Status: Finalised Material from: Linus, Esti
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1. Impact
During the last days of January north-central U.S and Canada experienced a severe cold spell. The National Weather Service in Chicago estimates 2019 is the fourth longest streak ever. Daily records for the city were shattered, according to the National Weather Service Chicago. On Wednesday, 30th January, the record for lowest maximum temperature was broken with minus -29 C, previously it was 3 degrees in 2004. The minimum temperature measured in Chicago Midway Airport was -29.4 on 31st January 2019. Mt. Carroll reached 38 degrees below zero on Thursday, and it set a new all-time record for the state of Illinois. Previously, the lowest temperature ever recorded in the state was minus 36 at Congerville on January 5, 1999.
https://www.bbc.co.uk/news/world-us-canada-47088684
2. Description of the event
3. Predictability
3.1 Data assimilation
3.2 HRES
The plot below shows the evolution of 2-metre temperature in Chicago on 31 January in observations (black) and HRES (red) and ENS control forecast (blue). The forecasts were colder than the observations, possibly because the "heat island" of the city is not included in the forecast.
3.3 ENS
The plots below show EFI and SOT for 24-hour mean temperature valid on 31 January.
The plot below shows the forecast evolution of 24-hour mean temperature (based on 6-hourly data) for Chicago . The blue box and whisker shows the ensemble, red dot HRES and red box-and whisker model climate.Already the forecast from 14 January was shifted towards colder conditions.
3.4 Monthly forecasts
The plots below show weekly 2-metre temperature anomaly for 28 January - 3 February. It is worth noting that the temperatures turned warmer in the second half of the week.
