000
AXPZ20 KNHC 200352
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED OCT 20 2010

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0315 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N84W 8N90W 8N100W 6N112W 9N126W 
9N140W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF THE AXIS
BETWEEN 127W-129W.

...DISCUSSION...

ALOFT...
A RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE AREA N OF 10N. A 
WELL-DEFINED MIDDLE/UPPER LEVEL CYCLONIC CIRCULATION IS CENTERED 
NEAR THE CALIFORNIA/BAJA CALIFORNIA BORDER IN THE VICINITY OF 
32N118W MOVING SLOWLY E WITH A TROUGH SSW TO 21N122W. GLOBAL 
MODELS FORECAST THE CYCLONIC CIRCULATION TO MOVE INLAND NORTHERN 
BAJA CALIFORNIA OVERNIGHT...THEN TURN NE AND MOVE ACROSS ARIZONA 
WED INTO THU. THIS IS SYSTEM IS RESULTING IN NUMEROUS SHOWERS 
AND SCATTERED TSTMS OVER AND NEAR NORTHERN BAJA CALIFORNIA...
WITH THE ACTIVITY GRADUALLY DIMINISHING AS THE LOW MOVES FURTHER 
E AND AWAY FROM THE DISCUSSION AREA. THE ASSOCIATED CYCLONIC 
FLOW COVERS THE AREA N OF 22N AND E OF 128W TO NW MEXICO. A 
JET STREAM BRANCH WITH WINDS IN THE RANGE OF 40-70 KT ROUNDS THE 
BASE OF THIS UPPER LEVEL LOW. SW TO W WINDS ARE LOCATED S OF THE 
JET TO 15N W OF 130W. THESE WINDS ARE ADVECTING A FAIR AMOUNT OF 
MID/UPPER LEVEL MOISTURE OVER THE WESTERN PORTION OF THE AREA N 
OF 19N W OF 129W.

A RIDGE COVERS ROUGHLY THE REGION S OF 20N BETWEEN 100W AND 
132W. WATER VAPOR IMAGERY INDICATES A LARGE AREA OF MODERATE TO 
STRONG SUBSIDENCE WITHIN THE RIDGE. A DIFFLUENT PATTERN TO THE W 
OF THE RIDGE IS HELPING TO SUSTAIN THE ITCZ CONVECTION. ABUNDANT 
MID/UPPER MOISTURE IS BEING ADVECTED EASTWARD FROM THE DEEP 
TROPICS OF THE CENTRAL PACIFIC TO JUST ALONG 140W. 

TO THE NW OF THE REGION...A DEEP LAYER TROUGH IS FAST APPROACHING
THE AREA. THE ASSOCIATED COLD FRONT IS ABOUT 400 NM NW OF THE 
30N140W. IT IS FORECAST TO MOVE INTO THE NW CORNER WED AFTERNOON
...AND EXTEND FROM 30N138W TO 28N140W BY EARLY WED EVENING 
PRECEDED
BY SW WINDS TO 20 KT WITHIN ABOUT 180 NM TO ITS E AND N OF 28N. 
SEAS
ARE EXPECTED TO BUILD UP 10 FT IN NW SWELL WITHIN 180 NM TO ITS 
SE
...AND POSSIBLY UP TO 11 FT IN NW SWELLS BEHIND IT WHERE WINDS 
ARE FORECAST TO BE LESS THAN 20 KT. BY 48 HOURS...THE FRONT IS
FORECAST BY THE MODELS TO WEAKEN FROM 30N131W TO 27N136W AND 
BECOME 
STATIONARY TO 26N140W. LATEST MODEL GUIDANCE SHOWS THAT WINDS 
WILL
BE LESS THAN 20 KT E OF FRONT TO A LINE FROM 30N120W TO 25N129W 
TO
18N140W WITH SEAS TO 8 FT IN NW SWELLS...WHILE W OF THE FRONT 
WINDS WILL BE LESS THAN 20 KT WITH SEAS TO 11 FT IN NW TO N 
SWELLS.

OVER THE REMAINDER OF THE AREA ENVIRONMENTAL CONDITIONS ARE 
RELATIVELY
STABLE AND DRY AS SUPPRESSION OF DEEP MOISTURE CONTINUES UNDER 
THE
DOMINANCE OF MODERATE SUBSIDENCE. SOME HIGH CIRRUS CLOUDS FROM 
PREVIOUS CONVECTION OVER CENTRAL AMERICA AND A FEW THAT EARLIER 
OCCURRED NEAR THE ITCZ REGION ARE STREAMING WESTWARD TO THE S OF 
9N AND E OF 100W.

SURFACE...
A 1022 MB HIGH IS ANALYZED NEAR 31N134W WITH A RIDGE SE TO 
21N119W. HIGH PRES COVERS THE AREA N OF 16N AND W OF 118W. NE
TO E TRADE WINDS TO 20 KT WITH SEAS TO 8 FT ARE CONFINED S OF
THE RIDGE FROM 10N TO 18N W OF 130W. THESE TRADES ARE FORECAST 
TO DIMINISH TO LESS THAN 20 KT WITHIN ABOUT 18 HOURS. 

SW WINDS TO 20 KT OVER THE EASTERN PORTION OF THE AREA FROM 
3N TO 8N E OF 95W ARE FORECAST TO EXPAND W TO 97W IN ABOUT 48 
HOURS. SE TO S WINDS OF 20 KT S OF 10N W OF 122W ARE FORECAST
TO SHIFT FURTHER E IN 48 HOURS WITH SEAS TO 8 FT IN SW SWELL.

CROSS EQUATORIAL SW SWELLS GENERATED BY SOUTHERN HEMISPHERIC 
LOW PRES SYSTEMS WITH WAVE PERIODS OF 15 TO 16 SECONDS ARE 
BEGINNING TO SPREAD ACROSS THE SOUTHERN WATERS AND ARE EXPECTED
TO REACH THE COASTS OF CENTRAL AMERICA AND MEXICO S OF 22N BY 
LATE WED. 

$$
AGUIRRE