Philippe (2011)

A tropical wave that moved off the coast of Africa late on 22 September developed quickly into a closed low and became Tropical Depression Seventeen at 0600 UTC on 24 September about 225 nautical miles south of the southern Cape Verde Islands. The system strengthened to Tropical Storm Philippe later that day and wandered generally west-northwestward into the central Atlantic. Philippe was long-lived (24 September–8 October 2011) and experienced several periods of strengthening and weakening while moving across the tropical and western Atlantic. It turned northward and then northeastward in the western Atlantic before becoming extratropical on 8 October and being absorbed by a larger low over the north-central Atlantic on 9 October.

Philippe did not make landfall at any time during its life. It remained well offshore of the Caribbean, the U.S. East Coast, Bermuda, and the Azores throughout its existence, and no coastal watches or warnings were issued.

The maximum analyzed intensity was 80 kt (about 92 mph) with a minimum central pressure of 976 mb, reached around 1800 UTC 6 October and maintained through 1200 UTC 7 October. That peak corresponds to a Category 1 hurricane on the Saffir-Simpson scale. Philippe also likely reached near-hurricane strength on earlier occasions, but the post-analysis supports the two confirmed periods as a Category 1 hurricane.

Because Philippe stayed over open water, there were no reports of storm surge impacts along coastlines and no land-based rainfall totals attributed to the storm in the report. There were also no ship reports of tropical-storm-force winds. Consequently, there were no reported casualties or damage—no direct or indirect deaths or destruction linked to Philippe.

Noteworthy items include that Philippe’s development from the African coast to a tropical depression occurred faster than the Tropical Weather Outlook initially anticipated, so genesis was under-forecast by a day or two. Forecast track errors were comparable to typical official errors and had useful skill over simple climatology; intensity forecasts performed reasonably well relative to recent years but showed biases during rapid weak- or strengthening periods.