Lightning Forecasting at the Storm Prediction Center Joe

Lightning Forecasting at the Storm Prediction Center Joe Schaefer with help from Phillip Bothwell, David Bright and Russell Schneider

Current uses of the NLDN by the SPC • First strike detection – convective initiation • Subjective measure of convective intensity & trend • Verification and validation of thunderstorms • Detection of convection in regions of sparse radar coverage (esp. for Fire Weather)

Lightning (CG) & Fire Starts

SPC Lightning Forecasts • General Thunder in Convective Outlook • “Enhanced Thunder” – Presently experimental on Internet – Operational Product next year • Fire Weather Outlook Two types of Internal Thunderstorm Guidance

Enhanced Thunder 19 July 2005 200000 Z – 201200 Z

Ensemble Forecasts • Current SPC SREF processing – All operational computations on NOAA CCS • SREF products specialized for the national mission of the SPC • 16 member SREF (1 time-lagged Eta member) – Include the -3 hr operational Eta in all calculations • Add the +3 hr operational Eta to spaghetti plots

CLOUD PHYSICS THUNDER PARAMETER Percent of members with appreciable CAPE in the 0 o. C to -20 o. C layer SREF MEAN CPTP = 1 (DASHED) SREF PROB CPTP >= 1 (SOLID & FILLED) F 15 SREF PROBABILITY CLOUD PHYSICS THUNDER PARAMETER >= 1

- Pr (CPTP) >= 1 x Pr (PCPN) >=. 01” Uncalibrated probability of lightning F 15 SREF 3 -hr COMBINED PROBABILITY OF LIGHTNING

F 15 SREF 3 -hr COMBINED PROBABILITY OF LIGHTNING (Calibrated) & LIGHTNING STRIKES

Statistical Forecasts Based on Phillip Bothwell’s Dissertation work • Perfect Prog Forecast Technique Principal Component Analysis determines predictors Logistic regression • 40 km grid resolution at 3 hour time intervals • Uses Lightning Climatology (no knowledge of ongoing activity Forecasts • Probability of 1 or more CG flashes • Probability of 100 or more CG flashes.

OBJECTIVES • Technique applicable to ANY analysis or gridded data set (i. e. , forecast for the next 3 hours… 57 to 60 hours, or any time period in between) • System can run on data from. ANY forecast model. inter-model comparisons (different models…e. g. , RUC and ETA) intra-model comparisons (different cycles of same model). • Distinguish low lightning producers from high producers

12 -15 UTC 15 -18 UTC LTG CLIMATOLOGY: Probability of one or more CG flashes / 40 x 40 km grid box / 3 hrs. Relative minimum during daytime hours 18 -21 UTC Centered on July 22 Relative maximum during daytime hours 21 -00 UTC

00 -03 UTC 03 -06 UTC LTG CLIMATOLOGY: Probability of one or more CG flashes / 40 x 40 km grid box / 3 hrs. Relative maximum during overnight hours 06 -09 UTC Centered on July 22 Relative minimum during overnight hours 09 -12 UTC

57 -60 Hour Lightning Forecast 12 Z July 13, 2004 Forecast Observed

There can be a big difference between storms that produce only one flash and…

… those that have large numbers of flashes! Previous attempts at predicting events with significant flash rates have not met with much success! NOAA Photo Library NWS Historical Collection

Significant CG Lightning Events 100 or more CG flashes/40 x 40 km/3 hrs • Kempf and Krider (2003) as well as others have found a strong connection between daily rain volumes and corresponding counts of CG lightning • Intense areas of CG lightning can often be associated with strong to severe storms

Probability of 100 or more CG Flashes 9 -12 hour Forecast 18 Z Sep. 18, 2004 Solid Probability 21, %, 2%, 5% Dashed Observed 100, 200, 399 Flashes Climatology 03 Z – 06 Z 5 Days Centered on Sep. 20

Future use of Lightning Data • Become more quantitative • Track development & evolution of total lightning within individual thunderstorms • Prediction of critical lightning characteristics – Positive CG Strokes – Fire Weather (house fires? ) – Forecasts of severe lightning events • We need to learn more …