Extratropical transition of Atlantic tropical cyclones: An examination of the factors influencing transition and post-transition intensity change

Dr Jenni Evans

Collaborative research with Chris Velden (CIMSS/SSEC/Univ. Wisc)

Case study: Hurricane Danielle (1998): Work with Robert E. Hart, PhD candidate

The case study of Hurricane Danielle (1998) was chosen as Danielle was an intense storm at both tropical (CAT-2: 965 hPa/90 kt) and extratropical stages (964 hPa/60 kt peak intensity as an extratropical system). As an extratropical system, Danielle generated severe weather in Britain.

Danielle transitioned far from land, thus the satellite-derived wind products are expected to greatly enhance our analysis of Danielle. Selection of a storm far from land allows us to isolate better the internal [storm] physical processes critical to transition without the complication of land effects.

Imagery of "tropical" Danielle

Infrared imagery of "extratropical" Danielle

AMSU imagery of "extratropical" Danielle

Distribution and quality indicators of satellite-derived winds used for 2 September 1998 at 1800UTC

Animation of surface wind (color) and potential vorticity (surfaces) analyses of Hurricane Danielle (1998) from 29 August through 5 September 1998. Analyses were derived through a continuous FDDA cycle, assimilating satellite-derived wind data into MM5 on a NOGAPS base state.

Sensitivity studies of satellite-derived wind data assimilation into MM5: variation of weightings on satwinds and background analyses

Example of the results of satellite-derived wind data assimilation into MM5: variation of convective parameterizations

Background Climatology (Hart and Evans 2000)*

Monthly composites of extratropically transitioning storm tracks in the Atlantic

Hart R. E., and J. L. Evans, 2000: A climatology of the extratropical transition of Atlantic tropical cyclones. J. Climate, (in press).

This research is supported through a grant from the National Science Foundation (NSF).

Page last updated 4 December 2000