La Nina 2011-12 is fast becoming a memory as Pacific water temperatures warm back to Neutral (near normal or long term average) conditions.
Projected ENSO Model Data
Neutral conditions are expected to take hold during the spring and continue into the summer. In Neutral conditions, little if any effects from ENSO are anticipated across the country. That being said, I expect our La Nina pattern to fade as a "the song is ended but melody lingers on" type of pattern for the near term with the atmosphere still reeling from some of the La Nina effects. I feel we are seeing a good example of this with the recent notable early severe weather across the center and southern portions of the country. La Nina's do tend,
on average, to be busier in the severe weather department.
Of course; the strongest influence by far on our weather continues to be the NAO/AO oscillation which has been nearly consistently positive since last Autumn (check it out; Fig -1 below). This was the main reason the winter was
so mild as explained in earlier blogs. Looking at the Winter 2012 preliminary statistics at Detroit all data
includes leap day, 2/29.
Detroit
Ave High: 39.5 Precipitation
Ave Low: 26.4 7.70"/ +1.26
Wntr Ave: 33.0 /6th warmest/ Snow thru 2/29th
(warmest winter since 2001-02 @ 33.8) 25.8"/-8.3"
Flint
Ave High: 38.1 Precipitation
Ave Low: 24.2 5.85/ +0.82
Wntr Ave: 31.2 /5th warmest/ Snow thru 2/29th
(warmest winter since 2001-02 @ 31.7) 32.3"/-6.3"
Saginaw
Ave High: 36.9 Precipitation
Ave Low: 24.2 5.85/ +0.82
Wntr Ave: 30.6 /3rd warmest/ Snow thru 2/29th
(warmest winter since: 2001-02 @ 30.5 41.9"/+7.6
1997-98 @ 30.9)
_______________________________________________________________________
Fig -1
With the NAO remaining positive throughout the winter, the dominant analogue winters were virtually useless. The last time a winter was so "contrary" to popular analogue opinion and Outlook was back in the
Winter of 2001-02. Interestingly, the "popular call" that winter was also for below normal temperatures; instead it too turned out to one of the
warmest winters /5th/ on record in Southeast Lower Michigan and much of the country. While this past winter was a La Nina winter, the Winter of 2001-02 was a Neutral Winter that subtly evolved toward a El Nino late winter (but ENSO's influence too, like this past winter was negligible). The trump card in any winter season on the temperature side and lesser extent snow of course; is the prevailing phase of the NAO/AO!
There were two coincidences between these two winters one straight forward and one; conjecture and controversial. It was suggested in some
scientific papers written about the 2001-02 winter and the questionable strong solar flare influence on the planetary winds. As in the past winter, the NAO also remained strongly positive for much of the Winter of 2001-02 which certainly accounted for the largest mild impact on the winter then and now! This near term peak in solar flare activity (relative to recent trends) during this
past fall and
winter; albeit weaker in strength, is just an intriguing parallel between the two winters and accompanying solar flare periods, and of course like 2001-02, research would have to be done.
While on the subject of solar activity another very interesting article was written by
Joe D'Aleo on the recent
minimum solar activity, before the sun's latest burst into its 23rd cycle. I personally feel more research should be done on the correlation between sun spot activity and weather and climate patterns on earth.
Solar Variation and Weather
There are some suggestions that there may also be regional climate impacts due to the solar activity. Measurements from NASA's Solar Radiation and Climate Experiment show that solar UV output is more variable than the total solar irradiance. Climate modelling suggests that low solar activity may result in, for example, colder winters in the US and southern Europe and warmer winters in Canada and northern Europe, with little change in globally-averaged temperature. More broadly, links have been suggested between solar cycles, global climate and events like El Nino. In other research, Daniel J. Hancock and Douglas N. Yarger found "statistically significant relationships between the double [~21 year] sunspot cycle and the 'January thaw' phenomenon along the East Coast and between the double sunspot cycle and 'drought' (June temperature and precipitation) in the Midwest."
Recent research at CERN's CLOUD facility examined links between cosmic rays and cloud condensation nuclei, demonstrating the effect of high-energy particulate radiation in nucleating aerosol particles which are precursors to cloud condensation nuclei. Dr. Jasper Kirby, a team leader at CLOUD, said, "At the moment, it [the experiment] actually says nothing about a possible cosmic-ray effect on clouds and climate, but it's a very important first step."
1983–1994 data from the International Satellite Cloud Climatology Project (ISCCP) showed that global low cloud formation was highly correlated with galactic cosmic ray (GCR) flux; subsequent to this period, the correlation breaks down.Changes of 3–4% in cloudiness and concurrent changes in cloud top temperatures have been correlated to the 11 and 22 year solar (sunspot) cycles, with increased GCR levels during "antiparallel" cycles. Global average cloud cover change has been found to be 1.5–2%. Several studies of GCR and cloud cover variations have found positive correlation at latitudes greater than 50° and negative correlation at lower latitudes. However, not all scientists accept this correlation as statistically significant, and some that do attribute it to other solar variability (e.g. UV or total irradiance variations) rather than directly to GCR changes. Difficulties in interpreting such correlations include the fact that many aspects of solar variability change at similar times, and some climate systems have delayed responses.
Spring 2012 Outlook
Temperatures:
Look for temperatures to average mainly above normal during the Spring of 2012. The strong NAO/AO+ pattern of the fall-winter continues to dominate as we move into spring-time.
Precipitation:
Rainfall during the spring and especially summer is more variable; occasionally areas of above, below or around normal can exist in the same season over a relatively small area. During the Spring of 2012; I look for precipitation to average normal to above normal across much of the region.
Severe Weather:
Since a strong jet stream is an important ingredient for severe weather, the position of the jet stream determines the regions more likely to have severe weather.
Contrasting El Niño and La Niña winters, the jet stream over the United States is considerably different. During El Niño the jet stream is oriented from west to east over the northern Gulf of Mexico and northern Florida. Thus this region is most susceptible to severe weather. During La Niña the jet stream extends from the central Rockies east - northeastward to the eastern Great Lakes. Thus severe weather is likely to be further north and west during La Niña than El Niño. As stated above; while La Nina conditions over the Pacific are disappearing, a La Nina-like scenario would bring at least average to even above average severe weather to the region.
Spring Analogues:
As mentioned, analogue data was virtually useless with the main driver of the winter the NAO+/AO+. However, in the analogues years where the patterns seemed the closest to our recent mild winter conditions and prevailing NAO+/AO+, the springtime temperatures and precipitation are shown below. In addition, included is the the springtime precipitation for all the previous winter analogues. The data maps show the warm weather continued to prevail from the Plains eastward across the country. Below normal temperatures were found out west. Overall; precipitation averaged normal to above east of the Mississippi in both sets of years of the analogue data.
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian
