[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171732
TWDAT

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

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 2N AT THE PRIME MERIDIAN 5N18W 3N30W
2N40W EQ50W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM
EITHER SIDE OF THE AXIS BETWEEN 32W-44W.

...DISCUSSION...
GULF OF MEXICO...
A COLD FRONT CONTINUES TO SLOWLY SEEP S AND AS OF 15 UTC WAS
ANALYZED FROM NEAR MARCO ISLAND FL TO 25N84W THEN STATIONARY TO
25N93W CURVING SHARPLY S TO MEXICO NEAR 19N92W. SFC OBS AND A
QSCAT PASS THIS MORNING HELPED LOCATE THIS BOUNDARY. THESE OBS
ALSO SHOW GALE FORCE WINDS OCCURRING W OF THE FRONT S OF
25N...AS A STRONG GRAD PERSISTS BETWEEN THE FRONT AND A 1035 MB
HIGH IN NE MEXICO. ELSEWHERE BEHIND THE FRONT...WINDS ARE ON THE
STRONG SIDE...GENERALLY NELY BETWEEN 20-30 KT. DENSE LOW/MID
LEVEL CLOUDINESS AND ISOLATED SHOWERS LINGER BEHIND THE FRONT W
OF 89W. THIS INCLUDES MEXICO WHERE THINNING LOW CLOUDS ARE
BANKED ACROSS THE SLOPES OF THE SIERRA MADRE. MORE ORGANIZED
PRECIP EXISTS FURTHER N ACROSS TEXAS AND LOUISIANA ASSOCIATED
WITH A LARGE MOISTURE PLUME ADVECTED BY THE UPPER LEVEL
SUBTROPICAL JET FROM THE EPAC. THIS PRECIP IS IN THE FROZEN FORM
WITH FREEZING RAIN AND/OR LIGHT SNOW BEING REPORTED AT SEVERAL
STATIONS ...WHICH IS BY NO MEANS A COMMON OCCURRENCE FOR THAT
PART OF THE COUNTRY. S OF THE FRONT...CONDITIONS ARE WARM AND
HUMID WITH LIGHTER WINDS AND ONLY SCATTERED LOW TO MID LEVEL
CLOUDS. OVER THE NEXT DAY OR TWO...NWP MODELS SHOW THE FRONT
BECOMING DIFFUSE...NEARLY STATIONARY OR LIFTING N IN THE GULF AS
THE UPPER SUPPORT/DYNAMICS CONTINUE TO PULL AWAY.

CARIBBEAN SEA...
TRADE WINDS IN THE S CARIBBEAN REMAIN STRONG BUT HAVE DROPPED
JUST BELOW GALE FORCE AS CONFIRMED BY A 1042 UTC QSCAT PASS
WHICH INDICATED E/NELY TRADES MAINLY IN THE 25-30 KT RANGE N OF
COLOMBIA. THESE WINDS ARE EXPECTED TO REMAIN SIMILAR OVER THE
NEXT COUPLE DAYS. OTHERWISE...VERY DRY AIR IN THE MID AND UPPER
LEVELS COVERS THE ENTIRE REGION GENERATED BY STRONG CONFLUENCE
ALOFT BETWEEN RIDGING TO THE N/NW...TROUGHING TO THE SW AND NE
AND S-SWLY FLOW ACROSS THE SE CARIB. THE DRIEST AIR IS FROM
15N-20N BETWEEN 72W-85W. BENEATH THE STRONG MID-LEVEL
CAP...PATCHES OF LOW LEVEL CLOUDS AND EMBEDDED ISOLATED SHOWERS
ARE SCATTERED ACROSS THE SEA. OVERALL...NUMERICAL MODELS SHOW
LITTLE CHANGE IN MOISTURE ACROSS THE CARIB OVER THE NEXT DAY OR
SO AS DRY AIR ALOFT CONTINUES TO SUPPRESS CONVECTIVE ACTIVITY.

ATLANTIC OCEAN...
THE VERY BROAD MID TO UPPER LEVEL RIDGE IN THE W AND CENTRAL
ATLC IS BEING SUPPRESSED S AS A DEEP LAYER TROUGH SLIDES E N OF
IT. THE ASSOCIATED COLD FRONT CONTINUES TO MOVE AND AS OF 15 UTC
WAS ANALYZED FROM JUST E OF BERMUDA TO S FLORIDA ALONG 32N65W
28N76W 26N80W. BEHIND THE FRONT...NLY WINDS ARE INCREASING TO 25
KT OR SO DUE TO THE TIGHTENED PRES GRAD SET UP BETWEEN THE FRONT
AND A STRONG SFC RIDGE CENTERED IN THE OHIO VALLEY. SHOWER
ACTIVITY IS LIMITED NEAR THE FRONT BUT DENSE LOW AND MID LEVEL
CLOUDS AND ISOLATED SHOWERS EXIST BEHIND IT. A CUT OFF UPPER
LEVEL LOW...ALSO WEAKENING THE MID-LEVEL RIDGE...IS CENTERED
NEAR 26N53W. THIS UPPER LEVEL SYSTEM DOES HAVE A CLEAR SFC
BOUNDARY ASSOCIATED WITH IT...WHICH IS ANALYZED ALONG 14N58W
24N50W. IR IMAGES SUGGEST AREAS OF SCATTERED SHOWERS ALONG AND
TO THE E OF THE TROUGH BETWEEN 45W-52W FROM 21N-25N. DEBRIS
MOISTURE IS THEN CARRIED SE AND AROUND THE BASE OF A SHARP UPPER
LEVEL TROUGH EXTENDING FROM SPAIN TO 21N33W. THIS TROUGH DOES
NOT APPEAR TO HAVE A SFC REFLECTION YET...BUT A KINK IN THE
ISOBARIC PATTERN HAS DEVELOPED SO IT MAY BE FORMING. GFS SHOWS
THIS TROUGH CUTTING OFF TONIGHT OR TOMORROW WHICH LOOKS
REALISTIC BASED UPON ITS STEEPNESS. IN THE TROPICAL
ATLC...EXTENSIVE WLY UPPER LEVEL FLOW ON THE N SIDE OF A VERY
BROAD RIDGE IS THE RULE. THIS FLOW IS SPREADING SOME MID AND
HIGH LEVEL CLOUDINESS...WITH POSSIBLE ISOLATED SHOWERS ...ACROSS
THE OCEAN FROM 13N-17N. ELSEWHERE AT THE SFC...A 1028 MB HIGH
DOMINATES THE CENTRAL AND ERN ATLC...INTERRUPTED BY THE SFC
TROUGH MENTIONED.

$$
CANGIALOSI




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