000
AXPZ20 KNHC 171602
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN MAR 17 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 AXIS EXTENDS FROM 10N85W TO 06N90W. THE ITCZ 
AXIS FROM 06N90W TO 04N100W TO 00N108W ACROSS THE EQUATOR. NO 
SIGNIFICANT CONVECTION IS NOTED.

...DISCUSSION...

SHIP AND LAND BASED OBSERVATIONS ARE INDICATING PLUMES OF 15 TO 
20 KT WINDS PERSIST OUT OF THE GULF OF PAPAGAYO AND FONSECA THIS 
MORNING. THIS IS LOWER THAN THE PAST SEVERAL DAYS AND IS 
INDICATIVE OF A DIMINISHING TREND FOR THE GAP WINDS DUE TO WEAK 
TRADE WIND FLOW OVER THE SW CARIBBEAN. WINDS TO 20 KT MAY STILL 
BRIEFLY APPEAR NEAR THESE AREAS DURING THE EARLY MORNING OVER 
THE NEXT COUPLE OF DAYS...BUT OVERALL LIGHT TO MODERATE FLOW 
WILL PREVAIL. LINGERING E-NE SWELL FROM THE EARLIER GAP WINDS 
CONTINUES TO SUPPORT 8-10 FT SEAS S OF 11N BETWEEN 95W AND 113W. 
SEAS WILL SUBSIDE TO LESS THAN 8 FT HERE BY MON AFTERNOON.
 
A POSITIVELY TILTED UPPER-LEVEL TROUGH EXTENDS ACROSS MEXICO 
FROM THE EASTERN RIO GRANDE VALLEY THROUGH CABO CORRIENTES TO 
12N120W. THE PRIMARY ENERGY WITHIN THE TROUGH HAS ALREADY PASSED 
INTO THE NW GULF OF MEXICO. THE TROUGH IS EXPECTED TO WEAKEN IN 
PLACE OVER THE NEXT DAY OR SO...BUT THE 70-90 KT UPPER JET ON 
ITS SE SIDE WILL REMAIN. THE REAR RIGHT QUADRANT OF THIS JET IS 
ENHANCING LIFT N OF THE ITCZ BETWEEN 95W-115W. PRECIPITABLE 
WATER IMAGERY SHOWS PLENTIFUL LOW-LEVEL TROPICAL MOISTURE IN 
THIS AREA. DIMINISHING SHOWERS AND THUNDERSTORMS ARE NOTED VIA 
INFRARED SATELLITE IMAGERY AND LIGHTNING DATA FROM 10N-15N 
BETWEEN 105W-110W IN THE REGION OF INCREASED MOISTURE AND LIFT. 

AN EXPANSIVE DEEP-LAYER LOW LIES N-NE OF THE HAWAIIAN ISLANDS. 
THE SOUTHWESTERLY UPPER JET ON THE SE SIDE OF THE LOW IS 
TRANSPORTING MOISTURE INTO WESTERN WATERS N OF 20N...MAINLY 
MANIFESTED AS CIRRUS. THE MORE ABUNDANT LOW-LEVEL MOISTURE LIES 
FATHER W WITH THE COLD FRONT ASSOCIATED WITH THE UPPER LOW. THAT 
FRONT IS STILL WELL W OF THE AREA FROM 32N146W TO 18N153W. THE 
UPPER LOW IS FORECAST TO WEAKEN AS IT MOVES NORTHEASTWARD 
THROUGH EARLY TUE. THE COLD FRONT IS EXPECTED TO BEGIN TO 
DISSIPATE AS IT CLIPS NW WATERS OVERNIGHT MON NIGHT WITH LITTLE 
FANFARE EXCEPT SOME SCATTERED SHOWERS AND POSSIBLY AN ISOLATED 
THUNDERSTORM. WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW 
ADVISORY CRITERIA.

THE 1028 MB SUBTROPICAL HIGH LIES NEAR 42N135W. THE PRESSURE 
GRADIENT IS WEAK BETWEEN THE SUBTROPICAL HIGH AND THE ITCZ OVER 
WESTERN WATERS. TRADE WINDS HAVE BEEN REDUCED TO A MODERATE TO 
FRESH NE BREEZE OVER MOST OF THE AREA. THE SUBTROPICAL HIGH IS 
EXPECTED TO WEAKEN AS THE AFOREMENTIONED DEEP-LAYER LOW N-NE OF 
THE HAWAIIAN ISLANDS MOVES NORTHEASTWARD TOWARD IT. THIS WILL 
KEEP TRADE WINDS WELL BELOW ADVISORY CRITERIA THROUGH AT LEAST 
TUE MORNING.

THE PRESSURE GRADIENT BETWEEN THE SUBTROPICAL RIDGE AND TROUGHING 
OVER THE U.S. DESERT SW IS FORCING FRESH TO STRONG NW WINDS 
ALONG THE COAST OF SOUTHERN CALIFORNIA N OF THE AREA. WHILE 
WINDS S OF 30N ARE EXPECTED TO REMAIN A MODERATE TO FRESH 
BREEZE...N-NW SWELL IS BEING PROPAGATED INTO NE FORECAST WATERS 
WITH SEAS REACHING TO 8 FT. THE WINDS WILL DIMINISH AS THE 
SUBTROPICAL HIGH WEAKENS AND SEAS SHOULD SUBSIDE TO LESS THAN 8 
FT BY MON AFTERNOON.

$$
SCHAUER/CHRISTENSEN