[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211716
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT 21 MAY 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
1645 UTC.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE ALONG 29W S OF 15N MOVING W 15 KT.
QUIKSCAT FROM THIS MORNING SHOWED THE WAVE'S LOCATION WITH
VISIBLE IMAGERY ALSO DISPLAYING CURVATURE IN THE LOW-CLOUD
FIELD.  LOW-LEVEL MOISTURE BEHIND THE WAVE IS INTERACTING WITH
AN UPPER TROUGH TO PRODUCE WIDELY SCATTERED SHOWERS IN THE CAPE
VERDE ISLANDS.

TROPICAL WAVE APPROACHING S AMERICA ALONG 48W S OF 14N MOVING W
15 KT.  THE WAVE SHOWS A FAIR SIGNATURE ON VISIBLE SATELLITE
PICTURE WITH CONVECTION W OF THE WAVE AXIS IN THE ITCZ...
MEANING THE WAVE IS EXPERIENCING ELY SHEAR...WHICH IS RATHER ODD
FOR AN EARLY-SEASON WAVE.  SCATTERED TSTMS ARE OVERSPREADING S
AMERICA FROM 2N-7N BETWEEN 49W-53W.

TROPICAL WAVE IN THE CENTRAL CARIBBEAN SEA ALONG 76W S OF 14N
MOVING W 10-15 KT.  CLUSTER OF WEAK CONVECTION IS OVER CENTRAL
COLOMBIA DENOTING THE WAVE'S LOCATION...OTHERWISE THE WAVE ISN'T
AFFECTING THE WEATHER MUCH OVER THE CARIBBEAN.

...ITCZ...

ITCZ AXIS IS ALONG 11N15W 7N21W 8N28W 6N36W 7N47W 9N61W.  WIDELY
SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF LINES 7N32W
5.5N44W AND 3.5N38W 1.5N46W.  ISOLATED MODERATE CONVECTION
WITHIN 60 NM OF 7.5N57W AND 7.5N22.5W.

...DISCUSSION...

GULF OF MEXICO...
A COLD FRONT HAS NOSED INTO THE NORTHERN GULF FROM NEAR
BOOTHVILLE LOUISIANA EASTWARD TO JUST S OF CEDAR KEY FLORIDA.
ISOLATED TSTMS ARE WITHIN 30 NM OF THE FRONT WITH OTHER ISOLATED
SHOWERS BEHIND THE FRONT OVER FLORIDA.  OTHERWISE WEAK HIGH
PRESSURE... 1014 MB HIGH... IS THE ONLY SIGNIFICANT WEATHER
FEATURE OVER THE W GULF WITH VERY LIGHT WINDS EXCEPT IN THE
IMMEDIATE VICINITY OF THE FRONT.  A DEEP MID/UPPER TROUGH FROM
NE FLORIDA TO THE BAY OF CAMPECHE CONTINUES TO BRING DRY AIR IN
THE MID/UPPER LEVELS... MOSTLY SHUTTING DOWN THE AFTERNOON TSTMS
THAT TYPICALLY FORM ALONG THE GULF COAST SEABREEZES.  THE FRONT
IS EXPECTED TO SHIFT SOUTHWARD LATER TODAY BUT DISSIPATE DURING
DAYTIME HEATING TOMORROW BEFORE PASSING S FLORIDA.  ANOTHER COLD
FRONT SHOULD MOVE INTO THE REGION

