Tornadoes / Thunderstorms
Preparedness
Your Emergency Services Division takes severe weather preparedness very seriously. Since severe weather is the Number One potential widespread risk to Washtenaw County residents and businesses, storm preparedness activities take top priority over everything else that we do. As StormReady accredited coordinators for the National Weather Service Skywarn Spotter program, we are engaged in numerous severe weather related activities year round.
Skywarn Program
Your Emergency Services Division conducts several Skywarn Spotter training programs every year. The courses are held throughout the community at the beginning of every severe weather season. The presentations are free of charge and are open to anyone at least 18 years old who is interested in being trained on severe weather recognition, reporting and protection procedures.
This course is one and one half hours long, and Skywarn Spotter identification codes are issued to all who complete the training. Washtenaw County currently has approximately 300 trained:
- Amateur radio operators
- Citizens
- Firefighters
- Paramedics
- Police officers
- Public works officials
Severe Weather Emergency Operations Center Activation
When the National Weather Service (NWS) issues a severe thunderstorm or tornado watch, the Emergency Services Division staff is notified immediately via InteractiveNWS (iNWS) alert in the Emergency Operations Center (EOC), and by radio, text message, and email if out of the office or during off hours. We then immediately activate the Emergency Operations Center with the communications and warning, direction and control, and public information duties being staffed. The EOC's communications system is activated including the Amateur Radio Skywarn network. Our weather radar and storm tracking system is immediately fired up and monitored closely for approaching or developing severe weather, matching Skywarn spotter reports to real time radar data and issuing warnings to the public in conjunction with NWS meteorologists.
Satellite Storm Tracking
This is a weather satellite image (infrared and color enhanced) from the EOC's tracking system of a line of intense storms clearly indicated from near Lansing stretching all the way down into the Texas panhandle. The more red the color is, the colder the cloud tops are and therefore the higher they are in the atmosphere which indicates their relative severity. These images are updated in the EOC every 5 minutes, and animates to show overall direction of travel.
Doppler Reflectivity
EOC Doppler radar showing a distinct "V-notch" with "hook echo" as trained spotters report the tornado and initial damage in Dexter Township. The tornado continued on the ground for over 7 miles, doing extensive damage with wind speeds of 135-140 mph as it moved to the southeast. The tornado eventually weakened and lifted near the intersection of Zeeb Road and Dexter-Ann Arbor Road.
Doppler Velocity
The same storm using a velocity display showing intense local rotation (look at the center of the picture where the red and green colors appear to touch. This indicates that winds are going away from and going towards the radar station in the same general area.) This display is extremely useful at detecting tornadoes in the absence of a trained spotter by using Doppler shift technology and color enhanced imagery.
Weather Coverage
Washtenaw County is covered by National Oceanic and Atmospheric Administration (NOAA) Weather Radio Station KEC-63 at 162.550 MHz.
Watches & Warnings
Severe Thunderstorm Watch
Conditions are favorable for the development or approach of severe thunderstorms in and close to the watch area. Stay tuned to NOAA Weather Radio or local media and be prepared to take cover indoors.
Tornado Watch
Conditions are favorable for the development or approach of severe thunderstorms and tornadoes in and close to the watch area. Stay tuned to NOAA Weather Radio or local media and be prepared to take cover indoors.
Severe Thunderstorm Warning
A severe thunderstorm (a storm with winds in excess of 58 miles per hour or with 1 inch or larger hail, or both) is indicated on radar or has been reported by a Skywarn spotter. Take cover immediately in a sturdy building. Stay away from windows and do not use the telephone or appliances unless it is a life threatening emergency. To keep informed until the storm passes and the warning expires, use a battery powered radio tuned to: WEMU (89.1 FM).
Tornado Warning
A tornado (violently rotating column of air in contact with the ground) or funnel cloud (developing tornado) approaching the ground surface has been indicated on radar or has been reported by a Skywarn spotter. Take cover immediately in a sturdy building. Go to the lowest level of the structure preferably into a small windowless room and crouch under a sturdy desk or table. Stay away from windows and do not use the telephone or appliances unless it is a life threatening emergency. To keep informed until the storm passes and the warning expires, use a battery powered radio tuned to: WEMU (89.1 FM).
Flood & Flash Flood Watch
Conditions are favorable for flooding and flash flooding (inundation of flooding waters within 6 hours) in and close to the watch area. Stay tuned to NOAA Weather Radio and local media. Be aware of current conditions, especially if you live or work near a flood prone area or are near a river, creek or stream. Prepare to take immediate action to protect life and property.
Flood & Flash Flood Warning
Flooding or flash flooding is imminent or is occurring now. If rising water nears, immediately evacuate to higher ground. Do not attempt to drive through flooded roadways or underpasses. To keep informed until the flooding subsides and the warning expires, use a battery powered radio tuned to: WEMU (89.1 FM).
Wind Speed Estimation
| Miles Per Hour | Description |
|---|---|
| 0 |
Smoke rises vertically |
| 1-3 | The direction of the wind is shown by smoke but not wind vanes |
| 4-7 | Wind is felt on the face, leaves rustle, wind vanes move |
| 8-12 | Leaves and small twigs are in motion, small flags are extended |
| 13-18 | Dust and loose paper is raised, small branches move |
| 19-24 | Small leafy trees sway, crested wavelets form on lakes and ponds |
| 25-31 | Large branches are in motion, whistling is heard on power lines |
| 32-38 | Whole trees in motion, inconvenience in walking against wind |
| 39-46 | Twigs break off trees, difficult to walk against the wind |
| 47-57 | Minor structural damage such as chimneys and shingles |
| 58-72* | Damage to chimneys and antennas, shallow rooted trees uprooted |
| 73-113 * | Roof surfaces peel, windows break, moving cars pushed off road |
| 113-157* | Roofs, weak buildings, mob. homes destroyed, large trees uprooted |
Hail Size Estimation
| Size | Description |
|---|---|
| 0.25 inches |
Pea size |
| 0.50 inches |
Marble size |
| 0.75 inches |
Dime size |
| 1.00 inches* |
Quarter size |
| 1.75 inches* | Golf ball size |
| 2.75 inches* | Baseball size |