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BTV Aviation Best Practices Update

BTV Aviation Best Practices Update. Forecasting Thunderstorms. BTV Thunderstorm Climatology 2005-2012. Warm season Apr 15 – Oct 15 211 events identified with explicit TS or TSRA in a METAR or SPECI at KBTV Average of 26 discrete events per year Peak June – August -> variable by year.

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BTV Aviation Best Practices Update

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  1. BTV Aviation Best Practices Update Forecasting Thunderstorms

  2. BTV Thunderstorm Climatology 2005-2012 • Warm season Apr 15 – Oct 15 • 211 events identified with explicit TS or TSRA in a METAR or SPECI at KBTV • Average of 26 discrete events per year • Peak June – August -> variable by year

  3. BTV Thunderstorm Climatology • Examined each event by - ceiling - visibility - duration - IFR duration • Data from NCDC

  4. TSRA Ceilings • Average ceiling 4,500 feet • IFR cigs -> 14 events, or ~ 7% • MVFR cigs -> 63 events, or ~ 30% • VFR cigs -> 134 events, or ~ 63%

  5. TSRA Visibility • Average visibility 4.9 sm • IFR visibility 101 events -> or ~48% • MVFR visibility 20 events -> or ~ 9% • VFR visibility 90 events -> or ~ 43%

  6. TSRA Duration • Average duration 58 minutes • Only 32% last ≥ 1 hour • Only 7% last ≥ 2 hours

  7. TSRA Duration Large positive skew. Median 44 minutes…more representative

  8. TSRA IFR Duration • Average IFR duration of only 11 minutes • However ~ 52% of all events have NO IFR and 94% have IFR for less than 30 minutes. • For the IFR only subset, average IFR is only 22 minutes.

  9. TSRA IFR Duration But recall that 52% of all events have no IFR, or zero minutes

  10. Other Considerations • Anybody have a guess on the total percentage of warm season (Apr 15 – Oct 15) IFR due explicitly to thunderstorms at KBTV? 3.3%

  11. Considerations • So 96.7% of warm season IFR at KBTV occurs from other weather phenomena - rain showers - mist/fog - low ceilings • Incidentally, KMPV TSRA aviation climatology is very similar to KBTV.

  12. Verification and Scoring • How confident are you that one of these things will hit a specific terminal directly?

  13. Verification and Scoring • Historically, we do quite poor with thunderstorm verification at WFO BTV

  14. Verification and Scoring • National scoring counts IFR in 5 minute increments • Temporal resolution in a TAF is typically 1 hour (rarely less) • National verification scoring system does not do us any favors

  15. Verification and Scoring • Example: KBTV 061730Z 0618/0718 23008G17KT P6SM FEW035 SCT060 TEMPO 0620/0621 VRB18G32KT 2SM +TSRA BR BKN025CB FM062100 27006KT P6SM –SHRA BKN050 FM072200 VRB03KT P6SM SCT050 FM071400 29007KT P6SM SKC= METAR KBTV 061754 24010KT P6SM SCT060 SCT120 27/21 A2992 AO2 …. METAR KBTV 061854 23011G19KT P6SM SCT045 BKN080 27/22 A2990 AO2… METAR KBTV 061954 23006KT P6SM VCTS BKN045 OVC070 27/22 A2989 AO2… SPECI KBTV 062014 26014G27KT 5SM –TSRA BR SCT028 OVC040CB 24/20 A2988 AO2… SPECI KBTV 062019 27021G39KT 2SM +TSRA BR BKN025 OVC035CB 21/19 A2995 AO2… SPECI KBTV 062036 25008KT 4SM –TSRA BR SCT035 OVC040CB 20/19 A2999 AO2… METAR KBTV 062054 26006KT 6SM BR SCT050 BKN090 19/19 A3002 AO2… METAR KBTV 062154 27005KT P6SM FEW120 22/19 A3003 AO2…

  16. Example Contd. • So we had a really good TAF going - concise - correct timing - added value to customer - 1 hour of IFR • Observational data -> 17 minutes of IFR • POD of 1, FAR of 66% • Even good TAFs typically have marginal FAR rates

  17. Points to take home • On IFR resolution - recall the 7-year average IFR duration of 11 minutes per storm • On temporal resolution - recall the median duration of 44 minutes • Recall our poor track record of TSRA POD • Recall TSRAs constitute only 3.3% of all IFR at KBTV during the warm season (2006-2012) - other terminals similar

  18. Recommendations • Generally don’t put explicit TSRA in the TAF beyond 3 hours. • Beyond 3 hours use VCTS (only if confident) • Within 3 hours limit explicit mention of TSRA IFR in FM or TEMPO groups to 1 hour (vsby only) • Use restrictions of VFR/MVFR most of the time • IFR only if you see the “white of it’s eyes” (visibility only).

  19. Recommendations • Remember no use of CB in a FM or TEMPO group w/o TSRA. • Must keep our aviation partners in mind with a value added product - i.e. if confident put it in • Focus on the non-thunderstorm IFR in the warm season -> 96.7% at KBTV.

  20. Examples • Low confidence within 6 hours (Sct/Pulse) KBTV 061730Z 0618/0718 23008G17KT P6SM FEW035 SCT060 FM062000 27006KT P6SM VCTS BKN050 FM072300 VRB03KT P6SM SCT050 FM071400 29007KT P6SM SKC= • Medium confidence within 4 hours (Broken line) KBTV 061730Z 0618/0718 23008G17KT P6SM FEW035 SCT060 FM062100 27010G18KT 5SM –TSRA BR SCT035 BKN050CB FM072200 25006KT P6SM -SHRA SCT050 BKN090 FM072300 VRB03KT P6SM SCT050 FM071400 29007KT P6SM SKC= • High confidence within 2-3 hours (Squall line/MCS) KBTV 061730Z 0618/0718 23008G17KT P6SM FEW035 SCT060 FM062000 27006KT 5SM –TSRA BR SCT025 BKN050CB TEMPO 0620/0621 VRB15G25KT 2SM +TSRA BR BKN025CB FM072200 VRB03KT P6SM SCT050 FM071400 29007KT P6SM SKC=

  21. QUESTIONS?

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