Tropical Depression One-E Discussion Number 1

Wiki-Hurricanes Forecast Center

2:00 PM PDT Tue Jun 25 2019

The area of interest about 275 miles southwest of Lázaro Cárdenas, Mexico, has organized into the season's first tropical depression. The convective pattern of the disturbance has been well organized since last night, with deep convection over the circulation and hints of spiral banding on both the northeast and southwest flanks. There was some ambiguity as to whether a well-defined, closed low existed; visible satellite imagery was fairly suggestive, but an ASCAT pass from after midnight showed little to no organization to surface wind features. Both ASCAT passes missed the system this morning, but a timely ScatSat pass did show a sufficiently-organized center to designate a tropical cyclone. The same instrument recorded maximum winds of 30kt. This is in line with a Dvorak estimate of T2.0/30kt from TAFB and is the intensity set for this advisory.

The intensity forecast for One-E is complicated, starting right at initialization and materialized through the fact the ECMWF does not portray a tropical cyclone. This is a stark difference from the recent run of the HWRF, which develops One-E into a Category 1 hurricane over the coming days. At a glance, the environment is conducive for intensification, with wind shear under 10kt, ocean temperatures around 28C, and mid-level relative humidity values near 60 percent for the next 36 hours or so. At least part of the difference in model forecasts appears tied to a broad area of vorticity to the southeast of One-E. Interaction between the depression and this area of enhanced spin may result in competition for convergence and difficulty for consolidation assuming it persists. The HWRF does not appear to have a good handle on this feature in its most recent run, but it did in the prior 0z run which peaked One-E as a weak tropical storm. For now, the higher-end solution has been discounted and only minimal development is likely. After 36 hours, One-E will enter a much drier environment, with higher shear and lower ocean temperatures. Degeneration to a remnant low is expected in about 72 hours, with dissipation about a day later.

Over the past few days, the system was being steered by a shallow 700mb ridge south of Baja California. Now that it has gained more vertical depth, the primary steering feature is expected to be an expansive 500mb high over northern Mexico. Therefore, a west-northwest trajectory with little deviation is expected over the next 3 days. After degeneration in 3 days, a curve toward the west or west-southwest is plausible in the typical easterly trade wind flow across the East Pacific.


INIT 25/2100Z 30 KT 35 MPH

12H 26/0600Z 35 KT 40 MPH

24H 26/1800Z 40 KT 45 MPH

36H 27/0600Z 35 KT 40 MPH

48H 27/1800Z 30 KT 35 MPH

72H 28/1800Z 25 KT 30 MPH...POST-TROP/REMNT LOW

96H 29/1800Z...DISSIPATED

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