000
AXPZ20 KNHC 230955
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL 
1005 UTC MON SEP 23 2013

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 
0930 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

THE MONSOON TROUGH AXIS EXTENDS FROM NW COLOMBIA NW ACROSS 
CENTRAL AMERICA TO CENTRAL NICARAGUA WHERE IT ENDS. IT RESUMES 
AT 14N105W TO 11N110W TO 11N121W...THEN TRANSITIONS TO THE ICTZ 
TO 09N130W TO 08N140W. SCATTERED MODERATE/ISOLATED CONVECTION IS 
WITHIN 120 NM S OF THE TROUGH BETWEEN 119W-121W...AND ALSO 
WITHIN 120 NM N AND 60 NM S OF THE ITCZ BETWEEN 122W-125W.

...DISCUSSION...
                                                        
SATELLITE WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG 
SUBSIDENCE PRESIDING ACROSS JUST ABOUT THE ENTIRE AREA W OF 112W 
N OF THE ITCZ/MONSOON TROUGH REGION. A MID/UPPER RIDGE EXTENDS 
FROM AN ANTICYCLONE OVER CENTRAL MEXICO NEAR 24N102W WSW TO 
20N140W. THE RIDGE IS PART OF BROAD SCALE RIDGING THAT COVERS 
THE ENTIRE WITH ONLY THE TAIL END OF AN UPPER TROUGH THAT HAS 
MOVED WELL INLAND THE CENTRAL U.S. EXTENDING SW TO ACROSS FAR NW 
MEXICO AND NORTHERN BAJA CALIFORNIA. DRY AND STABLE CONDITIONS 
ARE PRESENT THROUGHOUT...EXCEPT IN THE TROPICS ALONG THE MONSOON 
TROUGH AND ITCZ...AND ALSO IN THE FAR EASTERN PORTION SE OF 
SOUTHEASTERN MEXICO (MORE ON THIS LATER). ASIDE FROM THE 
CONVECTION DESCRIBED ABOVE UNDER ITCZ/MONSOON TROUGH...WIDELY 
SCATTERED SHOWERS AND ISOLATED TSTMS ARE NOTED FROM 06N TO 11N W 
OF ABOUT 110W. PATCHES OF BROKEN STRATOCUMLUS CLOUDS MOVING SW 
TO W ARE PRESENT FROM 15N TO 21N BETWEEN 121W-133W...AND ALSO 
FROM 20N TO 22N BETWEEN 111W-121W. THE 06 UTC SURFACE ANALYSIS 
REVEALS A RIDGE STRETCHING INTO THE AREA THROUGH 32N135W TO 
29N122W. A RELATIVELY WEAK PRES PATTERN IS IN PLACE THROUGHOUT 
AS SUGGESTED BY THE LIGHT WINDS DISPLAYED IN THE LATEST ASCAT 
PASS. THE EXCEPTION REMAINS IN THE FAR NE PORTION OF THE AREA N 
OF 26N E OF 118W WHERE NW 20 KT WINDS CONTINUE WITH SEAS TO 9 FT 
IN NW SWELLS. THESE WINDS ARE FORECAST TO DIMINISH TONIGHT AS 
THE CULPRIT TIGHT PRES GRADIENT BETWEEN THE RIDGE AND LOW PRES 
OVER NW MEXICO AND THE SW U.S. SLACKENS. A COLD FRONT IS 
FORECAST TO APPROACH THE FAR N CENTRAL AND NW WATERS TONIGHT AND 
TUE WHILE WEAKENING AS INDICATED BY THE GLOBAL MODELS. THIS WILL 
BE IN RESPONSE TO STRONGER HIGH PRES SITUATED NW OF THE AREA 
THAT BEGINS TO BUILD SEWD ACROSS THE N CENTRAL AND NW PORTIONS.  
THIS NEW STRONGER HIGH PRES WILL RESULT IN A TIGHTENING OF THE 
PRES GRADIENT AGAIN IN THE FAR NE PORTION BEGINNING LATE TUE 
WITH NW TO N WINDS INCREASING TO 20 KT WITH HIGHER WINDS OF 20-
25 KT JUST N OF 30N. WAVEWATCH GUIDANCE SUGGESTS THAT SEAS BUILD 
TO THE RANGE OF 10-11 FT N OF 27N BETWEEN 119W-127W TUE NIGHT... 
WITH HIGHER SEAS TO 12 FT JUST N OF 30N BETWEEN 122W-125W.

