Review of NWS Warning Fundamentals

1
Review of NWS Warning Fundamentals

• DLOC Workshop 2008
• Brad Grant
• WDTB

2
Outline

• Policy and Format
• Functional considerations
• Storm-Based Warnings Tips

3
Mission Connection of Warnings(from NWSI-511)

• Purpose Tornado Warnings are issued to protect
  lives and property. WFO forecasters issue Tornado
  Warnings to provide the public and emergency
  managers with advance notice of tornadoes.
• Issuance Criteria Using WarnGen, WFOs should
  issue Tornado Warnings when there is radar or
  satellite indication and/or reliable spotter
  reports of a tornado (Note non-scheduled,
  event-driven product)

4
Content of a TOR

• Tornado Warnings will follow a standard bullet
  style format. WFOs should keep bullets brief.
  WFOs should include a call to action statement.
  The WFO Shift Leader on duty may discontinue call
  to action statements in warnings during
  widespread tornadic outbreaks. Locations should
  be larger towns and other familiar landmarks.
  WFOs may reinforce the warning with recent
  history to support their reasoning. Names of
  states and counties (or parts of counties) should
  be spelled out.
• WFOs should use the nine part divisions (i.e.,
  northeast, east central, etc.) to identify
  portions of states or counties under warnings.
  WFOs may use mileage markers as reference points
  in rural areas when a storm is occurring or
  forecast to move over a major highway.
• If a tornado moves over costal waters, a Special
  Marine Warning will be issued (see NWSI 10-313)

5
Format of a TOR

• a. Type of warning warning location(s)
• b. Valid time (15 to 45 minutes)
• c. Time, basis for warning forecast impacts
• d. Indicate which locations are to be impacted
  during the warning, using the nationally
• approved pathcast and non-pathcast formats (see
  Section 4.3.5)
• e. A BRIEF concluding paragraph with additional
  information, and call-to-action should
• be included and
• f. The latitude and longitude pairs outlining the
  area of greatest impact polygon drawn
• in WarnGen will be included after the fourth
  bullet and call to action. Forecasters should
• draw the polygon to be a subset of the warned
  county(ies) and show the area where
• severe weather is most likely to occur (i.e.,
  unless severe weather is expected to cover the
• entire county, do not mirror the warned county
  outline).

6
Mission Connection of Warnings(from NWSI-511)

• Purpose Severe Thunderstorm Warnings are issued
  to protect lives and property. WFO forecasters
  issue Severe Thunderstorm Warnings to provide the
  public and emergency managers with advance notice
  of damaging wind gusts and large hail.
• Issuance Criteria WFOs should issue Severe
  Thunderstorm Warnings when there is radar or
  satellite indication and/or reliable spotter
  reports of wind gusts equal to or in excess of 50
  knots (58 mph) and/or hail size of 3/4 inch
  (penny) diameter or larger.

7
Content of a SVR

• Severe Thunderstorm Warnings will follow a
  standard bullet style format. WFOs should keep
  bullets brief. WFOs should include a call to
  action statement. The WFO Shift Leader on duty
  may discontinue call to action statements in
  warnings during widespread svr wx outbreaks.
  Locations should be larger towns and other
  familiar landmarks. WFOs may reinforce the
  warning with recent history to support their
  reasoning. Names of states and counties (or parts
  of counties) should be spelled out.
• WFOs should use the nine part divisions (i.e.,
  northeast, east central, etc.) to identify
  portions of states or counties under warnings.
  WFOs may use mileage markers as reference points
  in rural areas when a storm is occurring or
  forecast to move over a major highway.
• WFOs should NOT combine Severe Thunderstorm and
  Flash Flood Warnings. Warnings WILL include the
  possibility of tornadoes if a Tornado Watch is in
  effect.
• If a severe thunderstorm moves over costal
  waters, a Special Marine Warning will be issued
  (see NWSI 10-313).

8
Format of a SVR

• a. Type of warning warning location(s)
• b. Valid time (30 to 60 minutes)
• c. Time, basis for warning forecast impacts
  (range of hail sizes and wind gusts)
• d. Indicate which locations are to be impacted
  during the warning, using the nationally
• approved pathcast and non-pathcast formats (see
  Section 4.3.5)
• e. A BRIEF concluding paragraph with additional
  information, and call-to-action should
• be included and
• f. The latitude and longitude pairs outlining the
  area of greatest impact polygon drawn
• in WarnGen will be included after the fourth
  bullet and call to action. Forecasters should
• draw the polygon to be a subset of the warned
  county(ies) and show the area where
• severe weather is most likely to occur (i.e.,
  unless severe weather is expected to cover the
• entire county, do not mirror the warned county
  outline).

9
Warning Creation Considerations

• Duration should be 30-45 min in most cases (dont
  have a 1 hour warning out for fast-moving
  storms)
• After 45 min, WFOs should issue a new TOR (60 min
  for new SVR) to extend valid time
• Size matters (08 NOAA performance measure will
  evaluate normalized county area
• Dont try to match polygons to county borders
• Dont edit the warning headers
• Limit call to action statements (and dont be
  careless)

Whole process should only take a minute or two.
10
Mission Connection of FF Warnings(from NWSI
10-922)

• Purpose Flash flood warnings are issued when
  flooding is imminent. This product will be
  reserved for those short-term events which
  require immediate action to protect lives and
  property, such as dangerous small stream flooding
  or urban flooding and dam or levee failures. The
  geographic areas addressed by flash flood
  warnings may be counties, portions of counties,
  river/stream basins, or other definable areas
  (e.g., deserts, valleys). Flash flood warnings
  may include observations and forecasts for
  specific points. Flash flood warnings and tornado
  warnings will not be combined in the same
  product. Flash flood warnings should not be
  combined with severe thunderstorm warnings.

