A radar and surface data analysis of a warm front in Hurricane Ida (2009)

In November 2009, Hurricane Ida approached the north-central Gulf Coast and made landfall in the Mobile Bay area where the University of South Alabama (USA) Mesonet stations are located. Detailed wind, rainfall, pressure, and temperature data were collected by 14 stations as well as by surface stations from other providers. In addition WSR-88D data are available from the Mobile Regional Airport.

Hurricane Ida (2009) made landfall along the Alabama coast at 1200 UTC on 10 November 2009. Although the impacts from Ida were minimal, heavy rainfall exceeding 140 mm over small areas occurred in southwest Alabama ahead of a small warm front, which caused uplift as it moved northward. Prior and during landfall, Ida was significantly sheared and landfall of the storm center was preceded by an elongated deck of thick stratus. Decreased solar radiation and evaporative cooling form stratiform precipitation ahead of the warm front likely contributed to cooling of the air mass ahead of the front. Surface measurements and radar imagery will be analyzed to substantiate this hypothesis. Onshore flow behind the warm front brought in warm, moist air from the Gulf of Mexico. Detailed surface maps of potential temperature overlain with Doppler radar imagery will be presented to document the evolution of the warm front and the associated rainfall. Timeseries of potential temperature, wind speed and direction, pressure, rainfall, and solar radiation from surface stations provide further details of the structure and intensity of the warm front as it passed through.