[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 042325
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE JUL 04 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND THE 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 IS ALONG 28W/29W S OF 15N MOVING W 10-15
KT.  IT IS DIFFICULT TO PINPOINT ANY AXIS WITHIN A LARGE AREA OF
ANOMALOUS LOW-LEVEL CYCLONIC FLOW FROM 20W-35W AND THE WAVE IS
PUT AT THE LEADING EDGE OF THICKER MID/UPPER LEVEL CLOUDINESS.
ISOLATED MODERATE CONVECTION IS WITHIN 60 NM OF LINE 8N22W
6N32W.  THE GFS FORECASTS THE WAVE TO AFFECT THE LESSER ANTILLES
ON SUN WITH SHOWERS/TSTMS.

CENTRAL ATLC TROPICAL WAVE IS ALONG 43W/44W S OF 13N MOVING W 15
KT.  THIS WAVE IS RATHER LOW-AMPLITUDE AND ITS EFFECTS ARE
LIMITED TO THE ITCZ WHICH SHOWS A SLIGHT NORTHWARD BEND NEAR THE
WAVE AXIS.  ISOLATED SHOWERS ARE FROM 5N-10N BETWEEN 42W-48W.
MOISTURE FROM THIS WAVE SHOULD BEGIN TO AFFECT THE WINDWARD
ISLANDS ON THU AS THE WAVE ACCELERATES WESTWARD UNDER STRONG ELY
FLOW OVER THE CENTRAL TROPICAL ATLC.

CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 70W S OF 20N MOVING W
20 KT.  WAVE IS RESPONSIBLE FOR WIDELY SCATTERED SHOWERS/TSTMS
FROM 15N-23N BETWEEN PUERTO RICO AND 72W AND POSSIBLY FOR AN
INCREASE IN TSTMS OVER NW VENEZUELA.  AS THE WAVE LEAVES...
DRIER CONDITIONS SHOULD BE OBSERVED OVER THE E CARIBBEAN
TOMORROW WITH MOST EFFECTS ON WED W OF HISPANIOLA N OF JAMAICA.

LOW-AMPLITUDE TROPICAL WAVE IS S OF 12N ALONG 85W OVER CENTRAL
AMERICA INCREASING TSTMS IN THE EPAC ITCZ.

...ITCZ...
ITCZ AXIS IS ALONG 13N16W 6N50W 9N61W.  ISOLATED MODERATE
CONVECTION IS FROM 6N-10N BETWEEN 33W-40W AND WITHIN 90 NM OF
6N30W.  ISOLATED SHOWERS ARE FROM 4N-8N BETWEEN 47W-53W.

...DISCUSSION...
GULF OF MEXICO...
UPPER PATTERN HAS RETROGRESSED A BIT FROM YESTERDAY WITH UPPER
RIDGING NOW ACROSS THE WESTERN GULF ALONG 93W/94W.  DIFFLUENCE
ON THE N END OF THE HIGH COMBINED WITH DAYTIME HEATING AND A
PERSISTENT LOW OVER CENTRAL TEXAS HAS CAUSED A FEW SHOWERS/TSTMS
OVER THE FAR NW GULF N OF 27N W OF 89W WITH MOST OF THE ACTIVITY
INLAND.  DRIER AIR ALOFT AND SUBSIDENCE IS BEING BROUGHT INTO
THE E GULF BY AN UPPER LOW JUST E OF MIAMI WITH A NOTABLE
ABSENCE OF TSTMS ACROSS MOST OF FLORIDA TODAY.  LIGHT E TO SE
WINDS ARE ACROSS THE REGION AND SHOULD REMAIN LIGHT FOR AT LEAST
THE NEXT FEW DAYS.  RELATIVELY WET CONDITIONS SHOULD REMAIN FOR
THE NW GULF STATES FOR AT LEAST THE NEXT FEW DAYS AS THE PATTERN
IS FORECAST TO CHANGE LITTLE.  A WETTER DAY IS LIKELY FOR
FLORIDA ON WED AS THE UPPER LOW MOVES INTO THE STRAITS OF
FLORIDA.

