40 th annual meeting, national weather association, broadcast meteorology workshop oct. 18, 2015...

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Understanding SPC’s Outlooksor

Everything you wanted to know about outlook probability to category conversion but were afraid to ask.

Greg Carbin, Jared Guyer, Bill Bunting, Russ Schneider

NOAA/NWS Storm Prediction Center

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Severe Thunderstorm Outlook Categories

Bottom line…

It’s about forecasting the overall coverage of severe storms…

…and the intensity of those storms!

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

What does Jimthink will happen tomorrow?

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

5%

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

15%

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

15%sig

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

30%

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

30%sig

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

45%

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

45%sig

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

60%

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 2 CategoriesTotal of all hail, wind, & torn events

60%sig

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

From Probabilities to Day 1 CategoriesHail, wind, & torn events

are considered separately.Significant severe usually

results in a category upgrade.

Why Are These Numbers Important?

Five year sample: 2010 - 2014

Day 1 Probabilistic Outlooks Day 2 & 3 Probabilistic Outlooks

Because SPC Severe Weather Outlooks probabilities are reliable.

Forecast Exercise

Case Studies for Day 2 SWO

Probability Practice

Greg Carbin, Jared Guyer and Patrick Marsh

NWS-NCEP-Storm Prediction Center

Severe Weather Forecast Exercise

- 00Z 500 mb heights, temps (C), isotachs (kt)

- 00Z surface pressure, 2m temps/dewpoints (F), 10m wind (kt)

- 00Z surface pressure, CAPE, HLCY

- What states were most impacted by severe weather on this day?

- Were there significant tornadoes (F2-3)? How many and where?

- Were there violent tornadoes (F4-5)? How many and where?

- What happened?

- 00Z Supercell Composite Parameter (SCP)

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #1 – 500 mb

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #1 – MSLP/T/Td

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #1 – MSLP/CAPE/SRH

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #1 – Supercell Composite

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #2

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #2 – 500 mb

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #2 – MSLP/T/Td

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #2 – MSLP/CAPE/SRH

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #2 – Supercell Composite

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #3

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #3 – 500 mb

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #3 – MSLP/T/Td

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #3 – MSLP/CAPE/SRH

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #3 – Supercell Composite

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #4

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #4 – 500 mb

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #4 – MSLP/T/Td

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #4 – MSLP/CAPE/SRH

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Case #4 – Supercell Composite

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

Here’s what happened…

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

TOR = 5F2+ = 1F4+ = 1DPI = 4.8

CASE #1 verification

13 July 2004: Roanoke, IL F4 and later derecho. ~400 total reports.

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

TOR = 5F2+ = 1F4+ = 1DPI = 4.8

CASE #1 verification

45% SIGModerate Risk

60% Moderate Risk

13 July 2004: Roanoke, IL F4 and later derecho. ~400 total reports.

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

TOR = 30F2+ = 20F4+ = 7DPI = 1156Fatalities= 89

CASE #2 verification

Infamous 1985 OH/PA tornado outbreak

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

TOR = 30F2+ = 20F4+ = 7DPI = 1156Fatalities= 89

CASE #2 verification

Infamous 1985 OH/PA tornado outbreak

60% SIGHigh Risk

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

TOR = 7F2+ = 4F4+ = 1DPI = 38Fatalities= 6

CASE #3 verification

3 June 1980: “Night of the Twisters!” Grand Island, NE tornado cluster.

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

TOR = 7F2+ = 4F4+ = 1DPI = 38Fatalities= 6

CASE #3 verification

30% SIGEnhanced Risk

3 June 1980: “Night of the Twisters!” Grand Island, NE tornado cluster.

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

TOR = 50F2+ = 27F4+ = 4DPI = 633Fatalities= 21

26 April 1991: Andover, KS and Red Rock, OK. TORNADO OUTBREAK!

CASE #4 verification

40th Annual Meeting, National Weather Association, Broadcast Meteorology Workshop Oct. 18, 2015

TOR = 50F2+ = 27F4+ = 4DPI = 633Fatalities= 21

CASE #4 verification

45% SIGModerate Risk

60% SIGHigh Risk

26 April 1991: Andover, KS and Red Rock, OK. TORNADO OUTBREAK!

Severe Weather Forecast Exercise

- Summary: Why is tornado forecasting so hard?

- A wide range of large-scale conditions…

- Generally poor forecasts of storm-scale conditions…

- Any time of year…

- Just about anywhere…

- Tornadoes kill people and can ruin your day!

http://www.spc.noaa.gov

Gregory.Carbin@noaa.gov