Status: Ongoing analysis Material from: Linus, Ivan
1. Impact
In the middle of February 2021 a severe cold spell hit North America and snowy conditions reached as far as Texas.
https://www.bbc.co.uk/news/world-us-canada-56095479
2. Description of the event
The plots below show analysis of T850 (shade) and z500 (contour) from 12 to 17 February, every 24 hour.
3. Predictability
3.1 Data assimilation
3.2 HRES
3.3 ENS
Prediction of the onset of the event
The plots below show EFI for 3-day mean temperature valid 11 February. The outlined box is centered on Dallas, Texas.
The plot below shows the forecast evolution for 1-day temperature mean averaged on 11 February inside the box outlined in the plots above (1x1 degree around Dallas). The plot includes HRES (red dot), ENS control (purple dot), ENS distribution (blue boxes, median square and mean diamond) and model climate distribution (red boxes). The value from one station inside the box is plotted in green. While the forecast from 4-5 February predicted very cold temperatures, the forecasts from 6-7 February was much warmer.
The plots below show the forecasts from 5 February 00UTC (left) and 6 February (middle) and 8 February (right). The lines represents HRES (red), ENS control (purple), ENS members (blue) and observations (black).
Prediction of the peak of the event
The plots below show EFI for 3-day mean temperature valid 14-16 February. The outlined box is centered on Dallas, Texas.
The plot below shows the forecast evolution for 3-day temperature mean averaged inside the box outlined in the plots above (1x1 degree around Dallas). The plot includes HRES (red dot), ENS control (purple dot), ENS distribution (blue boxes, median square and mean diamond) and model climate distribution (red boxes). The value from one station inside the box is plotted in green.
3.4 Monthly forecasts
The plots below show the weekly 2-metre temperature anomaly for the week starting 15 February from the extended-range forecast system.
