000
AXPZ20 KNHC 292209
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED SEP 29 2010

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 
2115 UTC.

...ITCZ...

AXIS ANALYZED ALONG 10N104W TO 09N108W TO LOW PRES 10.5N116.5W 
1011 MB TO LOW PRES 13N134.5W 1010 MB TO 12N140W. SCATTERED TO 
NUMEROUS MODERATE CONVECTION NOTED WITHIN 120 NM S OF AXIS E OF 
108W.

...DISCUSSION...

W OF 125W...

A MID/UPPER LEVEL ANTICYLONE NEAR 22N135W WITH A NARROW RIDGE 
EXTENDING TO WELL N OF THE AREA WITH A CREST AT 35N129W WAS 
DRIFTING NW AHEAD OF A RATHER VIGOROUS SHORTWAVE TROUGH LIFTING 
NE THROUGH THE FAR NW CORNER OF THE AREA. AT THE SURFACE...A 
STATIONARY FRONT WAS JUST NW OF THE AREA DRAPED FROM 32N140W TO 
24N150W...AND JUST N OF THE HAWAIIAN ISLANDS. SATELLITE WATER 
VAPOR IMAGERY DEPICTED MODERATE SUBSIDENCE OVER MOST OF THIS 
PORTION OF THE REGION RESULTING IN STABLE ENVIRONMENTAL 
CONDITIONS WITH BROKEN TO OVERCAST STRATOCUMULUS CLOUDS N OF 
20N...AND LIMITED  MOISTURE IN THE TROPICAL ZONE. DEEP 
CONVECTION OCCURRING ALONG THE ITCZ PERSISTED WITHIN AN UPPER 
LEVEL DIFFLUENT ASYMPTOTE...AND WAS INDUCING FURTHER DIVERGENCE 
ALOFT W OF 132W. MUCH OF THIS CONVECTION WAS BEING FORCED BY LOW 
LEVEL CONVERGENCE ASSOCIATED AROUND AN ELONGATED 1010 MB LOW 
NEAR 13N134W.

E OF 125W...

A MID/UPPER LEVEL CYCLONIC CIRCULATION WAS ALONG THE BORDER OF 
THE FAR NE PART OF THE AREA NEAR 31N119W MOVING SLOWLY W. A 
TROUGH EXTENDED SW FROM THE CIRCULATION TO NEAR 20N130W. THE 
MID/UPPER LOW WAS TRAPPED IN BETWEEN TWO ANTICYCLONES...THE 
FORMER NEAR 21N136W...AND A MUCH LARGER BLOCKING ANTICYCLONE 
ANCHORED OVER THE CENTRAL PLAINS. AN UPPER LEVEL ANTICYCLONE WAS 
LOCATED NEAR 20N112W WITH A RIDGE W TO 21N124W...AND ANOTHER NW 
TO THE CENTRAL PLAINS HIGHER. THIS ANTICYCLONE REMAINED OVER AND 
JUST TO THE N OF A NEARLY STATIONARY SURFACE LOW NEAR 
17N105.5...AND WAS CONTINUING TO PROVIDE ANTICYCLONIC OUTFLOW TO 
SUPPORT SCATTERED MODERATE/ISOLATED STRONG CONVECTION THAT WAS 
WITHIN 180 NM W OF THE LOW. THIS LOW WAS SITUATED ON THE FAR 
WESTERN PERIPHERY OF AN ELONGATED MONSOONAL GYRE THAT HAS 
PERSISTED ACROSS THE FAR EPAC...SRN MEXICO...AND CENTRAL AMERICA 
THE PAST WEEK OR SO...AND THAT HAS EXTENDED INTO THE W CARIBBEAN 
IN RECENT DAYS AND PROVIDED THE ENVIRONMENT TO SPAWN WHAT IS NOW 
THE REMNANTS LOW OF FORMER TROPICAL STORM NICOLE...CENTERED OVER 
THE STRAITS OF FLORIDA. THIS PACIFIC LOW IS FORECAST TO REMAIN 
RELATIVELY STATIONARY AND EMBEDDED WITHIN AN ELONGATED LOBE OF 
THIS CYCLONIC GYRE...AND IS NOT EXPECTED TO BECOME MUCH BETTER 
ORGANIZED...DESPITE ITS LOCATION NEAR THE UPPER HIGH...AS IT IS 
JUST FAR ENOUGH TO THE S OF THE UPPER HIGH TO BE FEELING NE WIND 
SHEAR FROM FLOW AROUND THE NE FLANK OF THE UPPER HIGH.

THE BROAD CYCLONIC GYRE CONTINUES TO DOMINATE A LARGE PORTION OF 
THE FORECAST AREA...NAMELY S OF 18N AND E OF 112W...WITH 
ANTICYCLONIC CROSS HEMISPHERIC SE TO S FLOW E OF 120W...BECOMING 
CONFLUENT SW TO W FLOW FROM 8N TO 14N BETWEEN 85W AND 105W WITH 
SEAS HERE UP TO 9 FT. A CYCLONIC CIRCULATION DENOTING A 1004 MB 
LOW...LIKELY PORTIONS OF THE REMNANT LOW OF MATTHEW...NEAR 
14N92W DRIFTING E. MIDDAY ASCAT PASSES SHOWED SW WINDS OF S OF 
THE ITCZ FROM 106W EXTENDING ENE TO THE COAST OF GUATEMALA AND 
SAN SALVADOR. THIS LOW HAS BEGUN TO GAIN SOME CONVECTION TODAY 
AS IT MOVES E AND NEARS THE PACIFIC COASTLINES...AND IS FORECAST 
TO MOVE INLAND AND CROSS CENTRAL AMERICA IN THE NEXT FEW DAYS. N 
WINDS OF 20 TO 25 KT ARE EXPECTED TO BECOME ESTABLISHED THROUGH 
THE ISTHMUS OF TEHUANTEPEC IN ABOUT 36 HOURS.

ELSEWHERE...15-17 SEC LONG PERIOD SWELL CONTINUES TO PUSH SE 
FROM THE N CENTRAL PACIFIC IN TO THE DISCUSSION AREA. SEAS
ARE SUBSIDING SOME OVER THE NW PORTION OF THE AREA. THIS
INITIAL SWELL TRAIN WILL CONTINUE TO SPREAD SE ACROSS NW HALF OF 
THE BASIN AND GRADUALLY SUBSIDE. A SECOND SURGE OF NW SWELL WILL 
REACH FAR NW WATERS BY LATE THU TUE WITH SEAS PERHAPS IN THE
8 TO 10 FT RANGE.

$$
STRIPLING