Debby (2018)

An extratropical low northwest of the westernmost Azores developed into Subtropical Storm Debby on 7 August 2018 about 800 nautical miles west of those islands. The system moved generally northward and then northeastward over the next two days, transitioned to a fully tropical storm around 0000 UTC 8 August, reached its peak on 9 August while located about 365 nmi southeast of Cape Race, Newfoundland, then lost deep convection and became a remnant low by 1800 UTC 9 August before being absorbed by a larger extratropical low on 10 August.

Debby remained well offshore for its entire life; it did not make any landfalls and no coastal watches or warnings were required.

The storm’s maximum sustained winds were 45 knots (about 52 mph) and its lowest central pressure was 998 millibars, making it a moderate tropical storm at peak intensity rather than a hurricane.

Because Debby stayed at sea, coastal storm surge impacts were not reported. Rainfall and surge totals on land were negligible or not recorded in the NHC report; the primary meteorological observations came from satellites and several ships that measured tropical-storm-force winds.

There were no reports of damage or casualties associated with Debby. The regions closest to its track — the Azores area and the waters southeast of Newfoundland — did not report impacts from the storm.

Noteworthy aspects include Debby’s non-tropical origin (it formed from an extratropical low), a short window of subtropical-to-tropical transition, and a genesis that was not well predicted in advance. NHC track forecast errors were slightly above recent averages at some short lead times, while intensity forecast errors were comparable to or slightly better than long-term means for the 12– to 36‑hour periods.