[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 041755
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU 04 NOV 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM
THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON
SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED OVER THE W CARIBBEAN AND CENTRAL AMERICA
ALONG 87W S OF 20N MOVING W 15 KT. THE WAVE IS LOCATED WITHIN
A DIVERGENT MIDDLE TO UPPER LEVEL PATTERN WHICH IS PROVIDE THE
SUPPORT FOR AN AREA OF NUMEROUS MODERATE TO STRONG CONVECTION
FROM 15N-19N BETWEEN 78W-90W. WHILE CURRENTLY SHOWING NO SIGNS
OF ORGANIZATION...THIS ACTIVITY IS SPREADING STEADILY WESTWARD
AND WILL PRODUCE LOCALLY HEAVY RAINFALL OVER CENTRAL AMERICA N
OF NICARAGUA AND THE YUCATAN PENINSULA DURING THE NEXT DAY OR
TWO. CONVECTION IS ALREADY AFFECTING COASTAL REGIONS OF
NICARAGUA...HONDURAS...BELIZE AND THE E YUCATAN. CLOUD TOP
TEMPERATURES ASSOCIATED WITH THIS ACTIVITY ARE QUITE COLD AND AN
EARLIER TRMM SATELLITE PASS INDICATES RAIN RATES OVER 1 INCH OR
25 MM PER HOUR.

...ITCZ...

ITCZ AXIS IS ALONG 12N10W 7N25W 10N45W 11N60W 10N80W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION FROM 4N-11N BETWEEN 17W-30W.
WIDELY SCATTERED MODERATE CONVECTION FROM 10N-14N BETWEEN
50W-70W.

...DISCUSSION...

GULF OF MEXICO...
STRONG MID/UPPER LEVEL CLOSED LOW CONTINUES TO LIFT RAPIDLY NEWD
OVER GREAT LAKES REGION OF THE UNITED STATES WITH ASSOCIATED
TROUGH TRAILING SW OVER TEXAS AND NW MEXICO.  ATTENDANT COLD
FRONT ENTERS THE AREA OVER THE FLORIDA PANHANDLE SWD TO THE BAY
OF CAMPECHE.  GIVEN THAT THE UPPER LOW IS PULLING AWAY FROM THE
AREA...MIDDLE TO UPPER LEVEL DYNAMICS/LIFT ALONG THE FRONT HAS
DECREASED AND DEEP CONVECTION IS MUCH LESS NUMEROUS THAN
YESTERDAY.  ADDITIONALLY...THE EXTREME S EXTENT OF THE FRONT HAS
BECOME NEARLY STATIONARY.  HOWEVER...WATER VAPOR IMAGERY SHOWS
A S STREAM IMPULSE MOVING INTO W MEXICO FROM THE PACIFIC.
THIS DISTURBANCE SHOULD PROVIDE THE IMPETUS FOR THE FRONT TO
PROGRESS EWD ACROSS THE GULF TONIGHT AND TOMORROW CLEARING S
FLORIDA BY FRI AFTERNOON. MIDDLE TO UPPER LEVEL DYNAMICS/LIFT
WILL REMAIN FAIRLY WEAK LIMITING WIDESPREAD CONVECTION ALONG THE
FRONT BUT THERE WILL BE SUFFICIENT LOW LEVEL MOISTURE POOLING TO
PRODUCE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS.  THE
STRONGEST OF THIS ACTIVITY SHOULD BE FOCUSED OVER N FLORIDA NEAR
A STRONG UPPER JET WHICH WILL SKIRT THE AREA AND OVER THE BAY OF
CAMPECHE WHERE DEEP TROPICAL MOISTURE FROM AN APPROACHING
TROPICAL WAVE WILL INTERACT WITH THE FRONT.  STRONG HIGH
PRESSURE CONTINUES TO BUILD SWD BEHIND THE FRONT FROM THE GREAT
BASIN OF THE UNITED STATES OVER N MEXICO AND W GLFMEX.  THE
PRESSURE GRADIENT ASSOCIATED WITH THIS PATTERN IS PRODUCING
MODERATE TO STRONG NLY FLOW BUT WINDS HAVE RELAXED SINCE
YESTERDAY'S GALE EVENT. OVER THE REMAINDER OF THE GULF...STRONG
DEEP LAYERED RIDGE EXTENDS FROM THE BAHAMAS WESTWARD OVER S
FLORIDA TO THE CENTRAL GULF NEAR 23N90W. SUBSIDENCE AND MIDDLE
TO UPPER LEVEL DRY AIR ASSOCIATED WITH THIS PATTERN IS PRODUCING
STABLE CONDITIONS OVER MUCH OF FLORIDA AND THE SE GULF.

