El Nino Arrives Early For The Winter of 2006-07 - Southeast Lower Michigan Winter Outlook

                  El Nino Arrives Early For The Winter of 2006-07
                       Southeast Lower Michigan Winter Outlook

                                             WINTER 2006-07 OUTLOOK
                    By: William R. Deedler, Weather Historian, NWS Detroit/Pontiac
                                                    November 2nd, 2006

Temperatures:

Look for temperatures to average around normal to above as the interaction of the newly formed El Nino with the North Atlantic Oscillation should make for a challenging and fairly interesting winter.

Snowfall:

Snowfall is expected to average around normal as a combination of an active southern stream storm track (including a combination of: Eastern Great Lakes intensifying low pressure systems, Colorado and Texas Lows and Canadian Clippers bring moisture.

EL NINO ARRIVES EARLY

A rather quickly changing Pacific water temperature scenario presents addition challenges this time to the projected near term late fall and winter weather outlook for Southeast Lower Michigan . Initially, the majority of Pacific Ocean sea surface temperature /SST/ models indicated pretty much near normal, or Neutral state for the autumn into at least, the early winter period. By mid-summer, projections were for the Neutral pattern to persist at least into mid autumn and hinted at a weak El Nino thereafter, into the upcoming winter. That all changed from August into September when the central and eastern Pacific water temperatures warmed fairly quickly, resulting in the announcement of the birth of a new El Nino by mid September.

Climate Prediction National Outlook :

As a result of El Nino conditions affecting North America , a milder than normal winter is anticipated for much of the west and northern portion of the country in the NOAA national winter outlook. While milder than average trends are projected across much of the northern half of the country, what do weak to moderate El Ninos historically bring locally to Southeast Lower Michigan ? We will explore that question along with some other important meteorological factors that will influence our winter weather.

SST TREND, 1970S ALL OVER AGAIN?

The overall Pacific water temperatures have been oscillating around a degree or so above and below normal for several years now after the pronounced La Nina of 1999 & 2000. As a result, generally a weak El Nino, Neutral or weak La Nina phase (with Neutral being the most dominant) in the Pacific (during the El Nino of 2002, however, the SST did rise temporarily to the moderate category). As stated in past Outlooks, a similar pattern was also observed after a strong La Nina (1974 & 76) during the mid 1970s into the early 80s.

Below normal October, below normal winter?

This idea of a “below normal October, below normal winter possible?” came up and was investigated somewhat in our last El Nino Winter Outlook in 2002-03 under Contrary Indicators. It was found that in that particular set of El Nino winters when there was an abrupt change in the upper air pattern in October (NAO shifted to negative and strong northwest flow) which resulted in a colder than normal October, those following winters were also colder (or at least, below normal). Following up on that, another October fact that hints at that same line of thinking involves our coldest winters. Out of the 20 coldest winters in Detroit , 15 of the Octobers averaged below normal beforehand (remember though these were all types of winters, not just weak to moderate El Ninos) . Also, these were just our 20 coldest winters and not all the below normal winters. In addition, in our current local study, out of five below normal Octobers, four of the following winters averaged below normal and one around normal. Clearly, however, more study involving all below normal winters (and proceeding Octobers) is necessary to resolve a more definite trend.

Epilogue:

With the data presented above, which is especially consistent with a weak to moderate El Nino and NAO overall unpredictability (and recent trend) it prudent, at this time, to use a two-tier temperature outlook for this up coming winter. Again, look for around normal to above normal temperatures with near normal snowfall for Southeast lower Michigan. We shall see.

Look for possible updates to this forecast anytime during the winter.