No Real Cold AirNovember 2nd, 2013 at 2:05 am by Bill Steffen under Bill's Blog, Weather
Meteorologists look at a handful of index values that can give us a clue on long-range weather. Here we have left to right the Arctic Oscillation (AO), the North Atlantic Oscillation and (NAO) and the Pacific North America Pattern (PNA) as of Saturday morning. Generally speaking, when the AO and NAO are negative, we get a trough in the Eastern U.S. and that usually brings cooler weather. It can mean blocking to our north, forcing colder air down into the U.S. from Canada. A negative PNA usually means a trough in the Western U.S. and ridging in the East. The sum total of the three index values above (from Friday night) would indicate that the really cold stuff is going to stay away up north in Canada for at least a while. Note that the AO seems to want to start downward around the 2nd week of November. That might indicate a cold shot around the 3rd week of November. The overnight GFS plot model doesn’t take G.R. below 30 into mid-November, with lots of days in the mid 40s to mid 50s. The average high is 54 now…so we’re not drastically warmer than average here. Many of the same features that we had last winter are still there (cool Pacific Decadal Oscillation, warm Atlantic Monthly Oscillation (AMO) and a neutral El-Nino Southern Oscillation. This would favor a SW to NE storm track. This would favor the coldest air relative to average across the northern Rockies into the northern Plains (Montana, the western Dakotas). Cold shots into Michigan would be relatively short-lived.
There has been a trend in recent years toward less snow in November and more in February in West Michigan. I also want to point out this table of peak flow on the Grand River. It doesn’t include the April 2013 flood, which was approx. 34K cfs. Look at 1904-05 and 1947-48. Hmmm – seems the worst floods on the Grand River came in consecutive years! Could we have another high water event this spring? Also, look at the flow levels. The floods of 1904-05 were considerably greater than the flood of last year. In the 1904 flood, the water covered most all of downtown G.R. west all the way to John Ball Park! See pics. at this link. Like I said, many of the parameters haven’t changed since last winter.