GLOBALS MODELS ARE IN VERY GOOD AGREEMENT THAT LOW PRES FORMS IN 
THE DEEP TROPICS NEAR 11N AND BETWEEN 120W-123W DURING TODAY 
...THEN LIFTS NEWD THROUGH WED. LATEST SATELLITE IMAGERY SHOWS 
RECENTLY DEEP CONVECTION IN THAT AREA. THIS MAY BE THE FIRST 
SIGNS OF THE LOW FORMING. WILL DEPICT THIS FEATURE AS A 1008 MB 
LOW ALONG THE MONSOON TROUGH ON THE MANUAL GRAPHICS VALID AT 48 
AND 72 HOURS FROM 00 UTC LAST NIGHT. 

THE MODELS ARE ALSO KEEN ON THE EXISTENCE OF LOW PRES OVER THE 
FAR EASTERN PORTION OF THE AREA IN THE GENERAL VICINITY TO THE S 
OF SOUTHEASTERN MEXICO...AND THAT LINGERS THERE OVER THE NEXT 
FEW DAYS. A PARTIAL ASCAT PASS FROM 0328 UTC LAST NIGHT HINTED 
AT THIS WITH THE WIND VECTORS THERE DEPICTING BROAD CYCLONIC 
TURNING THERE. LATEST SATELLITE IMAGERY SHOWS CLUSTERS OF 
SCATTERED MODERATE TO STRONG CONVECTION IS CONCENTRATED FROM 10N 
TO 12N BETWEEN 87W-90W...AND ALSO N OF 10N BETWEEN 90W-94W. THIS 
CONVECTION EXTENDS TO INLAND WESTERN EL SALVADOR AND TO JUST 
INLAND GUATEMALA. SCATTERED MODERATE/ISOLATED STRONG CONVECTION 
IS SEEN FROM 13N TO 15N BETWEEN 94W-95W INCLUDING THE SE PART OF 
THE GULF OF TEHUANTEPEC. SIMILAR CONVECTION IS WITHIN 45 NM OF 
11N98W...AND ALSO WITHIN 30 NM OF 15N97W AND 30 NM OF 10N103W. 
SCATTERED SHOWERS AND ISOLATED TSTMS ARE ELSEWHERE N OF 10N E OF 
110W. THE DEEP CONVECTION IS EXPECTED TO CHANGE LITTLE OVER THE 
NEXT 48 HOURS IT REMAINS UNDER A REGION OF UPPER LEVEL 
DIFFLUENCE LOCATED BETWEEN THE UPPER ANTICYCLONE OVER CENTRAL 
MEXICO...AND ANOTHER ONE OVER SOUTHERN GUATEMALA. WITH REGARDS 
TO THE LOW PRES THE MODELS SUGGEST STILL CONFIDENCE LEVEL IS LOW 
TO MEDIUM WITH THIS SCENARIO. FOR NOW WILL FORECAST A TROUGH IN 
THE AFOREMENTIONED AREA BEGINNING WITH THE MANUAL GRAPHICS VALID 
AT 48 AND 72 HRS.
 
WITH RESPECT TO MARINE INTERESTS...SW 15-20 KT WINDS WITH SEAS 
TO 8 FT IN A SE SWELL COMPONENT ARE EVIDENT FROM 08N TO 10N 
BETWEEN 113W-117W...AND IN A SW SWELL COMPONENT ALSO FROM 08N TO 
10N BETWEEN 95W-106W. BY 24 HOURS...THESE CONDITIONS WILL BE 
FORECAST WITHIN THE DOMAIN COVERING FROM 09N TO 12N BETWEEN 114W-
125W WITH SEAS 8 FT IN MERGING SE AND NW SWELLS. THESE 
CONDITIONS ARE FORECAST TO DIMINISH BY EARLY TUE EVENING.

$$
AGUIRRE