TY - JOUR
T1 - Anticipating deviant tornado motion using a simple hodograph technique
AU - Nixon, Cameron J.
AU - Allen, John T.
N1 - Funding Information:
Acknowledgments. We would first like to acknowledge meteorologist Matt Ziebell and the National Weather Service Weather Forecast Office in Lubbock, Texas, for the inspiration behind examining deviant tornadoes. We would also like to acknowledge Dr. Matthew Bunkers of the National Weather Service Weather Forecast Office in Rapid City, South Dakota, for his invaluable encouragement, guidance, and contributions from the beginning to the finishing of this endeavor. Finally, we would like to acknowledge the extremely valuable contributions of Dr. Harold Brooks of the National Severe Storms Laboratory and the three reviewers, whose insightful comments allowed the impact of this study to be both stronger and better communicated. This research was supported by the Earth and Ecosystem Science Ph.D. program at Central Michigan University.
Funding Information:
We would first like to acknowledge me-teorologist Matt Ziebell and the National Weather Service Weather Forecast Office in Lubbock, Texas, for the inspiration behind examining deviant tornadoes. We would also like to acknowledge Dr. Matthew Bunkers of the National Weather Service Weather Forecast Office in Rapid City, South Dakota, for his invaluable encouragement, guidance, and contributions from the beginning to the finishing of this endeavor. Finally, we would like to acknowledge the extremely valuable contributions of Dr. Harold Brooks of the National Severe Storms Laboratory and the three reviewers, whose insightful com-ments allowed the impact of this study to be both stronger and better communicated. This research was supported by the Earth and Ecosystem Science Ph.D. program at Central Michigan University.
Publisher Copyright:
© 2021 American Meteorological Society.
PY - 2021
Y1 - 2021
N2 - The paths of tornadoes have long been a subject of fascination since the meticulously drawn damage tracks by Dr. Tetsuya Theodore ‘‘Ted’’ Fujita. Though uncommon, some tornadoes have been noted to take sudden left turns from their previous path. This has the potential to present an extreme challenge to warning lead time, and the spread of timely, accurate information to broadcasters and emergency managers. While a few hypotheses exist as to why tornadoes deviate, none have been tested for their potential use in operational forecasting and nowcasting. As a result, such deviations go largely unanticipated by forecasters. A sample of 102 leftward deviant tornadic low-level mesocyclones was tracked via WSR-88D and assessed for their potential predictability. A simple hodograph technique is presented that shows promising skill in predicting the motion of deviant tornadoes, which, upon ‘‘occlusion,’’ detach from the parent storm’s updraft centroid and advect leftward or rearward by the low-level wind. This metric, a vector average of the parent storm motion and the mean wind in the lowest half-kilometer, proves effective at anticipating deviant tornado motion with a median error of less than 6 kt (1 kt ≈ 0.51 m s-1). With over 25% of analyzed low-level mesocyclones deviating completely out of the tornado warning polygon issued by their respective National Weather Service Weather Forecast Office, the adoption of this new technique could improve warning performance. Furthermore, with over 35% of tornadoes becoming ‘‘deviant’’ almost immediately upon formation, the ability to anticipate such events may inspire a new paradigm for tornado warnings that, when covering unpredictable behavior, are proactive instead of reactive.
AB - The paths of tornadoes have long been a subject of fascination since the meticulously drawn damage tracks by Dr. Tetsuya Theodore ‘‘Ted’’ Fujita. Though uncommon, some tornadoes have been noted to take sudden left turns from their previous path. This has the potential to present an extreme challenge to warning lead time, and the spread of timely, accurate information to broadcasters and emergency managers. While a few hypotheses exist as to why tornadoes deviate, none have been tested for their potential use in operational forecasting and nowcasting. As a result, such deviations go largely unanticipated by forecasters. A sample of 102 leftward deviant tornadic low-level mesocyclones was tracked via WSR-88D and assessed for their potential predictability. A simple hodograph technique is presented that shows promising skill in predicting the motion of deviant tornadoes, which, upon ‘‘occlusion,’’ detach from the parent storm’s updraft centroid and advect leftward or rearward by the low-level wind. This metric, a vector average of the parent storm motion and the mean wind in the lowest half-kilometer, proves effective at anticipating deviant tornado motion with a median error of less than 6 kt (1 kt ≈ 0.51 m s-1). With over 25% of analyzed low-level mesocyclones deviating completely out of the tornado warning polygon issued by their respective National Weather Service Weather Forecast Office, the adoption of this new technique could improve warning performance. Furthermore, with over 35% of tornadoes becoming ‘‘deviant’’ almost immediately upon formation, the ability to anticipate such events may inspire a new paradigm for tornado warnings that, when covering unpredictable behavior, are proactive instead of reactive.
KW - Forecasting techniques
KW - Mesoscale forecasting
KW - Nowcasting
UR - http://www.scopus.com/inward/record.url?scp=85101381979&partnerID=8YFLogxK
U2 - 10.1175/WAF-D-20-0056.1
DO - 10.1175/WAF-D-20-0056.1
M3 - Article
AN - SCOPUS:85101381979
VL - 36
SP - 219
EP - 235
JO - Weather and Forecasting
JF - Weather and Forecasting
SN - 0882-8156
IS - 1
ER -