EDITED at 9:30 am MST - have added the new NAM forecast of precipitation through 5 am on Friday, the 5th, since it is so different than the GFS. See below.
The moisture plume from low-latitudes that I showed in yesterday's post has moved northward, directly toward the LA Basin during past 24-hours. The graphic above is from CIRA (at Colorado State) and shows their blended PW analysis for 12 UTC this morning (December 2nd). This is a very impressive moisture intrusion and it will serve to increase the chances of rainfall across Arizona as the week progresses. Graphic below shows CG lightning flashes detected for 12-hours ending at 1:30 am MST this morning. There was considerable thunderstorm activity west and southwest of California during the night - both directly associated with the Pacific 500 mb cyclone and also within the tropical moisture plume.
The forecast models continue to weaken the cyclone rapidly as it begins to move toward the coast today, But the GFS has begun to again forecast rainfall over the Southwest, as the weakened short-wave moves across northern Arizona (GFS had gone dry for the last couple of days, after earlier forecasts that had indicated both the moisture plume and rainfall coming into Arizona). The GFS operational forecast from 00 UTC last evening (above)now forecasts a widespread precipitation event for Arizona for period ending 5 am MST on Friday the 5th. So, it appears that the most interesting weather for southern Arizona will occur from late tomorrow into Thursday.
Below is the NAM forecast from 12 UTC this morning for precipitation through 5 am MST on Friday, i.e., for period ending at same time as GFS forecast shown above. Although NAM forecasts moisture plume to affect all of Arizona, it only forecasts precipitation for the higher elevations of northern Arizona - so two quite different model forecasts.
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