[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 072343
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT MAR 07 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...

THE ITCZ AXIS IS CENTERED ALONG 6N10W CROSSING THE EQUATOR NEAR
19W EXTENDING TO 2S30W AND INTO NE BRAZIL NEAR 4S44W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS S OF 2N BETWEEN 22W-29W.
ISOLATED MODERATE CONVECTION IS FROM THE EQUATOR TO 5N BETWEEN
12W-20W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE DOMINATES MUCH OF THE GULF AND THE SE CONUS
WITH MODERATE TO STRONG SUBSIDENCE IN PLACE OVER THE REGION.
SOUTHEASTERLY SURFACE FLOW OF UP TO 25 KT RESIDES ON THE WRN
PERIPHERY OF A SURFACE RIDGE THAT EXTENDS FROM A 1030 MB HIGH IN
THE W ATLC NEAR 30N71W. EASTERLY WINDS OF 20-25 KT CONTINUE
THROUGH THE STRAITS OF FLORIDA AND ACROSS THE SE PORTION OF THE
GULF S OF 24N. THESE WINDS ARE TRANSPORTING PATCHES OF LOW-LEVEL
CLOUDS WITH ISOLATED VERY LIGHT SHOWERS FROM THE ATLC THROUGH
THE STRAITS OF FLORIDA INTO THE GULF WATERS. THE SURFACE HIGH IS
FORECAST TO REMAIN NEARLY STATIONARY AND AS A RESULT...THE
OVERALL WEATHER PATTERN ACROSS THE GULF WILL CHANGE LITTLE
THROUGH MONDAY. LOOKING AHEAD...A COLD FRONT MAY APPROACH THE NW
GULF WATERS BY WED.

CARIBBEAN SEA...
FRESH TO STRONG WINDS ASSOCIATED WITH A 1030 MB SURFACE HIGH
CENTERED IN THE W ATLC NEAR 30N71W ARE ADVECTING POCKETS OF
SHALLOW MOISTURE WITH EMBEDDED LIGHT SHOWERS ACROSS PARTS OF
CUBA...HISPANIOLA...AND THE NW CARIBBEAN SEA. AN EARLIER ASCAT
PAST SHOWED NE-E WINDS OF 20-30 KT OVER MUCH OF CARIBBEAN SEA.
ALSO...A GALE WARNING REMAINS IN EFFECT FOR THE SW CARIBBEAN
FROM 10N-13N BETWEEN 75W-77W OFF THE COLOMBIAN COAST WHERE WIND
SPEEDS ARE IN THE 30-35 KT RANGE. THE INCREASED SURFACE WINDS
ARE THE RESULT OF A TIGHTENING SURFACE PRESSURE GRADIENT BETWEEN
THE AFOREMENTIONED HIGH OVER THE W ATLC AND LOWER PRESSURE OVER
NRN SOUTH AMERICA. AN AREA OF CLOUDINESS WITH EMBEDDED SHOWERS
IS NOTED OVER THE SW CARIBBEAN LIKELY RELATED TO THE SHEAR OF
THE LOW LEVEL WIND/SPEED CONVERGENCE. THE SPEED CONVERGENCE OVER
THIS REGION IS THE RESULT OF STRONG TRADE WINDS OVER THE
SOUTH-CENTRAL CARIBBEAN WITH WEAKER TRADES LYING TO THE WEST.
THIS CLOUDINESS IS AFFECTING THE ATLANTIC SIDE OF WESTERN PANAMA
AND COSTA RICA. ALOFT...STRONG SUBSIDENCE IS RESULTING FROM
CONFLUENCE IN WESTERLY UPPER LEVEL FLOW AND IS LIMITING DEEP
CONVECTION ACROSS THE BASIN.

ATLANTIC OCEAN...
A DEEP LAYERED TROUGH REMAINS OVER THE CENTRAL ATLC WITH AN
ELONGATED UPPER-LEVEL LOW NEAR 29N55W. THIS TROUGH SUPPORTS A
COMPLEX AREA OF LOW PRESSURE WITH A DISSIPATING 1010 MB LOW
CENTERED NEAR 30N51W. A STATIONARY FRONT MEANDERS S-SW TO A
PARTIALLY OCCLUDED 1008 MB SFC LOW LOCATED NEAR 24N52W. THE
ASSOCIATED COLD FRONT EXTENDS SW ALONG 20N51W TO JUST SOUTH OF
BARBADOS IN THE WINDWARD ISLANDS. A ROPE CLOUD DELINEATES THE
LEADING EDGE OF THE FRONT. BUOYS 41040 AND 41101 LOCATED E OF
THE LESSER ANTILLES ARE REPORTING NW WINDS OF AROUND 20 KT
INDICATING THE FRONTAL PASSAGE. IT IS UNUSUAL TO SEE A COLD
FRONT MAKING ITS WAY SO FAR SOUTH INTO THE DEEP TROPICS.
BARBADOS REPORTED SOME SHOWER ACTIVITY AND NLY WINDS OF 15-20
KT.  THE FRONT WILL PUSH SE ACROSS THE REMAINDER OF THE WINDWARD
ISLANDS AND INTO THE FAR SOUTHERN WATERS OF THE TROPICAL N ATLC
THROUGH SUN NIGHT. ACROSS THE W ATLC...A RELATIVELY COOLER AND
DRIER AIRMASS REMAINS IN PLACE THANKS TO THE AFOREMENTIONED 1030
MB SFC HIGH CENTERED NEAR 30N71W. BROKEN COLD AIR STRATOCUMULUS
CLOUDS ARE NOTED ACROSS THE W ATLC INTO THE BAHAMAS AND CUBA
UNDER A PREVAILING NE-E FLOW. FARTHER TO THE EAST...AN UPPER-
LEVEL LOW CONTINUES TO SPIN OVER THE E ATLC JUST WEST OF THE
CANARY ISLANDS. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS
UPPER LOW IS SUPPORTING AN AREA OF SCATTERED SHOWERS BETWEEN THE
CANARY AND THE MADEIRA ISLANDS. AT THE SURFACE...A RIDGE
ANCHORED ON A 1030 MB HIGH OVER THE AZORES DOMINATES THE E ATLC.
A BROAD UPPER-LEVEL RIDGE COVERS MUCH OF THE DEEP TROPICS AND IS
HELPING TO INDUCE CONVECTION ALONG THE ITCZ AXIS.

$$
GR





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