bright band

Radar measures reflectivity. Reflectivitiy is proportional to the diamater of the partical to the sixth power dbz~(D)^6.

Snow and rain reflect different amounts of radiation. This causes problems to decide how much it is actually raining or snowing.

Melting snow can be very deceiving. When snow starts to melt it gets a watery shell around the flakes. To a radar beam it looks like a 10 cm rain drop.

Often this phenomenon is evident on radar in what is called a "bright band" where the radar shows a high echo but there are actually less rain that is thought to be there.

Hot day in the Midwest

Two weeks ago the Midwest had lots of snow. Yesterday, May 14 2013, the Midwest had broke record temperatures. It was HOT! Click the link to view a Mesowest profile of the day. Notice the winds coming from the southwest. Also, take a look at the humidity. It was very dry in the hottests areas.

http://mesowest.utah.edu/cgi-bin/droman/mesomap.cgi?profile_id=DDhi1Pq0901JCegT

Milwaukee Heat Burst

At 20:00 (8:00 PM) there was a sharp rise in temperature. This temperature rise is related to an increase in wind speed. The increased wind speed was caused by a heat burst. In a heat burst, virga evaporates, cooling the air making, and becomes more dense. The air suddenly sinks and compression causes adiabatic warming. At the surface, people experience sudden gusts of warm air.

Mesowest profile of temperature and wind in Milwaukee on May 14, 2013:
http://mesowest.utah.edu/cgi-bin/droman/meso_base.cgi?profile_id=pJGv1rH0902JSAza

National Weather Service description of the Heat Burst:
http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=mkx&storyid=94614&source=0 

Virga and heat burst video (go to 8:00 PM)
http://f5.aos.wisc.edu/webcam_movies/latest_sunrise_to_sunset_northwest_640x480.mov

More about heat bursts:
http://www.crh.noaa.gov/oun/?n=heatburst_info

Downslope Windstorm

Northern Utah is waiting for another downslope windstorm. The National Weather Service, however, emphasized this wind storm will not be as strong as the storm in December, 2011. The GFS model for 04/09/13 at 03 UTC (6:00 P.M. local time) shows a large pressure gradient between Utah and Wyoming. This will induce high winds along the Wasatch Front as air plunges down the mountain side.

GFS 04/09/13 03 UTC: Sea Level Pressure and 3hr Precipitation

The NAM for the same time also shows a large pressure gradient. Below are the predicted surface winds at 03 UTC.

NAM HIRES, Northern Utah: 04/09/13 03 UTC: 10-m winds and 3hr Precipitation

Check out the Wasatch Weather Weenies blog for more about the downslope windstorm.

kbkb Current Conditions

My weather station is now up and running. Click this link to see the current weather conditions on the Spanish Fork east bench. My stations can also be found on Mesowest at E2355.