Winter 1995 as an analog to winter 2006. | DocWeather: New Climate Research

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Winter 1995 as an analog to winter 2006. - 11.25.05

Looking back helps us to look forward. The winter of 1995 can offer insights into the upcoming winter.

The analog year for January and February of 2006 is the winter of 1995. In that year the eclipse points were in a similar position to the points that are active in 2006 until the eclipse changes the points in late March. With the eclipses of October 1995 the eclipse grid was placed over the Great Basin. The disturbance diamond was over the desert Southwest. There was a cooling towards neutral temperatures in the E. Pacific after the moderate el Nino of the year before. So there was little ENSO influence.

Fig.1

The first figure shows the effects of the 1995 eclipse grid placement when all of the jet curves were influenced towards high-pressure values from planetary positions (blue curves). Climatically, in the summer and early fall, the polar jet is at its highest latitude of the year. In 1995, with strong high-pressure values on the points there was little incentive for the storm track to fall to the south due to the particular placement of the highs on the continent. As a result the fall storms skirted the northern tier of states and these sections experienced a mild fall and early winter. By the middle of November only the farthest northern stations had experienced a killing frost. The eclipse in October 1995 had placed the disturbance diamond over the Great Basin. In that position planetary aspects kept high-pressure values on the eclipse points for the first few weeks of November. The result was continental blocking, a zonal flow in the polar jet and mild weather to the north. This pattern has repeated in the fall of this year(2005).

Fig.2

All the while the Sun in 1995 was moving far to the south and the global patterns of warmth and cold were shifting in the oceans. By late November 1995, as the polar jet had moved inevitably to the south the eclipse positions set up a pattern where the polar jet oscillated strongly between periods of zonal flow (east/west) to periods of meridional (north/ south) flow in the polar jet on the continent. This took over as the season moved from fall to winter. This was due, on one hand, to the movement of the polar jet to a more southerly position, as is normal climatology for the North American continent. However, the dynamics of the eclipse grid were very different as a result. In figure 2 the more southerly winter placement of the polar jet is depicted with the same high-pressure blocking. Instead of blocking the polar jet is now digging a trough in the Midwest.

The formation of a digging trough at mid-continent is the result of a particular feature in the eclipse grid. As can be seen from the chart, the eclipse grid has a gap between the 45Â° pair of jet curves on the East Coast and the 72Â° pair of jet curves over the Great Basin. During the winter of 1995 the gap in the grid was in the exact position to allow the Hudson Bay Low to send digging troughs spinning down into the Midwest. This pattern unfolded in the winter months of 1995 when planetary motions put high-pressure values on both pairs of jet curves. It is interesting to note that the appearance of high-pressure influences gave very different results when the polar jet was placed climatologically to the north (summer) or south (winter) of the northern tier.

Fig.3

In figure 3 the West Coast winter and summer patterns for 1995 are depicted on one chart. The summer pattern shows a red arrow moving horizontally across the PNW when high-pressure dominated the chart. The winter pattern shows a blue arrow moving vertically down the coast when high-pressure on the 72Â° jet curves from the eastern pair, pushed a ridge up along the West Coast into Alaska. In winter, a blocking ridge surging into Alaska is a climatic norm when surges of high-pressure moving northward along the coast get caught in the easterly flow of winds around the poles. The easterly (east to west) flow of the polar winds moves far to the south in winter, entraining highs that are surging up the coast and pinching them off to eventually settle over Alaska. A winter ridge moving up the West Coast into Alaska often portends cold into the West Coast in the days that follow the surge. The time frame from the beginning of a typical surge to the formation of a high latitude block is about one week. When a high establishes itself as a block in the Gulf of Alaska, the polar jet, moving along the northeastern flank of the Alaskan ridge, digs south along the coast bringing cold and fronts into the PNW and N California (blue arrow).

Fig.4

Figure 4 shows that these types of storms from the north have a tendency to move from western Canada into the northern Plains states, down into the central Plains and then recurve up the East Coast when high-pressure from the pair of 45Â° jet curves on the east coast sets up blocking patterns off of the coast that steer storms into New England. This sets up the classic nor'easter pattern that brings copious snow to the Northeast. This was a pattern in 1995 when the Hudson Bay low teamed up with an active high over the western Atlantic to create a series of nor'easters along the Atlantic Coast. This included the mammoth, memorable blizzard of '96 along the whole East Coast.

Fig.5

In figure 5 the placement of the eclipse grid for the winter of 2006 can be seen. The eclipse points are in a similar placement to winter 1995. These will shift to the west in March 2006. So far this year (2005) the eclipse pattern has been true to the analog. For long stretches this fall the lunar node, aspecting the eastern pair of points, was stuck in a strong high-pressure mode for months on end. The high-pressure that resulted was the source of the prolonged warmth along the northern tier and the extreme dryness on the West Coast. It is interesting to note that the driest fall on record for the West Coast was the fall of 1995 when the eclipse points were almost exactly placed as they are in this fall of 2005. The first rains of the season that year were on December 10th. This year (2005) the first winter storm was on November 25th.

Similar to 1995, in the 2005/2006 chart it can be seen that the space between the 45Â° jet curves on the East Coast and the 72Â° jet curves over the Great Basin is in line with Hudson Bay. In the past week (third week of November) there has been a shift from the mild, zonal (west/ east) flow across the United States to a more meridional (north/ south) pattern for the polar jet. Based on these observations the analog year suggests that the Midwest will be the site of cold temperatures once the polar jet moves to its mean winter position in the south. This will especially be the case when high-pressure builds a ridge over western Canada or Alaska. Look for a surge of high-pressure along the West Coast in the first week of December. This will be short-lived. In the last week of December 2005 and the first two weeks of January 2006 there should be ample surges establishing a strong block in Alaska. This will kick in the Hudson Bay low to begin sending fronts southward along a track from the northern Plains into the Central states. Continental storms this winter will most likely drop through the Midwest and re-curve up the East Coast drawing moisture from the Gulf of Mexico and depositing it along the eastern side of the Appalachians as ice and sleet. On the West Coast, December should be a time of cold, unsettling intrusions interspersed with large sections of mild calm weather as the highs build and then surge into Alaska driving the polar jet down along the coast. Look for strong rains and possible floods in the PNW when the surges start in earnest.