[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 291126
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST THU JAN 29 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N9W 2N16W EQ30W 1N45W EQ51W.
SCATTERED MODERATE CONVECTION IS WITHIN 45 NM OF THE AXIS
BETWEEN 14W-26W. ISOLATED MODERATE CONVECTION IS WITHIN 180 NM N
AND 60 NM S OF THE AXIS W OF 34W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYER TROUGH OVER MUCH OF THE E CONUS IS SUPPORTING A
COLD FRONT EXTENDING FROM THE FLORIDA BIG BEND NEAR 30N84W TO
24N92W THEN SURGING S THROUGH THE BAY OF CAMPECHE TO S MEXICO
NEAR 18N95W. IN THE WAKE OF THE FRONT...A COOLER AIRMASS IS IN
PLACE ADVECTED BY N-NE 15-20 KT WINDS...STRONGEST NEAR THE
MEXICAN COAST ENHANCED BY THE LOCAL TOPOGRAPHY. LOW LEVEL
CONVERGENCE IS SUPPORTING SCATTERED SHOWERS AND ISOLATED TSTMS
WITHIN 90 NM EITHER SIDE OF THIS FRONT. SOME OF THE ACTIVITY IS
BEING ENHANCED BY UPPER DIVERGENCE ASSOCIATED WITH A JET MAX
OVER THE SE CONUS. AHEAD OF THE FRONT...DRY AIR AND ATMOSPHERIC
STABILITY IS INHIBITING DEEP CONVECTION. THE AFOREMENTIONED
FRONT IS TEMPORARILY SLOWING ITS SE PROGRESSION...BUT IS
FORECAST TO SURGE SWD ON FRI AS AN UPPER TROUGH OVER THE W CONUS
SHIFTS E AND A SFC HIGH BUILDS OVER THE SE CONUS...LEADING TO
GALE CONDITIONS OVER THE SW GULF.

CARIBBEAN SEA...
TIGHT PRESSURE GRADIENT...BETWEEN STRONG HIGH PRES OVER THE
CENTRAL ATLC AND LOWER PRES OVER SOUTH AMERICA...IS MAINTAINING
MODERATE TO FRESH TRADES ACROSS THE REGION. THESE WINDS ARE
FORECAST TO DECREASE ON FRI AS THE HIGH MOVES NE AND A COLD
FRONT TRACKS INTO THE NW CARIBBEAN. NE 20-25 KT WINDS AND
RELATIVELY COOLER AND DRIER AIR ARE EXPECTED TO BUILD BEHIND THE
FRONT BEGINNING FRI NIGHT. IN THE MEANTIME...GENERALLY FAIR
CONDITIONS PERSIST WITH DEEP LAYER DRY AIR IN PLACE.
HOWEVER...TYPICAL ISOLATED SHOWERS ARE BEING CARRIED BY THE
TRADE WINDS ACROSS THE E CARIBBEAN...WHERE SOME UPPER LEVEL
MOISTURE IS BEING ADVECTED BY SW FLOW ALOFT.

ATLANTIC OCEAN...
TRANQUIL WEATHER IS THE THEME ACROSS MUCH OF THE DISCUSSION ZONE
AS A SFC HIGH PRES RIDGE ALONG 32N/33N DOMINATES THE REGION. THE
ASSOCIATED PRESSURE GRADIENT ON ITS SRN PERIPHERY IS PRODUCING A
LARGE AREA OF NE/E 20-25 KT TRADES S OF 24N E OF THE BAHAMAS.
HOWEVER...THE RIDGE HAS BEEN WEAKENED OVER THE FAR NW AND NE
PARTS OF THE AREA DUE TO A PAIR OF COLD FRONTS. THE FRONT OVER
THE W ATLC HAS SLOWED IN ITS FORWARD MOTION...CURRENTLY LYING
ALONG THE S GEORGIA/N FLORIDA COAST. STRONG SLY WINDS ARE
BLOWING WITHIN A FEW HUNDRED NM E OF THE BOUNDARY. NUMEROUS
SHOWERS AND TSTMS ARE LOCATED WITHIN 180 NM OF THE FRONT
ENHANCED BY AN UPPER JET. THE OTHER FRONT EXTENDS SWD FROM A
STORM FORCE LOW WELL N OF THE AZORES TO 32N35W. THE ASSOCIATED
UPPER SUPPORT APPEARS TO BE SHARPENING SOME WHICH MAY ALLOW THE
FRONT TO DIG FARTHER S LATER TODAY. OTHERWISE...ABUNDANT DRY
STABLE AIR IS LIMITING THE DEVELOPMENT OF DEEP CONVECTION
...CAPPING THE TYPICAL PATCHES OF LOW CLOUDS AND EMBEDDED
SHOWERS WITHIN THE TRADE WIND FLOW.

$$
CANGIALOSI/COHEN



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