Ernesto (2018)

A low pressure area developed over the central North Atlantic from a non-tropical weather system and became a subtropical depression about 0600 UTC on 15 August 2018, roughly 700 nautical miles west‑southwest of the western Azores. It strengthened to a subtropical storm later that day, transitioned to a tropical storm on 16 August as its convection became more organized, and moved northeastward in the mid‑latitude westerlies. The system lost its convection over colder waters late on 17 August, became a post‑tropical low near 0000 UTC 18 August (about 700 n mi north‑northeast of the Azores), merged with a frontal system, and its remnants dissipated over the British Isles on 19 August.

There were no landfalls by the subtropical or tropical phases of Ernesto. After losing tropical characteristics, its remnants passed near the British Isles as an extratropical low before dissipating on 19 August.

The peak intensity as a tropical cyclone was 40 knots (46 mph) with a minimum estimated central pressure of 1003 millibars while classified as a tropical storm. In the best track, Ernesto’s maximum sustained winds did not exceed tropical‑storm strength and the intensity estimates were conservatively based on subjective satellite and scatterometer data.

No storm surge measurements or notable coastal surge impacts were reported in the advisory or post‑event data for Ernesto. Rainfall totals of consequence were not reported in the NHC report; the storm remained over open water during its tropical phase and no significant rainfall observations from land stations were documented in the report.

There were no reports of damage or casualties associated with Ernesto. Forecasts had mixed success: official track and intensity errors were generally smaller than 5‑year means for similar forecasts, but the genesis was not well predicted far in advance — the system’s development was first mentioned as a low‑probability event more than four days ahead and the high likelihood was not identified until genesis. No coastal watches or warnings were required.