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Experimental CCA Forecasts of Canadian Temperature
and Precipitation -- Mar-Apr-May 1998
Contributed by Amir Shabbar1 and Anthony Barnston2
1Climate Research Branch, Atmospheric Environment Service, Downsview, Ontario, Canada
amir.shabbar@ec.gc.ca
2Climate Prediction Center, NOAA, Camp Springs, Maryland
Over the last few years of this Bulletin, forecasts of Canadian temperature and precipitation using
the multivariate statistical technique of canonical correla-tion analysis (CCA) have been presented.
For Canada, we have developed the predictive relationships between evolving large scale patterns
of quasi-global sea surface temperature, Northern Hemisphere 500 mb circulation, and the
subsequent Canadian surface temperature and precipitation. Here, we present forecasts for
Mar-Apr-May 1998 using the predictor fields through November 1997. These forecasts are made
with a lead time (the time from the end of the predictor period to the end of the predictand
season) of 6 months. Further detail about Canadian CCA-based seasonal climate prediction is
found in Shabbar (1996a, 1996b) and Shabbar and Barnston (1996).
Figure 1 shows the CCA-based temperature forecast for the Mar-Apr-May 1998 period,
expressed as a standardized anomaly. Table 1 shows the value of the standard deviation in C at
selected stations. The mean skill over all 51 stations, and the associated field significance, are
given in the caption beneath the forecast map. The field of cross-validated historical skill
(correlation) for the Mar-Apr-May forecast time period at this lead time is shown in Figure 2. The
forecast has a mean national score of 0.31. The field significance is 0.001, which greatly surpasses
the traditional 0.05 rejection cutoff. Field significance reflects the probability of randomly
obtaining an overall map skill equal to or higher than that which actually occurred. It is evaluated
using a Monte Carlo procedure in which the forecast versus observation correspondences are
shuffled randomly 1000 times. The skill of the temperature forecast is highest in winter and spring
in Canada.
Local skill are highest throughout western Canada and Ontario and central Quebec. Virtually all
of Canada south of the 60th parallel is expected to have a positive temperature anomaly; negative
temperature anomalies are forecast over the Canadian arctic, especially over the Mackenzie
district.
Figure 3 shows the CCA-based precipitation forecast for the Dec-Jan-Feb 1997-98 period,
expressed as a standardized anomaly. Table 1 shows the value of the standard deviation (mm) at
selected stations. The spatial field of cross-validated historical skill (correlation) for this lead and
time period is shown in Fig. 4. The forecast has modest expected skill, with a mean national score
of 0.15 and a weak field significance of 0.168. Local skills exceed 0.3 over an area just west of
Hudson Bay and over western Quebec. Most of southern Canada west of the Rocky Mountains is
expected to have a deficit in Mar-Apr-May precipitation. Only the west coast of British
Columbia, parts of the Northwestern Territories and central Quebec show above normal values.
Both atmospheric and oceanic indices have been showing a strong warm phase of ENSO for
several months. Most statistical and dynamical models are predicting the current warm ENSO
episode to peak during the Jan-Feb 1998 period. Analysis of past moderate to strong episodes
shows a tendency for milder than normal conditions to persist through the spring season in
Canada. The Mar-Apr-May 1998 forecast recognizes the strong influence of the warm event on
the Canadian climate over the spring season.
Table 1. Standard deviation of temperature (Temp) and precipitation (Prcp) for the 3 month
period Mar-Apr-May at selected Canadian stations.
| Station | Temp (oC) | Prcp (mm) |
| Whitehorse | 2.1 | 8.5 |
| Fort Smith | 3.1 | 12.0 |
| Innujjuak | 2.4 | 17.4 |
| Eureka | 2.8 | 2.6 |
| Vancouver | 1.0 | 29.9 |
| Edmonton | 2.5 | 15.6 |
| Regina | 3.0 | 19.5 |
| Winnipeg | 2.8 | 27.4 |
| Churchill | 2.5 | 19.1 |
| Moosonee | 2.4 | 24.8 |
| Toronto | 1.9 | 27.9 |
| Quebec City | 1.6 | 34.1 |
| Halifax | 1.3 | 46.7 |
| St. John's | 1.5 | 44.4 |
Shabbar, A., 1996a: Seasonal prediction of Canadian surface temperature and precipitation by
canonical correlation analysis. Proceedings of the 20th Annual Climate Diagnostics Workshop,
October 23-37, Seattle, Washington, 421-424.
Shabbar, A., 1996b: Seasonal forecast of Canadian surface temperature by canonical correlation
analysis. 13th Conference on Probability and Statistics in the Atmospheric Sciences. American
Meteorological Society, San Francisco, California, February 21-23, 339-342.
Shabbar, A. and A.G. Barnston, 1996: Skill of seasonal climate forecasts in Canada using
canonical correlation analysis. Mon. Wea. Rev., 124, 2370-2385.Fig. 1. CCA-based temperature
forecast for the 3 month mean period of Dec-Jan-Feb 1998. Forecasts are represented as
standardized anomalies.
Fig. 1. CCA-based temperature forecast for the 3-month mean period of Mar-Apr-May 1998.
Forecasts are represented as standardized anomalies.
Fig. 2. Geographical distribution of cross-validated historical skill for the forecast shown in Fig.
1, calculated as a temporal correlation coefficient between forecasts and observations. Areas
having forecast skill of 0.30 or higher are considered to have utility. The mean score over 51
stations is 0.31 Field significance is 0.001.
Fig. 3. As in Fig. 1 (CCA anomaly forecast), except for Mar-Apr-May 1998 precipitation.
Fig. 4: As in Fig. 2 (geographic distribution of correlation skill) except for the precipitation
forecast shown in Fig. 3. The mean score over 69 stations is 0.16. Field significance is 0.168 (see
text).
