000
AXPZ20 KNHC 130949
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI 
1005 UTC FRI SEP 13 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...TROPICAL LOW...

SATELLITE IMAGERY THIS EVENING AND RECENT SHIP REPORTS SUGGEST 
THAT A LOW PRES CENTER IS ALONG THE MONSOON TROUGH NEAR 15N101W. 
SURFACE PRESSURES ACROSS THE REGION ARE VERY LOW... AND THE 
ESTIMATED CENTRAL PRES OF THIS LOW CENTER IS 999 MB. THE SW 
MONSOON FLOW IS SURGING INTO THE SOUTHERN PERIPHERY OF THE LOW 
PRES...OVER THE AREA FROM 08N TO 13N BETWEEN 95W AND 105W. A 
PAIR OF ALTIMETER PASS OVER THE MAIN AREA OF WINDS IN THE PAST 
12 HOURS INDICATED SEAS APPROACHING 12 FT. THE LATEST BURST OF 
CONVECTION IS DUE TO THE STRONG SW FLOW CONVERGING WITH NE 
DRAINAGE FLOW OFF THE COAST OF MEXICO. THIS BROAD AREA OF FRESH 
TO STRONG SW MONSOONAL FLOW IS EXPECTED TO CONTINUE FOR THE NEXT 
FEW DAYS AND WILL MAINTAIN AN ENVIRONMENT FAVORABLE FOR SMALL 
LOW CENTERS TO FORM IN THIS GENERAL AREA. ABUNDANT TROPICAL 
MOISTURE PERSISTS ACROSS THE REGION...AND WITH SURFACE PRESSURES 
BELOW NORMAL...IMPROVED ORGANIZATION OF THIS LOW CENTER COULD 
OCCUR DURING THE NEXT FEW DAYS AS THE LOW DRIFTS OFF TOWARDS THE 
NW. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE 
IN THE NEXT 48 HOURS. REGARDLESS OF TROPICAL CYCLONE 
DEVELOPMENT...CLUSTERS OF MODERATE TO STRONG CONVECTION WILL 
CONTINUE INTERMITTENTLY ACROSS THE PACIFIC COASTAL ZONES OF 
SOUTHERN MEXICO DURING THE NEXT 48 HOURS...AND WILL LEAD TO 
PERIODS OF HEAVY RAIN...WHICH COULD CAUSE LIFE-THREATENING FLASH 
FLOODING AND MUDSLIDES. A VERY LONG FETCH OF STRONG ONSHORE SW 
WINDS WILL ALSO PRODUCE VERY ROUGH SEAS AND STRONG CONFUSED SURF 
ALONG THE MEXICAN COASTLINE...LEADING TO  DANGEROUS SURF 
CONDITIONS AND WIDESPREAD RIP CURRENTS.

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

THE MONSOON TROUGH REMAINS ILL DEFINED FROM THE SW CARIBBEAN SEA 
AND THROUGH NORTHERN CENTRAL AMERICA TO THE AFOREMENTIONED DEEP 
LOW PRES NEAR 15N101W 999 MB TO 15N113W TO LOW PRES NEAR 11N121W 
1009 MB TO 10N140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION IS NOTED WITHIN 75 NM N OF THE MONSOON TROUGH AXIS 
AND WITHIN 150 NM S OF THE MONSOON TROUGH AXIS BETWEEN 103W AND 
110W. SCATTERED MODERATE CONVECTION IS ALSO NOTED WITHIN 60 NM 
IN THE NW QUADRANT OF THE LOW PRES NEAR 11N121W.

...DISCUSSION...

THE MAIN FORECAST ISSUE OVER THE NEXT SEVERAL DAYS REMAINS THE 
DEVELOPMENT TRACK OF THE 999 MB LOW PRES CENTERED NEAR 15N101W. 
CURRENTLY AN UPPER LEVEL RIDGE EXTENDS W TO E ALONG 22N FROM 
140W TO 22N115W...THEN NE ACROSS BAJA CALIFORNIA SUR TO W TEXAS. 
DRY AND SUBSIDENT NORTHERLY FLOW BETWEEN THE UPPER RIDGE AND A 
SHARP UPPER TROUGH ALONG ROUGHLY 100W IS SUPPRESSING CONVECTIVE 
DEVELOPMENT FROM JALISCO TO MICHOACAN AND ADJACENT PACIFIC 
WATERS. DIVERGENT SOUTHERLY FLOW ALOFT ON THE EAST SIDE OF THE 
UPPER TROUGH IS ENHANCING THE NOCTURNAL CONVECTION ALONG THE 
COAST OF GUERRERO EASTWARD THROUGH THE GULF OF TEHUANTEPEC. THE 
UPPER TROUGH IS DRIFT W OVER N CENTRAL MEXICO OVER THE NEXT 24  
TO 48 HOURS...AND MOST MODEL GUIDANCE IS SHOWING THE LOW PRES 
FOLLOWING WITH A NORTHWARD THEN NORTHWEST TRACK PARALLEL TO THE 
COAST OF MEXICO. 

1019 MB HIGH PRES IS CENTERED NEAR 26N133W. SHIP OBSERVATIONS 
AND SCATTEROMETER DATA INDICATE FRESH N FLOW OFF THE COAST OF 
THE BAJA PENINSULA. AN ALTIMETER PASS FROM A FEW HOURS PRIOR 
INDICATED SEAS TO 7 FT IN THIS AREA.  


$$
CHRISTENSEN