000
AXPZ20 KNHC 130920
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU OCT 13 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0800 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION IRWIN IS CENTERED NEAR 18.3N 107.7W AT 
13/0900 UTC MOVING NE OR 055 DEG AT 11 KT. ESTIMATED MINIMUM 
CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 
KT WITH GUSTS TO 40 KT. SCATTERED MODERATE CONVECTION IS LIMITED 
TO WITHIN 75 NM W SEMICIRCLE OF CENTER. THE LATEST NHC FORECAST 
SHOWS NO CHANGE IN INTENSITY FOR THE SYSTEM DESPITE 
TRANSITIONING TO A REMNANT LOW OVERNIGHT TONIGHT. IRWIN WILL 
MOVE E NE TODAY AND THEN TAKE A SOUTHWARD TURN OVERNIGHT TONIGHT 
BEFORE HEADING BACK W OVER THE WEEKEND. SEE THE LATEST NHC 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC 
FOR MORE DETAILS.
 
...ITCZ/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM CENTRAL BELIZE TO THE 1009 MB 
REMNANT LOW OF FORMER TROPICAL DEPRESSION TWELVE-E NEAR 17N93W. 
THE MONSOON TROUGH THEN RESUMES FROM 18N114W TO 10N128W TO 
08N140W. CONVECTION ALONG THE TROUGH IS LIMITED TO THE SOUTHERN 
YUCATAN PENINSULA AND ALONG THE PACIFIC COAST OF CENTRAL AMERICA 
WHERE SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION LIES N 
OF 12N E OF 96W.

...DISCUSSION...

1022 MB HIGH PRES OVER NW WATERS NEAR 30N139W WILL DISSIPATE 
TODAY AS THE COLD FRONT TO ITS NW APPROACHES THE AREA. THE PRES 
GRADIENT BETWEEN THIS HIGH AND TROUGHING OVER NW MEXICO IS 
SUPPORTING A SMALL AREA OF FRESH N WINDS OVER N CENTRAL FORECAST 
WATERS WHICH WILL DIMINISH WITH THE HIGH PRES SYSTEM. FRESH N 
WINDS CURRENTLY OVER THE NORTHERN GULF OF CALIFORNIA WILL ALSO 
DIMINISH TODAY. THE AFOREMENTIONED COLD FRONT WILL BRING 20 KT N 
WINDS AND A NEW BATCH OF NW SWELL INTO NORTHWESTERN FORECAST 
WATERS BY FRI MORNING. WATER VAPOR IMAGERY SHOWS AN UPPER LOW 
CENTERED NEAR 13N120W. THIS UPPER LOW IS TRANSPORTING TROPICAL 
MOISTURE ALOFT INTO THE AREA W OF BAJA CALIFORNIA SUR WHERE 
CIRRUS IS NOTED ON INFRARED IMAGERY FROM 20N TO 27N BETWEEN 110W 
AND 123W. THIS LOW WILL MOVE W TODAY BEFORE BEING PICKED UP BY 
THE DEEP LAYER TROUGH ASSOCIATED WITH THE COLD FRONT IN NW 
WATERS.

FORMER HURRICANE JOVA HAS DISSIPATED OVER W CENTRAL MEXICO AND 
FORMER TROPICAL DEPRESSION TWELVE-E HAS TRANSITIONED TO A 
REMNANT LOW OVER SOUTHERN MEXICO. THE VAST EXPANSE OF FRESH TO 
STRONG SOUTHWESTERLY WINDS THAT HAD OCCUPIED MUCH OF THE REGION 
S OF THESE TROPICAL CYCLONES ALONG WITH IRWIN THIS TIME 
YESTERDAY HAS SHRUNK EASTWARD AND HAS WEAKENED A BIT. THE 0336 
UTC ASCAT PASS SHOWS THE STRONGEST WESTERLY WINDS NOW LIE N OF 
10N E OF 100W. FORECAST GUIDANCE SUGGESTS THAT A BROAD AREA OF 
LOW PRES THAT MAY INCLUDE THE REMNANTS OF T.D. TWELVE-E WILL 
DEEPEN IN THE VICINITY OF THE YUCATAN PENINSULA OVER THE NEXT 
FEW DAYS AND FORCE STRONG N FLOW THROUGH THE GULF OF 
TEHUANTEPEC. WINDS ARE NOT EXPECTED TO REACH GALE FORCE THERE.

THE 0516 UTC ASCAT PASS SHOWS FRESH S WINDS HAVE DEVELOPED S OF 
THE MONSOON TROUGH FROM 03N TO 09N BETWEEN 120W AND 130W. LOW 
PRES IS EXPECTED TO DEVELOP ALONG THE MONSOON TROUGH JUST N OF 
THIS AREA ON FRI AND THESE FRESH WINDS ARE EXPECTED TO FEED INTO 
THIS LOW. THE LOW WILL MOVE NE AT 10 KT FRI THROUGH SUN MORNING 
BUT WILL LIKELY SEE LITTLE CHANGE IN INTENSITY AS IT WILL LIES 
UNDER SOUTHEASTERLY SHEAR.

$$
SCHAUER