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Regarding Jack's observations of the convergence moving off the Sierras eastward into Western NV. I have seen this pattern on many occasions both as a Meteorologist at the ZLA CWSU and as a glider pilot (I happened to be flying my Discus glider on that 9/2 Labor day in the Western Mojave Desert).
I have come to the conclusion that it is a fairly large scale phenomena (sub-synoptic or large mesoscale) having to do with differential heating between the Nevada Great Basin Plateau and the lower coastal regions of California from the Great San Joaquin and Sacramento Valley westward. Certainly, the crest of the Sierras form convergence zone first due to elevated heating. But by mid afternoon, the upslope on the Sierras advects this boundary eastward. The Sierras can be thought of as the diffential heating boundary (like a coastline) between the elevated Nevada Plateau and the cooler more stable Sacremento/San Joaquin Valley.
By the way, there was a bit of a convergence zone in the Western Mojave Desert around 00Z to 01Z along a ENE to WSW axis shown in Jack's output. That zone is fairly typical when broad Southwestlies start encroaching into the western deserts. On that day, during our Region 12 Soaring Championships, 20 sailplanes had to glide into stable air in the extreme Western point of the Mojave Desert to a turnpoint and then back east to the convergence zone. There, thermals took us to almost 16,000 msl over Rosamond, Ca.
A general observation about using the RUC and other NCEP models for soaring weather and other mesoscale phenomena. I believe there is a wealth of information even at this 20km RUC (let alone upcoming 8-4km resolution in the NMM and Windowed ETA) than most forecasters realize. The key to mining this information is the visualization tools like Dr Jack has prepared to bring these features out.
Good work Jack!
PS - to Dr Stan Benjamin. I have been making this point to my management people in NWS that we need much better tools for visualizing NCEP model data. Recently I was asked to comment on how the RUC compared to the ETA and GFS suites. I told our NWSHQ Chief, that he should be careful of forecaster oppinions because there comments are highly skewed by what visulization methods are used.
Walt Rogers
MIC ZLA CWSU, Palmdale, CA
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