Monday, September 10, 2012

An Upside-Down Week

Yesterday afternoon the large complex of storms (see previous post) produced a number of severe storm reports in the Yuma area - including a report that I-8 was closed due to downed power lines. The system then produced additional severe winds across southern California - reports are listed at SPC -


Locally it has been an interesting week with early morning storms developing very close to Tucson - followed, most days, by quite suppressed afternoons from eastern Pima County eastward to New Mexico. This morning produced another such upside-down event. The early WRF-GFS predicted a small MCS to form over eastern Pima County around 3 am MST (composite radar forecast for 3 am below). The TUS radar composite (above for 6:12 am) shows the storms that were ongoing at sunrise. Rains were not heavy and there were only a couple of lightning flashes and rumbles of thunder. Model forecast the development with good spatial accuracy, but continues to be too early in time. Storms were not as strong as forecast and rains were not nearly as heavy as other events this week.

The early WRF-GFS forecast skewT plot for TUS at 3 am MST (above) was quite similar to the morning sounding that was launched at 4 am MST (below). So, the model performance was very similar to yesterday. Here at house there is only 0.01" in the gauge after the morning sprinkles - storms went by to the east yesterday am and to the west this am.

The data from the ALERT network are a bit difficult to use this morning - the past 24 hours contains rain from both mornings. At 7 am 64 sites had reported rainfall during past 24-hours. At noon yesterday 35 sites had rain during past 6-hours (largest amount 0.75" at the Oracle ranger Station); this morning 28 stations had rain for the 6-hours ending at 7 am (greatest amount only 0.35" at Coronado Camp). So the morning coverage was similar both yesterday and today at about 35% each day. here at house the event yesterday also produced only 0.01". Will try to write more on this week with the flip-flopped diurnal cycle later.

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