000
AXPZ20 KNHC 122154
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI OCT 12 2007

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY 
THROUGH 2145 UTC.

...ITCZ...
INTERTROPICAL CONVERGENCE ZONE...AXIS IS ALONG 14N91W 15N107W 
11N115W 11N130W 11N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION NOTED FROM 9N TO 17N E OF 110W. EMBEDDED LOW PRES 
NEAR 14N104W HAS ESTIMATED SURFACE PRESSURE OF 1005 MB WITH 
CONVECTION MAINLY WELL W OF CENTER. MODEL GUIDANCE SUGGESTS THAT 
THIS WEAK LOW LEVEL CYCLONE WILL DRIFT W ALONG 15N THROUGH 48 
HOURS...MOSTLY MAINTAINED BY THE WIND SHIFT ASSOCIATED WITH 
THE ITCZ OR MONSOON TROUGH THAT IS DEFINED BY QSCAT WINDS ALONG 
16N97W 12N115W.

...DISCUSSION...
AN UPPER ANTICYCLONE IS NEAR 28N138W WITH A SHORTWAVE RIDGE 
EXTENDING N TO A CREST BECOMING UNSTABLE NEAR 37N137W. THIS 
RIDGE IS EXPECTED TO COLLAPSE SE LATER TONIGHT OVER THE NW 
CORNER OF THE DISCUSSION AREA BECOMING PART OF LARGE ANTICYCLONE 
THAT WILL DOMINATE THE SUBTROPICAL UPPER LEVELS OVER THE NEXT 
FEW DAYS. AN UPPER SHORT WAVE TROUGH ALONG THE WESTERN SEABOARD 
CONUS EXTENDS SW INTO THE DISCUSSION AREA ALONG 32N121W 26N130W 
23N140W. AN ASSOCIATED SURFACE FRONT IS DEFINED BY A THIN LINE 
TOWERING CUMULUS ALONG 33N124W 30N130W 28N140W. THE FRONT IS 
WEAK AND ACCOMPANIED BY 15-20 KT NLY WINDS...BUT N SWELLS TO 9 
FT.  

AN UPPER LEVEL ANTICYCLONE IS NEAR 21N106W WITH A RIDGE 
EXTENDING WSW THROUGH SMALL EMBEDDED ANTICYCLONES AT 17N120W AND 
14N139W FINALLY TO A CREST AT 15N143W. THE ANTICYCLONE AT 
14N139W IS ENHANCING CONVECTION ALONG THE ITCZ NEAR 11N139W WITH 
THE DEBRIS MOISTURE REMAINING FROM 9N TO 14N BETWEEN 137W AND 
141W. SOME UPPER MOISTURE IS SWINGING ESE THROUGH THE UPPER 
TROUGH...AND OVER SOUTHERN CALIFORNIA BUT REMAINING N OF 31N 
OVER THE PACIFIC. OTHERWISE THE UPPER LEVELS ARE DRY OVER THE 
ENTIRE AREA W OF 118W.  

A DEEP LAYERED TROUGH EXTENDS SW ACROSS CENTRAL AMERICA ALONG 
21N85W 15N93W TO NEAR 13N110W. UPPER DIFFLUENCE ALONG THE TROUGH 
IS ENHANCING CONVECTION ALONG THE ITCZ BETWEEN 85W AND 112W.  
THIS TROUGH SEPARATES ANTICYCLONIC FLOW OVER NW MEXICO FROM 
UPPER ANTICYCLONIC FLOW OVER THE TROPICAL E PACIFIC ASSOCIATED 
WITH A RIDGE ALONG 13N80W 7N95W. THE UPPER LEVELS APPEAR MOIST S 
OF 20N E OF 115W.

$$
NELSON