IOP 5: 2100 UTC March 18 - 1200 UTC March 19
(1300 PST March 18 - 0400 PST March 19)

Sierra Nevada; Independence, CA
18 PST
by Vanda Grubisic

Report written by Vanda Grubisic, Sunday, March 21

Synoptic overview:

The Eta, GFS, and COAMPS models continued to forecast westerly flow over the Sierra Nevada for March 18 and early March 19. The Eta and GFS models were both predicting a maximum of 15 knots at 700 mb and 25 knots at 500 mb. This maximum was forecast to occur at around 00 UTC on March 19. Owens Valley was at the souther edge of this westerly flow, suggesting a stronger event in the northern Sierra. The forecast for the Pacific cold front had shifted further south to SF bay, and the front was oriented in a more N-S direction. The front was forecast to reach its southernmost location by 00 UTC March 19 and slowly dissipate from the south end northward. COAMPS was forecasting wave activity over Owens Valley beginning at 18 UTC March 18, reaching a maximum at 00 UTC March 19, and ending by 12 UTC March 19. All factors appeared to be leading to a moderate wave event sin the afternoon and evening of March 18, expected to be stronger in the northern part of the valley.


The plan of operations for IOP 5 on March 18-19:

1. MAPR: on all the time
2. MISS: to be located in Big Pine, one radiosonde launch at 00 UTC
3. MGLASS: one radiosonde launch at 00 UTC from Madera (north of Fresno)
4. Lemoore: one radiosonde launch at 00 UTC


Summary of operations and observations:

Lenticular clouds started developing north of Bishop around 13 PST. Visible satellite imagery at that time was already showing strong wave clouds in the northern Sierra (downwind of the Carson Range and further north) with wave clouds starting to appear over the Mono Lake area. A sequence of visible images was downloaded and saved for this day, showing development of a wave cloud down to the narrowest point of the Owens Valley (south of Bishop) but not further south.

Digital photos were taken of the wave clouds that were visible from Bishop, as well as Independence. There were two wave crests, one immediately downwind of the Sierra and one over the White and the Inyo ranges. Westerly winds at the ground were observed in Bishop, but not further south.

White Mountains; north of Bishop, CA
1730 PST
by Alex Reinecke

MISS was located east of Big Pine (MISSBP location) near Owens River. There was much ground clutter at this site, both at lower levels as well as further aloft. Weak westerly winds at this site were documented between 06 and 08 UTC March 19 between 1.5 and 2 km AGL. Winds below 1.5 km were southerly the entire time. The ground AWS at the MISS site was showing southerly winds from 21 UTC March 18 through 03 UTC March 19, turning gradually into northerly near local midnight (08 UTC March 19).

A radiosonde was launched from the MISS site at 0019 UTC while lenticular clouds were located due west (two sondes were used at this site due to problems with the RH sensor on one of the sondes). Winds were weak below 650 mb, then NW then W and stronger further aloft. Temperature profile was nearly adiabatic with a smallish inversion near 580 mb.

Sierra Nevada; MISS site, east of Big Pine
0000 UTC

MAPR experience some problems with the generator at the beginning of the IOP. It was restarted and it functioned fine during the rest of the time. The winds at the MAPR site were weak, southerly below 2 km. The reflectivity was noisy and winds missing during most of the time (signal contamination by bird in low wind conditions?). Some weak westerly winds (5 m/s) were documented between 01 and 03 UTC between 2.5 and 3 km.

Two radiosondes were launched from MGLASS from Madera at 00 and 01 UTC. Only the data from the 01 UTC launch were reported, as there were problems with the data retrieval from the sonde launched at 00 UTC. The sounding shows a weak stable layer with the base at approximately 720 mb and westerly winds increasing significantly above 650 mb.

Two radiosondes were launched from Lemoore, one at 01 UTC and the other near 06 UTC (21:45 PST). Only data from the later launch was reported, showing much weaker westerly winds than MGLASS sounding at 01 UTC.