000
AXPZ20 KNHC 210941
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU FEB 21 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 
0900 UTC.

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

THE MONSOON TROUGH NOT DISCERNIBLE ON 06 UTC ANALYSIS. THE ITCZ 
AXIS EXTENDS FROM 04N90W TO 06N115W TO 08N140W. SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION WAS NOTED WITHIN 60 NM ON
EITHER SIDE OF ITCZ AXIS BETWEEN 115W AND 125W.

...DISCUSSION...

AN UPPER LEVEL SHORT WAVE TROUGH IS DIGGING SE FROM THE NE 
PACIFIC INTO SOUTHERN CALIFORNIA ON THE HEELS OF A MUCH STRONGER 
DISTURBANCE THAT PUSHED THROUGH THE AREA YESTERDAY AND IS NOW 
LIFTING EASTWARD THROUGH THE SOUTHERN ROCKIES. A COLD FRONT 
ASSOCIATED WITH THE SYSTEM FROM YESTERDAY MOVED INTO NW MEXICO 
BUT IS NOT CLEARLY DISCERNIBLE AS IT MOVES INTO MORE MOUNTAINOUS 
TERRAIN AND AS ITS UPPER SUPPORT SHIFTS NE OF THE REGION. A DEEP 
LAYER RIDGE IS CENTERED N OF HAWAII AND IS SUPPORTING 1035 MB 
HIGH PRES NEAR 35N147W WITH A SURFACE RIDGE EXTENDING EAST 
TOWARD THE SOUTHERN TIP OF THE BAJA PENINSULA. 

THE INFLUENCE AT THE SURFACE OF APPROACHING UPPER SHORT WAVE 
TROUGH WITH THE SURFACE RIDGE HAS BEEN KEEPING THE GRADIENT 
FAIRLY TIGHT OFF NORTHERN BAJA...WITH SCATTEROMETER DATA AND 
SHIP OBSERVATIONS FROM LATE YESTERDAY INDICATING 20 TO 25 KT NW 
FLOW MAINLY N OF 25N AND E OF 125W. ALTIMETER PASSES SHOWED SEAS 
AS HIGH AS 15 FT...LIKELY IN NW SWELL. THESE WINDS WILL DIMINISH 
TODAY AS THE SHORT WAVE TROUGH PASSES INLAND AND RIDGING BUILDS 
ACROSS THE AREA. SEAS WILL SUBSIDE AS WELL BUT MORE GRADUALLY 
DUE TO NW SWELL.

FARTHER WEST...THE STRONG RIDGE WILL MAINTAIN A BROAD AREA OF 
FRESH TO STRONG TRADE WINDS...MAINLY N OF 10N AND W OF 130W. NW 
SWELL WITH SEAS 8 FT OR GREATER WILL CONTINUE TO DOMINATE THE 
WATERS W OF 120W AND MIX WITH THE NE WIND WAVES IN THE AREA OF 
THE FRESH TO STRONG TRADE WINDS. UPPER LEVEL HIGH DENSITY WIND 
DATA DEFINE A NEGATIVELY TILTED UPPER TROUGH FROM 18N125W TO 
06N120W...AIDING IN SUSTAINING CLUSTERS OF MODERATE TO STRONG 
CONVECTION ALONG THE ITCZ BETWEEN 115W AND 125W. 

LOOKING AHEAD TO SUN THROUGH TUE...ALTHOUGH THERE ARE SOME 
DIFFERENCE IN STRENGTH AND TIMING...THE MAIN THEME OF GLOBAL 
MODELS IS THAT THE DEEP LAYER RIDGE N OF HAWAII FINALLY BREAKS 
DOWN WITH ARRIVAL A PROGRESSIVE UPPER TROUGH THAT COMES INTO 
PHASE WITH PERSISTENT UPPER LOW THAT HAS BEEN ANCHORED NE OF THE 
BIG ISLAND OF HAWAII. THIS WEAKENS THE BOUNDARY LAYER RIDGE 
ALLOWING TRADE WINDS TO FINALLY DIMINISH W OF 130W. 

GAP WINDS...
FRESH TO STRONG WINDS WILL CONTINUE TO PULSE IN THE GULF OF 
PAPAGAYO...WITH THE STRONGEST WINDS OCCURRING DURING THE 
OVERNIGHT AND EARLY MORNING HOURS WITH ENHANCEMENT BY NOCTURNAL 
DRAINAGE FLOW. ASSOCIATED SIGNIFICANT WAVE HEIGHTS WILL PEAK TO 
AROUND 8 FT TODAY. THE AREAL COVERAGE OF THESE WINDS WILL SHRINK 
TO E OF 88W THIS AFTERNOON...AND LIKELY TO MODERATE TO FRESH 
LEVELS OVERALL THIS WEEKEND AS HIGH PRES N OF THE AREA WEAKENS 
AND CONDITIONS BECOME LESS FAVORABLE.

$$
CHRISTENSEN