11
FFW Issuance Guidelines

• Criteria A flash flood warning will be issued
  for a county or counties (zones -Alaska, Guam,
  and American Samoa) in a WFOs CWFA when
• a. Flash flooding is reported and/or
• b. A dam or levee failure is imminent or
  occurring and/or
• c. A sudden failure of a naturally-caused stream
  obstruction (including debris slide, avalanche,
  or ice jam) is imminent or occurring, and/or
• d. Precipitation capable of causing flash
  flooding is indicated by radar, rain gages,
• and/or satellite and/or
• e. Local monitoring and prediction tools
  indicate flash flooding is likely and/or
• f. A hydrologic model indicates flash flooding
  for locations on small streams, or
• g. A previously issued flash flood warning needs
  to be extended in time.
• h. Flash flooding is imminent or occurring in
  one or more additional counties
• (zones - Alaska, Guam, and American Samoa)
  currently not under a valid flash
• flood warning. Note a new warning may be issued
  for an already covered county
• if deemed necessary by a forecaster (e.g., for
  different area of a large county).

12
FFW Format

• Issuance Time Flash flood warnings are
  non-scheduled, event-driven products.
• Valid Time A flash flood warning will be
  valid until the time when flooding (requiring
  immediate actions to protect lives and property)
  is expected to end, as indicated in the second
• bullet, or until the product is cancelled.
  When determining the valid time or considering an
  appropriate time for warning cancellation, the
  ending time for the flooding should be the
• determining factor rather than the end of
  heavy precipitation. (most offices use 2- 3 hours
  for product duration routinely)

13
Follow-UpsSevere Weather Statement (SVS)

• Purpose Severe Weather Statements provide the
  public and emergency managers with updated
  information for specific Severe Thunderstorm and
  Tornado Warnings. Updated information includes
  reports of observed severe weather. They also
  inform the public and emergency managers when all
  or portions of a warning have been canceled or
  have expired.
• Issuance Criteria WFOs should issue a Severe
  Weather Statement to provide notice a Severe
  Thunderstorm or Tornado Warning has been canceled
  for all or portions of the warning. WFOs should
  issue a SVS at least once during the valid time
  of a Severe Thunderstorm or Tornado Warning. WFOs
  may issue a Severe Weather Statement to provide
  notice that a Severe Thunderstorm or Tornado
  Warning has expired. WFOs should issue a Severe
  Weather Statement to notify customers that
  erroneous counties included in original Severe
  Thunderstorm or Tornado Warnings (either in the
  FIPs/Zone UGC code or in the body of the warning)
  have been removed.

14
SVS Content

• WFOs should issue Severe Weather Statements to
  address the status of severe weather warnings.
• WFOs will not use Severe Weather Statements to
  expand in area or extend the valid time of
  Tornado and Severe Thunderstorm warnings.
• If the area of greatest impact changes during
  the valid time of the Severe Thunderstorm or
  Tornado Warning, forecasters should update the
  latitude and longitude pairs of the polygon
  within the warned county or counties.

15
Storm-Based Warning Tips
16
Tip 1 Represent the Threat

• Track the Hazard

This is the low-level vortex movement!
17
Draw Polygon to Convey Damaging Wind Threat
18
Tip 2 Be Aware of Text Overload in Big Warnings
1
2
19
Radar Images 15-45 min After Start Time
20
Tip 3 Dont Slice the Bologna (Warning) Too Thin

• Polygon and Text should represent the Threat!

• BULLETIN - EAS ACTIVATION REQUESTED
• TORNADO WARNING
• NATIONAL WEATHER SERVICE JACKSONVILLE FL
• 415 PM EST TUE MAR 22 2005
• THE NATIONAL WEATHER SERVICE IN JACKSONVILLE HAS
  ISSUED A
• TORNADO WARNING FOR...
• WAYNE COUNTY IN SOUTHEAST GEORGIA
• THIS INCLUDES THE CITY OF JESUP
• UNTIL 500 PM EST
• AT 414 PM EST...NATIONAL WEATHER SERVICE
  DOPPLER RADAR INDICATED A DEVELOPING TORNADO 14
  MILES SOUTHWEST OF ODUM...OR ABOUT 7 MILES NORTH
  OF PATTERSON...MOVING NORTHEAST AT 35 MPH.
• THE TORNADO IS EXPECTED TO BE NEAR...
• JESUP AND 6 MILES SOUTHEAST OF ODUM BY 435 PM
  EST

21
Tip 4 Watch Your Polygon
Cant expand!
CWA Border
22
Follow-ups can Make the Warning Smaller
23
Cancellations
Better to issue a new warning than to cancel (in
most cases)
24
Tip 5 Bigger is Usually Better
One TOR issued at 2215z to cover threats from
BOTH storms
County-Based VerificationProbability of
Detection (POD) 100 Lead Time 25
minutes False Alarm Rate 0
25
Tip 6 Keep a Slight Overlap with No GAP
B
A
26
With Storm Merger Imminent, How Do You Draw Your
New Polygon?
B
A
27
New Polygon is Larger (Due to Uncertainty)
B
A
28
Plan Ahead for New Interactions
A
B
29
How to Keep Track of Warnings
30
Summary

• Warn and track for the main threat
• Keep users at forefront (reduce text overload)
• Remember the KISS principle (and think ahead)
• Practice using the WES