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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 - PowerPoint PPT Presentation
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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 …