[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231109
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST FRI FEB 23 2007

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... METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N11W 4N20W EQ29W 2S37W 3S43W.
WIDELY SCATTERED MODERATE CONVECTION IS FROM 1N-4N E OF
15W...FROM 3N-5N BETWEEN 30W-43W AND S OF 1N W OF 36W SPREADING
ACROSS PORTIONS OF FAR NE BRAZIL...FRENCH GUIANA...AND SURINAME.
ISOLATED MODERATE IS WITHIN 90 NM EITHER SIDE OF AXIS BETWEEN
17W-26W.

...DISCUSSION...

GULF OF MEXICO...

FAIR WEATHER EXISTS UNDER STRONG SFC HIGH PRES ANCHORED WELL N
IN CENTRAL CANADA. A 1022 MB HIGH EMBEDDED IN THE RIDGE HAS BEEN
NEARLY STATIONARY OVER THE PAST 24-36 HOURS NEAR 28N89W. A WEAK
COLD FRONT CUTS THRU THE RIDGE EXTENDING FROM CENTRAL FL ACROSS
THE NE GULF WATERS TO THE MS/LA BORDER. THE FRONT IS DIFFICULT
TO TRACK ON SATELLITE IMAGERY AS THERE IS LITTLE OR NO
CLOUDS/MOISTURE ASSOCIATED WITH IT. SLIGHTLY LOWER PRESSURES...A
DEWPT GRAD AND A SLIGHT WIND SHIFT DEFINE THE BOUNDARY.
ELSEWHERE A WEAK SURFACE TROUGH OVER BAY OF CAMPECHE IS CAUSING
PATCHY LOW/MID-LEVEL CLOUDS S OF 26N BETWEEN 88W-96W. IN THE MID
AND UPPER LEVELS...RIDGING IS ALSO THE THEME EXTENDING N FROM
CENTRAL AMERICA WITH A SUBTROPICAL JET BRANCH RIDING ALONG THE
NRN PERIPHERY ADVECTING A CONSIDERABLE AMOUNT OF UPPER MOISTURE
ACROSS NRN MEXICO AND INTO THE N GULF...CURRENTLY CONFINED N OF
27N W OF 88W. THE TAIL END OF UPPER TROUGHING LIES OFF THE U.S.
EAST COAST PROVIDING THE UPPER SUPPORT FOR THE AFOREMENTIONED
COLD FRONT. THE REMAINDER OF THE AREA IS UNDER A SUBSIDENT
ENVIRONMENT WITH LITTLE CLOUD COVER.

THE WEAK COLD FRONT IS EXPECTED TO BECOME NEARLY STATIONARY AND
DIFFUSE FROM SOUTH FLORIDA TO NEW ORLEANS THIS AFTERNOON. A
SECOND STRONGER COLD FRONT WILL MOVE OFF THE TEXAS COAST LATE
SAT PRECEDED BY MOIST S-SWLY WINDS ENHANCING SCATTERED
SHOWERS/TSTMS N OF 27N ALONG THE GULF COAST.

CARIBBEAN...

OVER THE PAST SEVERAL HOURS SATELLITE IMAGERY AND SFC OBS
SUGGESTS THAT A WEAK SFC LOW...ANALYZED AT 1013 MB...HAS
DEVELOPED NEAR THE NRN COAST OF HISPANIOLA. THIS FEATURE IS NOT
A BIG WEATHER FEATURE ONLY PRODUCING AN AREA OF LOW TO MID LEVEL
CLOUDS AND SOME PSBL SHOWER ACTIVITY FROM 18N-21N BETWEEN
71W-74W. ELSEWHERE THERE ARE ONLY A FEW SMALL PATCHES OF LOW TO
MID-LEVEL MOISTURE STIRRED UP AND DRIVEN BY MODERATE TO FRESH
TRADES...EXCEPT STRONGER OFF THE COAST OF COLOMBIA. THE
LARGE-SCALE ENVIRONMENT IS DOMINATED BY A STRETCHED E/W
MID-LEVEL RIDGE ALIGNED ALONG 15N PROVIDING AN ABUNDANCE OF
MODERATE/STRONG SUBSIDENCE ACROSS THE ENTIRE AREA...SUPPRESSING
THE LOW LEVEL CLOUDS FROM BECOMING DEEP IN NATURE. THE MOST
STABLE CONDITIONS LIE FROM WRN COLOMBIA TO EL SALVADOR WHERE WV
ENHANCEMENTS ARE SHOWING UP IN THE DRIEST RANGE. THIS IS DUE TO
UPPER LEVEL CONFLUENCE BETWEEN THE RIDGE AND A 500 MB LOW
CENTERED OVER VENEZUELA NEAR 7N66W.

