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Tropical Depression Nine-E Discussion Number 1

Wiki-Hurricanes Forecast Center

2:00 PM PDT Thu Jul 26 2018

The area of disturbed weather located about 1,850 miles southwest of the southern tip of the Baja California Peninsula has sufficiently organized to be declared a tropical depression. A series of ASCAT passes shortly after 5z and 17z indicated a well-defined and closed circulation, while recent satellite imagery shows that deep convective activity continues to fire over the center. The convection is not particularly well organized, resulting in Dvorak estimates of T1.5/25kt. This is in line with ASCAT and represents the initial intensity.

Nine-E is moving just north of due west, steered on the southwestern periphery of a mid-level ridge centered southwest of California. This ridge is likely to remain stout over the next few days, and so no change in trajectory is expected. Even if this high pressure did not exist, Nine-E's shallow nature and forecast degeneration would keep it on a westward course under the influence of the climatological east-to-west low-level trade wind flow. The storm should pass into the Central Pacific tomorrow, continuing comfortably south of the Hawaiian Islands in 3 to 4 days.

Satellite imagery reveals that Nine-E is heavily sheared, the byproduct of a displaced anticyclonic to its west as well as an abnormally strong TUTT north of Hawaii. These upper-level winds may relax ever so slightly tonight, but are expected to increase to the ballpark of 20-25kt tomorrow and on. Sea surface temperatures and mid-level relative humidity values are both favorable, but the shear is likely to be too overwhelming for intensification. None of the global models show any further development of Nine-E, while the HWRF shows slight intensification over the four days before degeneration on day 5. The LGEM and HWRF, however, show slow development throughout the period, particularly by days 4 and 5 when shear is weaker. Given the degree of shear in the short-term, though, I'm not convinced Nine-E will survive to take advantage of the more favorable environment next week. For now, the forecast maintains Nine-E as a tropical depression and dissipates it in day 5. This is fairly low confidence, however.

FORECAST POSITIONS AND MAX WINDS

INIT 26/2100Z 25 KT 30 MPH

12H 27/0600Z 30 KT 35 MPH

24H 27/1800Z 30 KT 35 MPH

36H 28/0600Z 25 KT 30 MPH

48H 28/1800Z 25 KT 30 MPH

72H 29/1800Z 25 KT 30 MPH

96H 30/1800Z 25 KT 30 MPH

120H 31/1800Z...DISSIPATED