High-Resolution RUC CAPE Values and Their Relationship to Right Turning Supercells By: Andy Mair Mentor: Dr. William A. Gallus Jr. Department of Geological and Atmospheric Sciences Iowa State University, Ames, IA

Introduction Supercell movement important to severe weather prediction Storm Chasing Goal: Find a link between CAPE and right turning supercells

Terminology CAPE = Convective Available Potential Energy -Energy for convection RUC = Rapid Update Cycle - Computer model that runs hourly GMT Time (z)= Standard time across the world (-6 hrs in Central time zone) Right Turning Supercells

= 22 A A A B B C O hr30 min 1 hr

Previous Research Very little research Bunkers Theory (1999) Few older methods

Hypothesis A supercell will become a right turning supercell due to mesocyclone strengthening. Therefore, CAPE should increase when a supercell right turns because CAPE has been shown to strengthen the mesocyclone.

Methodology Data collected from June 2008 Anywhere in US, mainly in southern midwest Prevent Changes in RUC 13 km High Resolution RUC 82 Cases, 54 straight path supercells, 28 right turning cases

Methodology- Initiation/ Dissipation Initiation when storm shows 40 dBZ reflectivity Dissipation- - Storm falls below 40 dBZ - Storm merges with another storm

Methodology – Tracking/ Turning Turning if 20 degree change in storm motion vector observed Determined using GR2 Analyst storm motion Left turners were not used Collected right turning and straight path storms Collected data every half hour

Methodology- Collecting CAPE Used Surface Based CAPE RUC downloaded from NCDC NOMADS site Converted and used in Grads Used CAPE value on the hour When in between hours averaged hour before and hour after

Observations- Non turners

Very diverse data Average initiation CAPE: 1351 J/kg Average Dissipation CAPE: 1215 J/kg

Observations- Right Turners

CAPE values fall approximately 2 hours before turning Initiation CAPE : 1953 J/kg Dissipation CAPE : 1220 J/kg Average CAPE drop of 733 J/kg

CAPE Diurnal Cycle

Results

Conclusions Right turners initialize in higher CAPE values Right turners CAPE values fall 1-2 hours prior to turning Original hypothesis was incorrect

Further Research Low level wind shear 0-1 or 0-3 km helicity EHI (Energy Helicity Index) Expanded to more years and months

Acknowledgements Dr. Gallus for his assistance on the project Jeff Duda for help on running and using Grads Dave Flory for help with my procedure Justin Schultz for his guidance Ryan Alliss for statistical analysis help

Resources Brandes, 1977: Mesocyclone Evolution and Tornadogenesis: Some Observations. Monthly Weather Review 106, 995–1011. Bunkers, Klimowski, Zeitler, Thompson, and Weisman: Predicting Supercell Motion Using a New Hodograph Technique. Weather and forecasting 15, 61–79. Colquhoun, J. R., 1980: A method of estimating the velocity of a severe thunderstorm using the vertical wind profile in the storm’s environment. Eighth Conf. on Weather Forecasting and Analysis, Denver, CO, Amer. Meteor. Soc., 316– 323. Donaldson, and Desrochers 1989: Improvement of Tornado Warnings by Doppler Radar Measurement of Mesocyclone Rotational Kinetic Energy. Weather and forecasting 5, 247–258. Kerr, and Darkow, 1996: Storm-Relative Winds and Helicity in the Tornadic Thunderstorm Environment. Weather and forecasting 11, 489–505. Maddox, 1976: An Evaluation of Tornado Proximity Wind and Stability Data. Monthly Weather Review 104, Richard, and Edwards, 2000: An Overview of Environmental Conditions and Forecast Implications of the 3 May 1999 Tornado Outbreak. Weather and forecasting 15, 682–699.

Questions ??? Thank You! Andy Mair