000 AXPZ20 KNHC 130944 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Mon Mar 13 2023 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 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 0930 UTC. ..SPECIAL FEATURES... Heavy Rainfall over Ecuador: The large-scale environment remains favorable for continued periods of heavy rainfall over portions of NW South America through late this week. Although the threat of heavy rain will exist on a daily basis, the risk is higher in Ecuador now through Tue morning, when very heavy rain and significant flash flooding is possible. After Tue, the rain in Ecuador should diminish in intensity slightly, while the biggest threat shifts southward into Peru. Please refer to your local meteorological service for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from a 1012 mb low near 08N87W southwestward to 05N92W and to 03N104W, where latest scatterometer data indicates that it transitions to the ITCZ to to 00N116W to 01S127W and to 02S140W. A second surface trough extends from 03.4S100W to 02S115W. Scattered moderate convection is seen within 60 nm of the ITCZ between 120W-126W. Similar activity is within 60 nm south of the second trough between 107W-115W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... High pressure of 1023 mb is centered west of these waters near 26N128W. The gradient between this high and lower pressures over northern Mexico is inducing moderate to fresh NNW winds in the offshore waters to the west of Baja California south of 30N and east of 117W. Farther north and west, gentle to moderate winds prevail. Moderate to locally fresh NW winds are occurring in the southern and central Gulf of California, and mainly at gentle speeds in the northern Gulf. Mostly moderate NW to N winds are present to the S and SW of Cabo San Lucas, extending offshore. Gentle winds prevail elsewhere east of 110W. Seas are 5-7 ft to the west of Baja California and 3-4 ft elsewhere, except 1-2 ft in the northern Gulf of California, and 5-6 ft between Cabo San Lucas and the Revillagigedo Islands. For the forecast, fresh to locally strong NNW winds will continue near, and within 120 nm west of the coast of Baja California through early this afternoon. Weak high pressure will shift eastward over the area Tue allowing for gentle winds. Moderate to fresh NW winds in the central and southern sections of the Gulf of California will remain through tonight. Relatively quiet conditions are expected elsewhere through Tue. A cold front will reach the Baja California Norte offshore waters early Wed, and move southeastward over the northern Gulf of California late Wed, then weaken and dissipate by early Thu over the central Gulf of California. Fresh southwest to west winds are expected in the northern Gulf of California Wed and Wed night ahead of the front. In the wake of the front, fresh NW to N winds are expected offshore Baja California Thu and Thu night and Wed night into Thu for the northern Gulf of California. The front will also bring moderate NW swell to the Baja California Norte waters. The next Gulf of Tehuantepec gap wind event is forecast to bring fresh to strong N winds early Wed through Wed night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please refer to the Special Features section for details on the potential for heavy rainfall over NW South America through late this week. Moderate E to SE winds offshore of western Panama and Costa Altimeter data indicates seas of 4-6 ft over these waters. Light to gentle winds prevail elsewhere across the Central America and South America waters. A partial overnight ASCAT pass suggests that low pressure may have formed to the west of central Costa Rica near 08N87W. Seas are 3-4 ft north of 09N and west of 88W. Seas of 4-6 ft remain elsewhere, the highest of which are along the equatorial offshore waters between Ecuador and the Galapagos Islands. Satellite imagery shows increasing scattered shower and thunderstorm activity within the area of the low pressure, roughly from 06N to 10N and between 85W-90W. Conditions aloft are favorable for this activity to remain active today, and continue through late on Tue. For the forecast, light to gentle variable winds are expected over just about the entire offshore waters through the forecast period. Winds in the Gulf of Papagayo region will become fresh NE to E on Thu, then diminish Thu night. Scattered showers and thunderstorms offshore southern Nicaragua and northern Costa Rica will continue through late Tue. REMAINDER OF THE AREA... High pressure of 1023 mb is analyzed near 26N128W. The associated gradient is allowing for generally light to gentle variable winds to exist to the N of about 21N and west of 119W, where decaying W to NW swell continues to support seas of 7-8 ft. A tighter gradient between the ridge associated to the 1023 mb high center and relatively lower pressure in the tropics is maintaining moderate to fresh N to NE winds from 17N to 22N and between 112W-118W as were highlighted in an overnight ASCAT pass over that part of the area. Seas with these winds are 5-7 ft. For the forecast, W to NW long-period swell that is propagating through the western waters will continue to decay through early this evening, at which time seas are forecast to lower below 8 ft. Fresh to strong SW winds ahead of a cold front that is currently approaching the waters northwest of the area near 34N140W should move from west to east across the waters north of 25N on Mon through early Tue. The cold front is forecast to reach from near 30N138W to 29N140W by early this evening, then begin to weaken as it reaches from near 30N128W to 26N134W and to 25N140W by early Tue evening and from near 30N118W to 25.5N132W by early Wed. It should then dissipate Wed night. A new frontal boundary will approach the NW forecast waters Wed evening, with a warm front to precede it over the far northern waters. The gradient associated with this system is forecast to support fresh to strong E to SE winds along with building seas north of 27N and west of 128W through Thu evening. $$ Aguirre