ConvectiveWarningFun damentals

Convective Warning Fundamentals: 

Convective Warning Fundamentals DLOC Workshop 2007 Brad Grant WDTB

Outline: 

Outline Format Basic knobology Functional considerations Upcoming changes (storm-based warnings paradigm)

Mission Connection of Warnings(from NWSI-511): 

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)

Content of a TOR: 

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)

Format of a TOR: 

Format of a TOR a. Type of warning; warning location(s) b. Valid time 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).

Mission Connection of Warnings(from NWSI-511): 

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.

Content of a SVR: 

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 thundertorm moves over costal waters, a Special Marine Warning will be issued (see NWSI 10-313).

Steps to Create a Warning: 

Steps to Create a Warning With latest Radar Product (Z or SRM) displayed (zoomed with 6 frames), start WarnGen Drag Me to Storm Toggle back several frames to make sure DMTS dot is over trackable point of interest (meso, core, leading edge, etc.):Note pathcast updated on display pane using latest storm motion vector. Click on Redo Box button to redraw warning area using new vector Select Track Type Select Product type Select Time Range : Duration (< 1 hr) Call to Action (Optional bullets) Create Text

Steps to Create a Warning: 

Steps to Create a Warning Edit Text Window Review Warning Storm movement, pathcasts, reports Hit “SEND” * AT 115 PM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED NEAR AURORA...OR 10 MILES EAST OF MONETT...AND MOVING EAST AT 115 MPH.

Warning Creation Considerations: 

Warning Creation Considerations Duration should be 30-45 min in most cases (don’t 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 Don’t try to match polygons to county borders Don’t edit the warning headers Limit call to action statements Whole process should only take a minute or two.

Follow-UpsSevere Weather Statement (SVS): 

Follow-Ups Severe 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.

SVS Content: 

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 (See handout on Creating Properly Formatted Follow-Ups In WarnGen).

Changes in Warning Policies: 

Changes in Warning Policies A Storm-based (or threat-based) warning (SbW), is simply: SbW = WCW – FAA (“unnecessary”) where WCW is whole county warning (magenta outline), and FAA is the area where no perceived imminent threat exists (magenta shaded regions). - = In the new approach, all we’re trying to do is reduce the alerted territory where no imminent threat is perceived.

Slide14: 

From County-Based Warnings to Storm-Based Warnings Three simultaneous tornadoes within line of severe thunderstorms County-Based Tornado Warnings 8 Counties under warning Almost 1 million people warned Storm-Based Tornado Warnings 70% less area covered ~600,000 fewer people warned More specific Increased clarity Supports new dissemination technology

Slide15: 

In the current system, six full counties are warned. Storm-Based Tornado Warnings provide much improved service. Storm-Based Warnings Provide Improved Service Strong circulation within line of severe thunderstorms Tornado warning area based on storm without regard to county boundaries

Slide16: 

Current County-Based Verification System County-Based Verification Probability of Detection (POD) = 100% Lead Time = 25 minutes False Alarm Rate = 0%

Caution #1 Don’t cut the bologne too thin: 

Caution #1 Don’t cut the bologne too thin If you draw the polygons too small, you risk missing events (and thus negatively impacting POD). One must incorporate uncertainties due to: Location of event vs. radar location of signature Changes in storm motion Storm evolution (e.g. cyclical mesocyclone) Resolution of display used These uncertainties should lead to a larger warning polygon, but not one extending into areas where no threat exists (as has been the case with whole county warnings). White polygon shown to the right is too small, given potential for storm to deviate to the right, or tornado to deviate to the left as it weakens. Blue polygon is a better definition of the tornado threat area.

Caution #2“Polygonology”: 

Caution #2 “Polygonology” Areas in gap between polygons are not warned. Overlap not a big problem, but should be minimized as much as possible. County borders are not important, but CWA borders are! The polygon you draw is the polygon that the media will display in the future. Confusion from issuing too many warnings for a given county. May occur when issuing different polygons for different threat types.

Caution #3Doing Follow-ups: 

Caution #3 Doing Follow-ups Be Careful when trying to modify polygons Can’t make it bigger; can make it smaller

Caution #4: 

Caution #4 Loading Warnings

Summary: 

Summary Warn for the Threat Keep Users in Mind Remember the KISS principle Practice Using Test Mode