AXPZ20 KNHC 142115

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2115 UTC Tue Aug 14 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 2100 UTC.


1009 mb low pressure is centered near 11N119W along a tropical wave extending form 05N to 17N along 119W/120W, moving west at 10 to 15 kt. The surface low is centered south of a mid/upper level ridge, resulting in deep layer easterly shear. The surface center is partially exposed, with scattered moderate to isolated strong convection currently extending within 180 nm in the northwest quadrant of the low. A recent ScatSat pass showed 20 to 25 kt winds within 90 nm in the northern quadrant of the low. Showers and thunderstorms continue to become better organized, and a tropical depression is likely to form tonight or Wed while the disturbance moves westward.


The monsoon trough extends from 09N79W to developing low pressure centered near 11N119W. Scattered moderate strong convection is noted within 90 nm south of the monsoon trough between 105W and 109W.



Weak ridging persists across the waters east of Baja California, supporting gentle to moderate NW flow and 3 to 5 ft seas in the adjacent offshore waters.

Gentle to moderate SE breezes continue across the Gulf of California, although brief pulses of moderate to fresh W to SW winds are possible over the far northern Gulf tonight into Wed, and again nightly through the week.

Farther south, long period SW swell will move into the offshore waters between Puerto Angel and Baja California Sur through Wed, with seas peaking at 7 to 10 ft Wed evening into Thu morning, and highest seas across the waters between Guatemala and Cabo Corrientes. This will produce very large and dangerous surf conditions along the coastlines and outer reefs with localized breaking waves 15-20 ft Wed through Thu morning.

Looking ahead, fresh to strong gap winds are expected by Thu night in the Gulf of Tehuantepec.


Gulf of Papagayo: Fresh gaps winds are expected during the overnight hours through mid week followed by fresh nocturnal easterly flow through Fri morning.

Gentle to occasionally moderate E winds are forecast elsewhere N of the monsoon trough which is meandering between 09N and 11N. Moderate to locally fresh southerly winds are forecast S of the monsoon trough through early next week. Long period S to SW swell has spread into the regional waters overnight and has raised offshore seas to 6 to 8 ft on either side of the Galapagos Islands. A stronger and larger pulse of SW swell will move into the regional waters tonight. This next pulse of cross equatorial swell will raise seas to 7-9 ft Wed through early Thu before slowly subsiding through Fri, and produce large and dangerous surf conditions along the coasts and outer reefs.


Weak 1010 mb low pressure is centered near 17N132W, moving W-NW at 10 to 15 kt. There is no significant convection near the low, and it is weakening rapidly. Fresh winds are still likely on the northern periphery of the low center, and seas may still be reaching 8 ft. Building high pressure north of the area will allow the area of fresh easterly winds and 8 ft seas to expand, even as the low pressure opens into a trough over the next couple of days, reaching 140W by Wed night.

Farther to the northwest, the remnant low of Kristy is centered near 24N139W, with an estimated pressure of 1014 mb. The low is weakening, and a recent scatterometer pass showed generally moderate winds near the low pressure as it drifts west of the area.

Long-period cross-equatorial southerly swell, in the form of 7 to 10 ft seas, will propagate N across the tropical waters S of 20N E of 120W tonight through Thu, and then subside to less than 8 ft on Thu night.

$$ Christensen