John (2012)

A small tropical storm formed about 200 nautical miles southwest of Manzanillo, Mexico, on 2 September 2012. John moved steadily northwestward for its short life, passing just north of Socorro Island early on 3 September, then encountering stronger wind shear and cooler, drier air. Convection diminished and John weakened to a remnant low on 4 September about 340 n mi west of the southern tip of the Baja California Peninsula; the remnant low dissipated several hundred nautical miles west of west-central Baja on 7 September.

John did not make any landfalls on the Mexican mainland or the Baja Peninsula. Its center passed close to Socorro Island on 3 September, but there were no watches or warnings issued and no reported landfalls associated with the system.

The storm’s maximum sustained winds were 40 knots (about 46 mph) and its lowest estimated central pressure was 1000 millibars. At its peak it was a weak tropical storm (below hurricane strength) and never reached higher categories.

There were no reported storm surge measurements tied to John, and no reported significant rainfall totals from the system in populated areas. Observations from Socorro Island were incomplete during John’s passage; however, surface pressures there were noted to be unusually low the day before the storm passed.

No deaths, injuries, or damage were reported in association with John. The storm’s impacts were minimal and confined to the open ocean and Socorro Island area where observations were limited.

Noteworthy aspects include the complex origin of John from interactions between two tropical disturbances (one that also contributed to Atlantic Hurricane Isaac) and the important role of satellite microwave and scatterometer data in identifying the small circulation. Forecasts of formation were generally successful, and official short-term track and intensity forecasts for John had smaller errors than recent 5-year averages.