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Is this Bangor or Bermuda? - 01.07.07


The Northeast is caught in some unusual weather patterns. Find out why in Doc Weather.

Folks from the Northeast have been writing Doc Weather with apocalypse on their minds. No freezing ground is to be seen, tree buds are stirring and insects are hatching as if it were late spring, and yet it is early winter. The charts for the coming next few months don't offer much solace for those who enjoy the brisk side of winter in the North Country. This winter, the eclipse grid patterns for the next couple of months don't show a lot of cold signals for the northeast. The current configuration of jet curves that will be influencing the northeast has historically produced moderate conditions for the year in which they occurred. The times when New England gets a lot of cold action are when either a set of 45° jet curves sits off of the coast (be prepared for February 2008) or more significantly when the disturbance diamond sits over the Mississippi Valley and a set of 45° jet curves sits off of Greenland forming a Greenland block. Neither of these cold producing patterns looks to be the case this year.


Fig.1


Fig.1
Record cold New England-January 2004

The cold producing configuration of the Greenland block was present in the November 2003 eclipse pattern that set up the record cold outbreak for New England in January 2004. In that pattern the high latitude 72°jet curves over the Mississippi Valley pushed a moderate ridge of high pressure up into the Dakotas while the 45° jet curves over the Atlantic also supported high pressure over Greenland. Both of these sets of curves were under the high pressure influence of Jupiter and Saturn at that time. High pressure kept the mid continental ridge strong and the Greenland ridge strong just off the coast of the Maritimes. For the record cold outbreak for January 2004, a low, sagging off of the 72° jet curves over the Mississippi, got stuck between the ridge over the Mississippi and the ridge over Greenland. As it sagged between the ridges the prevailing northwest winds brought intense cold out of Canada and Alaska into the NE.


Fig.2


Fig.2
Very warm winter New England- 2001-02

The pattern for the very warm winter of 2001-02 in the Northeast had a pair of 45° jet curves over the Mississippi Valley with a pair of 22° jet curves over the southwest. The prevailing circulation that winter was from the southwest into the northeast as a strong high lodged over the southeast on the two 45° jet curves for most of the winter bringing warmth into the eastern seaboard.


Fig.3


Fig.3
Winter 2007

The current pattern for the Northeast has two 45° jet curves over the western mountains with two 22° jet curves over the southeast. When the current El Nino influence begins to move into the east Pacific (mid January) the jet stream should begin to drop along the West Coast with a ridge over Hawaii. Look for cold to intrude into the inter mountain states and snow begin to pick up in the southwest. That pattern is illustrated in the diagram as the blue to red arrow moving south along the West Coast from the Gulf of Alaska.

If a ridge does form over the intermountain areas of the west it will most likely not push up so far north that the resulting cold coming down from Canada will move into the northeast. It looks like the cold will take a track farther west than that because there does not appear to be a strong influence for Greenland blocking this year. This kind of pattern is known as a cascade in the Doc Weather system. It is formed when a flow is established down the slope of the jet curves starting at a high latitude on the 72° jet curves to the west and then moving southeastward to the 45° jet curves and then down to the 22° jet curves. This cascade flow is depicted by the blue arrow. Statistically when the set of 22° jet curves that are on either side of the two eclipse points are located in a particular longitude, the high latitude locales in the eclipse area are usually not the site of anomalous precipitation or temperature fluctuations usually due to the effects of the descending cascade pattern. As a result of the cascade the tendency statistically is for the weather in the high latitude areas in the longitude of the eclipse points to be more moderate than in other positions. Low latitudes in the longitude of the eclipse points can be the site of unusual weather because of the southeast flow of the cascade. This may mean some surprises for Florida if not this season then late next fall when the grid sifts to the west.

By contrast, if the high to the southeast gets strong that could send storms up the coast for Nor'easters but those storms do not often involve extreme cold temperatures. For the Northeast, there will undoubtedly be some situations of cold weather dropping down into that sector but the way that the jet curve pattern is situated in the cascade at this time points to a pattern of scarcity of prolonged cold events for the northeast at least until the eclipse in March.

The March eclipse may shift things around and stir up a different pattern but by that time the El Nino should be over and the shift will most likely resemble the analog years of 1998 and 1988. In both of those years the springtime temperatures averaged slightly above normal, even though 1998 was the spring after a strong El Nino and 1988 was the spring after a La Nina. What they had in common was the placement of the eclipse grid jet curves in the current configuration. In standard practice conditions slightly warmer or cooler than the norm would simply be labeled "climatology" meaning taken as an average over the season the climate situation was near normal.