OLYMPEX
Science Summary for 1 November 2015
 
Postfrontal Convective Rain and Snow

Prepared by
Robert A. Houze, Jr., Lynn McMurdie, and Joe Zagrodnik


NOTES:
The date starts at 0000 UTC.
This report may be updated as new information becomes available.
Data discussed here were compiled in near real time and have not yet been quality controlled.
Updated reports can be found at http://olympex.atmos.washington.edu/index.html?x=Science_Summaries

Postfrontal precipitation occurred throughout this day. Figure 1 shows snow falling at the Hurricane Ridge site on the lee side of the Olympic Mountains. At 500 hPa, three identifiable short wave troughs were embedded in the broader trough passing from west to east across the region (Figure 2a). The 500 hPa temperatures were low (Figure 2b), consistent with the unstable condition seen in the lower troposphere in the Quillayute sounding taken at 1200 UTC (Figure 3). It was especially unstable below 700 hPa. The IR satellite sequence in Figure 4 shows the postfrontal convective cloud regime moving over the Olympic Peninsula throughout the day. In the 0500 UTC image (upper right), cloud features can be seen that correspond to the three short wave troughs in Figure 2a. The sequence of radar images in Figure 5 shows that the convection passing over the region had mesoscale dimensions, and toward the end of the day was organized in to southwest-northeast bands. Lightning was detected in these convective features, as shown in Figure 6. Lightning was also seen by the OLYMPEX ground crew both near Lake Quinault and over the Wynoochee site. They also observed graupel mixed with the rain on the ground at Wynoochee (Figure 7). The showery character of all the precipitation is illustrated by the Parsivel data from three sites in Figure 8.


cam

Figure 1. Webcam shot, Hurricane Ridge, 1618 UTC 1 November 2015


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                                                                                                                          (a)                                                                                       (b)

Figure 2. 500 hPa height with (a) vorticity and (b) temperature and wind at 1800 UTC 1 November 2015.



Figure 3. Quillayute souding, 1200 UTC 1 November 2015.



   
 

Figure 4 .Sequence of infrared images for 0000, 0500, 0900, 1300 UTC 1 November 2015.






Figure 5. Sequence of Langley radar reflectivity images for 1 November 2015. Time are UTC.


lightning


Figure 6.  Lightning at 1630 UTC 1 November 2015, superimposed on IR image.




Figure 7.  Graupel observed mixed with rain at Wynoochee (~1 km elevation) and snow shower seen from Wynoochee at ~2100 UTC 1 November 2015.







Figure 8. Parsivel data for 1 November 2015 at Kalaloch on the coast north of the Quinault, the Fishery site slightly inland in the Quinault Valley, and the Bishop site on the east end of Lake Quinault.