
TO PRODUCE ISOLATED MODERATE CONVECTION.  FARTHER E... MID/UPPER
TROUGH ALONG 25W N OF 20N IS PULLING OUT OF THE REGION AS A
MID/UPPER HIGH BUILDS OVER THE E ATLC.  THIS HIGH IS NEAR 11N38W
WITH RIDGING E TO 12N16W IN W AFRICA... NE THRU THE CAPE VERDES
TO 22N18W AND WESTWARD TO 12N50W IN THE TROPICAL ATLC.
DIFFLUENCE S OF THE RIDGE IS LEADING TO ENHANCING ITCZ TSTMS E
OF 40W WITH MODERATE/STRONG SUBSIDENCE E OF 30W BETWEEN 10N-20N
ON THE E SIDE OF THE HIGH.  SAHARAN DUST IS STILL OBSERVED
ACROSS THE ATLC S OF A LINE FROM THE CANARY ISLANDS TO 18N50W
22N66W.  SURFACE PRESSURES HAVE RISEN SIGNIFICANTLY IN THE E
ATLC WITH A 1026 MB HIGH JUST S OF THE AZORES NEAR 34N28W
RIDGING SW TO 23N45W.  THIS INCREASE IN PRESSURE HAS RESULTED IN
TRADES PICKING UP TO NEAR NORMAL E OF 35W BUT ARE STILL BELOW
AVERAGE W OF 35W DUE TO THE SURFACE TROUGH AROUND 50W
INTERRUPTING THE RIDGE.

$$
BLAKE




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