[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171755
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU JAN 17 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 6N10W 3N24W 1S36N 2N47W EQ50W.
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF AXIS BETWEEN
18W-24W. SIMILAR CONVECTION IS 70 NM S OF AXIS BETWEEN 15W-25W.
CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE FROM
2S-6N WEST OF 40W. PART OF THIS CONVECTIVE ACTIVITY IS
ASSOCIATED WITH A SFC TROUGH ALONG 48W S OF 8N WHICH IS
PRODUCING A NWD MODULATION OF THE ITCZ.

...DISCUSSION...

GULF OF MEXICO...
THE GALE CENTER THAT WAS AFFECTING THE GULF OF MEXICO YESTERDAY
HAS WEAKENED...BUT IS FORECAST TO RE-GAIN GALE FORCE WINDS WHEN
IT RE-EMERGES ALONG THE CAROLINA COAST LATER TODAY. AS OF 15Z...
A 1011 MB LOW WAS ANALYZED OVER THE FLORIDA PANHANDLE NEAR
APALACHICOLA WITH THE ATTENDANT COLD FRONT EXTENDING SW ACROSS
THE BAY OF CAMPECHE INTO SOUTH-CENTRAL MEXICO WHERE IT BECOMES
STATIONARY. SATELLITE AND RADAR IMAGERY REVEALS A WELL-DEFINED
AREA OF STRONG SHOWERS AND TSTMS BETWEEN THE FRONT AND THE SW
COAST OF FLORIDA/LOWER KEYS. CIRRUS DEBRIS CLOUD FROM THIS
CONVECTION IS STREAMING ACROSS SOUTH FLORIDA. BROKEN TO OVERCAST
COLD AIR STRATOCUMULUS CLOUDS ARE FOUND BEHIND THE FRONT MAINLY
N OF 25N. SMALL AREA OF SHOWERS AND ISOLATED TSTMS HAS DEVELOPED
OVER THE BAY OF CAMPECHE NEAR 20N95W. LOW CLOUDS ARE BANKING UP
AGAINST THE EASTERN SLOPES OF THE SIERRA MADRE MOUNTAINS
PARTICULARLY N OF MINATITLAN AND COATZACOALCOS IN MEXICO. THE
COLD FRONT IS FORECAST TO STALL ACROSS THE GULF TONIGHT WITH A
NEW LOW PRES DEVELOPING ALONG THE FRONT NEAR 26N95W FRI. THE LOW
WILL MOVE NE FRI NIGHT AND INLAND W FLORIDA SAT WHILE DRAGGING A
SECOND STRONG COLD FRONT ACROSS THE AREA FRI NIGHT AND SAT.
STRONG NLY WINDS...PROBABLY REACHING GALE FORCE AND BUILDING
SEAS WILL FOLLOW THE FRONT. A POSITIVE-TILTED LONG-WAVE TROUGH
CURRENTLY OVER THE MAJORITY OF WESTERN U.S. WILL HELP IN THE
FORMATION OF THE NEW LOW CENTER/FRONT. WINDS AHEAD OF THE FRONT
ARE IN THE 20-25 KT RANGE IN RESPONSE TO THE TIGHT PRESSURE
GRADIENT BETWEEN HIGH PRESSURE CENTERED OVER THE NE U.S. AND THE
LOW OVER THE FLORIDA PANHANDLE.

CARIBBEAN SEA...
NO MAJOR CHANGE HAS EXPERIENCED THE WEATHER PATTERN ACROSS THE
CARIBBEAN SEA DURING THE PAST FEW DAYS. A MID-LEVEL RIDGE...
ANCHORED ON A HIGH JUST NE OF DOMINICAN REPUBLIC EXTENDS ACROSS
THE GREATER ANTILLES AND THE CARIBBEAN SEA TO THE YUCATAN
PENINSULA SUPPRESSING THE DEVELOPMENT OF DEEP CONVECTION.
HOWEVER...THERE ARE SOME POCKETS OF LOW-LEVEL CLOUDS WITH
EMBEDDED SHOWERS MOVING WWD ACROSS THE AREA UNDER THE INFLUENCE
OF A PREVAILING ELY FLOW. THESE WINDS ARE ALSO HELPING TO INDUCE
THE FORMATION OF STREAMERS OR CLOUD LINES ACROSS THE EASTERN
CARIBBEAN DOWNSTREAM OF THE LESSER ANTILLES. THE SAN JUAN
DOPPLER RADAR SHOWS ISOLATED TO SCATTERED SHOWERS CROSSING FROM
THE N LEEWARD ISLANDS TO THE UK/US VIRGIN ISLANDS AND PUERTO
RICO. FRAGMENTS OF LOW LEVEL MOISTURE ARE ALSO SEEN OVER THE
CENTRAL CARIBBEAN...LIKELY RELATED TO THE SHEAR OF THE LOW-LEVEL
WIND/SPEED CONVERGENCE.  THE SPEED CONVERGENCE OVER THIS REGION
IS A RESULT OF STRONG TRADE WINDS OVER THE CENTRAL CARIBBEAN SEA
TO THE COLOMBIA COAST...WITH WEAKER TRADES TO THE WEST. LOOKING
AHEAD...A STRONG COLD FRONT WILL MOVE INTO THE NW CARIBBEAN SAT
NIGHT ACCOMPANIED BY STRONG N WINDS AND BUILDING SEAS.

ATLANTIC OCEAN...
A COLD FRONT ENTERS THE AREA NEAR 31N45W THEN CONTINUES SW TO
NEAR 24N68W. AT THIS POINT...A DYING FRONT CONTINUES WWD TO NEAR
THE NW BAHAMAS. A BROKEN BAND OF MAINLY LOW CLOUDS AND POSSIBLE
SHOWERS ARE ASSOCIATED WITH THE FRONT...MAINLY E OF THE 60W. A
PRE-FRONTAL TROUGH RUNS FROM 25N56N TO THE N COASTAL WATERS OF
PUERTO RICO. LITTLE SHOWER ACTIVITY IS RELATED TO TROUGH.
FARTHER NORTH...A 1033 MB SURFACE HIGH CENTERED JUST WEST OF THE
MADEIRA ISLANDS CONTINUES TO DOMINATE MUCH OF THE ERN ATLC.
MODERATE TO STRONG EASTERLY TRADES SOUTH OF THIS FEATURE
CONTINUE TO PRODUCE A REGION OF FAIRLY DENSE STRATOCUMULUS
CLOUDS GENERALLY N OF 20N AND EAST OF 40W. FINALLY...AT UPPER
LEVELS...A RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE DISCUSSION
AREA. WITHIN THE BROAD LONGWAVE TROUGH ALONG 35W...A CUT-OFF
LOW IS LOCATED IN THE CENTRAL ATLC NEAR 27N33W WITH A TROUGH
EXTENDING SW TO ANOTHER WEAK UPPER-LEVEL LOW WHICH IS CENTERED
NEAR 15N49W. A STRONG 70- TO 90-KT JET DIGGING INTO THE BASE OF
THE TROUGH IS PRODUCING A WIDE BAND OF TRANSVERSE HIGH CLOUDS
ACROSS THE TROPICAL ATLC FROM NORTHERN SOUTH AMERICA TO THE NW
COAST OF AFRICA.

$$
GR


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