000 AXPZ20 KNHC 180954 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sun Mar 18 2018 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 0945 UTC. ...SPECIAL FEATURES... Gale Warning: Deepening surface low pres northwest of the area will drop southeastward towards the far northwest corner of the area behind a strong cold front that will move into the extreme northwest part of the area Mon night. The pres gradient ahead of the low will intensify increasing the wind field to the gale force range (25 to 35 kt) from the southwest in direction there, with seas in the range of 11 to 14 ft. Strong to near gale force southwest to west winds are forecast elsewhere to the north of 27N and west of 138W on Mon night, with seas 9 to 13 ft Mon night. By Tue evening the low pres is expected to have lifted just far enough north of the area to allow the culprit tight gradient to relax, and winds to lower to just below gale force. Please refer to the Pacific high seas forecast for more details on this upcoming event under AWIPS/WMO headers MIAHSFEP2/FZPN03. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from low pres over NW Colombia to the Pacific coast of Colombia at 08N84W to 06N92W to 05N101W to 05N107W, where latest scatterometer winds indicate the ITCZ axis begins and continues westward to 06N120W to beyond 06N140W. Scattered moderate convection is within 60 nm south of the axis between 92W and 94W, and within 30 nm south of the axis between 97W and 99W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A dissipating cold front extends from extreme southwestern Arizona to across the extreme northwest portion of the Gulf of California, and continues southwestward to near 27N121W. A 1021 mb high is centered at 25N120W, with a ridge extending southeastward to just west of the Revillagigedo Islands. The cold front will dissipate this afternoon as its upper level support shifts eastward to across Baja California and over northern/central Mexico. The 1021 mb high will remain about stationary through tonight, then become centered slightly to the southwest on Mon and Tue. Fresh to locally strong northerly winds will develop from 21N to 22N between 110W and 112W this morning, diminish to fresh winds this afternoon and start up again late tonight. By early on Mon, these winds are expected to develop again generally from 18.5N to 20N between 105.5W and 106.5W, with little change into Mon night. Seas associated with these winds are forecast to reach a maximum value of 8 ft. Mid to upper level moisture in the form of overcast cloudiness is well west of these waters, but is streaming eastward in advance of a strong mid to upper level trough that is presently well to the west of the discussion area. Some of this moisture may begin to move in over the far northern portion of Baja California and southern California on Tue. Gulf of California: A dissipating cold front is moving across the far NW portion of the gulf this morning. Strong southwest to west winds are occurring from 29.5N to 30.5N. The front will be followed by strong northwest to north winds through this morning, diminishing to moderate winds this afternoon. Elsewhere over the gulf, moderate northwest flow will be present, except increasing to fresh northwest to north winds over the southern portion tonight, and continue through Mon before increasing to strong early Mon evening and continuing through Tue. Seas with these winds will be in the range of 5 to 6 ft. Gulf of Tehuantepec: Strong north flow will surge through the gulf waters on Tue night, increasing to minimal gale force early on Wed. Gale conditions of 30 to 40 kt are then expected to continue through late Thu night, with seas reach a range from 10 to 15 ft downstream of the gulf near 14.5N95.5W on Wed night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to locally strong NE nocturnal winds, with seas of 5 to 7 ft will diminish to moderate intensity this afternoon, then increase again to strong tonight, and continue through Mon. Gulf of Panama: Fresh northerly winds will diminish to moderate winds this afternoon, then briefly increase to fresh tonight before diminishing again to moderate intensity on Mon. Elsewhere, gentle to moderate offshore flow will prevail N of 08N while light to gentle SW winds are forecast S of 08N. REMAINDER OF THE AREA... Please see see Special Features Section above for details on upcoming gale force winds to impact the far NW portion of the area in the short-term. A cold front will approach the far NW corner this morning, with the pres gradient tightening up ahead of it. This will develop strong south to southwest winds from 26N to 28N W of 136W tonight. The cold front will reach from near 32N134W to 24N140W by early on Mon. Strong south to southwest winds are forecast for N of 25N within 300 nm east of the cold front, with seas of 8 to 10 ft. Southwest to west strong winds are expected N of 29N and W of 138W early on Mon, with seas of 8 to 10 ft in advance of a second cold front. By early Mon evening, strong to near gale force SW to W winds along with seas of 9 to 12 ft are expected within 120 nm east and southeast of this second cold front along a position from 32N138W to 29N140W. Deepening surface low pres northwest of the area will drop southeastward towards the far northwest corner of the area behind the second cold front late Mon night intensifying the wind field there leading to gale force winds southwest winds there, and strong to near gale force southwest to west winds elsewhere to the north of 27N and west of 138W. Rather large seas, around the range of 10 to 18 ft, are forecast to move into the NW and N central portions over the area Mon through Tue night. The mid/upper level low pres system and related trough that will induce and drive the aforementioned surface low and cold front will be preceded by mid to upper level moisture in the form of overcast cloudiness. Areas of rain along with scattered showers and isolated thunderstorms under upper level divergence that is present to the the east and southeast of the mid/upper low have moved over the area north of about 26N and west of 125W. This moisture and related precipitation is expected to move east-northeast through Tue per model moisture guidance fields. $$ Aguirre