Detecting Tropical Cyclone Structural Change with the TRMM Precipitation Radar (PR) and Advanced Microwave Sounding Unit (AMSU)

The Extratropical Transition (ET) of a Tropical Cyclone (TC) from a warm-core, symmetric structure to a cold-core, asymmetric structure can result in intense baroclinic storms that are difficult to handle by operational forecasters. The tools used to distinguish these events are primarily model based and can produce varying depictions of the ET process resulting in errors intrinsic to the model.

Bright band heights retrieved from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and 0° C isotherms from the Advanced Microwave Sounding Unit-A (AMSU) are used as a surrogate for examining the warm or cold core structure as well as the symmetry of a TC that allows for an unbiased representation of ET. Results from several cases in both the North Atlantic and North Pacific basins are presented to elucidate the distinct lowering of bright band heights and freezing levels with a displacement of the warm core away from the TC center that occurs when tropical systems undergo ET.