Basically, I look for normal to above normal snow and precipitation across Southeast Lower
Ok Ok Ok....Back to the Outlook
ENSO - La Nina
latest(11/7/11) Pacific water temperatures in Nino 1+2, 3 and 4 (Fig-1a, b, c, d & e), shows the
distinctive and fairly steady cooling of the areas of the Pacific Ocean since the summer used in
determining the pattern. For scientific purposes, Nino 3.4 is used to determine officially, whether or
not a La Nina is in effect. I also included the ENSO graph back to 1950. The latest as of 11/07
weekly SST departures below normal are:
Niño 4 -0.5ºC
are at/below -0.5C along with La Nina-type atmospheric conditions. To officially be classified as a "full-fledged"
La Nina, the temperature must average at/or below -0.5C for a period of at least 5 consecutive overlapping
and just below normal (for now) as La Nina subtlety becomes more east-centrally based rather than just east
(the cooler below average waters meander west with time). I believe the La Nina is beginning to mature and
according to the latest models (fig 1- e) should peak roughly within a month of Christmas-time or holiday season.
For a more in depth look/summary of the model predictions head over to International Research Institute /IRI/.
Southern Oscillation Index /SOI/
Those above numbers would be 0.97 and 1.08, respectively on the SOI Tahiti - Darwin graph scale below.
Let's get right to it...
a waxing and waning of La Ninas, several at or close to the timing of our present La Nina. It’s not surprising the current dominant La Nina(s) pattern has been somewhat unusual in recent decades (between the 1980s and mid 2000s) when El Ninos and Neutral patterns held sway. Just by looking at the cyclical nature of these guys (ENSO, PDO and NAO and others) is that any surprise? The last time we left the cool or negative biases of these cycles was in the 1970s. This predominant La Nina (and multi-La Nina) pattern we are now experiencing was last seen in the early to mid 1970s time frame and extended back into the early 1950s. Therefore and surmising: the majority of analogues in the study are those just recently experienced, several between the 1950s-70s and then way back into the late 1800s to the early1900s.
The solar cycles (S) are also included with this simplistic legend and rough timing of cycle estimates. Why include the solar cycle? I guess my answer (and question) is: why not? It may have little significance on a winter season most times but what about when the solar sunspot activity is at a lull or on the low side, like the past few years (though it is now beginning to increase). It’s a well known fact that the earth cooled during very extensive lulls in sun spot activity such as the Maunder Minimum. What effects do changes in solar energy have on planetary or geostrophic wind patterns continue to be debated. This is a “hotly” (pardon the pun) debated subject across the globe especially in Europe where new research papers released this year ignited more chatter. A Google search on this topic yields some wide ranging results and opinions. In my Winter Outlook, a majority of the analogue La Nina winters occurred on the lower side of the solar cycle. Below is the legend I devised for the solar cycle timing in each La Nina winter.
Symbol Solar Cycle Meaning____________________________
+ At the lower half of solar cycle
++ Near current cycle either declining or rising
+++ At or near current cycle and rising
In this particular event, I feel we will average below normal putting a range of -1.0 to -3.0 (I bring this up again in the storm track portion of the Outlook).
Season snowfall totals were all over the board, which really isn’t surprising if one considers the vivacious jet stream and storm tracks associated with these years - where just a variation of 50 miles or so can make all the difference in the world. Two of the most obvious trends in the analogues are the snowier winters recently and the snowier locations over the northern two thirds of Southeast Michigan. This area extended from Detroit's northern suburbs, northward across the Flint and Port Huron areas into the Thumb Region and Saginaw Valley. Saginaw's average snowfall was a whopping 14.4" above normal because there are plenty of (9 out of 14 ) snowy winters here. As one travels south, the snowier winters are still strong but lose some of their numbers with six at both Flint and Detroit. Closer to normal snowfalls prevailed on average at both of these locations though they were still on the high side (I elaborate on this further in the storm track section).
Below are the composite maps for the analogue years in the local study. Remember these maps average what happened over the region and do not take into account any recent trend observed over the region. They are only a “guidance tool” to past similar type La Nina winters.
Jet axis holds keys to this winter
A third area of phasing also is likely over the Ohio Valley into New England. This will be one of the major wild cards this winter as to snowfall amounts in S E Mich. This is not as clear cut as the past few La Nina winters. As mentioned above, the northern areas of Southeast Lower Michigan had higher amounts of snow relative to normal in the analogues than the south. In my mind, two main reasons can account for this. First being: the storm track that rides up from the Southern Plains area crosses over or near Southeast Lower Michigan rather than south of the region and thus, the majority of the snow rides further north with it (this would also open up the door for more mixed precipitation). Second, our Ohio Valley snow machine is either less pronounced this winter OR parks further south.
I mentioned the "sling-shot" pattern in my earlier discussion in regard to the jet stream. Plain and simple, by looking at the storm track map you can see how the Arctic/Polar jet prefers to take a dive southward (southeast or even southwest) to the lee of the southern Rocky Mountains in these analogue winters. This in turn, loads the storm "sling-shot "and shoots it east northeast toward the Great Lakes and then "somebody gets stung in the....";-). Who gets stung remains to be seen as the pattern evolves. If the storms ride further north than expected, this could also botch up the temperature forecast too with the upper level ridge holding stronger in the Southeast.
Well, that's pretty well covers what we are up against this winter. I will discuss some of the things I mentioned in the Outlook as the winter evolves.
Constructive comments or thoughts on the outlook are welcome.I noticed I have a good number of viewers from outside the U.S. I'd like to heard from you too. I wonder how you came across my blog?
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian