Unusual Radar Echoes - Spring 2010

• Between the mornings of May 15 and 19, a strange phenomenon was detected by the National Weather Service Radar in Spokane (located 3 miles north of Fairchild AFB).
• This phenomenon developed each day at approximately the same time (around 430 am) and over the same location, near the Turnbull National Wildlife Refuge south of Cheney.
• Each day the phenomenon seemed to fan out with the prevailing low-level winds and disperse by 5 am. 
   

May 15th

• The first morning detection occurred shortly after 425 am near point "A".
• The radar echoes (originally blue and green colors) fanned out to the northwest and north-northeast.
• Prevailing low-level winds were out of the southeast.

May 16th

• On the morning of the 16th, the echoes first appeared around 434 am, again near point "A".
• The radar echoes fanned out to the northwest, ending up somewhere near Edwall and Reardan.
• Prevailing low-level winds were out of the southeast.

May 17th

• A day later, the echoes appear at 431 am.
• The echoes again fan to the northwest.
• Prevailing winds were from the southeast.

May 18th

• Unlike the previous three mornings, there were showers falling in the general vicinity.
• Also unlike the previous 3 mornings, the strange echoes moved off to the east-northeast.
• The prevailing low-level winds were out of the south to southeast.

May 19th

• The morning was clear and fairly cool.
• This morning also saw the echoes moving to the northeast.
• This was similar to the low-level winds, which were from the southwest.
• Officials at Turnbull Wildlife Refuge, under the radar echo, reported nothing unusual at the time.

Daily Location of this phenomenon

• Point "A" on the previous radar images correlates with the green arrow on the image to the right.
• This places the origin near Long Lake in the Turnbull Wildlife Refuge, southwest of Cheney.
• On other days, the echoes originated slightly east, near Turnbull Slough.

How Deep are the Radar Echoes?

• Using a radar cross-section, we can estimate how deep or thick these returns are.
• The based of the radar beam is around 2250 ft MSL.
• The top of the green (or most dense echoes) is around 4000 ft, and the darker blue echoes extend to nearly 5000 ft MSL.

• After some very cold temperatures (below freezing on the mornings of May 21-25), the echoes returned to the area in June.
• The weather during this period was cooler and wetter than what occurred in May.
• On one occasion, the odd echoes originated from two additional locations.

June 6th

• The morning was clear and cool.
• The low-level winds were from the east.

June 7th

• This was a wet morning, at least northeast of the site. Notice the showers (yellow and green echoes over the Spokane Valley and Coeur d'Alene).
• The echo near Marshall late in the loop was a rapidly forming shower.
• Low-level winds were from the southwest.

June 8th

• This was a clear and dry morning. Cool temperatures prevailed.
• Low-level winds were from the south.
• The echo splits late in the loop.

June 10th

• The morning weather was cloudy with numerous showers north and east of the site (not seen on this loop).
• Low-level winds were from the southwest.
• Radar echoes formed near Reardan and extreme NW Spokane County.

June 10th Locations

• On the morning of June 10th, additional echoes originated over extreme NW Spokane County, and near Reardan.
• Both sites were near bodies of water.

By Jonathan Fox