[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 012351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

EAST ATLANTIC TROPICAL WAVE ALONG 29W S OF 15N MOVING W 15 KT.
THE SAL UPPER AIR SOUNDING IS MOSTLY INCONCLUSIVE REGARDING WAVE
PASSAGE...BUT THE DAKAR TIMESECTION SUGGESTS A BACKWARD-LEANING
STRUCTURE GIVEN THAT THE LOW-LEVEL PERTURBATIONS PRECEDED THE
MID-LEVEL PERTURBATION BY 18-24 HRS. A WEAK CIRCULATION IS NOTED
WITHIN THE ITCZ NEAR 29W...BUT WHAT IS MORE IMPRESSIVE IS THE
WIDESPREAD DUST OUTBREAK MOVING OFF THE AFRICAN COAST BEHIND THE
WAVE FROM 9N-26N.

LARGE AMPLITUDE CENTRAL ATLANTIC TROPICAL WAVE TILTED ALONG
6N41W 14N44W 21N44W MOVING W 10-15 KT. VISIBLE IMAGERY AND AN
1800 UTC OBSERVATION FROM SHIP PBKY INDICATE THAT BROAD LOW PRES
HAS DEVELOPED ALONG THE WAVE AXIS NEAR 9N43W WITH A MINIMUM PRES
OF 1010 MB. THE FORMATION OF THE LOW IS NOT YET INDICATIVE OF
TROPICAL DEVELOPMENT SINCE THE CIRCULATION IS STILL QUITE
BROAD...THERE IS ESSENTIALLY NO DEEP CONVECTION NEAR THE
CENTER...AND A FEW OTHER VORT MAXES ARE STILL BEING OBSERVED
PRIMARILY WITHIN THE TRAILING ITCZ. THE GFS AND UKMET MODELS
INTERMITTENTLY PRESCRIBE TO A LOW ALONG THE WAVE AS IT NEARS THE
LESSER ANTILLES BUT NONE OF THE GUIDANCE LATCHES ON TO A
CONSOLIDATED SFC CIRCULATION. MOISTURE ASSOCIATED WITH THE WAVE
WILL BEGIN TO SPREAD OVER THE LESSER ANTILLES SUN EVENING WITH
EPISODES OF SHOWERS/TSTMS LIKELY FOR MUCH OF NEXT WEEK. ISOLATED
SHOWERS/TSTMS FROM 4N-14N BETWEEN 36W-46W.

WEST CARIBBEAN TROPICAL WAVE ALONG 8N81W 16N80W 22N77W MOVING W
20 KT. AN UPPER LOW CENTERED ALONG THE SRN COAST OF CUBA IS
IMPEDING THE FORWARD PROGRESS OF THE NRN PART OF THE WAVE AND
HAS LED TO A STRONG SW/NE TILT. AN UPPER RIDGE STRADDLES THE
WAVE AXIS FROM THE YUCATAN CHANNEL TO S OF HAITI AND IS
PROVIDING A DIFFLUENT ENVIRONMENT FOR SCATTERED MODERATE
CONVECTION FROM 12N-19N BETWEEN 76W-85W...INCLUDING OVER
JAMAICA...NICARAGUA...AND HONDURAS. THE WAVE IS EXPECTED TO
EXPAND TO THE N AND EXTEND FROM THE YUCATAN TO THE SE GULF BY
SUN AFTERNOON. SHOWERS/TSTMS ARE LIKELY OVER THE W CARIBBEAN ON
SAT SPREADING OVER W CUBA...THE SE GULF...AND YUCATAN ON
SUN...THEN INTO THE CNTRL GULF ON MON. THIS PATTERN IS QUITE
SIMILAR TO THE PRECURSOR TO TROPICAL STORM BRET...SO THIS AREA
WILL NEED TO BE MONITORED OVER THE NEXT SEVERAL DAYS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N10W 10N21W 11N28W...THEN ALONG
9N30W 13N38W 12N43W...THEN ALONG 7N44W 7N56W 15N71W. SCATTERED
MODERATE CONVECTION FROM 6N-10N E OF 17W. SCATTERED MODERATE
WITHIN 90 NM OF THE AXIS BETWEEN 21W-26W AND 29W-33W. WIDELY
SCATTERED MODERATE WITHIN 200 NM OF THE AXIS BETWEEN 51W-65W.

