000
AXPZ20 KNHC 051530
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT JAN 05 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

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

THE MONSOON TROUGH IS ALONG 07N77W TO LOW PRES NEAR 06N79W 1009 
MB TO 05N87W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS 
FROM 05N87W TO 05N100W TO 07N113W THEN RESUMES FROM 07N117W TO 
06N130W TO 05N140W. SCATTERED MODERATE CONVECTION IS WITHIN 60 
NM S OF THE MONSOON TROUGH E OF THE LOW...WITHIN 45 NM N OF THE 
ITCZ BETWEEN 103W AND 108W...AND ALSO WITHIN 60 NM N OF THE ITCZ 
BETWEEN 117W AND 127W.

...DISCUSSION...

WESTERLY FLOW DOMINATES THE MID AND UPPER LEVELS ACROSS THE 
DISCUSSION WATERS. AN UPPER TROUGH IS DIGGING FROM SOUTHERN NEW 
MEXICO SOUTHWESTWARD ACROSS THE SOUTHERN GULF OF CALIFORNIA TO 
NEAR 19N119W. A 75-100 KT UPPER JET IS TRANSPORTING MID LEVEL 
MOISTURE FROM THE DEEP TROPICS S OF HAWAII AHEAD OF THE TROUGH 
TO ACROSS CENTRAL MEXICO. OTHERWISE...MAINLY DRY AND STABLE AIR 
IS PRESENT N OF 20N E OF 120W. A BROAD UPPER LEVEL DIRTY RIDGE 
STRETCHES FROM 32N123W TO 20N125W TO 12N125W. ANOTHER UPPER 
TROUGH EXTENDS FROM THE FAR WESTERN GULF OF MEXICO SOUTHWARD 
ACROSS SE MEXICO TO NEAR 08N98W. A WEAKER SHORT WAVE TROUGH 
STRETCHES FROM CENTRAL COSTA RICA TO WESTERN COLOMBIA HELPING TO 
ENHANCE CONVECTION E OF A SURFACE LOW JUST W OF THE COAST OF 
COLOMBIA.

AT THE SURFACE...1025 MB HIGH PRES IS POSITIONED NEAR 30N126W 
WITH A RIDGE REACHING SE TO NEAR 20N110W. A TIGHT PRES GRADIENT 
SW OF THIS RIDGE AND N OF THE ITCZ IS AIDING THE PRESENCE OF 
FRESH TO STRONG TRADE WINDS ACROSS THE W CENTRAL WATERS. THE 
AREA OF STRONGEST TRADES WILL EXPAND BY SUN MORNING AS A COLD 
FRONT CURRENTLY FROM 30N130W TO 23N140W SHIFTS EASTWARD WHILE 
WEAKENING...USHERING IN STRONGER HIGH PRES BEHIND IT. FRESH TO 
STRONG WINDS WILL ALSO FOLLOW IMMEDIATELY BEHIND THE FRONT... 
WITH IT DISSIPATING TO A TROUGH BY LATE SUN OR MON MORNING. A 
SET OF LONG PERIOD NW SWELL UP TO 11 FT IS COMMINGLING WITH NE 
WIND WAVES IN THE AREA OF ENHANCED TRADES...AS WELL AS MORE PURE 
NW SWELL OUTSIDE OF THE TRADES ALL THE WAY TO 106W. THE SWELL 
WILL GRADUALLY DECAY TO LESS THAN 8 FT OVER ITS SE-S EXTENT THIS 
WEEKEND. THIS WILL OCCUR WHILE A REINVIGORATING AREA OF NW SWELL 
ARRIVES BEHIND THE COLD FRONT...PUSHING SEAS UP TO 14 FT MAINLY 
WITHIN THE AREA OF STRONGEST TRADES BY TOMORROW.

A PINCHED PRES GRADIENT PRESENT OVER THE GULF OF CALIFORNIA 
BETWEEN SURFACE TROUGHING ALONG THE WESTERN COAST OF MEXICO AND 
THE ABOVE DISCUSSED RIDGE WILL MAINTAIN PRIMARILY MODERATE TO 
FRESH NORTHERLY WINDS THROUGH THE NEXT 48 HOURS.

GAP WINDS...
GULF OF TEHUANTEPEC...AN OVERNIGHT OCEANSAT SCATTEROMETER PASS 
INDICATED A HANDFUL OF FLAGGED 30-34 KT WIND BARBS AND ONE 
EXPLICIT 34 KT BARB. WHILE THERE STILL MAYBE OCCASIONAL 
CALIBRATION ISSUES WITH THIS INSTRUMENT...THE WINDS SAMPLED BY 
NON-FLAGGED BARBS WERE STILL NEAR GALE FORCE WITH THE PASS 
OCCURRING PRIOR TO THE STRONGEST WINDS LIKELY PRESENT AFTER 0550 
UTC. AN EXAMINATION OF HI-RESOLUTION ASCAT DATA FROM A 0327 UTC 
PASS SHOWED 30 KT WIND BARBS ON THE FAR WESTERN FRINGE OF THE 
GALE AREA (THE PASS MISSED THE IMMEDIATE GULF OF TEHUANTEPEC). 
BASED ON THE ASCAT 5 KT OR SO LOW BIAS AT 30 KT AND THE PASS 
BEING ON THE WESTERN EDGE OF THE PRESUMED GALE AREA...THE GALE 
WARNING HAS BEEN RE-RAISED WITH THIS MORNINGS FORECAST PACKAGE. 
WHILE WINDS WILL CONTINUE TO PULSATE FROM NEAR GALE TO GALE 
FORCE LEVELS (STRONGEST DURING THE LATE NIGHT AND EARLY MORNING 
HOURS WITH ADDITIONAL DRAINAGE FLOW)...HAVE ELECTED TO KEEP THE 
GALE WARNING IN PLACE THROUGHOUT THE NEXT 48 HOURS TO AVOID 
FLIP-FLOPPING IN THE FORECAST. A REINFORCING NORTHERLY SURGE 
WILL LIKELY INCREASE WINDS TO AT LEAST 40 KT BY 06-12 UTC MON 
WHICH WILL BUILD SEAS DOWNSTREAM TO 15 FT.

GULF OF PAPAGAYO...A 0326 UTC ASCAT PASS SHOWED 20-25 KT WINDS 
IN THE GULF OF PAPAGAYO A FEW HOURS PRIOR TO PEAK DRAINAGE FLOW 
WITH 30 KT NE WINDS POSSIBLE EARLIER THIS MORNING. THESE WINDS 
ARE BEING ENHANCED BY STRONG TO GALE FORCE TRADES IN THE SW 
CARIBBEAN SEA. FRESH TO STRONG NE WINDS WILL CONTINUE TO PULSE 
IN THE GULF OF PAPAGAYO THROUGH THE NEXT FEW MORNINGS AS THE 
TRADES IN THE CARIBBEAN HOLD IN PLACE.

$$
LEWITSKY