The Structure of Hazardous Weather Associated with California Narrow Cold Frontal Rainbands

The organization and structure of two narrow cold frontal rainbands (NCFR) observed by instrumented aircraft during the PACJET-2000 field experiment are presented. Doppler radar observations are shown which reveal the severe nature of the events. Strong surface winds, pea-size hail, and heavy rainfall accompanied the passage of the rainbands over the coastal regions of Northern and Central California. There were many similarities in NCFR structure to that observed in mid-latitude "Supercell" thunderstorms including echo overhang, echo-free faults near the leading edge, and possible waterspouts. The NCFR's differed in vertical structure from the supercells in that they were about one-half as tall. The relatively short vertical extent limits the detection of these storms by coastal National Weather Service Doppler radars because of beam overshooting During the PACJET research program an attempt was made to aid the forecasting of hazardous weather phenomena through the use of instrumented aircraft observations provided (via a satellite data link) to National Weather Service forecasters. Preliminary results indicate the success of this effort, as the forecasters were able to use the data in preparation of warnings.