000 AXPZ20 KNHC 210343 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC SAT DEC 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0315 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS EXTENDS FROM A 1006 MB LOW PRES NEAR 06N79W TO 08N90W TO 06N100W...WHERE IT TRANSITIONS TO THE ITCZ TO 09N113W TO 08N125W TO 08N140W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF THE ITCZ W OF 135W...AND ALSO WITHIN 30 NM OF THE ITCZ BETWEEN 105W-107W. ...DISCUSSION... A RATHER VIGOROUS UPPER LOW IS RAPIDLY MOVING SEWD OVER SOUTHEASTERN ARIZONA WITH AN UPPER TROUGH EXTENDING FROM THE LOW SW ACROSS CENTRAL BAJA CALIFORNIA TO 24N118W AND TO NEAR 23N127W. BROAD SCALE MID/UPPER ANTICYCLONIC FLOW IS PRESENT TO THE NW OF THE TROUGH...AND IS FUNNELING UPPER LEVEL FLOW NLY FLOW INTO THE BASE OF THE TROUGH. AN ACTIVE JET STREAM BRANCH STRETCHES FROM 23N130W EWD THROUGH THE BASE OF THE TROUGH...THEN TURNS NE AT 22N115W TO ACROSS N CENTRAL MEXICO AND TO FAR W TEXAS. SATELLITE WATER VAPOR IMAGERY SHOWS OVERCAST TO BROKEN MID AND UPPER LEVEL CLOUDS STREAMING E AND NE WITHIN ABOUT 450 NM S OF THE JET STREAM BRANCH. WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE POSSIBLE UNDERNEATH THESE CLOUDS. THE WATER VAPOR IMAGERY ALSO DEPICTS MODERATE TO STRONG SUBSIDENCE INDUCING DRY AND STABLE ATMOSPHERIC CONDITIONS TO THE NW OF THE TROUGH WHERE BROKEN STRATOCUMLUS CLOUDS ARE SEEN SPREADING SW. SIMILAR DRY CONDITIONS ARE NOTED ACROSS THE ERN PORTION OF THE AREA SE OF THE JET STREAM RELATED CLOUDS...WITH THE EXCEPTION OF THE SMALL AREA FROM 11N TO 15N BETWEEN 110W-116W WHERE AN UPPER LEVEL DISTURBANCE EMBEDDED IN THE SW TO W FLOW S OF THE JET STREAM BRANCH IS TRIGGERING OFF SCATTERED MODERATE CONVECTION WITHIN 30 NM OF 13N115W. THE SURFACE COLD FRONT ASSOCIATED WITH THE UPPER TROUGH IS ANALYZED FROM A 1002 MB LOW OVER SE ARIZONA SSW TO OVER THE FAR SRN PART OF THE GULF OF CALIFORNIA...AND TO NEAR 23N119W BEFORE IT LOSES ITS IDENTITY. IT IS MOVING SE AT 20 KT. THE 00 UTC ANALYSIS REVEALS A VERY TIGHT PRES GRADIENT BEHIND IT INDUCED BY STRONG HIGH PRES OF 1033 MB WELL N OF THE AREA AT 39N141W WITH A RIDGE STRETCHING SEWD TO 32N134W TO NEAR 22N125W IS BRINGING NW WINDS OF 20-25 KT N OF 24N BETWEEN 115W-123W. SEAS WITHIN THIS AREA ARE 8-13 FT IN NW SWELL...EXCEPT 10-15 FT IN LONG PERIOD NW SWELLS N OF 26N. THE UPPER TROUGH WILL QUICKLY SHIFT INLAND THE CENTRAL U.S. OVER THE NEXT 24-36 HRS. BY THEN...THE PREVIOUSLY MENTIONED COLD FRONT WILL HAVE DISSIPATED INLAND MEXICO. THE N WINDS 20-25 KT ARE FORECAST TO DIMINISH TO 20 KT OR LESS BY EARLY SAT WITH THE LARGE NW SWELLS BEGINNING TO SLOWLY SUBSIDE. SEAS OF 8-11 FT ARE EXPECTED AT THAT TIME N OF 18N BETWEEN 115W- 133W. THE 1033 MB HIGH IS FORECAST TO MOVE EWD OVER THE NEXT 24-48 WHILE SLIGHTLY WEAKENING. THE PRES GRADIENT BETWEEN THE HIGH AND LOWER PRES ALONG THE ITCZ CONTINUES TO RESULT IN FRESH TO STRONG TRADE WINDS BETWEEN THE RIDGE AND ITCZ...FROM ROUGHLY N OF 16N W OF 123W AS WAS INDICATED BY A COUPLE OF SHIP REPORTS IN THAT AREA...AND BY THE LATEST ASCAT PASS FROM FRI AFTERNOON. THE PRES GRADIENT WILL GRADUALLY RELAX THROUGH SAT NIGHT WITH THE SLIGHT WEAKENING OF THE PRESENT 1033 MB HIGH CENTER. VERY LONG PERIOD NW SWELLS...WITH WAVE PERIODS BETWEEN 19-22 SEC MOVING ACROSS THE FAR NW PORTION WILL CONTINUE TO PROPAGATE THROUGH THESE WATERS THROUGH SAT...AND REACH THE REMAINDER OF THE WESTERN PART OF THE AREA BY LATE SAT. THESE SWELLS WILL GRADUALLY BUILD AS THEY PROPAGATE SEWD ACROSS THE AREA AND MIX WITH DECAYING NLY SWELLS BEHIND THE CURRENT COLD FRONT. GULF OF TEHUANTEPEC...THE NEXT GAP WIND EVENT IS FORECAST TO BEGIN LATE AROUND EARLY MON AFTERNOON WITH WINDS REACHING GALE FORCE AGAIN GOING IN MON EVENING. THIS NEXT EVENT WILL LIKELY BE ANOTHER STRONG ONE AS MARINE GUIDANCE INDICATES THAT IT WILL PERSIST THROUGH THE MIDDLE OF NEXT WEEK. GULF OF CALIFORNIA...RECENT W TO NW WINDS OF 20-25 KT OVER THE FAR NRN PORTION OF THE GULF HAVE DIMINISH TO 15-20 KT AS THE PRES GRADIENT THERE SLACKENS. HIGH PRES WILL BUILD BACK INTO THE REGION THIS WEEKEND FROM THE NW...AND INCREASE THE PRES GRADIENT TO SUPPORT NW WINDS OF 15-20 KT ACROSS THE ENTIRE GULF OF CALIFORNIA ON SUN EVENING. THESE WINDS WILL INCREASE FURTHER LATE SUN NIGHT INTO MON. $$ AGUIRRE