Friday, July 22, 2016

Near-Severe Outflow Event Early Morning Hours Today

Ron Holle sent the following:

There was a major wind event at our house I Oro Valley around 3 to 3:30 am this morning. The house was shaking and wind was whistling around the edges – sounded like Boulder! No lightning or rain.

The airport had gusts to 47 mph a little earlier, and D-M reached 38 mph. There was a power outage here at Vaisala around 1:30 am.

Was it an outflow?

I hadn't looked at the surface obs when I did the morning post today. But the following stations had gusts over 40 mph early this morning:

Mt. Hopkins         G61 @ 2:19 am
Pioneer Airfield   G 54 @ 12:56 am
FHU                     G 51 @ 12:43 am 
TUS                      G 47 @ 0153 am

Basically, I found that all of the observing stations from FHU to Nogales to Sells to PHX to Muleshoe Ranch back to FHU had early morning gusts of 30 mph or more from the long-lived outflow. It developed as storms moved from Mexico into southwest Cochise County around midnight and passed Sky Harbor at 4:40 am MST, with the visibility reduced to 3 miles in dust. The only sites within the large area outlined that did not gust to 30 mph or greater were Sollers and Rincon RAWS sites at high elevations.

I could find no really strong, Boulder-like winds in the MesoWest data in Oro Valley, but these sites are further west than Ron, who is nearer the west end of the Catalinas, where there may have been some orographic enhancements.

I also took a look at the 00 UTC runs of the WRF models and found that, while there was nothing forecast by the NAM version, the GFS version did forecast a large, nighttime outflow.

The WRF-GFS radar forecast above was valid at 10:00 pm MST last night and the 10-m wind forecast below was valid at 11:00 pm. The location of the outflow event was very good, although the actual event occurred 2 to 4 hours later than forecast.

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