CARIBBEAN...
THE W CARIBBEAN REMAINS THE MOST ACTIVE IN TERMS OF DEEP
CONVECTION COURTESY OF A TROPICAL WAVE ALONG 87W. THE WAVE IS
LOCATED WITHIN AN AREA OF MIDDLE TO UPPER LEVEL DIVERGENT FLOW
ASSOCIATED WITH A DEVELOPING ANTICYCLONE OVER THE SW CARIBBEAN.
THIS PATTERN IS PRODUCING A LARGE ARE OF STRONG
SHOWERS/THUNDERSTORMS OVER THE W CARIBBEAN NOW MOVING INTO
CENTRAL AMERICA.  SEE TROPICAL WAVE DISCUSSION ABOVE FOR MORE
DETAILS.  WATER VAPOR IMAGERY SHOWS THAT THE MIDDLE TO UPPER
LEVEL RIDGE IS BUILDING SLOWLY NWD PUSHING THE SHEAR AXIS AND
STABLE AIR PREVIOUSLY DRAPED ACROSS THE AREA INTO CUBA.
ELSEWHERE OVER THE E CARIBBEAN...STRONG MIDDLE TO UPPER LEVEL
RIDGE JUST N OF THE AREA IS PUSHING SWD OVER HISPANIOLA AND
PUERTO RICO ALLOWING A VERY DRY/STABLE AIRMASS TO SPILL SWD FROM
THE ATLC.  THE DRY AIR IS CURRENTLY DELINEATED BY A SHARP TROUGH
EXTENDING OVER THE LESSER ANTILLES NEAR 15N TO JUST N OF THE ABC
ISLANDS.  SCATTERED SHOWERS/THUNDERSTORMS CONTINUE JUST S OF THE
TROUGH WHERE MOISTURE IS PREVALENT.  HOWEVER...THE TROUGH SHOULD
CONTINUE TO DROP SWD TO THE N COAST OF S AMERICA DURING THE NEXT
DAY OR SO ALLOWING DRY/STABLE CONDITIONS TO INFILTRATE THE
ENTIRE E CARIBBEAN.

SUBTROPICAL ATLANTIC...
WELL DEFINED DEEP LAYERED RIDGE REMAINS OVER THE W ATLC ANCHORED
BY A ANTICYCLONE NEAR THE N BAHAMAS.  STRONG SUBSIDENCE AND
MIDDLE TO UPPER LEVEL DRY AIR IS PRODUCING STABLE CONDITIONS
ACROSS A LARGE PORTION OF THE ATLC W OF 50W.  THE ONLY WEATHER
OF NOTE WITHIN THIS AREA IS A NARROW BAND OF SCATTERED SHALLOW
TOPPED SHOWERS WITHIN 90 NM AHEAD OF A COLD FRONT ALONG 31N50W
28N65W 31N72W. SHIFTING EWD...LARGE DEEP LAYERED LIES LIES OVER
THE CENTRAL ATLC JUST N OF THE AREA BETWEEN 40W-60W.  A PAIR OF
SHORTWAVE DISTURBANCES ARE ROTATING AROUND THIS SYSTEM...ONE
ENTERING THE AREA NEAR 31N35W SWD ALONG 22N40W 20N50W THEN A
SHEAR AXIS TO THE LESSER ANTILLES NEAR 15N AND A SECOND DROPPING
SWD JUST E OF BERMUDA.  THE EASTERNMOST SHORTWAVE IS PROVIDING
GOOD UPPER LEVEL SUPPORT FOR A COLD FRONT WHICH ENTERS THE AREA
NEAR 31N36W SWD ALONG 23N50W THEN DISSIPATING TO PUERTO RICO. AN
AREA OF SCATTERED MODERATE CONVECTION LIES AHEAD OF THE FRONT N
OF 25N BETWEEN 30W-34W.   OVER THE FAR E ATLC...MIDDLE TO UPPER
LEVEL RIDGE IS BEING ERODED BY A TROUGH DIGGING SWD FROM SPAIN
TO THE CANARY ISLANDS.  THE FEATURE IS PRODUCING A SMALL AREA OF
SCATTERED SHOWERS/THUNDERSTORMS JUST N OF THE CANARY ISLANDS.

TROPICAL ATLANTIC...
MID/UPPER LEVEL RIDGE REMAINS OVER THE E TROPICAL ATLC ALONG
10N/11N E OF 40W. DIFFLUENCE NEAR THE RIDGE AXIS IS ENHANCING
ITCZ CONVECTION E OF 30W. STRONG ZONAL UPPER LEVEL WESTERLY FLOW
ASSOCIATED WITH AN E/W ORIENTED SUBTROPICAL JET FROM THE E
CARIBBEAN TO W AFRICA NEAR MAURITANIA PENETRATES INTO THE
TROPICAL REGION W OF 40W.

$$
RHOME




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