000
AXPZ20 KNHC 291601
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED SEP 29 2010

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ...

AXIS CENTERED ALONG 11N95W 10N110W TO A 1010 MB LOW NEAR 11N118W
TO 10N126W TO A 1010 MB LOW NEAR 13N134W TO 11N140W. SCATTERED 
MODERATE CONVECTION WAS NOTED WITHIN 120 NM S OF THE AXIS BETWEEN
133W-136W...AND 60 NM S OF AXIS BETWEEN 102W-107W.

...DISCUSSION...

W OF 125W...

A MID/UPPER LEVEL ANTICYLONE NEAR 21N136W WITH A RIDGE EXTENDING
TO WELL N OF THE AREA WITH A CREST AT 35N130W WAS DRIFTING N 
AHEAD OF A RATHER VIGOROUS SHORTWAVE TROUGH LIFTING ENE THROUGH
THE FAR NW CORNER OF THE AREA. AT THE SURFACE...A STATIONARY 
FRONT WAS JUST WAS OF THE AREA DRAPED FROM 32N141W TO WELL SW TO 
JUST N OF THE HAWAIIAN ISLANDS. SLY UPPER LEVEL FLOW WAS 
INCREASING AHEAD OF THE TROUGH IN A VERY PRONOUNCED JET STREAM 
WITH WINDS IN THE RANGE OF 40-60 KT. 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 WAS MOVING INTO A ZONE OF DIFFLUENT FLOW ALOFT AND 
INDUCING FURTHER DIVERGENCE ALOFT W OF 135W. THIS WAS ALSO 
INDUCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN
120 NM E AND W QUADRANTS OF THE 1010 MB LOW NEAR 13N134W.

E OF 125W...

A MID/UPPER LEVEL CYCLONIC CIRCULATION WAS OVER THE FAR NE PART
NEAR 31N119W MOVING W AT 15 KT. A TROUGH EXTENDED SW FROM THE 
CIRCULATION TO NEAR 26N124W...WHILE A SECOND SHARP AND NARROW 
TROUGH AXIS EXTENDED SE ACROSS EXTREME NRN MEXICO AND INTO THE 
NW GULF OF MEXICO...WHERE IT LINKED TO THE SW PERIPHERY OF A 
DEEP UPPER TROUGH AFFECTING THE E HALF OF THE U.S. AND MOST OF 
THE GULF OF MEXICO. THE MID/UPPER LOW ACROSS NE PORTIONS OF THE 
AREA...AND ITS ASSOCIATED TROUGH WERE TRAPPED IN BETWEEN TWO 
ANTICYCLONES...THE FORMER NEAR 21N136W...AND A MUCH LARGER 
BLOCKING ANTICYCLONE ANCHORED OVER THE WESTERN U.S. AN UPPER
LEVEL ANTICYCLONE WAS LOCATED NEAR 20N112W WITH A RIDGE NW TO 
22N125W...AND ANOTHER SE TO THE NORTHERN ISTHMUS OF TEHUANTEPEC.
THE ANTICYCLONE REMAINED OVER AND JUST TO THE N OF A NEARLY 
STATIONARY SURFACE LOW NEAR 18N106W...AND WAS CONTINUING TO 
PROVIDE ANTICYCLONIC OUTFLOW TO SUPPORT SCATTERED MODERATE/
ISOLATED STRONG CONVECTION THAT WAS WITHIN 180 NM NW OF THE LOW 
HAD DEVELOPED ASSOCIATED WITH 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 TROPICAL STORM NICOLE CENTERED NEAR CENTRAL CUBA. 
THIS LOW IS FORECAST TO REMAIN STATIONARY AND EMBEDDED WITHIN AN 
ELONGATED NODE 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.

THIS BROAD CYCLONIC GYRE CONTINUES TO DOMINATE A LARGE PORTION 
OF THE FORECAST AREA...NAMELY S OF 18N AND E OF 115W...WITH 
ANTICYCLONIC CROSS HEMISPHERIC SE TO S FLOW...BECOMING CONFLUENT 
SW TO W FLOW FROM 8N TO 14N BETWEEN 86W AND 100W WITH SEAS HERE
UP TO 9 FT. A CYCLONIC CIRCULATION DENOTING A 1004 MB LOW...
POSSIBLY THE REMNANT LOW OF MATTHEW...NEAR 14N92W MOVING W 
AT 7 KT. ASCAT DATA FROM FROM NEAR 0420 UTC SHOWED W TO SW WINDS 
OF 20 TO 30 KT S THROUGH SW OF THIS LOW EXTENDING W TO 100W. 
SHIP 'PHFV" JUST E OF THE LOW RECENTLY REPORTED SW WINDS OF 30 
KT INDICATING THE STRONG SW WINDS WITHIN THE MONSOON GYRE OVER
THE FAR EASTERN PORTION OF THE REGION. N WINDS OF 20 TO 25 KT ARE
EXPECTED TO BEGIN THROUGH THE ISTHMUS OF TEHUANTEPEC IN ABOUT
48 HOURS PERHAPS ENERGIZING THE LOW OVER THE NEXT 48 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.

$$
AGUIRRE