Published on February 11, 2008
Cool-Season California Tornadoes January 8-11, 2005: Cool-Season California Tornadoes January 8-11, 2005 Lindsay Tardif, Kristin Cummings and Greg Veras Plymouth State University Motivation: Motivation Found four consecutive days with tornadoes reported in California in SPC archive. Tornadoes in California are considered to be an unusual and rare event. Unusual compared to Great Plains tornadoes Purpose of Study: Purpose of Study Investigate synoptic and mesoscale features associated with cool season tornadoes in California. Compare findings to previous studies of California Cool Season Tornadoes. Data: Data Investigated January 8-11, 2005 Used upper-level analyses (NOAA NOMADS NARR) 250mb winds and geopotential heights 500mb vorticity 700mb and 850mb temperature and geopotential heights NCEP Surface Analyses from NCDC archive Soundings and Radar from SPC archive North American Regional Reanalysis (NOAA NOMADS) 950mb wind divergence with geopotential heights 0-1km wind shear Common Cool Season California Tornado Features: Common Cool Season California Tornado Features Favorable regions include the Central Valley, south coast, north-central coast, and southeast deserts Surface cold front Short-wave trough with accompanying upstream jet Positively tilted mid-latitude trough Strong cyclonic vorticity advection Strong 0-1km wind shear values (~6-10 s-1) Cold air advection aloft Interaction of low-level flow with coastal mountains Median CAPE values ~500 Jkg-1 Monteverdi et al., 1988; Braun and Monteverdi, 1991; Blier and Batten, 1994; Hanstrum et al., 2002; Monteverdi, J.P., C.A. Doswell III, and G.A. Lipari, 2003 January 8th (00:20Z January 9th): January 8th (00:20Z January 9th) Oroville, CA (Butte County) 1 Tornado: F1 Radar Loop2100Z -0200Z: Radar Loop 2100Z -0200Z Slide8: 00Z Surface Analysis 00Z 950mb Divergence Slide9: 00Z KOAK Sounding 00Z 0-1km Wind Shear ML CAPE: 226 Jkg-1 SFC CAPE: 38 Jkg-1 Veering Winds 4-8 s-1 Slide10: 00Z 250mb Winds and Geopotential Heights 00Z 500mb Absolute Vorticity and Geopotential Heights January 9th(01:11Z January 10th): January 9th (01:11Z January 10th) Hemet, CA (Riverside County) 1 Tornado: F0 Radar Loop2133Z- 0204Z: Radar Loop 2133Z- 0204Z Slide13: 00Z Surface Analysis 00Z 950mb Divergence Slide14: 00Z KVBG Sounding 00Z 0-1km Wind Shear ML CAPE: 541 Jkg-1 SFC CAPE: 169 Jkg-1 Veering Winds: SFC to 700mb 6-8s-1 Slide15: 00Z 250mb Winds and Geopotential Heights 00Z 500mb Absolute Vorticity and Geopotential Heights January 10th(14:45Z January 10th): January 10th (14:45Z January 10th) El Rio, CA (Ventura County) 1 Tornado: F0 Radar Loop1300Z-1702Z: Radar Loop 1300Z-1702Z Slide18: 12Z Surface Analysis 15Z 950mb Divergence Slide19: 12Z KVBG Sounding 15Z 0-1km wind shear ML CAPE: 1257 Jkg-1 SFC CAPE: 1 Jkg-1 Veering Winds: SFC to 850mb 0-4 s-1 Slide20: 12Z 250mb Winds and Geopotential Heights 12Z 500mb Absolute Vorticity and Geopotential Heights January 11th (14:15z January 11th): January 11th (14:15z January 11th) Vacaville, CA (Solano County) 1 Tornado: F0 Radar Loop1230Z-1604Z: Radar Loop 1230Z-1604Z Slide23: 12Z 950mb Divergence 12Z Surface Analysis Slide24: 12Z 0-1km Wind Shear 12Z KOAK Sounding ML CAPE: 491 Jkg-1 SFC CAPE: 94 Jkg-1 Veering Winds: SFC to 700mb 4-6 s-1 Slide25: 12Z 500mb Absolute Vorticity and Geopotential Heights 12Z 250mb Winds and Geopotential Heights Summary of Features: Summary of Features Oroville, Hemet and Vacaville had similar features. Low-level convergence and lee trough east of coastal mountains. Surface fronts were not located in vicinity of tornado reports. 0-1km wind shear positioned over region of tornado reports Soundings showed veering wind and low CAPE values. Advection of vorticity. Summary of Features continued: Summary of Features continued Jets were positioned for upper-level divergence over the regions of both Hemet and Vacaville. Hemet and El Rio tornadoes formed along bow echoes. El Rio case was different than the other three cases. Surface convergence west of coastal mountain range Surface front was present 0-1km wind shear absent High CAPE values Weak vorticity advection Conclusions: Conclusions Some features found were similar to the expected common features of cool season California tornadoes including: Vorticity advection Strong 0-1km wind shear values Presence of a jet Low-level convergence along coastal mountains Location of tornadoes were in favorable regions for cool season tornadoes Unlike previous studies Oroville, Hemet, and Vacaville tornadoes did not form in the vicinity of a front. References : References Blier, W. and K.A. Batten (1994). On the Incidence of Tornadoes in California. Weather and Forecasting, 9, 301-315. Braun, S.A. and J.P. Monteverdi (1991). An Analysis of a Mesocyclone-Induced Tornado Occurrence in Northern California. Weather and Forecasting, 6, 13-31. Hanstrum, B.N., G.A Mills, A. Watson, J.P. Monteverdi, and C.A. Doswell III (2002). The Cool-Season Tornadoes of California and Southern Australia. Weather and Forecasting, 17, 705-7??. Monteverdi, J.P., S.A. Braun, and T.C. Trimble (1988). NOTES AND CORRESPONDENCE: Funnel Clouds in the San Joaquin Valley, California. Monthly Weather Review, 116, 782-789. Monteverdi, J.P., C.A. Doswell III, and G.A. Lipari (2003). NOTES AND CORRESPONDENCE: Shear Parameter Thresholds for Forecasting Tornadic Thunderstorms in Northern and Central California. Weather and Forecasting, 18, 357-370. National Climatic Data Center. (2005, May). Retrieved November 20, 2006, from website http://nomads.ncdc.noaa.gov/data.php?name=access #narr_datasets_ NOAA ARL Hysplit Model. Retrieved December 5, 2006, from website http://www.arl.noaa.gov/ready/open/hysplit4.html Plymouth State Weather Center. Retrieved December 1, 2006, from website http://vortex.plymouth.edu Storm Prediction Center. (2006, December). Retrieved November 15, 2006, from website http://www.spc.noaa.gov/exper/archive/events/ Unisys Weather. (2006, October). Retrieved November 20, 2006, from website http://weather.unisys.com/ Slide30: Questions?