Point LRF Forecasting Method

By: Brad Satkowski

Main Topics

• Explanation of method• Forecasts• Verifications• Forecast evaluation• Recommendations

Explanation of Method

• 3 sites in United States and 3 in Europe used– Pittsburgh, Dallas, Chicago, Lisbon, Rome, Oslo

• Recent 30 day temperature departure from normal• NAO and AO values documented during these

times• Find 5 other time spans with similar AO and NAO

trends• Past anomalies used to make forecast for March

2003 based on recent AO and NAO values

Forecasts

• Forecasts made on February 25, 2003• AO value on this date was approximately –0.500• NAO value on this date was approximately –1.000• Both had been negative for most of winter• Assumed trend would continue• Wrong assumption!

Forecasts

City Forecast

Pittsburgh 3-4ºF below normal

Dallas 1-2ºF below normal

Chicago 1-2ºF below normal

Lisbon 1-2ºF below normal

Rome 1-2ºF above normal

Oslo 2-3ºF below normal

VerificationsCity Forecast Verification

Pittsburgh 3-4ºF below normal +1.2ºF

Dallas 1-2ºF below normal -1.2ºF

Chicago 1-2ºF below normal -0.6ºF

Lisbon 1-2ºF below normal +1.9ºF

Rome 1-2ºF above normal -1.4ºF

Oslo 2-3ºF below normal +3.2ºF

Forecast Evaluation• Negative AO and NAO assumption

Date AO NAO

Feb. 25 -0.500 -1.000

February +0.128 -0.019

March +0.933 -0.072

Forecast Evaluation

• Dallas verifies, Chicago close• All other cities not even close to verifying• Persistent trough in Midwest allowed Dallas and

Chicago to verify• Trend seems to exist between AO and NAO

values, and temperature anomalies• Difficult to forecast AO and NAO

Recommendations

• Avoid forecasting extreme anomalies– Pittsburgh was big mistake

– Large anomalies occur less frequently

– Uncertainty also a factor

• Use more than just recent trends– Assumption of negative AO and NAO trend was wrong

– Different forecasts would have been made if entire month of February was analyzed

Conclusions

• Relationship between AO and NAO values and temperature anomalies seems to exist

• Must be careful when looking at AO and NAO trends

• More accurate predictions of AO and NAO can lead to better forecasts, especially for Europe and Eastern United States