[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 212336
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON JAN 21 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N9W 4N25W 2N40W EQUATOR 50W.
SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 150 NM N OF
THE AXIS BETWEEN 24W-29W AND WITHIN 120 NM S OF THE AXIS BETWEEN
30W-34W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM EITHER
SIDE OF THE AXIS W OF 45W.

...DISCUSSION...

GULF OF MEXICO...
A LOW-LEVEL TROUGH HAS DEVELOPED IN THE MIDDLE GULF ANALYZED
ALONG 88W/89W S OF 27N AT 21Z. VISIBLE IMAGERY SHOWS LOW-LEVEL
TURNING IN THE CLOUD ELEMENTS AND BUOY 42001 INDICATES WINDS
BACKING TO THE N JUST W OF THE BOUNDARY. A FAIRLY DENSE LOW TO
MID LEVEL CLOUD DECK AND EMBEDDED SCATTERED SHOWERS ARE WITHIN
180 NM E AND 60 NM W OF THE TROUGH AXIS. A LONG-TERM SAT LOOP
SHOWS THIS TROUGH BREAKING OFF FROM THE TAIL END OF A STALLED
FRONT IN THE FLA STRAITS AND TRACKING W WITH THE LOW-LEVEL FLOW.
SPEAKING OF THE LOW-LEVEL FLOW...IT REMAINS STRONG THIS EVENING
E OF 90W ESPECIALLY IN THE FL STRAITS WHERE 30 KT REPORTS HAVE
BEEN COMMON. DENSE MULTILAYER CLOUD COVER...SCATTERED SHOWERS
AND ISOLATED TSTMS ARE S OF 24N E OF 87W. SLIGHTLY LESS DENSE
CLOUDS AND ISOLATED ACTIVITY IS BETWEEN 93W-97W ASSOCIATED WITH
LOW-LEVEL RETURN FLOW ON THE SW PERIPHERY OF A VERY HEALTHY 1044
MB HIGH OVER SE VIRGINIA.

ALOFT...A SHORTWAVE IS PROGRESSING THROUGH THE CENTRAL
GULF WITH THE FLOW BECOMING MORE ZONAL W OF IT. MODEST
SUBSIDENCE LIES ABOVE THE MAJORITY OF THE REGION KEEPING MUCH OF
THE SHOWER ACTIVITY MENTIONED FAIRLY SHALLOW. HOWEVER...THE
UPPER LEVELS WILL LIKELY MOISTEN SOON IN THE W GULF AS A PLUME
OF PACIFIC MOISTURE MOVES TOWARD THE REGION.

CARIBBEAN...
THE BASE OF THE NEWLY FORMED LOW-LEVEL TROUGH IN THE GULF OF
MEXICO HANGS S INTO THE NW CARIB FROM THE YUCATAN PENINSULA TO
HONDURAS ALONG 21N87W 16N86W. SFC WEATHER STATIONS IN ISLAS DE
LA BAHIA IN THE GULF OF HONDURAS ARE REPORTING WLY WINDS
...SUGGESTIVE OF THE TROUGH AXIS EXTENDING VERY NEAR THE
ISLANDS. LIGHTNING DATA INDICATES SCATTERED TSTM ACTIVITY N OF
20N BETWEEN 82W-86W LIKELY INFLUENCE BY THIS TROUGH AND ENHANCED
FURTHER BY UPPER DIFFLUENCE TO THE E OF A SHORTWAVE ALONG 88W.
ELSEWHERE W OF 72W IS EXPERIENCING A VERY NICE EVENING BROUGHT
ABOUT BY ABUNDANT SUBSIDENCE UNDER WEAK UPPER RIDGING.

SCATTERED SHOWERS AND ISOLATED TSTMS ARE AFFECTING THE E CARIB
CURRENTLY NW OF A LINE FROM THE SRN WINDWARD ISLANDS TO S HAITI
ALONG 13N61W 18N72W. THIS MOISTURE SWATH IS ASSOCIATED WITH THE
TAIL END OF A WEAKENING FRONTAL TROUGH AND POSSIBLY SOME WEAK
MID-LEVEL INSTABILITY AS NOTED IN WATER VAPOR IMAGES. DRIER AIR
APPEARS TO BE APPROACHING AS INDICATED IN THE MIMIC TPW
ANIMATION REVEALING THE E EDGE OF THE MOISTURE FETCH OVER THE
LESSER ANTILLES.

ATLANTIC OCEAN...
THE W ATLC IS DOMINATED BY SWLY FLOW ALOFT WHICH IS PROVIDING
LIMITED SUPPORT FOR THE COLD FRONT EXTENDING FROM 32N52W TO
26N67W THEN STATIONARY THROUGH THE FLA STRAITS. DENSE MULTILAYER
CLOUDS AND EMBEDDED SCATTERED SHOWERS ARE WITHIN 240 NM BEHIND
THE FRONT. STRONG HIGH PRES HAS BUILT N OF THE AREA...ANALYZED
1044 MB OVER SE VIRGINIA. TIGHT PRES GRADIENT BETWEEN THE FRONT
AND THE HIGH IS PRODUCING STIFF NE WINDS PRODUCING HAZARDOUS
MARINE CONDITIONS.

DEEP LAYER RIDGE/TROUGH PATTERN LIES OVER THE CENTRAL AND
EASTERN ATLC WATERS. COMBINATION OF ABUNDANT SUBSIDENCE
ASSOCIATED WITH THE UPPER HIGH SITUATED NEAR 24N49W AND 1028 MB
SFC HIGH NEAR 29N46W IS PROVIDING TRANQUIL WEATHER AND LIGHT TO
MODERATE WINDS ACROSS THE MAJORITY OF THE CENTRAL ATLC. THE MAIN
FEATURE IN THE E ATLC IS A DEEP LAYER OCCLUDED CUT OFF LOW
ANALYZED 1009 MB AT THE SFC NEAR 32N30W. A WEAKENING COLD FRONT
EXTENDS FROM 32N24W SWD THROUGH 20N26W THEN CURVES SW TO 11N40W
AND CONTINUES FARTHER W AS A SFC TROUGH ACROSS THE LESSER
ANTILLES. SCATTERED SHOWERS AND TSTMS ARE LIKELY E OF THE
LOW...IN AN UPPER DIFFLUENT ZONE...N OF 25N BETWEEN 18W-27W AND
WITHIN 240 NM S SEMICIRCLE OF THE LOW. AN UPPER JET STREAK WELL
SE OF THE LOW IS ADVECTING MID-HIGH LEVEL CLOUDS ACROSS THE CAPE
VERDE ISLANDS AND IS FUELING CONVECTION IN THE ITCZ.

$$
CANGIALOSI


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