[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 011715
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI JUL 01 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 IS ALONG 27W/28W S OF 16N MOVING W 10-15
KT.  THE SAL SOUNDING FROM 12Z IS SUGGESTIVE THAT A WAVE HAS
PASSED WITH SE WINDS OF 25 KT AT 700 MB... THOUGH IT IS
DIFFICULT TO TELL WITH ONCE-A-DAY SOUNDINGS.  THERE IS A WEAK
LOW/MID-LEVEL CIRCULATION NEAR 10N28W THAT COULD REPRESENT THE
WAVE.  THE GFS HAS A REASONABLE SOLUTION SHOWING A WEAK SHIFT IN
THE WINDS AT MID-LEVELS AND AN INCREASE OF MOISTURE.  ISOLATED
MODERATE CONVECTION WITHIN 75 NM OF 10N28W.

LARGE AMPLITUDE CENTRAL ATLANTIC TROPICAL WAVE EXTENDS FROM
6N43W NNE TO 23N40W MOVING W 10-15 KT.  LATEST POSITION IS A
COMPROMISE BETWEEN A MID-LEVEL CIRCULATION A BIT FARTHER W AND A
LOW-LEVEL WAVE SIGNATURE FARTHER E.  ISOLATED MODERATE
CONVECTION IS FROM 7N-13N BETWEEN 35W-45W.  DRY AIR AHEAD OF THE
WAVE SHOULD KEEP THE LESSER ANTILLES WITH LESS SHOWER COVERAGE
THAN AVERAGE BEFORE THE WAVE ENTERS THE AREA ON SUN.

W-CENTRAL CARIBBEAN TROPICAL WAVE EXTENDS FROM 9N79W NNE TO THE
WINDWARD PASSAGE MOVING W 15-20 KT.  THIS CONTINUES TO BE A
POWERFUL WAVE WITH 25 KT WINDS ON THE BACKSIDE OF THE SYSTEM AND
A SURFACE REFLECTION AS NOTED BY THE LATEST QUIKSCAT.  THE WAVE
IS MOVING BENEATH A MID/UPPER RIDGE WHICH SHOULD ALLOW
CONVECTION TO REFORM NEAR THE WAVE AXIS THIS AFTERNOON.  IN
ADDITION THE WAVE IS APPROACHING A LARGE AREA OF DISTURBED
WEATHER IN THE SW CARIBBEAN ASSOCIATED WITH A NORTHWARD SHIFT IN
THE ITCZ A DIVERGENT ENVIRONMENT ALOFT.  SOUNDINGS FROM ACROSS
THE CARIBBEAN INDICATE THAT THERE IS A STRONG MID-LEVEL
PERTURBATION ASSOCIATED WITH THESE TWO FEATURES WITH S TO SW
WINDS AT 700 MB IN THE SRN CARIBBEAN AND UP TO 50 KT SE WINDS
OBSERVED IN AT KINGSTON.  THIS SYSTEM WILL HAVE TO BE WATCHED
FOR DEVELOPMENT GIVEN THE BUILDING UPPER RIDGE OVER THE NW
CARIBBEAN AND THE PRE-EXISTING DISTURBANCE.  THE WAVE IS
FORECAST TO MOVE OVER YUCATAN BY MON SPREADING HEAVY RAIN OVER
THE AREA.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 11N15W 10N22W 13N38W 8N52W 8N60W.
WIDELY SCATTERED MODERATE CONVECTION WITHIN 60 NM OF AXIS
BETWEEN 49W-57W.  SCATTERED MODERATE FROM 9N-11N BETWEEN
19W-23W.  A FEW TSTMS ARE WITHIN 75 NM OF 6N12W.

...DISCUSSION...

GULF OF MEXICO...
RELATIVELY QUIET ACROSS THE AREA WITH A SLOW-MOVING MID/UPPER
LOW NEAR 26N91W DIVIDING THE WEATHER ACROSS THE AREA.  ON THE
EASTERN SIDE OF THE LOW...CONDITIONS ARE WETTER-THAN-AVERAGE
WITH PLENTY OF DEEP-LEVELED MOISTURE IN THE E GULF SUPPORTING
DIURNAL TSTMS. TO THE NW OF THE LOW... MODERATE/STRONG
SUBSIDENCE IS KEEPING A LID ON MOST CONVECTION WITH
BELOW-AVERAGE DIURNAL CONVECTION EXPECTED W OF 92W.  MID/UPPER
RIDGING HAS FORMED OVER FLORIDA THOUGH IT NOT STRONG ENOUGH TO
SUPPRESS DAYTIME TSTMS.   A WEAK SURFACE TROUGH FROM TAMPA
FLORIDA TO THE MOUTH OF THE MISSISSIPPI RIVER IS A FOCUSING
MECHANISM FOR ISOLATED TSTMS WITHIN 75 NM OF THE TROUGH...MOST
NUMEROUS OVER SE LOUISIANA.  WLY WINDS IN THE LOW/MID LEVELS
SHOULD KEEP THE E COAST OF FLORIDA WET FOR THE NEXT COUPLE OF
DAYS.  RAINY WEATHER FROM A W-CENTRAL CARIBBEAN TROPICAL WAVE
SHOULD BEGIN MOVING OVER THE FAR SE GULF LATE SAT...POSSIBLY
INCREASING THE CHANCE OF RAIN FOR S FLORIDA ON SUN...AND
COVERING MUCH OF THE CENTRAL AND E GULF ON MON.  NO SIGNIFICANT
INCREASE IN MOISTURE IS LIKELY OVER THE W GULF THRU THE WEEKEND.

