[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 290000
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT MAR 28 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 4N9W 2N20W DIPPING TO S OF THE
EQUATOR NEAR 22W...AND EXTENDS WSW FROM THERE TO INLAND THE
COAST OF NE BRAZIL NEAR 3S41W. SCATTERED STRONG CONVECTION IS
ALONG AND WITHIN 150 NM N OF THE ITCZ BETWEEN 20W-26W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS S OF THE AXIS E OF 13W.

...DISCUSSION...

GULF OF MEXICO...
A LARGE DEEP UPPER LEVEL LOW MOVING E ACROSS MISSOURI EXTENDS A
BROAD TROUGH S ACROSS TEXAS AND NOW ENTERING THE FAR WRN GULF.
THE ASSOCIATED SURFACE COLD FRONT ENTERS THE AREA FROM THE FAR
WRN FL PANHANDLE JUST W OF PENSACOLA SSW TO 26N88W TO 23N90W
...AND INTO THE ERN BAY OF CAMPECHE. THE FRONT IS MOVING E ABOUT
20-25 KT. A SQUALL LINE IS OBSERVED WITHIN 130 NM E OF THE FRONT
N OF 27N. NWS DOPPLER RADAR AND RADAR IMAGERY ARE SHOWING
SCATTERED TSTMS QUICKLY FIRING ALONG AND E OF THE SQUALL LINE.
SCATTERED SHOWERS AND ISOLATED TSTMS ARE ALONG ...AND BETWEEN
THE FRONT AND THE SQUALL LINE.  A DIFFLUENT PATTERN TO THE E OF
THE TROUGH OVER THE SE U.S. AS SEEN ON SATELLITE WATER VAPOR
IMAGERY IS SUPPORTING THIS ACTIVITY ALONG WITH MODERATE TO
STRONG LOW-LEVEL INFLOW ARE PROVIDING FURTHER FUEL TO THE
ACTIVITY AS IT DEVELOPS. EXPECT SOME OF THE TSTMS TO POSSIBLY
REACH SEVERE LIMITS TONIGHT WHICH INCLUDES THE POSSIBILITY OF
WINDS GUSTS TO 50 KT. LATEST SURFACE ANALYSIS SHOWS HIGH PRES
FILTERING IN ACROSS THE GULF BEHIND THE FRONT. NW TO N GALE
WINDS BEHIND THE FRONT ARE IN THE 30-45 KT RANGE OVER THE SW
GULF. THESE WINDS WILL DECREASE TO LESS THAN GALE FORCE LATE
TONIGHT AS THE HIGH SHIFTS TO E OF THE GULF THROUGH MON. THE
PRES GRADIENT OUTSIDE TSTM ACTIVITY IS RESULTING IN SE TO S
WINDS OF 20-25 KT ACROSS MUCH OF THE MIDDLE AND ERN GULF
SECTIONS AS NOTED IN LATEST BUOY OBSERVATIONS.

LATEST MODEL GUIDANCE SUGGESTS THAT THE COLD FRONT WILL
REACH A LINE FROM TAMPA BAY TO NE YUCATAN PENINSULA EARLY
SUN...AND TO THE FAR SE WATERS BY EARLY SUN EVENING AS THE
UPPER TROUGH EXITS THE GULF...AND IS REPLACED BY ZONAL
FLOW THROUGH MON WHILE THE SURFACE HIGH SLIDES E. EXPECT
STABLE CONDITIONS TO PREVAIL THROUGHOUT UNDER SUBSIDENCE
IN THE WAKE OF THE TROUGH THROUGH EARLY NEXT WEEK.

CARIBBEAN SEA...
THE AREA OF BROAD ANTICYCLONIC FLOW THAT WAS EVIDENT OVER MUCH
OF THE CENTRAL AND ERN GULF THE PAST COUPLE OF DAYS HAS SHIFTED
EWD AHEAD OF THE GULF OF MEXICO COLD FRONT AND PRESENTLY
COVERS THE MAJORITY OF THE SEA...EXCEPT FOR THE FAR ERN PORTION.
ITS ASSOCIATED MEAN RIDGE AXIS ROUGHLY EXTENDS ALONG 76W.
ABUNDANT SUBSIDENCE RESULTING IN RATHER STABLE CONDITIONS IS
RESULTING IN ABUNDANT MODERATE SUBSIDENCE SEEN THROUGHOUT
JUST ABOUT THE ENTIRE SEA...AND IS FURTHER ENHANCED OVER THE NE
PORTION WHERE CONFLUENT FLOW INTO THE BASE OF THE CENTRAL ATLC
DEEP LAYER TROUGH MENTIONED BELOW UNDER ATLC OCEAN. ONLY VERY
NARROW LINES OF LOW CLOUDS WITH POSSIBLE ISOLATED SHOWERS MOVING
QUICKLY TO THE NW ARE NOTED OVER THE MIDDLE AND WRN CARIBBEAN
W TO 84W.

A JET STREAM BRANCH...WITH WINDS IN THE RANGE OF 40-60 KT
...EXTENDS FROM NORTHERN COLOMBIA NE INTO THE BASE OF
THE CENTRAL ATLC UPPER TROUGH MENTIONED BELOW. THE JET
IS TRANSPORTING BROKEN TO SCATTERED HIGH LEVEL CLOUDS NE
TO ACROSS THE FAR ERN CARIBBEAN SEA. PATCHES OF LOW-LEVEL
IN THE FORM OF SCATTERED TO BROKEN LOW CLOUDS MOVING W WITH
ISOLATED SHOWERS ARE OVER THE FAR ERN CARIBBEAN S OF 15N
E OF 70W. THIS MOISTURE IS GREATLY ATTRIBUTED TO THE
WEAKENING ATLC FRONTAL TROUGH E OF THE LESSER ANTILLES.
THE TROUGH IS FORECAST TO DRIFT N AND DISSIPATE OVER THE NEXT
48 HOURS...DIMINISHING THE CHANCES OF PRECIPITATION OVER THE
WINDWARD ISLANDS AND ERN CARIBBEAN SEA.

