000
AXPZ20 KNHC 130917
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN DEC 13 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...ITCZ...
AXIS IS ALONG 7N78W 8N85W 6N100W 8N126W 7N140W. SCATTERED 
MODERATE TO STRONG CONVECTION FROM 05N-09N BETWEEN 124W-133W.

...DISCUSSION... 
BROAD UPPER-LEVEL TROUGH WITH AXIS FROM NW MEXICO SW TO NEAR
15N111W...OTHERWISE NEARLY ZONAL FLOW COVERS THE AREA N OF 20N W 
OF THE TROUGH. A 90-110 KT JETSTREAM IS JUST NORTH OF AREA 
CROSSING SOUTHERN CALIFORNIA...ARIZONA AND NEW MEXICO INTO 
TEXAS. SOME MID/UPPER LEVEL MOISTURE IS NOTED ON WATER VAPOR 
IMAGERY N OF 25N...OTHERWISE MODERATE TO STRONG SUBSIDENCE WITH 
DRY STABLE AIR AT THE MIDDLE AND UPPER LEVELS OF THE ATMOSPHERE 
DOMINATES THE AREA N OF THE ITCZ W OF 110W.

AN UPPER ANTICYCLONE CENTERED OVER THE NW CARIBBEAN WITH A RIDGE 
EXTENDING ACROSS SE MEXICO AND MOST OF CENTRAL AMERICA INTO THE 
EPAC WHERE IS PRODUCING MODERATE TO STRONG SUBSIDENCE MAINLY E 
OF 100W. THE SUBSIDENCE HAS SUPPRESSED ANY STRONG CONVECTION 
ALONG THE ITCZ. AN UPPER-LEVEL TROUGH IS IN THE DEEP TROPICS 
WITH AXIS FROM 11N98W TO A CYCLONIC CIRCULATION NEAR 05N96W.

A WEAKENING COLD FRONT IS MOVING ACROSS THE N PORTION OF THE 
DISCUSSION AREA EXTENDING FROM 32N121W TO 26N133W. WINDS HAVE 
DECREASED TO BELOW 20 KT EITHER SIDE OF THE FRONT. OVERCAST LOW 
CLOUDS ARE W OF THE FRONT. THE FRONT WILL CONTINUE TO DISSIPATE 
DURING THE NEXT 12 TO 24 HOURS. A 1021 MB HIGH PRES NW OF THEJ 
FRONT IS CENTERED NEAR 30N139W. E OF FRONT A 1020 MB SURFACE 
HIGH IS CENTERED NEAR 26N119W. MODERATE TO STRONG TRADE WINDS ON 
THE SOUTHERN PERIPHERY OF THIS HIGH.

A COUPLE OF TROUGH ARE ANALYZED ALONG THE ITCZ. THE FIRST TROUGH 
IS FROM 12N-4N ALONG 111W. A 1008 MB LOW IS ALONG THE TROUGH NEAR
8N111W. BROKEN TO OVERCAST LOW CLOUDS ASSOCIATED WITH THE TROUGH
ARE N OF THE LOW. A SECOND TROUGH FROM 9N-6N ALONG 131W. A LARGE 
AREA OVER CONVECTON NEAR THE TROUGH IS ASSOICATED WITH THE ITCZ.

LARGE AND LONG PERIOD NW SWELL CONTINUES TO SPREAD ACROSS THE 
REGION BEYOND THE EQUATOR. HOWEVER THE SEA HEIGHTS ARE SUBSIDING 
ESPECIALLY OVER THE N PORTION OF THE AREA. A NEW BATCH OF NW 
SWELL WITH WAVE PERIODS BETWEEN 14 TO 15 SECONDS SHOULD REACH 
THE FAR NW PORTION OF THE AREA BY THIS EVENING.

NE TO E WINDS 20-25 KT ARE BLOWING ACROSS THE GULF OF PAPAGAYO 
AS THE PRES GRADIENT BUILDS ACROSS THE WESTERN CARIBBEAN 
ALLOWING ELY TRADE WINDS TO FUNNEL ACROSS COSTA RICA AND 
NICARAGUA INTO THE EASTERN PACIFIC.

NLY WINDS OF 20 KT ARE STILL BLOWING ACROSS THE GULF OF 
TEHUANTEPEC. THE WINDS SHOULD DECREASE BY 48 HOURS.
  
$$
DGS