Lightning Forecasting

at theStorm Prediction

CenterJoe Schaefer with help from

Phillip Bothwell, David Brightand

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 Thunder19 July 2005

200000Z – 201200Z

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

F15 SREF PROBABILITY F15 SREF PROBABILITY CLOUD PHYSICS THUNDER CLOUD PHYSICS THUNDER PARAMETER >= 1PARAMETER >= 1

SREF MEAN CPTP = 1 (DASHED)

SREF PROB CPTP >= 1SREF PROB CPTP >= 1 (SOLID & FILLED)(SOLID & FILLED)

CLOUD PHYSICS THUNDER PARAMETER Percent of members with appreciable CAPE in the 0oC to -20oC layer

F15 SREF 3-hr COMBINEDF15 SREF 3-hr COMBINEDPROBABILITY OF LIGHTNINGPROBABILITY OF LIGHTNING

- Pr (CPTP) >= 1 x Pr (PCPN) >= .01”

Uncalibrated probabilityof lightning

F15 SREF 3-hr COMBINED PROBABILITY F15 SREF 3-hr COMBINED PROBABILITY OF LIGHTNING (Calibrated)OF LIGHTNING (Calibrated)& LIGHTNING STRIKES& LIGHTNING STRIKES

Statistical Forecasts Based on Phillip Bothwell’s Dissertation work

• Perfect Prog Forecast TechniquePrincipal Component Analysis determines predictorsLogistic 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 fromANY 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

LTG CLIMATOLOGY:

Probability of one or more CG flashes / 40x40 km grid box / 3 hrs.

Centered on July 22

12-15UTC 15-18UTC

18-21 UTC 21-00UTC

Relative minimum

during daytime hours

Relative maximum

during daytime hours

LTG CLIMATOLOGY:

Probability of one or more CG flashes / 40x40 km grid box / 3 hrs.

Centered on July 22

00-03UTC 03-06UTC

06-09UTC 09-12UTC

Relative maximum

during overnight

hoursRelative

minimum during

overnight hours

57-60 Hour Lightning Forecast

12Z July 13, 2004

Forecast Observed

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

NOAA Photo Library

NWS Historical Collection

… those that have large numbers of flashes!

Previous attempts at predicting events with significant flash rates have not met with much success!

Significant CG Lightning Events100 or more CG flashes/40x40 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 Flashes9-12 hour Forecast18Z Sep. 18, 2004

Solid Probability 21,%, 2%, 5%Dashed Observed 100,200,399 Flashes

Climatology03 Z – 06Z

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 …