NWS Central Region Overview and plans for 2013

NWS Central Region

Overview and plans for 2013

Intro to IBW Project2013

IBW Project 2013Rationale

What ? • IBW is a simple, but important change to the existing warning system.

• Part of a gradual evolutionary process to improve usefulness and effectiveness of our severe convective warnings (Yes – with a thumbs up);

• It should NOT be misrepresented as an evolutionary leap turning the warning system upside down (No – with a finger wag).

• At its core; IBW consists of one change (in 2 parts):

• addition of a “considerable damage threat” warning tier for significant tornadoes (~EF2 or greater)

• addition of concise wording on impacts and risk commensurate with those threats.


Why ? Because the numbers say we should.

• 13% of all tornadoes in CR are EF2-5 262 fatalities (97% of all fatalities)

• 87% of all tornadoes in CR are EF0-1 7 fatalities (3% of all fatalities)

• All tornadoes are NOT the same ! By treating all tornadoes as one-size-fits-all, the existing system - by default - emphasizes warnings for weak tornadoes at the expense of warnings for life threatening tornadoes.

• This is a flaw in the current warning paradigm – and one that leaves the public more exposed to dangers of high-end tornadoes than they should be.

• Rationale 1: “Societal Needs” demand tornado warnings that emphasize high impact events – i.e. those most likely to do serious harm. If we are serious about reducing tornado deaths – this is where we should start.


Why ? Because public and partners say we should.

Key findings from NWS Service Assessments (not just 2011):

• Most identify local siren systems as first source of warning; but, perceptions exist that “sirens go off all the time and nothing happens”.

• Most seek confirmation from additional sources before seeking shelter.

• Extraordinary risk signals prompt people to take action; but, there is currently no mechanism to elevate the threat in NWS tornado warnings.

• Existing dissemination systems not fully compatible with storm-based warning polygons; causes confusion when there are multiple polygons. Polygonology!

• Rationale 2: Clear and credible risk communication is necessary for people to take immediate protective action.


Why ? Because Tornadoes are the only hazard whereby NWS does not include an expected magnitude as part of the warning message.

• What if we issued a flood warning for the Red River in Fargo, but refused to say how high the river stage would get ?

• What if we told ATC at O’Hare there would be fog, but refused to give them a predicted visibility ?

• What if we issued a Hurricane Warning for Mobile Bay but refused a prediction of wind speeds (CAT 1-5) or surge heights ?

• Rationale 3: Tornadoes are like any other hazard and require expressions of magnitude to elicit the most appropriate actions.


Concerns…

IBW will result in a diluted public response for base (non-tagged) Tornado Warnings, would it not ?

• Unknown but unlikely; it will take years of study to find out. But…

• IBW now places emphasis on those tornadoes likely to do serious harm; correcting, in part, a critical gap in the existing tornado warning paradigm. If there is a trade-off, it is the correct one.

• If public response for base Tornado Warnings is diluted – it is extremely unlikely to be less than response levels for SVRs.

• As it turns out, mortality rates from EF0-1 tornadoes are roughly equivalent to that from severe thunderstorm winds.


Concerns…

We don’t have the skill or tools to discern large tornadoes from small or no tornadoes, do we ?

• The 88D is designed for this task; It is not designed for detection of small tornadoes that can and often occur below the spatial and temporal resolution of the radar. • POD for EF0-1 tornadoes = 69% in CR• POD for EF2-5 tornadoes = 84% in CR• POD for EF3-5 tornadoes = 94% in CR

• While the ability to detect larger tornadoes with lead time has long been known, we are more interested in evaluating skill measures i.e. Hit Rate (1-FAR).

• In CR, Hit Rate since 2008 for all Tornado Warnings is 28%.


Concerns…


• Prior to 2012 very few studies (if any) have examined skill in discerning large tornadoes from small/no tornadoes; not easy to do this a lab setting as many warning inputs (e.g. spotter reports) are difficult to simulate.

• One of the primary benefits of the IBW project is ability to evaluate capacity for discerning hazard magnitude in TORs; and provide a baseline for future comparison.

• FY12 results in demo area produced promising inferences, but small sample size precludes definitive conclusions. Need a larger sample size.


Concerns…


Hit Rate (all CR tornadoes 2008-2012) = 28%Hit Rate (all tornadoes IBW 2012 demo) = 49% (CSI=0.51)

82 IBW defined Tornado Warnings issued (through December 2012).

EF0 EF561 IBW Tornado Events


Concerns…


Categorical Hit Rate (EF0-1 tornadoes IBW 2012 demo) = 49% (CCSI =0.39)Categorical Hit rate (EF2-5 tornadoes IBW 2012 demo) = 47% (CCSI = 0.39)

15 Tornado Warnings issued with “considerable” or higher tag and 7 verified with EF2+ events (47%).

EF0 EF5EF2EF151 IBW Tornado Events 10 IBW Tornado Events


Concerns…


Categorical Hit Rate (EF0-3 broadened category) = 54% (CCSI=0.45)Categorical Hit Rate (EF1-5 broadened category) = 73% (CCSI=0.58)

Of 15 tornado warnings with “considerable” or higher tags, 11 resulted in EF1 or greater intensity tornadoes. (73%).

EF5

EF3

EF1

EF0


Note the overlap at the top of EF0-1 and bottom of EF2-5; similar to results from 2012 IBW

From Smith et al. 2012

Positive relationship between Mx Vrot and EF-Scale

Risk Paradigm

Risk = f Hazard Character ; Vulnerability

•IBW does allow opportunity to assess discernment between no event, low impact, and high impact events through descriptions of potential tornado intensity.

