Thursday, February 11, 2016

Will Tucson Get Beyond The Middle?

[Update March 30: Tucson didn't even make it to the middle.] Back at the end of September, I showed a scatterplot of the combined total November through March precipitation at Tucson airport for each of the previous 66 years versus the Oceanic Niño Index (ONI, defined by the Climate Prediction Center) for January, i.e. for the middle of each of those five-month winters. I noted back then that, of the eight previous winters for which the January ONI was greater than +1.0 (i.e., moderate-to-strong El Niños), all eight of those winters were in the upper one-third of the five-month precipitation totals. Below is the same plot, but now with an additional point, labeled 2016 so far.

What can be said for this strong El Niño winter is that at least this year's five-month total won't be in the bottom one-third (assuming that we'll get at least a third of an inch between now and the end of March). [Didn't happen! Only 0.11 inch from mid-February through March.] After the jet breaks under the West Coast ridge near the end of next week, it would not be too crazy to hope for an inch of rain in the last week of February, and then another inch in March. That would put the five-month total just barely above the middle 1/3—comparable to the 1957-1958 El Niño winter, but not even as good as last winter, and nowhere near the 1997-1998 winter that might have been dreamed of.
(The Tucson total precipitation since October 1, 4.59 inches, is still almost an inch above normal. But half of this year's since-October-1-so-far total fell in the month of October.)