# Presentation: 512724

## Ready to begin

## Failure Modes

*David L. Andra, Jr.*
*Science and Operations Officer*
* **WFO Norman, Oklahoma*

*Warning Decision Making (WDM) Workshops, Boulder, CO, 2002*

## Failure Mode:

- The manner in which a system fails.

## Examples

-  Technology - WSR-88D klystron fails preventing access to critical data.
-  Conceptual – Forecaster fails to recognize small storm as mini-supercell.
-  Organizational – Absence of well defined job roles and mission priorities leads to failure in SA.

## Failure Mode and Effects Analysis

*A technique employed by engineers to improve system performance*.

## Failure Mode and Effects Analysis

-  1. Define failure mode.
-  2. Identify cause of failure.
-  3. Identify effects of failure.
-  4. Corrective action.

## An Example

-  _*Failure mode*_: Conceptual
-  _*Cause*_: Failed to identify mini-SC
-  Mini-SC characteristics not understood by forecaster
-  _*Effects*_: Injuries and loss of life
-  _*Correction*_: Training for staff on mini-SC structure and evolution

## Strategy to Improve

-  Try to eliminate the failure mode.
-  Minimize the severity of the failure.
-  Reduce the occurrence of the failure mode.
-  Improve the detection.

## Other Considerations

*Some failures are more preventable than others!*

## Examples

-  *Relatively easy to prevent*:
-  Failure mode: Conceptual
-  Cause: Classic SC not recognized
-  Forecaster only uses 0.5 deg R product
-  Effect: Loss of life, feature on Dateline
-  Correction: Training, etc.

## Examples

-  *Nearly impossible to prevent:*
- Failure mode: Technological
- Cause: mini-SC at long range and embedded stratiform pcpn, night, sparse population. Brief tornado.
- Effect: mobile home destroyed with loss of life.
- Correction: maybe better VCPs or new radar?

## Ten Recent Disasters(since 1989)

*Complete Embarrassment*

*AOG*

## By Failure Mode

## Failure Mode and Effects Analysis (FMEA) is only a tool to identify potential or actual points of failure and identify corrective action.

## A Case Analysis

*A nearly unwarned tornado in OKC metro area*
- WFO Norman
- October 22, 2000

## Surface 00Z

## Slide 17

## 00Z OUN Raob

## 00Z OUN Hodograph

## Considerations

- Tornado day before
- Midday AC “NO SVR”
- Tornado watch by early evening

- Dayshift held over “just in case”
- New staff member stopped by
- Initially one warning forecaster

## What happened

- 5 tornadoes in CWA
- One F1, remainder *rated* F0
- F1 occurred in relatively dense population area
- No significant injuries
- No significant lead time

## Several storms of concern

## Tornado warnings SE & NW

## About 30 minutes later

## Interesting signature W of RDA

## Tornado at cursor

## F1 tornado occurring

## Was this a failure?

*Could have had more lead time!*

## Failure Mode and Effects Analysis

-  1. Define failure mode.
-  2. Identify cause of failure.
-  3. Identify effects of failure.
-  4. Corrective action.

## Analysis

-  _*Failure mode*_: Organizational
-  _*Cause*_: Failed to identify mini-SC tornado threat
-  Ambiguity in staffing caused breakdown in lines of responsibility
-  _*Effects*_: Not too much, could have been worse!
-  _*Correction*_: Re-emphasize intra-staff coordination and strengthen structure of duties

## Questions and comments?