000
AXPZ20 KNHC 282212
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE SEP 28 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 
2100 UTC.

...ITCZ...

AXIS ANALYZED ALONG 11N105W TO LOW PRES 11N120.5W TO 10N125W TO 
14N134W TO 11N140W. SCATTERED MODERATE CONVECTION WAS NOTED 
WITHIN 180 NM S OF AXIS BETWEEN 105W AND 109W...BETWEEN 129W AND 
133W...AND W OF 136W. 
 
...DISCUSSION...

W OF 125W...

MID/UPPER LEVEL ANTICYLONE NEAR 20N135W WAS BEING SHUNTED 
SOUTHWARD FOR THE TIME BEING AS A RATHER VIGOROUS SHORTWAVE 
TROUGH WAS APPROACHING THE FAR NW CORNER OF THE REGION. THE 
ASSOCIATED COLD FRONT WAS ABOUT 130 NM NW OF 32N140W. SW UPPER 
LEVEL FLOW WAS INCREASING AHEAD OF THE TROUGH IN A VERY 
PRONOUNCED JET STREAM WITH WINDS OF 35-55 KT. SATELLITE WATER 
VAPOR IMAGERY DEPICTED MODERATE SUBSIDENCE OVER THIS PORTION OF 
THE REGION RESULTING IN STABLE ENVIRONMENTAL CONDITIONS WITH 
SCATTERED TO BROKEN STRATOCUMULUS CLOUDS NOTED N OF 19N...AND 
LIMITING MOISTURE IN THE TROPICAL ZONE. CONVECTION THAT WAS 
OCCURRING ALONG THE ITCZ WAS BEING AIDED BY DIFFLUENT FLOW
ON THE SW PERIPHERY OF THE ANTICYCLONE.

E OF 125W...

A MID/UPPER LEVEL CYCLONIC CIRCULATION WAS OVER THE FAR NE PART
NEAR 30N119W MOVING W AT 15 KT. A TROUGH EXTENDS SW FROM THE 
CIRCULATION TO A COL REGION AT 21N129W...WHILE A SECOND SHARP 
AND NARROW TROUGH AXIS EXTENDED SE ACROSS EXTREME NRN MEXICO TO 
JUST S OF THE MEXICO-TEXAS BORDER AND INTO THE GULF OF MEXICO.   
THE CIRCULATION AND ITS ASSOCIATED TROUGH WAS TRAPPED IN BETWEEN 
TWO ANTICYCLONES NEAR 19N135W...AND A MUCH LARGER ANTICYCLONE 
ANCHORED OVER THE WESTERN U.S. A TROPICAL UPPER RIDGE AXIS 
EXTENDED SOMEWHAT E TO W ACROSS SOUTHERN PORTIONS OF THE AREA 
FROM AN ANTICYCLONE NEAR 20N107W. THE ANTICYCLONE WAS NEARLY 
DIRECTLY OVERHEAD OF A SURFACE LOW AT 18N107W...AND WAS 
PROVIDING ANTICYCLONIC OUTFLOW TO SUPPORT SCATTERED CONVECTION 
THAT HAD DEVELOPED ASSOCIATED WITH THE LOW. THIS LOW WAS 
SITUATED ON THE 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 T.D. 16. THIS LOW IS FORECAST TO REMAIN EMBEDDED WITHIN AN 
ELONGATED NODE OF THE CYCLONIC GYRE AND IS NOT EXPECTED TO 
BECOME MUCH BETTER ORGANIZED...DESPITE ITS LOCATION UNDER THE 
UPPER HIGH. THE LIKELIHOOD IS LOW FOR IT TO BECOME A TROPICAL 
CYCLONE OVER THE NEXT 48 HOURS.

THIS BROAD CYCLONIC GYRE CONTINUES TO DOMINATE A LARGE PORTION 
OF THE AREA...NAMELY S OF 16N AND E OF 115W...WITH ANTICYCLONIC 
S TO SW FLOW...BECOMING CONFLUENT SW TO W FLOW BETWEEN 08N AND 
12N. AFTERNOON ASCAT PASSES DEPICTED 20 KT SWLY FLOW ACROSS MUCH 
OF THIS CONFLUENT AREA...WITH WWIII OUTPUT FORECASTING 8 TO 9 FT 
SEAS. CYCLONIC CIRCULATION WAS NOTED NEAR NEAR 14.5N93.5W... 
WHERE A 1006 MB SURFACE LOW IS ESTIMATED. A 1530 UTC ASCAT PASS 
SHOWED W TO SW WINDS OF 20 TO 30 KT S THROUGH SW OF THIS LOW 
EXTENDING W TO 98W...AND NLY WINDS OF 20-30 KT FLOWING FROM THE 
GULF OF MEXICO THROUGH THE ISTHMUS OF TEHUANTEPEC AND EXITING ON 
THE S SIDE THROUGH THE GULF NEAR 20 KT. SEAS IN THE STRONG W TO 
SW FLOW WERE FORECAST BY WWIII AT 8 TO 12 FT. SCATTERED TO 
NUMEROUS CONVECTION WAS OCCURRING IN THIS W TO SW FLOW S OF THE 
LOW. THIS MAY BE PARTLY RELATED TO THE REMNANTS OF MATTHEW. THE 
LOW IS FORECAST BY GLOBAL MODELS TO MOVE E-SE OVER THE NEXT FEW 
DAYS AND THEN INLAND OVER GUATEMALA AND EL SALVADOR.  

ELSEWHERE...15-17 SEC LONG PERIOD SWELL CONTINUES TO PUSH SE 
FROM THE N CENTRAL PACIFIC IN TO THE DISCUSSION AREA. ALTIMETRY 
DATA SHOWS SEAS BEGINNING TO SUBSIDE FROM A MAX OF 13 FT OVER NW 
WATERS FROM THIS SWELL TRAIN. THIS INITIAL SWELL TRAIN WILL 
CONTINUE TO SPREAD SE ACROSS NW HALF OF THE BASIN AND GRADUALLY 
SUBSIDE... WHILE A SECOND SURGE OF NW SWELL WILL REACH FAR NW 
WATERS TUE AND BRING THE SEAS BACK TO THE 10 TO 13 FT RANGE THIS 
AFTERNOON. LOOKING AHEAD...LONG PERIOD SW SWELL OF UP TO 15 FT 
IS FORECAST TO PROPAGATE TOWARD THE CENTRAL AMERICAN COAST BY 
THE WEEKEND.

$$
STRIPLING