Ag Weather Forum

Weather Tidbits And Commentary

Mike Palmerino
By  Mike Palmerino , DTN Senior Ag Meteorologist

A few weather tidbits and comments:

According to the state climatologist in Iowa, last week in Iowa was the driest statewide in almost 2 years with only a handful of stations picking up any measurable rain. This dry trend was perfect for harvest. It also shows how wet the pattern has become again since the drought of 2012.

Also noted is a report out of Tennessee that eastern Tennessee received its earliest measurable snowfall since 1925. However--early snowfall does not necessarily mean a snowy winter.

Despite the fact that no government agencies have declared an El Nino event in the Pacific Ocean, our feeling is we have been in an El Nino for the last month or so. Our calculation of the eastern Pacfiic sea surface temperature departure for the month of October has risen to a plus 1.3 from a plus 0.7 in September. The Southern Oscillation Index (SOI) is now at -9.3 in the 30 and 90-day readings. These are both above the thresholds of an El Nino. And we have also been seeing El Nino characteristics of the weather pattern in North America, South America and Australia.

It seems at this point in time that the upcoming winter will continue to feature some El Nino characteristics. The most likely characteristic will be an active storm track over the southern and eastern U.S. What is more questionable is how mild the winter will be. In a classic El Nino, the country is on the mild side due to a prevalent Pacific flow. This warming is most pronounced in the north-central U.S. However, the blocking high pressure patterns across the far northern latitudes that have been so prevalent during the past couple of years could continue to show up at times allowing for surges of cold air into the U.S. How this cold air phases with the storm track will determine how much snow we get and also how far to the north and west from the classic El Nino storm track we see winter storms travel.

It is interesting to note, going back to the comment from the Iowa state climatologist, that last week was the driest in the past couple of years. The last few weeks have featured little blocking in the far northern latitudes. Prior to this, blocking has been quite common during the past couple of years since the end of the year 2012. Blocking patterns tend to give you a more-favorable growing season due to their tendency to promote cool and unsettled conditions. They also tend to promote rather cold and sometimes snowy winters.

The latest theory recently presented by the University of Tokyo is that blocking patterns in the higher latitudes are increasing due to vanishing Arctic sea ice. This promotes a weakening of the jet stream in the far northern latitudes, allowing more high pressure to build and forcing the cold weather associated with the polar vortex further to the south. An interesting theory and one that I think should be given further attention.

Mike

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Michael Palmerino
11/5/2014 | 10:45 AM CST
Unfortunately there will be little warning. We had gone virtually all of October with little sign of blocking and more El Nino like characteristics of the weather. All of a sudden this past weekend the 8-10 day models started to completely change showing extensive blocking developing over Alaska and northern Canada for next week. This will lead to a major outbreak of cold air into the central US next week.
JERRY KOCHANIUK
11/5/2014 | 8:48 AM CST
Will there be any warning as to when & if this high latitude blocking begins to move & where it will set up shop?