Sep 112015
 
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The Atlantic Hurricane season must be damaging advertising revenue for the major U.S. television news networks. Other than tropical systems forming, then quickly falling apart, there just hasn’t been any of the damage they crave to drive the revenue. No scary hurricanes, no viewers.

On a side note, there has been much recent background noise around why we are seeing fewer strong Atlantic storms. One piece of information I find very interesting comes from a tweet by Dr. Philip Klotzbach at the University of Colorado. He and his colleague, Dr. Gray, are world-renowned hurricane forecasters. Below is the picture he tweeted.

12-month running average of the Atlantic Multidecadal Oscillation. (Klotzbach and Gray, originally 2008, updated)
12-month running average of the Atlantic Multidecadal Oscillation (AMO). (Klotzbach and Gray, originally 2008, updated)

Notice that the AMO has dropped over the last couple years. In 2010, I wrote a pretty long post discussing the future forecast for the AMO to do this. A strong influence for that post was an article from the Proceedings of the National Academy of Sciences (Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States, McCabe, Palecki, Betancourt, March 23, 2004
vol. 101 no. 12, PNAS) From that paper, I included the next chart.

Drought frequency (in percent of years) for positive and negative regimes of the PDO and AMO. (A) Positive PDO, negative AMO. (B) Negative PDO, negative AMO. (C) Positive PDO, positive AMO. (D) Negative PDO, positive AMO. The red areas show a greater than 30 percent likelihood of a drought. The blue areas show a lesss than 20 percent chance of drought.

Drought frequency (in percent of years) for positive and negative regimes of the PDO and AMO. (A) Positive PDO, negative AMO. (B) Negative PDO, negative AMO. (C) Positive PDO, positive AMO. (D) Negative PDO, positive AMO. The red areas show a greater than 30 percent likelihood of a drought. The blue areas show a less than 20 percent chance of drought.

Notice that in A and B, the AMO is negative and Arizona is wetter, regardless of the state of the Pacific Decadal Oscillation (PDO). I found one quote from the PDO-AMO article particularly salient:

Although it is always prudent to be conservative about water resources, particularly in the semiarid West, it may be particularly necessary in the next decade.

The article is dated March of 2004. That decade has ended. The AMO has appeared to have shifted to a negative phase. And, our 12-month average precipitation has been on the rise. Also, Dr. Klotzbach’s shows roughly 1995 as the start of the positive AMO. This also coincides with the downfall in our precipitation. Are they linked? Is the drought ending?

12-month and 2-year Flagstaff precipitation totals.

12-month and 2-year Flagstaff precipitation totals from 1950 to August 2015.

This month should be wet according to the long-range forecasts. The next 6-8 months should be wet, too. We will see. The recent 6-10 and 8-14 day outlooks have bounced around like a super ball lately. I think this is mostly due to an active hurricane season in the Eastern Pacific Ocean. The GFS model continues to have significant wet periods for Arizona in the period out to 2 weeks.

 

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