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On 29 October the region inland of Valencia was hit by very extreme rainfall, causing terrible flash floods. Currently more than 200 people are found dead.At least 232 people lost their lives.
Citation from BBC 1 Nov:
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The evaluation of the rainfall will focus on 24-hour rainfall on 29 October 00UTC - 30 October 00UTC in a 025x0.25 box centred on Chiva, 20 km west of Valencia (39.5N, 0.8W,).
The plots below show analyses of MSLP and 6 hour rainfall from 27 October 00UTC to 30 October 00UTC, every 12th hour.
The plots below show analyses of T850 and z500 from 26 October to 30 October.
Observation maps available on social media the day after the event. On the right, gridded analysis of the 24h precipitation where all the SYNOP stations are included (provided by AEMET)
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Resource: https://x.com/AEMET_CValencia/status/1854152815637066193
•The meteorological event:
–A combination of warm and moist air in the lower levels and cold air in mid-level, causing a conditional instability
–Convection triggered by the orographic lifting.
–Maintained by the lower level winds, and the vertical wind shear probably played a role.
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3.1 Data assimilation
3.2 HRES
The plots below show 24-hour precipitation in observations (first plot, to be added), concatenated short forecasts (second plot) for 29 October 00UTC to 30 October 00UTC. Note that there are more observations from AEMET (add plot). For example is Chiva (447 mm) missing in the current coverage.
The plots below show 24-hour precipitation in ENS control forecasts with different lead times.
The plots below show 24-hour precipitation in DestinE 4.4km with different lead times.
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Observation - green hourglass
Analysis - green dot
ENS control–red
ENS - blue box-and-whisker
AIFS - cyan dot
Desint4.4km - evergreen dot
AIFS-ENS - grey box-and-whisker
cy49r1 ENS - purple box-and-whisker
Model climate – cyan box-and-whisker
Ensemble mean as black diamonds. Triangle marks the maximum in the model climate based on 1800 forecasts.
The plots below show hit (green), misses (purple) and false alarms (cyan) of predicting precipitation above the 99th percentile of model climate, based on the ensemble median.
ecPoint
The two animations below compare forecasts from the raw ECMWF Ensemble with forecasts from the ecPoint post-processed version of that, for thresholds, respectively, of 150 and 300mm/12h. Probability of exceedance in percent is shown. Turis, where 666mm were provisionally recorded during this period, lies 10km south of the middle of three black markers (which is itself at the site of Chiva where very high totals were also registered).
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Raw ENS probabilities of >150mm/12h (valid time 06-18UTC 29th October 2024), from successive forecasts, at 12h intervals, from 25 Oct 00UTC to 29 Oct 00UTC (see titles)
Same as Raw ENS animation above, but output is from ecPoint, for a higher threshold: >300mm/12h.
Graph shows the maximum of the 99th percentile ecPoint field in forecasts leading up to the event (over Spain, but always, in practice, close to Turis). The map shows a 200-year return period estimate for 24h gauge-based rainfall totals from ERA5-ecPoint (data from 2000-2019).
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4. Experience from general performance/other cases
•Such events happens now and then in the Mediterranean region, compare with e.g a case from Italy in 2015 (ECMWF Newsletter 146), and Cat 2 events in Grazzini et al. classification
5. Good and bad aspects of the forecasts for the event
•No signal beyond 1 week
•From ~23 October a wet signal relative to model climate started to appear
•From ~24 October member were sticking up far above the model climate maximum
•From ~26 October, ensemble median similar to model climate maximum
•Ensemble median around 125 mm/24h is the shortest forecasts, compared to 450 mm in the worst observation
•EcPoints top percentiles reached the magnitude of the worst observation
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