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Saturday, October 13, 2018

Winter '17 / '18 - Correlation of Eurasia's OCT Snow Cover and Season-total Snowfall in NE and M-A Regions

REPOST from OCT-17 (lightly edited for clarity)
Updated with Winter '17 / '18 verifications for RIC and NYC and their outlooks for Winter '18 / '19

The correlation between the areal coverage of Eurasia/s OCT snow cover and season-total snowfall has become broad-brushed conventional wisdom (CW) following the innovative research by AER climatologist Dr. Judah Cohen.

But ... just how well does the CW hold up for NEWxSFC/s forecast stations across New England (NE) and the mid-Atlantic (M-A) regions?

To find out ... monthly period-of-record areal snow cover data for Eurasia from Rutgers Global Snow Lab were correlated with season-total snowfall data for the 27 NEWxSFC/s stations.

A positive and statistically significant correlation means the greater the areal snow cover over Eurasia in OCT ... the greater the season-total snowfall for the following winter.

An Excel radar chart shown below depicts the results of the analysis.

DISCUSSION:  Stations between the inner and outer rings have a positive correlation coefficient statistically different than zero.  The coefficients range between 0.289 (CAR) and 0.424 (ORH).   Correlation values in this range are classified generally as 'low' (moderate:  >= 0.5 - 0.7; strong:  >= 0.7 - 0.9).  Even though the correlations are weak ... they can still provide useful information for seasonal snowfall forecasts.

Translation:  greater season-total snowfall over select stations in the NE and M-A is correlated with greater OCT areal snow cover in Eurasia.

The analysis showed other significant correlations of interest.

- RIC/s season-total snowfall has a positive correlation with Eurasia/s AUG areal snow cover.
Eurasia/s AUG-17 snow cover was well below normal ==> lower season-total snowfall @RIC this winter.

VERIFICATION Winter '17 / '18:  RIC STP 12.4"  (AVG:  13.2")
OUTLOOK Winter '18 / '19:  Eurasia's AUG snow cover below average ==> STP below AVG

- NYC/s season-total snowfall has a negative correlation with Eurasia's JUN areal snow cover.
Eurasia/s JUN-17 snow cover was above normal ==> lower season-total snowfall @ NYC this winter.

VERIFICATION Winter '17 / '18:  NYC STP 35.4"  (AVG:  26.1")
OUTLOOK Winter '18 / '19:  Eurasia's JUN snow cover below average ==> STP above AVG

GREEN (RED):  positive (negative) correlation between monthly Eurasian areal snow cover and season-total snowfall.

VERIFICATION Winter '17 / '18
Eurasia's OCT-17 areal snow cover was greater than average (12,051,667 km^2 v 10,261,134 km^2).
Positive correlations for the stations listed below suggest Winter '17 / '18 STP would be above average

ABE:  46 / 31.4
BOS:  58.6 / 41.6
BTV:  81.5 / 69.8
PWM:  91.1 / 63.8

FINDINGS:  data analysis supports the CW for NE forecast stations but not so much across the M-A.

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