CARIBBEAN...
THERE HAS BEEN LITTLE MOVEMENT TO AN AREA OF DISORGANIZED
DISTURBED WEATHER IN THE SW CARIBBEAN WITH A NORTHWARD SHIFT IN
THE ITCZ AND UPPER DIFFLUENCE CAUSING BURST OF TSTMS.  SOUNDINGS
FROM ACROSS THE AREA INDICATE THE SYSTEM IS STRONGEST IN THE
MID-LEVELS WITH SIGNIFICANT TROUGHING NOTED AT 700 MB (~10,000
FT).  THE SYSTEM IS PRODUCING SCATTERED TSTMS S OF 16N BETWEEN
80W AND CENTRAL AMERICA IN A DIFFLUENT AREA ALOFT BETWEEN A
BUILDING UPPER HIGH S OF JAMAICA AND A WESTWARD MOVING UPPER LOW
OVER BELIZE.  A TROPICAL WAVE APPROACHING THE AREA WILL PROBABLY
JUST ENHANCE THE AREA'S CONVECTIVE DEVELOPMENT AND ADD TO THE
POTENTIAL OF ANYTHING FORMING IN THE VICINITY.  HEAVY RAINFALL
AND POSSIBLE FLOODING COULD OCCUR OVER CENTRAL AMERICA THRU
MON.  BROKEN/OVERCAST HIGH CLOUDS N OF JAMAICA BETWEEN
HISPANIOLA AND THE CAYMANS ARE CONVECTIVE DEBRIS CLOUDS FROM
EARLIER TSTMS WITH ISOLATED SHOWERS.  FARTHER E... THE CARIBBEAN
HAS DRIED OUT IN THE LESSER ANTILLES WITH PLENTY OF
MODERATE/STRONG SUBSIDENCE E OF 65W.  AN UPPER LEVEL TROUGH
APPROACHING THE LEEWARD ISLANDS COULD INCREASE THE CHANCE OF
RAIN FOR TOMORROW IN THAT AREA. THE FRINGES OF THE W-CENTRAL
ATLC TROPICAL WAVE SHOULD REACH THE E CARIBBEAN ISLANDS BY SUN
WITH A DEEPER SURGE OF MOISTURE OVERSPREADING THE REST OF THE
AREA E OF PUERTO RICO ON MON.

ATLANTIC...
UPPER RIDGE LIES ACROSS THE W ATLC FROM CENTRAL FLORIDA TO
26N60W WITH HIGH CLOUDS N OF THE AXIS.  THE SOUTHERN END OF A
MID-LATITUDE TROUGH DIPS INTO THE REGION NEAR 29N80W TO
31N75W... SUPPORTING ISOLATED MODERATE CONVECTION WITHIN 90 NM
OF THE AXIS.  MID/UPPER TROUGH EXTENDS FROM A CLOSED LOW NEAR
28N53W SW TO 20N66W JUST N OF PUERTO RICO.  A WEAK LOW-LEVEL
TROUGH IS BENEATH THE UPPER FEATURES WITH ISOLATED MODERATE
CONVECTION FROM 20N-26N BETWEEN 55W-65W.  FARTHER E... UPPER
RIDGING CONTROLS THE CENTRAL ATLC WITH A MID/UPPER LOW SCOOTING
ALONG THE NE SIDE NEAR 32N25W.  THE TROPICAL ATLC IS DIVIDED BY
A WEAK MID/UPPER TROUGH ALONG 20N35W TO 13N46W WITH VERY DRY AIR
IN THE MID/UPPER LEVELS W OF THE TROUGH AXIS.  AFRICAN HIGH
EXTENDS FROM SW MAURITANIA TO THE NORTHERN WINDWARD ISLANDS WITH
ONLY A SMALL BREAK FOR THE CENTRAL ATLC TROUGH.  AT THE
SURFACE...1026 MB HIGH IS NEAR 34N39W WITH SEASONABLE TRADES
OBSERVED THROUGHOUT THE E PART OF THE AREA... A BIT WEAKER THAN
AVERAGE W OF 50W.

$$
BLAKE


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