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Investigations of Using TAMDAR Soundings in the NCAR Auto-Nowcaster

Investigations of Using TAMDAR Soundings in the NCAR Auto-Nowcaster. H. Cai, C. Mueller, E. Nelson, and N. Rehak NCAR/RAL. Why We Need ANC ?. The Auto-nowcaster System is unique in its ability to provide nowcasts of storm initiation by….

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Investigations of Using TAMDAR Soundings in the NCAR Auto-Nowcaster

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  1. Investigations of Using TAMDAR Soundings in the NCAR Auto-Nowcaster H. Cai, C. Mueller, E. Nelson, and N. Rehak NCAR/RAL

  2. Why We Need ANC ?

  3. The Auto-nowcaster System is unique in its ability to providenowcasts of storm initiationby….. Detection and extrapolation of surface convergence boundaries …. ….that trigger thunderstorm initiation and impact storm evolution.

  4. Initiation nowcasts extrapolation nowcasts Example of Auto-Nowcaster Initiation Forecast 1 hour forecast Verification

  5. Where has the Auto-nowcaster been demonstrated ? • Weather Forecast Office Washington DC • Sydney Australia Forecast Office • U. S. Army White Sands Missile Range • Central U. S. for the FAA • Process of being transferred to: • Bureau Meteorology Beijing China • U.S National Weather Service – Dallas Weather • Forecast Office • AWIPS

  6. Auto-Nowcaster atFt. Worth WFO AREA WEATHER UPDATE NATIONAL WEATHER SERVICE FORT WORTH TX 310 PM CDT SUN APR 10 2005 > WARNING DECISION UPDATE FOR NORTH TEXAS MESOANALYSIS PROGRAMS SHOW 1000-1500 J/KG CAPE ALONG AND JUST AHEAD OF DRYLINE. THUS...CU/DEVELOPING STORMS ALONG/E OF DRYLINE SHOULD CONTINUE TO INTENSIFY. STORM INITIATION TOOL ALSO SUGGESTS HIGH POSSIBILITY OF DEVELOPMENT FARTHER SW...OVER CORYELL/LAMPASAS COUNTY AREA. DEEP-LAYER SHEAR MORE THAN SUFFICIENT FOR ORGANIZED STORMS AND AT LEAST MID-LEVEL MESOS. AS STORMS EVOLVE INTO THE EVENING...A MORE LINEAR MODE IS EXPECTED.

  7. Flow Chart for the Auto-Nowcaster System Data Sets Radar WSR-88D Satellite Mesonet Profiler Sounding Numerical Model Lightning Predictor Fields Fuzzy Logic Algorithm - Membership functions - weights - Combined likelihood field Forecaster Input Analysis Algorithms Final Prediction

  8. Flow Chart for the Auto-Nowcaster System Data Sets Radar WSR-88D Satellite Mesonet Profiler Sounding Numerical Model Lightning Predictor Fields Fuzzy Logic Algorithm - Membership functions - weights - Combined likelihood field Forecaster Input Analysis Algorithms Final Prediction

  9. Environmental conditions (RUC) Frontal likelihood Layered stability CAPE (max between 900 and 700 mb) Mean 875 to 725 mb Relative Humidity CIN (averaged between 975 and 700 mb) Boundary-layer Convergence LI (based on METARS) Vertical velocity along boundary (maxW) Boundary-relative steering flow New storm development along boundary Clouds Clear or Cumulus Vertical develop as observed by drop in IR temps Predictor Fields used for Combined Likelihood of Initiation Blue Regions - Little chance of storm development Green Regions - Moderate likelihood Red Regions - Areas of forecast initiation

  10. Predictor Fields Cumulus development Boundary characteristics Satellite Cloud Typing B-L characteristics Storm motion and trends Large-ScaleEnvironment

  11. Why TAMDAR Soundings Might Be Important for ANC ? • Lack of high spatial and temporal resolution soundings data has been hampering storm initiation forecast both for ANC and forecasters (TAMDAR advantage over NWS soundings) • Moisture information within and above the boundary layer is crucial for convection initiation (TAMDAR advantage over ACARS data)

  12. How TAMDAR Data are Usedin ANC ? • Calculating 2D CIN field based on TAMDAR soundings and METAR observations, and comparing it with RUC-derived CIN ---- to be used mainly for reducing false alarm rate • Calculating averaged relative humidity from TAMDAR soundings, and comparing it with RUC-derived averaged RH ---- to be used to modify storm initiation forecast

  13. Flow Chart for TAMDAR Data Processing

  14. Case Study Examples • Six cases from Summer 2005 over IL/IN region • TAMDAR- and RUC-derived CIN and averaged relative humidity fields are compared. • Most of the time both fields compared favorably without causing differences in forecasting convection initiation • There are cases where the differences between RUC- and TAMDAR-derived fields could cause a forecaster to change his/her storm initiation forecast

  15. Comparisons of Averaged Relative Humidity Between RUC and TAMDAR 07/18/2005

  16. Comparisons of Averaged Relative Humidity Between RUC and TAMDAR 08/12/2005

  17. A Case for Reducing FAR in ANC

  18. Comparison of CIN Between RUC and TAMDAR 07/26/2005 A forecaster could use the polygon tool to remove the storm initiation forecast at previous slide when he/she thought the convection would be capped based on large CIN from TAMDAR

  19. Summary • Based on limited number of case studies, it is found that TAMDAR-derived CIN field could have the potential to reduce false alarm rate for ANC storm initiation forecast. • The averaged relative humidity field derived from TAMDAR also showed some values in estimating the moisture content more accurately in some cases, which could have significant impacts to models such as VDRAS. • The TAMDAR impact depends heavily on the location and timing of convection. If the storms formed far away from where the TAMDAR soundings were located, the TAMDAR impacts are hard to show.

  20. END THANK YOU !

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