WITH RESPECT TO MARINE CONDITIONS...STRONG SE WINDS IN THE RANGE
OF 20-30 KT ARE BEING OBSERVED OVER THE NW CARIBBEAN W OF ABOUT
84W DUE TO THE TIGHT PRES GRADIENT BETWEEN HIGH PRES CENTERED N
OF THE SEA OVER THE ATLC NEAR 30N61W...AND LOWER PRES
OVER THE ERN GULF OF MEXICO DUE TO THE COLD FRONT ADVANCING EWD.

ATLANTIC OCEAN...
OVER THE W ATLC...DEEP LAYER RIDGING IS KEEPING HOLD OF THE WRN
PORTION OF THE ATLC AS IT GRADUALLY TRANSLATES EWD. AN UPPER
LEVEL RIDGE AXIS MOVING E EXTENDS FROM 32N68W TO 29N69W. THE
ASSOCIATED 1024 MB SURFACE HIGH CENTER IS LOCATED NEAR 30N61W
WITH A RIDGE SW TO S CENTRAL FL. A JET STREAM BRANCH WITH
MAXIMUM WINDS OF 60 KT POKES SE INTO CENTRAL BAHAMAS FROM THE
ERN GULF OF MEXICO. UPPER LEVEL MOISTURE IS BEING CHANNELED EWD
INTO THE WRN ATLC BY THIS JET STREAM BRANCH. THE ABOVE GULF
OF MEXICO COLD FRONT IS FORECAST TO MOVE OFF THE SE U.S. AND NE
FL COAST SUN MORNING PRECEDED BY INCREASING SLY WINDS OF 20-30
KT FOLLOWED BY SHIFTING WINDS TO W ALSO AT 20-30 KT. EXPECT AN
INCREASE OF SCATTERED SHOWERS AND TSTMS OVER THE THE NW PART
TONIGHT THROUGH SUN AHEAD OF THE FRONT. THE FRONT IS FORECAST TO
REACH FROM NEAR BERMUDA TO THE NORTHERN BAHAMAS TO STRAITS OF FL
MON EVENING...THEN BECOME STATIONARY ALONG 26N TUE.

OVER THE CENTRAL ATLC...A DEEP LAYER TROUGH EXTENDS FROM
22N58W NE TO 26N49W WHERE IT SHARPLY TILTS NE TO 28N41W TO NE
OF AREA AT 32N39W. THE ASSOCIATED SURFACE COLD FRONT ENTERS THE
AREA THROUGH 32N37W AND CONTINUES SW TO 24N42W WHERE IT BECOMES
STATIONARY TO 19N49W...THEN A FRONTAL TROUGH TO NEAR 12N57W.
LATEST SATELLITE IMAGERY SHOWS BROKEN MAINLY LOW AND MID LEVEL
CLOUDS ALONG WITH SCATTERED HIGH CLOUDS. SCATTERED SHOWERS AND
TSTMS ARE WITHIN THESE CLOUDS WITHIN ABOUT 90-200 NM E OF THE
FRONT N OF 26N. OVERCAST TO BROKEN LOW AND MID LEVEL CLOUDS WITH
SCATTERED SHOWERS ARE ELSEWHERE WITHIN 180 NM EITHER SIDE OF THE
STATIONARY FRONT ...AND WITHIN 90 NM EITHER SIDE OF THE TROUGH.

IN THE FAR ERN ATLC...ATLC COLD-AIR INSTABILITY IS BRINGING A
SMALL AREA OF SCATTERED TSTMS JUST N OF THE FAR NE PART OF THE
AREA. THIS ACTIVITY IS APPROACHING THE COAST. SCATTERED TO
BROKEN STRATOCUMULUS CLOUDS MOVING S WITH SCATTERED SHOWERS ARE
OVER THE NE PART OF THE AREA N OF 26N E OF 25W. FOR THE THIRD
DAY IN A ROW...SATELLITE VISIBLE IMAGERY SUPPORTED BY THE CIMSS
SAL ANALYSIS SHOWS AN AREA OF SAHARAN AFRICAN DUST THAT EMERGED
OUT OVER THE FAR ERN ATLC S OF 17N AND E OF 37W. AN EXTENSIVE
AREA OF DEEP HIGH PRES COVERS THE AREA S OF ABOUT 27N WITH
A MEAN ANTICYCLONIC CENTER OBSERVED FAR S NEAR 7N23W WITH A RIDGE
NW TO 15N31W...THEN TO 23N32W AND BECOMES RATHER WELL DEFINED
TO NE OUT OF THE AREA AT 32N31W. THE RIDGE IS ENHANCING
CONVECTION NEAR AND ALONG THE ITCZ W OF 38W WHERE SOME
DIFFLUENCE IS NOTED ON THE SW PERIPHERY OF THE RIDGE AXIS. THE
HIGH IS FORECAST TO SLIDE E OVER THE NEXT 48 HRS AS THE UPPER
TROUGH TO ITS NW PRESSES EWD.

$$
AGUIRRE



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