000 AXPZ20 KNHC 302204 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Mon Apr 30 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 northwest Colombia to across the northern Gulf of Panama, then turns west-northwest to across southern Panama and continues to 08N86W and to 07N100W, where latest scatterometer data indicates that the ITCZ axis begins and continues to 07N113W to 06N130W to 06N140W. Scattered strong convection is seen within 120 nm south of ITCZ axis between 132W and 136W, within 90 nm either side of the axis between 129W and 132W...within 90 nm south of the axis between 132W and 137W and within 60 nm north of the trough axis east of 79W. Scattered moderate to strong convection is within 150 nm south of the trough axis between 85W and 87W. Scattered moderate isolated strong convection is within 150 nm north of the trough axis between 98W and 100W. Scattered moderate convection is within 90 nm south of trough axis between 80W and 81W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A northwest to southeast oriented high pressure ridge, anchored by strong high pressure well north of the area, will prevail through the entire forecast period. A slightly tight pressure gradient between the ridge and broad low pressure over the western United States will continue to support fresh northwest winds across the open waters N of 27N west of the Baja Peninsula. Winds will diminish to a moderate NW to N breeze 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 the area of fresh northwest winds will subside to less than 8 ft Wed evening. Gulf of California: Fresh to strong southwest winds are forecast to develop again late tonight from 29N to 31N, and increase to near gale force early on Tue as the low pressure deepens over the western United States while at the same time high pressure ridging nudges southeastward across the waters to the west of Baja California, with the resultant tight gradient favorable for these winds to increase. Model guidance suggests that these winds then slowly diminish to strong intensity late Tue night into Wed and become variable of gentle to moderate intensity by Wed evening. Expect seas to build to 8 ft Tue, and subside to less than 8 ft Wed. Gulf of Tehuantepec: The next event of strong northerly winds is expected beyond the forecast period near 12Z on Sat. A rather pronounced jet stream branch extending from the deep tropics northeastward to across central Mexico is transporting ample deep layer moisture towards central Mexico. In addition, ripples of short-wave energy riding along this jet stream branch in combination with the deep moisture already in place are inducing clusters of scatterer moderate to strong convection along the 250 nm offshore waters boundary, with greater concentration of similar type activity just west and well to the southwest of the 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, should provide further impetus for convection to become more widespread over central Mexico though at least the next couple of days. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to locally strong nocturnal drainage flow is forecast to begin late tonight and continue through beyond the next couple of days. Gulf of Panama: Gentle to mainly moderate nocturnal flow is forecast for the next several nights. Elsewhere, light to gentle winds northeast to east will continue north of the trough axis, while gentle to moderate south to southwest winds remain south of the trough axis. Seas with these are forecast to be generally in the 4 to 6 ft range, with seas possibly slightly higher offshore Ecuador. Deep layer moisture in place over the far eastern Pacific is providing a favorable environment for pockets of mostly moderate convection to develop over much of these waters, with little change expected over the next couple of days. REMAINDER OF THE AREA... A broad and strong surface ridge, anchored by a nearly stationary 1035 mb high centered well north of the area at 43N140W, extends southeastward across the forecast waters. Fresh trades, and along with 6 to 8 ft seas will continue between the ridge and the ITCZ through Wed. $$ Aguirre