Tropical Storm Cosme Winds: 35 kt
Pressure: 1004 mbar
Advisory 4 / 2:00 AM PDT Sunday July 7, 2019

Cosme continues to just hang onto its status as a tropical cyclone. Infrared satellite imagery shows the storm has an exposed circulation with some new scattered blow-ups of convection which have formed since 06z displaced to the northeast. Wind shear, stronger than anticipated, perhaps induced by an upper-level trough situated over Baja California Sur, is currently affecting the system's ability to remain organized in any meaningful way. Dvorak estimates remain T1.5/25kt from SAB and T2.5/35kt from TAFB at 06z. Recent ASCAT passes show 30 kt winds near the north end of the circulation, but they did not capture the region of the likely strongest winds in the northeast quadrant, where gales are assumed to be present, but are not likely to be as intense as the previous advisory. Therefore, Cosme's intensity has been lowered to 35 kts.

Cosme is currently dealing with a sheared environment which will allow for the injection of very dry mid-level air located to the west into the system. The system is also located over a strong sea surface temperature gradient with fairly marginal waters varying between 25C and 27C oriented along an axis which the storm is expected to follow. The storm will have these marginal SSTs to work with for about the next twelve hours as it battles unfavorable shear and humidity levels before it reaches the end of a warm tongue and falls into waters below 25C. Beyond this point, even with shear potentially letting up, Cosme will not be in a conducive environment and will continue to weaken. Transition into a post-tropical cyclone is likely in 12 to 24 hours, and dissipation has been moved up to day 3.

The storm is tracking generally northwestward, which is expected to continue around the southwestern periphery of a mid-level ridge over northeastern Mexico. Cosme may begin to track more westerly as a result of recent weakening allowing for the influence of the low-level easterly trades to steer the shallow system.


INIT 07/0900Z 35 KT 50 MPH

12H 07/1800Z 30 KT 50 MPH

24H 08/0600Z 25 KT 45 MPH...POST-TROP/REMNT LOW

36H 08/1800Z 25 KT 40 MPH...POST-TROP/REMNT LOW

48H 09/0600Z 20 KT 35 MPH...POST-TROP/REMNT LOW

72H 10/0600Z...DISSIPATED

Forecaster Kalassak
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