•IBW method of conveying predicted Tornado hazard magnitude/intensity is the use of Damage/Threat Indicator Tags at the bottom of TOR/SVS texts.

•These are CAP (Common Alert Protocol) compliant and follow a model using Wind/Hail Threat Indicator Tags in SVR/SVS texts established in 2008.

•End users needs to know their vulnerabilities and know their protective options.

Probability of OccurrenceTime of OccurrenceMagnitude/IntensityLocation of Occurrence

• Outcome 1 – Risk Characterization: Developing and encapsulating the knowledge about the severe weather hazard, its potential impact, and its risk to life and property.

• Outcome 2 – Risk Communications • Outcome 3 – Risk Management

Outcome 1Risk

Characterization

Outcome 2Risk

Communications

Outcome 3Risk

Management

Risk ManagementEvaluation

• Outcome 1 – Risk Characterization • Outcome 2 – Risk Communications: Packaging and

delivering storm warnings (communicating) to convey the understanding of risk.

• Outcome 3 – Risk Management

Outcome 1Risk

Characterization

Outcome 2Risk

Communications

Outcome 3Risk

Management



• Outcome 1 – Risk Characterization• Outcome 2 – Risk Communications• Outcome 3 – Risk Management: What knowledge of

risk influences decisions yielding desired actions (societal response).

Outcome 1Risk

Characterization

Outcome 2Risk

Communications

Outcome 3Risk

Management

IBW Project 2013Preliminary analysis

• Six key areas of information that Core Partners focus on in a warning situation:• Threat and magnitude• Timing• Location• Duration• History• Confidence

• WxEm developed independent validation and verification (matrix) against these areas

• Final report quantifying our success against these key areas is available at

IBW Project 2013

IBW Project 2013

Tornado Tag TORNADO...RADAR INDICATED Evidence on radar and near storm environment is

supportive, but no confirmation.

TORNADO...OBSERVED Tornado is confirmed by spotters, law enforcement, etc.

Tornado Damage Threat Tag No tag Use most of the time

Tornado damage possible within the warning polygon.Tornado damage of EF0-EF1 expected. Tornado duration short-lived

TORNADO DAMAGE THREAT...CONSIDERABLE

Rare use – outbreak daysTornado damage likely within the warning polygonTornado damage of EF2-EF5 expected.Tornado duration long-lived

TORNADO DAMAGE THREAT...CATASTROPHIC

Exceedingly rare use – major impact to population centerSubstantial, observed evidence of a violent tornado occurring. Tornado damage of EF4-EF5 expected in a population center (town, city)Tornado duration long-lived

Tornado Tag In Severe Thunderstorm Warnings TORNADO...POSSIBLE Severe thunderstorm has some potential for

producing a tornado; forecaster confidence is not high enough to issue a Tornado Warning.

IBW Project 2013

Catastrophic Damage Threat Indicator (Tornado Emergency)

• Restrictions on its use to address past misuse of the product.

• TOR emergencies should only be considered when there is substantial visual evidence that a violent tornado is occurring and will imminently impact (or nearly impact) a population center of any size.

• This should be exceedingly rare and should never be issued on radar evidence alone. These are reserved for extraordinary events.

• Most times, a “considerable” damage threat tag will suffice. There really is no “wrong” choice concerning considerable vs. catastrophic tags for observed, violent (EF4-5) tornadoes.

IBW Project 2013

Tornado Possible Tag in SVRs

• Previously mandated in SVRs when Tornado Watch in effect

• Now can be used at forecaster discretion regardless of whether watch is in effect.

• Intended to be used when weak brief spin-ups are somewhat possible, but not likely - based on evaluation of environment (i.e. not to the level of a tornado warning).

• Ex. warm season QLCS events whereby 0-6km shear vector is oriented near perpendicular to orientation of squall line.

IBW Project 2013

“Polygonology”• Re-emphasize awareness of county boundaries• Understanding storm motion and propagation (keep

storm in polygon)• Importance of editing the default polygon

Building confidence in using tags• Understanding definition and when to use• Guidelines for TOR vs. SVR (2 out of 3)• Storm environments • QLCS Mesovortex conceptual model• Data/tools available for warning process

IBW Project 2013

In summary, we are providing enhancements by:• Improving communication of critical information• Making it easier to quickly parse out the most valuable information• Enabling users to prioritize the key warnings• Providing different levels of risk within the same product• Enabling the NWS to express a confidence level of potential impacts and risks

1950ZEF1

1958ZEF3

2003ZEF4

2014ZEF4 (Henryville)2007Z

EF3-4

2023ZEF3

2028ZEF4

2039ZEF1

1937Z

Vrot = 29 kts

Tornado Warning

Issued 1940Z

1942Z

Vrot= 44 kts

“considerable” damage threat tag possible

1947Z

Vrot = 41 kts

1951Z

Vrot = 53 kts

“considerable” damage threat tag definitely here.

1956Z

Vrot= 71 kts

2001Z

Vrot=80 kts

2005Z

Vrot= 75 kts

2010Z

Vrot= let’s just say this looks bad

“Tornado Emergency” was Issued at 1910z asTornado approachedHenryville

2014Z

Vrot= 70 kts

2019Z

Vrot= 78 kts

2024Z

Vrot = 71 kts

2029z

Vrot = 54 kts

2033z

Vrot = 46 kts

Questions?

IBW Project 2013

Contributors:

Dr. Greg Mann NWS DTXMike Hudson NWS CRHStacy Kraatz CMUWxEM

NWS Central Region Overview and plans for 2013

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