Miriam (2018)

A tropical wave that left the west coast of Africa in mid-August moved across the Atlantic into the eastern North Pacific and gradually organized. A broad low formed along the wave axis, and a tropical depression developed at 0600 UTC 26 August about 980 nautical miles west‑southwest of the southern tip of the Baja California peninsula. The system became Tropical Storm Miriam six hours later, moved generally westward then turned northwest and north after crossing 140°W into the central North Pacific, and weakened to a post‑tropical low on 2 September before dissipating early on 3 September. Miriam never approached close enough to land to require watches or warnings.

Miriam did not make any landfalls. Throughout its lifetime it remained well over open water and posed no direct threat to populated coastlines.

Miriam reached its maximum intensity on 31 August and 1 September. Peak sustained winds were estimated at 85 knots (about 98 mph) and the minimum central pressure was 974 mb, making it a Category 2 hurricane at peak intensity.

Because Miriam stayed far offshore, there were no reported storm surge measurements associated with the hurricane and no reports of tropical‑storm‑force winds at land or on ships. Likewise, the report contains no significant rainfall totals tied to Miriam for named cities or counties because it remained over the open ocean.

There were no reported deaths or damage from Miriam. The storm’s impacts were negligible because it stayed well away from land.

Notable aspects include that Miriam’s formation was not well anticipated: forecasts only gave a high probability of genesis about six hours before it formed. Forecast track performance for the National Hurricane Center was better than the recent 5‑year average, while early intensity forecasts had a high bias at 36–72 hours because model disagreements about wind shear affected predicted strengthening.