000 AXPZ20 KNHC 012201 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Tue May 1 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 07N77W to 07N86W to 07N95W, where latest scatterometer data indicates the ITCZ axis begins and continues to 07N108W, where it is briefly interrupted by a northeast to southwest oriented trough. It resumes just west of this trough near 09N109W to 07N120W to 08N130W and to beyond 07N140W. Scattered strong convection is within 120 nm south of the axis between 85W and 87W. Scattered moderate to strong convection is noted within 120 nm either side of axis between 106W and 108W. Scattered moderate isolated strong convection is within 120 nm north of the axis between 117W and 120W, and also within 120 nm north of the axis between 124W and 128W. Scattered moderate convection is within 120 nm south of the axis between 92W and 94W, within 90 nm north of the axis between 129W and 132W, within 60 nm north of the axis between 135W and 138W and also within 30 nm of 08N78W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A high pressure ridge, anchored by strong high pressure well north of the area, extends southeastward across the offshore waters to the west of Baja California. High pressure is present north of 15N. The pressure gradient between the ridge and a large area of low pressure over the Great Basin of the U.S. is bringing mainly generally moderate to locally fresh northwest to north winds across these waters. These winds will diminish to mainly moderate intensity, with a few pockets of fresh northwest winds along the central and southern sections of Baja California, on Wed night as the strong high pressure north of the area shifts southward and weakens. Current maximum seas of 8 ft in northwest swell within this area of moderate to locally fresh northwest winds will subside to less than 8 ft late Wed night. Gulf of California: Strong to near gale force southwest to winds over the northern portion of the gulf will gradually diminish to strong winds early on Wed, and to less than 20 kt by early Tue afternoon. Model guidance suggests that these winds will become variable of gentle intensity by Wed night. Expect seas to 8 ft associated with strong to near gale force winds to subside to less than 8 ft Wed afternoon. A brief surge of fresh northwest winds is forecast along the coast of Mexico from 22N to 25N and also within about 45 nm offshore Cabo Corrientes Fri night as the pressure gradient tightens some due to the combination of strong high pressure north of the area shifting southward and the troughing present just inland the coast of central and northwestern Mexico. Gulf of Tehuantepec: The next event of strong northerly gap winds is expected beyond the forecast period early Sun morning. A rather pronounced jet stream branch extending from the deep tropics northeastward to across central Mexico continues to advect ample deep layer moisture towards central Mexico. Ripples of short-wave energy riding along this jet stream branch, in combination with the deep moisture already in place, are inducing small clusters of scattered showers and isolated thunderstorms over the offshore waters just along the 250 nm boundary and well to the southwest of this same boundary. The upper-level southwest flow associated with the aforementioned jet stream will continue to advect additional moisture and related convective activity northeastward towards the waters offshore mainly central Mexico. This moisture, in combination with daytime heating and local effects, should provide further impetus for convection to increase over central Mexico through the end of the week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to locally strong northeast to east drainage flow that began early this morning has diminished to mainly fresh flow this afternoon. Expect for the fresh to locally strong flow to develop again tonight, and continue to pulse nocturnally at this same intensity through Thu. Gulf of Panama: Gentle to mainly moderate nocturnal flow is forecast through Thu. Elsewhere, light to gentle winds will continue north of the trough axis, while gentle to occasionally moderate south to southwest winds remain south of the trough axis. Seas are forecast to be generally in the 4 to 6 ft range. REMAINDER OF THE AREA... A broad and strong surface ridge, anchored by a nearly stationary 1031 mb high centered well north of the area extends southeastward across the forecast waters to just west of the Revillagigedo Islands. The pressure gradient between the ridge and ITCZ is allowing for fresh northeast trades and seas of 7 to 8 ft in a slowly subsiding northeast swell to exist from 09N to 13N and west of about 132W. This area of subsiding swell will shrink in size through Thu. A weak surface trough extending from 14N106W to 08N110W will continue to move westward over the next couple of days. The trough is situated to the southeast of a well pronounced upper level jet stream that is transporting abundant deep layer moisture, in the form of overcast to broken mostly mid and high clouds from the central region of the tropics, northeastward towards central Mexico. Convective type clouds are underneath these mid and high level clouds, with some producing scattered showers and isolated thunderstorms primarily from 10N to 15N between 107W and 115W. Expect this pattern of deep moisture and convection to change little through the end of the week. $$ Aguirre