Winter Forecast 2013-14

Every year since the early 1990s I have made a forecast for the upcoming winter. This year I issued my forecast in September, and now, in mid-October, I am finally getting around to posting it. Sorry for the delay!!

As always, I create a composite forecast using data from past years which are similar to this year. Mostly I look at changes in the tropical Pacific. I look for years which have spring-summer Pacific conditions similar to the current year. Then I create a composite picture of the fall-winter-spring months for those similar “analog” years.

The main Pacific indicators I use are the Multivariate ENSO Index (http://www.esrl.noaa.gov/psd/enso/mei/) and the Pacific Decadal Oscillation (PDO). Using data through July, 2013, I identified 5 past years with similar distribution of these variables:

1970-71  1973-74  1975-76  1988-89  2007-08

Here is what I found:

1. Precipitation

Most indicators suggest a wetter-than-average winter. The map below shows precipitation anomalies by climate division for the lower 48, based on a composite of the analog years. Indicated are significant positive anomalies for the Northwest — that is, wetter than average conditions — for November through January.

precip anomaly 2013

Looking at cumulative precipitation for Salem (below), most of the analog years were near or above average, with 1973-74 particularly wet.

 

 

 

salem temps

 

 

 

 

2. Temperature

The nationwide temperature anomalies (below) suggest near-average temperatures for the Northwest. Salem temperatures in the analog years showed near-average winter temperatures but generally cool springs.

temp anomaly 2013

salem temperatures

 

 

 

 

 

 

 

 

 

3. Snowfall

Average temperatures and wetter than average precipitation would suggest abundant mountain snowfall, and that is exactly what the analog years showed. Below is a chart with cumulative snowfall at Government Camp, on the slopes of Mt. Hood at about 4,000 feet. Four of the five analog years saw significantly above-average snowfall.

govtcamp snow

 

 

 

 

4. Summary

Based on the indicators described above, I predict:

– A wetter than average winter

– Average temperatures

– Above average snowfall; a good year for skiers!!

George Taylor

October, 2013

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