...DISCUSSION...

GULF OF MEXICO...
A HIGH PRES SFC RIDGE AND WIDESPREAD MID/UPPER LEVEL SUBSIDENCE
ARE BOTH LEADING TO MAINLY CLEAR SKIES OVER THE SRN 3/4 OF THE
GULF REGION. AN INVERTED MID-LEVEL TROF EXTENDS FROM THE BAY OF
CAMPECHE TO JUST S OF LOUISIANA AND IS MOVING W...BEGINNING TO
SOMEWHAT DRAG IN INCREASED MOISTURE FROM THE E. A WEAK SFC TROF
LIES ACROSS THE NE GULF WATERS AND HAD TRIGGERED ISOLATED
SHOWERS/TSTMS EARLIER IN THE DAY...BUT MOST OF THESE HAVE SINCE
DISSIPATED. THE MORE PRONOUNCED CONVECTION IS CURRENTLY OVER ERN
PARTS OF FLORIDA. INCREASED MOISTURE WILL BEGIN TO MOVE INTO THE
SE GULF ON SUN BEHIND A TRPCL WAVE...SPREADING SHOWERS/TSTMS
TOWARDS THE N GULF AND MEXICAN COASTS BY TUE AND WED.

CARIBBEAN...
WEATHER ASSOCIATED WITH THE W CARIBBEAN TRPCL WAVE IS DISCUSSED
ABOVE. OTHERWISE...ONLY ISOLATED SHOWERS/TSTMS ARE STREAMING UP
BEHIND THE WAVE FROM NE VENEZUELA INTO THE CNTRL CARIBBEAN ALONG
THE ITCZ. THE AIR MASS OVER THE E CARIBBEAN IS MAINLY
DRY...ESPECIALLY E OF 66W WHERE SUBSIDENCE IS OCCURRING IN THE
MID-LEVELS...SO MUCH OF THE LEEWARD AND WINDWARD ISLANDS ARE
UNDER FAIR SKIES. THIS WILL LIKELY CHANGE BY SUN AFTERNOON AS
MOISTURE MOVES IN FROM THE ATLC AND THE AREA OF DRY AIR SHIFTS
WWD TO THE W/CNTRL CARIBBEAN.

ATLANTIC...
A COUPLE OF WEAK SFC TROFS OVER THE W ATLC WATERS ARE EMBEDDED
BENEATH THE MOISTURE PLUME ASSOCIATED WITH THE SUBTROPICAL
JET...AND SO ARE HELPING TO CAUSE WIDELY SCATTERED SHOWERS/TSTMS
MAINLY WITHIN A BAND FROM 26N-31N BETWEEN 60W-78W. THE JET DIPS
SWD OVER THE CNTRL ATLC AROUND A MID/UPPER LEVEL CUT-OFF LOW
NEAR 28N51W WHICH IS CAUSING AN AREA OF WIDELY SCATTERED SHOWERS
FROM 27N-31N BETWEEN 45W-52W. A SECOND UPPER LOW IS DEPARTING
THE AREA NEAR 33N23W MOVING E TOWARDS SPAIN AND PORTUGAL WHILE A
REMNANT UPPER LEVEL SHEAR AXIS EXTENDS SW OF THE CANARY ISLANDS
TO 15N40W. AN UPPER RIDGE EXTENDS W OF AFRICA ACROSS THE CAPE
VERDES ALONG 16N WITH DEEP-LAYERED EASTERLIES PUSHED S OF 12N.
THE LOW-LEVELS REMAIN DRY AND STABLE OVER THE E ATLC...AND A NEW
SAHARAN DUST PLUME HAS SPREAD WWD ACROSS THE CAPE VERDES FROM
10N-24N E OF 30W.

$$
BERG


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