KNAU and Arizona News
Thu July 18, 2013
KNAU Meteorologist Lee Born: Monsoon And Rainfall Update
The monsoon season has arrived in full force. This week has brought some powerful storms to the region. Arizona Public Radio's Gillian Ferris spoke with meteorologist Lee Born about this summer's rainfall.
GF: Am I imagining that this summer's monsoon storms have been a little wetter than most, a little stronger?
LB: Nope. You're not imagining that at all. We've gotten quite a bit of rainfall since the monsoon started. When we got the average 3.3 days of average dew point of 55 degrees at Sky Harbor like we used to track it. That goes to July 5th, and that was the very first day if we go back to the old way. But, here in Flagstaff we could've taken it all back to July 2nd because that's when it started raining. And that's the day we got 1 3/4" at Flagstaff Pulliam Airport and everything flooded over there on Milton. And since then, we are at 3.64" here in Flagstaff, which is 360% of normal to date. So July is off to a great start here with the rain. And it's been spread out all over northern Arizona. This week, we've seen quite a lot of rain across the region. Kind of different light morning rain over the last week or so.
GF: I'm thinking that one of the characteristics of monsoon storms in Arizona is that they build all day and then they cut loose in the afternoon - and I suppose that's not a hard and fast rule for Mother Nature. But it seems that this summer's storms are all day, all night.
LB: Yeah, I think traditionally we think of the monsoon as a sunny morning, the heat builds, the moisture's in the air, the clouds start to build up, and then we see the mid-day, mid-afternoon thunderstorms and then we clear out. But, it has been a bit different so far with this monsoon with this abundant moisture in the atmosphere and the cloud cover that persists all day. It kind of puts a damper on the morning heating and you can't really get those strong thunderstorms to build. So, there's been so much moisture and so much cloud cover that it's been hard to really get thunderstorms to build up. The areas that do see the morning sun see the storms build first.
GF: Before the start of the monsoon we were breaking records for drought, and dryness and lack of precipitation. But now, just a few weeks into it, where are we?
LB: That's right. When we talked about a month ago I was talking about how dry it was and we were terribly dry; we were at 60% of average on the calendar year for 2013. But here in July because we're at 300% of normal, we've had all this rain that's really helped us out in the climatological book. And for the calendar year we're only about 6/10" below average - we're at 94% of average now - on the calendar year.
GF: Lee, any idea how long these all-day storms will last?
LB: Sure. And that's a good question. I think we're going to get more into a typical pattern here as we get into the coming weekend and into much of next week. The moisture is going to stick around. We're going to stay in this monsoonal-type southeast to easterly flow in the upper levels of the atmosphere which continues to transport in the rich Gulf moisture. But what's happened around here for much of this week is that there was so much moisture, that we just had all that morning cloud cover which was kind of pesky. But then what happened mid-week, particularly on Tuesday and Wednesday, is we had an upper level disturbance that moved through and was able to interact with that moisture. So, even though we did have the morning cloud cover, we were still able to get quite a bit of rain on Tuesday. We did have some minor flooding issues in some areas across Arizona that saw 2+ inches of rain due to that upper level disturbance. And that thing slowly slid through on Wednesday. But, that will be out of here today, out of here the rest of the weekend and I think we're more into a typical type monsoon where we see the big boilers get going in the morning, spread around town mid-day, and then we're all back on our bikes by late afternoon.