Monday, March 01, 2010

The Short-Term Details Can Be Tough!



First - view of the Catalinas this morning showing that the snow level came down fairly low before the precipitation event ended yesterday. Note the Kelvin-Helnholtz waves on the top of the cloud sitting on Mount Lemmon.
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Following up on Chuck's comment on predictability below. The event that ended yesterday evening was amazing well-forecasted by the models - although the NAM appeared to under-forecast the QPF, it did correctly forecast the bulk of the precipitation to fall after 5 am on Sunday. Moderate to heavy rains fell during the mid to late morning doubling and tripling the early morning amounts. Here at house we ended up with a total event rainfall of 0.92" by late afternoon. We drove across town from east to west between 10:00 and 11:00 am and the rain was really coming down, with ponding and rivers running down some streets - quite something. However, there seemed to be problems in telling users the correct details about what was going on - this may have been related to the fact that the NWS radar went down around midnight on Saturday night and it remained out-of-service this morning. So, a significant event transpired with no radar information available for southeastern Arizona. An urban and small stream flooding alert was issued an hour or two after our drive through the flooded streets.
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I've been poking at the Arizona Star and KVOA for their (or AccuWeather's) really bad forecasts 2 out of the last 3 Sunday mornings. So I was interested to see what was in yesterday's paper - and the banner forecast had an 80% chance of rain for yesterday. Not bad and close to the 100% NWS forecast that I found online for our grid point at around 7:00 am. A bit after this a winter storm warning was posted at 7:40 am for the mountains, which seemed a tad late given the winds and snow that had already swept through - again perhaps this was partly due to the lack of radar information.
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When we got home I checked online and found that the POPs had been reduced to 40% on the morning update around 9:30 am - clearly the wrong way to zig, given that rain amounts continued accumulating until late afternoon. Related to the radar problem? Finally at 3 pm I noticed that POPs for our grid point had come back up to 50%. So, yesterday the immediate details proved more difficult than the long-term, large-scale forecasts leading up to the event.
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Regardless, February has now closed out with total rainfall here at the house of 2.78 inches. The rainfall for 2010 has been an impressive 5.74 inches here at the house. No wonder dangerously deep potholes seem to be everywhere!

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