[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 191754
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN APR 19 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1730 UTC.

...ITCZ...
THE ITCZ IS CENTERED CROSSES TO SOUTH OF THE EQUATOR NEAR 00N00W
TO 04S10W TO 04S25W TO NE BRAZIL NEAR 00.5N50W. SCATTERED
MODERATE CONVECTION IS CENTERED ON THE EQUATOR WEST OF 40W IN A
90 NM WIDE BAND. OTHERWISE CONVECTION ASSOCIATED WITH THE ITCZ
IS SOUTH OF THE EQUATOR.

...DISCUSSION...

GULF OF MEXICO...
MOIST SOUTHWEST TO WEST FLOW ALOFT IS OBSERVED OVER THE GULF
REGION AS A DEEP LAYER TROUGH PROGRESSES ACROSS THE CENTRAL
CONUS. THE RETURN FLOW AROUND A 1022 MB SURFACE HIGH CENTERED
OVER THE W ATLC NEAR 31N72W IS RESULTING IN SE WINDS OF 15 TO 20
KT ACROSS THE GULF REGION MOSTLY EAST OF 90W AS THE PRESSURE
GRADIENT IS WEAKER OVER THE WESTERN GULF IN ADVANCE OF A COLD
FRONT OVER EAST TEXAS. THESE WINDS ARE ADVECTING ABUNDANT
LOW-LEVEL MOISTURE ACROSS THE GULF REGION...RESULTING IN
INCREASED INSTABILITY ACROSS MUCH OF THE NRN GULF. THIS
INSTABILITY AND A BROAD SURFACE TROUGH OVER THE WESTERN GULF IS
COMBINING WITH MIDDLE TO UPPER LEVEL ATMOSPHERIC DIFFLUENCE
ACROSS THE NW AND N/CENTRAL GULF TO SUPPORT SCATTERED SHOWERS
AND TSTMS N OF 26N EAST OF 92W TO ABOUT 85W. ACROSS THE SE GULF
...STABLE ATMOSPHERIC CONDITIONS ARE RESULTING IN GENERALLY FAIR
WEATHER CONDITIONS. THE SURFACE COLD FRONT ASSOCIATED WITH THE
CENTRAL CONUS DEEP LAYER TROUGH IS FORECAST TO MOVE OFF THE
TEXAS COAST THIS AFTERNOON...AND EXTEND FROM THE FLORIDA
BIG BEND TO THE BAY OF CAMPECHE BY MONDAY. INCREASED NLY WINDS
AND RELATIVELY COOLER AND DRIER CONDITIONS ARE FORECAST WITH THE
PASSAGE OF THIS FRONT.

CARIBBEAN SEA...
A SURFACE RIDGE LOCATED OVER THE W ATLC IS FORECAST TO MAINTAIN
FRESH NE TO E TRADE WINDS ACROSS THE CARIBBEAN SEA THROUGH
WEDNESDAY. GENERALLY FAIR WEATHER IS PRESENT ACROSS THE
CARIBBEAN...WHERE DEEP LAYER DRY AIR AND SUBSIDENCE IS RESULTING
FROM CONFLUENT WESTERLY FLOW ALOFT. HOWEVER...LOW LEVEL
CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 90 NM EITHER
SIDE OF A WEAKENING SURFACE COLD FRONT IN THE MONA PASSAGE.
A COUPLE OF SMALL AREAS OF SHOWERS IS NEAR 80W NORTH OF 15N
MOVING WEST ABOUT 10 KNOTS. SCATTERED SHOWERS HAVE DEVELOPED IN
THE LESSER ANTILLES FROM SAINT LUCIA TO ANTIGUA. THESE SHOWERS
ARE MOVING NORTHEAST 10 TO 15 KNOTS AND ARE PART OF AN AREA THAT
EXTENDS ABOUT 300 NM NORTHEAST OF THESE ISLANDS.

ATLANTIC OCEAN...
A FRONTAL SYSTEM IS LOCATED IN THE REGION WITH A WARM FRONT
THROUGH 32N52W TO A WEAKENING 1017 MB LOW NEAR 27N57W AND A COLD
FRONT FROM THE LOW TO NORTHWEST PUERTO RICO. SUBSIDENCE IN UPPER
NW FLOW ALOFT ACROSS THE W ATLC WEST OF THE COLD FRONT IS
ASSOCIATED WITH A LARGE SCALE TROUGH OVER THIS AREA AND AN
UPSTREAM RIDGE LOCATED OVER FLORIDA. AT THE SURFACE A 1022 MB
HIGH IS CENTERED NEAR 31N72W AND IS MOVING EAST 15 TO 20 KT.
GENERALLY FAIR WEATHER CONDITIONS ARE PRESENT WEST OF THE FRONT
EXCEPT FOR SOME SHOWERS IN THE NORTHEAST FLOW THAT EXTENDS ABOUT
300 NM NW OF THE COLD FRONT. SCATTERED SHOWERS AND THUNDERSTORMS
ARE ALONG THE FRONT MOSTLY EAST OF 80W. THE AREA OF CONVECTION
BROADENS FROM A NARROW BAND ALONG THE FRONT SOUTH OF 25N TO A
360 NM WIDE REGION NEAR 30N. ACROSS THE E ATLC...SUBSIDENCE
ASSOCIATED WITH A SURFACE RIDGE IS RESULTING IN GENERALLY FAIR
WEATHER CONDITIONS. THIS SURFACE RIDGE IS ANCHORED BY A 1029 MB
SURFACE HIGH NEAR 33N27W. ACROSS THE TROPICAL ATLC...AN UPPER
LEVEL RIDGE IS S OF 15N E OF 60W WITH THE UPPER LEVEL HIGH
CENTERED NEAR 4N49W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THIS
FEATURE IS ENHANCING CONVECTION ALONG THE ITCZ.

$$
LL



This weather bulletin was brought to you by:
www.nashvilleweather.net