CARIBBEAN SEA...
CYCLONIC FLOW AROUND THE UPPER LOW E OF MIAMI COVERS THE
NORTHERN CARIBBEAN AND IS ALLOWING PLENTY OF DIURNAL TSTMS OVER
THE GREATER ANTILLES.  WEAK RIDGING IS OVER THE NW CARIBBEAN
WITH LITTLE MOISTURE FOR SIGNIFICANT PRECIPITATION.  UPPER
TROUGH EXTENDS FROM THE LEEWARD ISLANDS TO THE SW CARIBBEAN WITH
VERY DRY CONDITIONS ALOFT KEEPING THE AREA WITHOUT MANY
SHOWERS.  THE EXCEPTIONS TO THIS RULE ARE NEAR A TROPICAL WAVE
AT 70W AND IN THE FAR SW CARIBBEAN WHERE SOME TSTMS HAVE
RETURNED S AND W OF 11N80W.  UPPER RIDGING IS EXPANDING
NORTHWARD OVER THE E CARIBBEAN WITH LOTS OF HIGH CLOUDS AND A
FEW SHOWERS.  LARGE AREA OF DRIER AIR/AFRICAN DUST IS SEEN IN
VISIBLE SATELLITE PICTURES FILTERING INTO THE E CARIBBEAN AND
THIS SHOULD MAKES CONDITIONS LESS UNSTABLE BEHIND THE TROPICAL
WAVE AT 70W FOR THE NEXT FEW DAYS.. SAVE A BRIEF WAVE PASSAGE IN
THE WINDWARD ISLANDS FOR THU.  THE BULK OF THE PRECIP BY LATE
THU SHOULD BE IN THE SW AND NW CARIBBEAN WITH PROBABLY ONLY
ISOLATED TRADEWIND SHOWERS IN THE NE CARIBBEAN OVER WATER.
UPPER CONDITIONS ARE RATHER HOSTILE FOR TROPICAL CYCLONE
DEVELOPMENT WITH STRONGER- THAN-AVERAGE WIND SHEAR AND LESS
MOISTURE THAN TYPICAL OVER THE AREA.  GALE CONDITIONS ARE
FORECAST FOR TOMORROW INTO THU OVER THE CENTRAL CARIBBEAN AS THE
ATLC RIDGE BUILDS IN STRONGLY BEHIND THE WAVE AT 70W.

ATLANTIC OCEAN...
GENERALLY UNSETTLED CONDITIONS ARE IN THE W ATLC WITH QUIETER
WEATHER FARTHER E.  BROKEN MULTI-LAYERED CLOUDINESS AND ISOLATED
TSTMS ARE W OF 68W S OF 29N ASSOCIATED WITH A WEAK TROUGH OF LOW
PRESSURE FROM CENTRAL CUBA THRU THE NW BAHAMAS AND INSTABILITY
PROVIDED BY A MID/UPPER LOW E OF MIAMI.  A SLOW SW DRIFT IS
LIKELY FOR THE LOW AS UPPER HEIGHTS BUILD OVER THE SE USA.
GENERALLY ZONAL FLOW ALOFT IS PRESENT E OF THE 70W WITH A WEAK
TROUGH NOTED ALONG 26N56W SW TO THE LEEWARD ISLANDS.. THOUGH
HAVING LITTLE EFFECT ON SENSIBLE WEATHER.  THE STORY ACROSS MUCH
OF THE REST OF THE AREA IS A NOTABLE LACK OF MOISTURE IN THE
MID/UPPER LEVELS AS OBSERVED ON WATER VAPOR IMAGES N OF 15N E OF
60W.  UPPER LOW IS NEAR 31N46W HEADED NORTHWARD OUT OF THE AREA
WITH A HIGH NEAR 24N33W AND WEAK TROUGHING OVER THE NE ATLC.
ELY FLOW ALOFT COVERS MUCH OF THE TROPICAL ATLC E OF 40W THOUGH
LARGE-SCALE DRYNESS AND A LACK OF INSTABILITY ARE NOT ALLOWING
ANY TROPICAL SYSTEM TO EVEN TRY TO GET GOING.  SOME CHANGE TO
THIS PATTERN SEEMS PLAUSIBLE IN A WEEK OR TWO AS THE CURRENT
NEGATIVE MADDEN-JULIAN OSCILLATION (MJO) TYPE CONDITIONS LEAVE
THE AREA... THOUGH THE MJO HAS NOT EXACTLY BEEN STRONG THIS
SUMMER.  FOR NOW HIGHER-THAN-AVERAGE SURFACE PRESSURES AND
TRADEWINDS RULE MOST OF THE ATLANTIC.

$$
BLAKE

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