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Important Disclaimer

The following calculation tool is provided for general guidance and is not an official forecast product.

Storms can dissipate, form, develop overhead, or change speed. This is a tool to assist, not replace, a designated weather watcher. Event organizers are encouraged to learn more about weather hazards and their potential predictability prior to using this tool. Event organizers are also encouraged to read all of the accompanying information fully and work through all of the related educational materials and modules.

Experimental products may not always update in a timely manner and may be discontinued at a future date. Experimental products may also not always reflect accurate, quality controlled information and should be used with caution.

 


Use this tool for guidance on when to evacuate or shelter attendees at an outdoor event based upon information about your event and nearby weather.

 

Step 1 - Plan

Enter how much time it will take to notify attendees about evacuation/sheltering and how much time it will take to physically evacuate/shelter all attendees. The tool will calculate the total amount of time (including a safety factor) that it will take to safely carry out the evacuation/sheltering plan. If no additional information is entered, a table will also be generated below with possible storm speeds and the corresponding storm distances away from your event at which a decision to evacuate/shelter must be made.

 

Step 2 - Monitor Weather

Enter information about nearby storms and the tool will estimate the amount of time left until a storm reaches the 8-mile lightning safety radius of your event's location. If latitude and longitude coordinates are entered below, then you will be provided a link to a custom radar display with range rings based on your event's location and the storm speed that was entered. If there are no storms nearby or no storms are moving towards the event location, then you can leave these entries blank.

 

Step 3 - Act

The tool will provide an estimate of the latest time that you could initiate your evacuation/sheltering plan and safely evacuate/shelter everyone based on the total evacuation time that was calculated, assuming that additional storms do not develop and storm speed remains constant.

 

Optional - Event Location Latitude/Longitude

If you would like to have a radar loop map generated with range rings around your location, then please enter the latitude (in degrees North) and longitude (in degrees East) coordinates of your event in the corresponding input fields. For best performance, latitude should be a positive number while longitude should be a negative number.

 

Step 1 - Plan
Alert and Activation Time:  minutes
Evacuation or Shelter Time:  minutes
25% Safety Factor:
 
Total Evacuation Time:
 
 
Step 2 - Monitor Weather

Time:

Use current time

Enter time manually

:

 AM

 PM

Storm Speed:  MPH
Distance Away (from event venue):  miles
Distance Away (from 8-mile radius):
 
Time Until Arrival (at 8-mile radius):
 
Time Until Arrival (hh:mm):
 
 
Step 3 - Act
Total Evacuation Time:
 
Total Evacuation Time (hours):
 
Act Time:
 
Storm Strike Time (at 8-mile radius):
 

 

 

Latitude:  ºN    Longitude:  ºE

      

 

 

More Information

Alert and Activation Time (required): The amount of time (in minutes) that it will take to notify everyone about evacuation/sheltering and activate any procedures that are required for evacuation/sheltering to take place.

Evacuation or Shelter Time (required): The amount of time (in minutes) that it will take to evacuate and/or shelter everyone at the event.

25% Safety Factor: The amount of time (in minutes) that should be taken into account when evacuating an event to consider possible changes in storm speed and any unexpected delays. Equivalent to 25% of the sum of the alert/activation time and evacuation/shelter time (rounded up to the nearest minute).

Total Evacuation Time: The amount of time (in minutes) required to safely carry out the full evacuation/sheltering plan, assuming that additional storms do not develop and that storm speeds remains constant. Determined by summing the alert/activation time, the evacuation/shelter time, and the 25% safety factor.

Time (optional): The current time. Can also be set to a custom time to plan out hypothetical scenarios. If left blank, act time and storm strike time will not be computed, but additional guidance will be provided based on the amount of information that was entered.

Storm Speed (optional): The speed at which a storm is moving towards the location of the event (in mph). If left blank, time until arrival, act time, and storm strike time will not be computed, but additional guidance will be provided based on the amount of information that was entered.

Distance Away (from event venue) (optional): How far away (in miles) a storm currently is from the location of the event. If left blank, time until arrival, act time, and storm strike time will not be computed, but additional guidance will be provided based on the amount of information that was entered.

Distance Away (from 8-mile radius): How far away (in miles) a storm currently is from the 8-mile lightning safety radius for the location of the event (distance away from the event location minus 8). So for instance, if you input that a storm is 20 miles away from the actual location of the event, this value would be 12. This value is the distance that is used for calculating the time until arrival.

Time Until Arrival: How much time remains until the storm reaches the event's 8-mile lightning safety radius, based on the inputted storm speed and the distance away from the 8-mile lightning safety radius (under the assumption that the storm speed does not change). The top row for this in step 2 is strictly in minutes while the bottom row will display the same amount of time as the top row, but in an hh:mm format where hh is the number of hours and mm is the number of minutes.

Act Time: The latest time at which the evacuation/sheltering plan can be initiated in order to be safely completed prior to the storm's arrival. This is based on the Alert/Activation time and Evacuation/Shelter time that was entered, and assumes that storm speed is constant and no additional thunderstorms develop. This can only be computed if valid input is entered for all 5 input fields. This will also be colored red if the current time is past the act time.
 
Storm Strike Time: The time at which the storm will reach the event's 8-mile lightning safety radius, assuming that the storm speed does not change. This can only be computed if valid input is entered for all 5 input fields.

Latitude/Longitude (optional): The latitude/longitude coordinates of the location of the event. If entered, a link (or multiple links) will be generated that will take you to a web page with a radar loop that has both the 8-mile lightning safety radius and an evacuation/sheltering decision point radius imposed on it to help you visualize the input that you entered into the tool and the different stages of the evacuation/sheltering plan. Latitude is in degrees North, while longitude is in degrees East. Values between -90 and 90 constitute valid latitude coordinates and values between -360 and 360 constitute valid longitude coordinates, but for best performance in the U.S., the latitude should be a positive number between 15 and 75 and the longitude should be a negative number between -180 and -60. Both numbers can be decimals.
 
 
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Tool developed by Rafal Ogorek at NWS Chicago. Based upon a previous tool created by Kristin Licko and a concept developed by the DuPage County Office of Homeland Security and Emergency Management. Please contact Mike Bardou (mike.bardou@noaa.gov) with questions or comments.