000
AXPZ20 KNHC 130340
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT OCT 13 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 4N91W 14N105W 
11N117W 11N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
IS NOTED FROM 7N TO 17N E OF 112W AND WITHIN 15 NM OF 12N137W.

AN EMBEDDED LOW PRES NEAR 14N105W HAS ESTIMATED SURFACE PRESSURE 
OF 1005 MB WITH CONVECTION SHEAR 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 31N139W WITH A SHORTWAVE RIDGE 
EXTENDING N TO A UNSTABLE CREST BEGINNING TO COLLAPSE SE NEAR 
37N134W. THIS RIDGE IS EXPECTED TO BECOME 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 32N119W 
27N125W 24N140W. AN ASSOCIATED SURFACE FRONT IS DEFINED BY A 
THIN LINE TOWERING CUMULUS ALONG 32N122W 28N127W THEN STATIONARY 
TO NEAR 28N140W. THE FRONT IS WEAK AND ACCOMPANIED BY 15 KT 
NLY WINDS...BUT N SWELLS TO 9 FT.  

AN UPPER LEVEL ANTICYCLONE IS STATIONARY NEAR 21N106W WITH A 
RIDGE EXTENDING WSW THROUGH SMALL EMBEDDED ANTICYCLONES AT 
18N118W AND 14.5N138.5W FINALLY TO A CREST AT 13N144W. THE 
ANTICYCLONE NEAR 14N139W IS ENHANCING CONVECTION ALONG THE ITCZ 
NEAR 12N138W WITH THE DEBRIS MOISTURE REMAINING FROM 9N TO 14N 
BETWEEN 137W AND 141W. SOME UPPER MOISTURE IS SWINGING ESE 
THROUGH THE UPPER TROUGH ACROSS THE CONUS DESERT SW...BUT 
REMAINING N OF 30.5N 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 
19N85W 15N92W TO NEAR 14N110W. UPPER DIFFLUENCE ALONG THE TROUGH 
ENHANCED CONVECTION EARLIER 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 7N90W. THE UPPER LEVELS APPEAR MOIST S 
OF 20N E OF 116W.

$$
NELSON