CARIBBEAN SEA...
SURFACE TROUGH REMAINS FROM NEAR THE WINDWARD PASSAGE THRU NW
JAMAICA TO NEAR NE HONDURAS WITH WLY WINDS AT LOW-LEVELS S OF
THE TROUGH AXIS TO 70W.  WIDELY SCATTERED SHOWERS/ISOLATED TSTMS
ARE FORMING WITHIN 90 NM OF THE TROUGH.  OTHER UNSTABLE
CONDITIONS ARE LOCATED OVER HISPANIOLA WHERE DEEP-LEVEL MOISTURE
SHOULD COMBINE WITH DIURNAL HEATING TO PRODUCE AFTERNOON TSTMS
WITH WIDELY SCATTERED ACTIVITY WITHIN 90 NM OF 17N71.5W
ALREADY.  HEAVY RAIN IS STILL POSSIBLE OVER AREAS OVER CENTRAL
AMERICA THAT RECEIVED PLENTY DURING HURRICANE ADRIAN AND THAT
AREA SHOULD REMAIN WETTER THAN AVERAGE WITH THE PACIFIC ITCZ FAR
TO THE N OF ITS CLIMATOLOGICAL POSITION.  ANOMALOUSLY STRONG
MID/UPPER HIGH IS NEAR BARBADOS RIDGING WESTWARD TO NICARAGUA
AND NORTHWARD INTO THE W ATLC.  ELY FLOW AT UPPER LEVELS LIES S
OF THE RIDGE AXIS...UNUSUAL FOR MAY WHICH USUALLY HAS 20-25 KT
WINDS COMING FROM THE WEST IN THOSE AREAS.  A DRIER PATTERN WILL
MOVE FROM W TO E AS THE SURFACE TROUGH SLIPS SE... WITH MUCH
GREATER-THAN- AVERAGE CHANCES OF RAIN ENDING MON ON JAMAICA AND
TUE ON HISPANIOLA THOUGH CONDITIONS STILL LOOK A BIT WETTER THAN
AVERAGE IN THE LEEWARD ISLANDS.

ATLANTIC OCEAN...
COLD FRONT IS SNEAKING INTO THE FAR NW PART OF THE REGION FROM
31N79W TO N-CENTRAL FLORIDA WITH BROKEN LOW CLOUDS BEHIND THE
FRONT.  IN ADDITION EARLIER CONVECTION LEFT AN OUTFLOW BOUNDARY
ALONG 29N78W 29N75W 31N73.5W WHICH IS CAUSING WIDELY SCATTERED
TSTMS WITHIN 30 NM OF THE BOUNDARY.  BROAD SURFACE LOW IS
STATIONARY NE OF THE BAHAMAS NEAR 25N67W WITH A LARGE AREA OF
OVERCAST MULTI-LAYERED CLOUDS IN ADDITION TO WIDELY SCATTERED
SHOWERS FROM 25N-31N BETWEEN 60W-70W AND S OF 26N BETWEEN
70W-75W.  TSTMS ARE EMBEDDED IN THE LARGER AREA OF RAIN...MOST
NOTABLY NEAR THE SE BAHAMAS AND WITHIN 60 NM OF 23N64W.  BROAD
MID/UPPER RIDGE FROM THE SE CARIBBEAN COVERS THE AREA WITH THE
RIDGE AXIS ALONG ABOUT 60W.  1012 MB LOW IS E OF THE LEEWARD
ISLANDS NEAR 19N57W BUT IS ONLY PRODUCING ISOLATED TSTMS FROM
16N-21N BETWEEN 50W-60W.  THE LOW LIES ALONG A LONG-LIVED
SURFACE TROUGH FROM 31N41 TO 24N44W WSW TO THE LOW CENTER.
WIDELY SCATTERED TSTMS ARE WITHIN 75 NM OF LINE 24N43W 30N39W...
PARTIALLY FORMING THERE BECAUSE OF LOW-LEVEL CONVERGENCE BETWEEN
SW WINDS FROM A LOW NEAR 33N43W AND ELY WINDS AROUND THE AZORES
HIGH.  UPPER TROUGH ENERGY IS ALSO FUELING THESE TSTMS AS
DIVERGENCE ALOFT IS OBSERVED ON WATER VAPOR IMAGES.  GENERALLY
ZONAL FLOW IS IN THE NE SUBTROPICAL ATLC WITH HIGH CLOUDS MOVING
FROM W-E FROM THE TSTMS NEAR 40W... THINNING SIGNIFICANTLY E OF
28W.  DOWN IN THE DEEP TROPICS... DRY AIR/SUBSIDENCE RULE FROM
THE CARIBBEAN MID/UPPER HIGH W OF 40W WHILE A TROUGH RUNS FROM
20N26W TO 5N38W... JUST W OF THE CAPE VERDE ISLANDS.  THIS
TROUGH IS COMBINING WITH LOW-LEVEL MOISTURE BEHIND A TROPICAL
WAVE TO FORM WIDELY SCATTERED SHOWERS OVER THE CAPE VERDES.
AFRICAN DUST REMAINS IN THE CENTRAL/E ATLC E OF 45W BETWEEN THE
ITCZ AND 21N.

$$
BLAKE

WWWW
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