Friday, July 2, 2010

Interesting Iowa weather

 Radar imagery from the morning of the 27th showed what could be either a gravity wave, bore, or cold outflow. The two waves seen as finelines of about 25 dBz are over AMW and approaching DSM.

The time series from the roof of the ISU Agronomy building:
http://mesonet.agron.iastate.edu/plotting/iemcc/?year=2010&month=6&day=27

The time series shows a small drop (1.2F in 5 minutes) in temperature and dew point, a brief recovery, then a second drop (3F in 7 minutes). The third drop is actually the outflow boundary from the storms to the west, not the north. So it is plausible that the bore or gravity wave arrived first followed closely by the outflow boundary. 

The temp and pressure relationship was non-existent for the 1st "wave" (dp = 0), but strong for the 2nd (dp = 0.5 hPa). the wind speeds in the 2nd wave peaked after the min pressure occurred during the t fall. The last wind speed increase occurred in the wake of the 2nd wave but prior to the rapid, small pressure oscillations. I wonder if the pressure sensor is affected at particular wind directions.