HIGH PRES...CURRENTLY CENTERED ACROSS THE OHIO VALLEY...WILL
BUILD SE N OF THE REGION THIS WEEKEND INCREASINGLY THE TRADES A
NOTCH. OTHERWISE NO BIG WEATHER CHANGES ARE EXPECTED.

WEST ATLANTIC...

GENTLE TROUGHING LIES ACROSS THE MAJORITY OF THE REGION ON THE S
SIDE OF A LARGE POLAR VORTEX. TWO SHORTWAVE TROUGHS ARE EMBEDDED
AND ROTATING IN THE BROAD CYCLONIC FLOW. ONE OF THESE BARELY
CLIPS THE AREA WITH ITS BASE NEAR 31N75W PROVIDING SUPPORT FOR
THE WEAK COLD FRONT MENTIONED IN THE GULF SECTION. THE OTHER IS
BETTER DEFINED STRETCHING FROM 32N50W TO NEAR 25N63W. BEHIND
THIS QUICK MOVING AXIS...SUBSIDENCE IS ENHANCED AND WIDESPREAD
PROVIDING STABLE CONDITIONS ALOFT. A RELATED ILL-DEFINED SFC
TROUGH RUNS FROM 28N63W ACROSS THE CENTRAL BAHAMAS. THIS
BOUNDARY IS NOT PRODUCING MUCH WEATHER ONLY DEFINED BY A BROKEN
LINE OF LOW-MID LEVEL CLOUDS AND A SLIGHT WIND SHIFT AS DEPICTED
WELL BY AN EARLIER QSCAT PASS.

AS THE LARGE TROUGH SLIDES NE AND STRENGTHENS...A TRAILING COLD
FRONT WILL STRETCH INTO THE REGION AND PUSH E WITH IT. THE FRONT
WILL EXTEND FROM 32N50W TO THE SE BAHAMAS TOMORROW AT THIS TIME
AND THEN CONTINUE TO MOVE E AND GRADUALLY WEAKEN ON SUN. HIGH
PRES WILL BUILD SE BEHIND THE FRONT.

EAST ATLANTIC...

SFC HIGH PRES IS THE RULE ANCHORED BY A 1026 MB ABOUT 200 NM NW
OF THE CANARY ISLANDS. THIS HIGH IS GENERATING MODERATE TO
STRONG TRADES ACROSS A GOOD PORTION OF THE AREA. ALOFT...THE
FLOW HAS FLATTENED AND IS NOW BASICALLY ZONAL ACROSS MOST OF THE
SUBTROPICAL AREAS PROVIDING TRANQUIL WX CONDITIONS. IN THE
TROPICS...THE PATTERN IS A LITTLE MORE COMPLEX WITH AN EXTENSIVE
BROAD FLAT RIDGE STRETCHED ACROSS THE EQUATORIAL ATLC. A CUT OFF
UPPER LOW IS LOCATED NEAR THE CAPE VERDE ISLANDS AND IS ERODING
THE N SIDE OF THE RIDGE ADVECTING SOME PATCHY HIGH CLOUDS FROM
14N-22N BETWEEN 22W-28W.

NWP MODELS SHOW LITTLE CHANGE AT THE SFC BUT AN AMPLIFICATION IN
THE UPPER PATTERN THIS WEEKEND AS A LARGE RIDGE DEVELOPS
OVERHEAD IN RESPONSE TO A DEEPENING TROUGH IN THE NW ATLC.

$$
CANGIALOSI




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