RaysWeather.Com Winter 2008-09 Fearless Forecast

Introduction

Here we are again, "going where forecast angels fear to tread" the Fearless Forecast for Winter 2008-2009. In the end, we'll conclude that this winter will have:

• More snow than recent winters but less than the 40-year average
• Overall temperature near to slightly above normal.

Last year's winter behaved almost exactly as expected. We forecast 60% of normal snow and temperatures 1°-2° below normal. The final tally for Winter 2007-08 was 48% of normal snow and temperatures were 1.08° above normal. Last year's forecast gets a grade of "A" by almost any standard. However, last year was a relatively easy long-range forecast (even though there is no "easy" long-range forecast) because of a strong La Nina signal. La Nina winters are notoriously dry and generally have much less than normal snow. An evaluation overall for seven winter forecasts since 2001 gives us two A's, three B's, one C, and one F.

Before getting into the details of the forecast, we cannot help ourselves but complain (again) about two types of winter forecasts in circulation:

1. Publishing a "forecast" in terms of probabilities is NOT a forecast. We still assert "Russell's Principal of Forecast Falsifiability"... If no actual set of conditions could make a forecast wrong, then it is not a forecast. How much guidance is it to say "we have equal chances of greater or less than normal temperatures" or "a 67% chance of drier than normal weather"? Given those statements if the coming winter turned out warmer and wetter than normal, the writer could say "Well, I said there was a 50% chance of it being warmer and a 33% chance of it being wetter." We encourage probability prognosticators to "suck it up, take a stand, and accept the consequences." Among the offending "forecasts" in this category is the NOAA three-month outlook (www.cpc.noaa.gov/products/predictions/long_range/seasonal.php). Let me be clear on this point, I have no argument with their science--they have some of the best scientists in the world; I just wish they would produce a more definitive product.

2. All forecasts (long or short range) should be required to give their sources or rationale. Otherwise, you can be sure that these "forecasters" are either: 1) copying someone else unethically or 2) pulling it from the same place my gastroenterologist is going soon for that infamous post-50 exam. I strongly encourage you to ignore any forecast that does not give its rationale or source. In this category of long-range forecasts is the Farmer's Almanac. (This principal also holds true for many daily internet and radio forecasts; ignore them if they do not tell you their source or rationale.) These forecasts will be right like a broken clock is right--twice a day, every day. Forecasting is hard and confusing enough without those inane products in circulation.

Okay... to the forecast...

Rationale

The RaysWeather.Com Winter 2008-09 Forecast is based on the following factors:

• The current state of the El Nino/Southern Oscillation (ENSO)
• A shrinking polar icecap
• Recent climate trends (overall precipitation, snow, and temperatures)

1. The current ENSO state is Neutral ("La Nada" as it has been recently named in jest.) The graphic below shows the October 16,2008, Pacific Sea Surface Temperature Anomalies. Notice the Equatorial Pacific is slightly cooler than normal west and slightly warmer than normal east, overall near normal.

   
    

   ENSO Neutral years are characterized by higher uncertainty than most other years. A weak signal from the Equatorial Pacific often means that other signals such as the Pacific-North American Oscillation (PNA), Arctic Oscillation (AO), and North Atlantic Oscillation (NAO) have a greater influence on the weather. However, these other signals are virtually impossible to forecast long-range. Other ENSO Neutral winters include our snowiest winter on record (1959-60) and our least snowy winter ever (2001-02). The overall average for the Southern Appalachians in ENSO Neutral winters is near normal snow and temperatures. (See the chart below for details.)

   
    

   Bottom line for ENSO Neutral winter overall: averages near normal but higher uncertainty. The other factors will shade our forecast from this base point.
   Even though the ENSO signal is officially neutral, there's a "hint of La Nina" in the data. That suggests that a prudent forecaster might shade the forecast on the warmer and drier side of normal.

2. Once in a while we see news reports of a "shrinking polar icecap". Those reports are true, and less polar ice should in general make it more difficult to produce cold polar temperatures and in turn moderate wintertime polar air intrusions into the United States. (See www.noaanews.noaa.gov/stories2008/20081016_arcticreport.html)

3. Current climate trends have three important data items.

   1. Our ongoing drought has resulted in low lakes and rivers and dry ground. Low water levels and dry ground help perpetuate relatively dry weather.
   2. The graph below may be the most telling of all the data we have to show you here: The current 10-average total annual snowfall is ALMOST ONE-HALF the 10-year average snow thirty years ago.
      
       
   3. Even though we have been in a "snow drought" for the past several years, temperatures are surprising close to normal: our 10-year average temperature is only 0.13° higher than the 40-year average temperature.

   The net effect of these "current climate trend" factors suggests that we should keep the forecast below normal precipitation and close to the ENSO guidance for temperatures.

Forecast

Boil it all down, and here's the RaysWeather.Com Winter 2008-09 Fearless Forecast:

• Total snowfall: 90% of the long-term average, but 135% higher than the 10-year average.
• Temperatures: Slightly above normal (0° to +1° from normal)
• Confidence level: Higher uncertainty than usual (and "usual" for a seasonal forecast is uncertain!)

Below is forecast snow totals for selected Western NC Cities: