Report written by Vanda Grubisic, Sunday, March 7
Synoptic overview:
With a low pressure center off the coast of Southern California, numerical models were predicting E-NE flow across the Sierra Nevada and Owens Valley from 16 to 21 UTC. At 18 UTC, the Eta and GFS models were predicting 30-40 knots at the mountain top level (700 mb) and 40-50 knots at 500 mb. This was a narrow window of opportunity for wave generation by the Inyo range with forecast winds turning northerly by 00 UTC March 4. The COAMPS forecast called for a more northerly wind during this period.
The plan of operations for IOP 1 on March 3:
1. MAPR: launch a radiosonde at 18 UTC
2. MISS: locate off the Mazurka Canyon Road between stations 5 and 6 of the DRI network at Kearsage, launch a radiosonde at 18 UTC
3. MGLASS: launch a radiosonde at 18 UTC from Delano (S of Visalia and Tulare on Route 99)
4. Lemoore: no operations
Summary of operations and observations:
The predicted period of easterly flow over Owens Valley occurred earlier, with a peak at 12 UTC (4 PST) on March 3. By the start of the IOP, the flow turned to northerly at all levels. The MAPR received signal returns up to 2 km above ground level in clear and dry air.
At 18 UTC (10 PST), balloons were launched from both the MAPR and MISS sites. Weather was nice and clear, with north winds at ground level and further up. The radiosonde equipment worked well, and the data was collected from the surface up to about 100 mb. At the MISS site, the signals were getting weak at about 250 mb. Both soundings are posted on the ATD Sierra Rotors Project web site (http://www.atd.ucar.edu/rtf/projects/srp2004/).
MGLASS launched a sonde one hour later than requested due to problems with a computer that have since been resolved. The sonde was launched at 19 UTC (11 PST), and showed north winds throughout.
The DRI ground network (http://www.wrcc.dri.edu/trex/) was functioning well, except for winds at station #4, which show 180 degrees offset from the rest (fixed on March 8), and some minor glitches in a few microbarographs.