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1. Overview

Between 30 September and 4 October 2026, Crete was hit by five consecutive days of intense rain and thunderstorms. Authorities placed the whole island on red alert, schools in Chania and Rethymno were closed on 1 October, and repeated 112 emergency alerts were issued for parts of Rethymno, Heraklion and Lasithi. The highest totals fell over the mountains: more than 220 mm was reported at Profitis Ilias (Heraklion) on 1 October, and the Lasithi Plateau received about 440 mm in two days and around 470 mm in four days, compared with a normal annual total of 700-900 mm. Damage was reported in all four regional units. In Mylopotamos (Rethymno), the village of Zoniana was flooded, the Diskouri bridge near Livadia was swept away and 30-40 residents were evacuated. An 80-year-old livestock farmer was found dead near Karines in Rethymno after being swept away by a stream. In Lasithi, landslides and torrents damaged roads and tourist areas around Ierapetra, and up to 85% of the crops on the Lasithi Plateau may have been affected. Between 1 and 4 October the Fire Service received 485 calls and moved 101 people to safety. Greece activated the Copernicus Emergency Management Service (EMSR933) to map the affected areas.

Sources: Euronews, ProtoThema, Greek City Times

2. Analyses and Observations

2.1 Event Definition

The evaluation will focus on the 5-day precipitation between 30 September 06UTC and 5 October 06UTC for a 0.5x0.5 degree box centred on 35.3N, 24.4E on Crete.

2.2 Analyses

The plots below show analyses of MSLP and 6 hour rainfall from 28 September 00UTC to 5 October 00UTC, every 12th hour.

The plots below show z500 and T850 from 24 September to 5 October 00UTC, every 24 hour.

2.3 Observations

2.4 Climatological perspective

3. Forecasts

3.1 Data assimilation and observation usage

3.2 Single Forecasts for the event based on 00UTC forecasts (defined in Section 2.1)

Observations and analysis for the event

Control forecast (IFS 9-km resolution)

DestinE (IFS 4.4km resolution)

AIFS-single (AIFSv1.0 ~0.25 resolution)

AIFS-CRPS ensemble (~0.25 degree resolution)

3.3 Ensemble distribution

EFI (based on IFS 9-km ensemble)

The plots below show the EFI for 5-day precipitation for 30 September 00UTC to 5 October 00UTC, from different initial dates.

Forecast Evolution plot

The plot below shows the evolution of the forecasts for 5-day precipitation (30 September 06UTC - 5 October 06UTC) for the box on Crete defined in Section 2.1.

3.4 Sub-seasonal forecasts

3.5 Comparison with other centres

4. Hazard Forecasts

5. Dedicated Experiments

6. Event Summary

6.1 Good and bad aspects of the forecasts for the event

• Predictability: the IFS ensemble gave an early signal. The EFI for the 5-day precipitation over Crete was 0.6-0.8 in the forecast from 26 September 00UTC (4 days before the start of the event) and above 0.8 from 27 September, while there was little signal from 25 September. In the forecast evolution plot the ENS median for the box increased from below 20 mm (24 September and earlier) to about 90-100 mm (26-27 September) and about 200 mm in the last forecast, compared with 215 mm observed (station average) and 189 mm in the analysis. The observed total was well above the 99th percentile of the model climate (about 83 mm); only 2 of the 1600 hindcast values reached it. Only from 29 September 00UTC did more than half of the ENS members exceed 150 mm.
• Systematic errors compared with observations: the short-range IFS forecast (HRES from 30 September 00UTC, 213 mm) matched the box observations well. However, all models put the maximum along the north coast and over the sea north of western and central Crete, and underestimated the rainfall over eastern Crete (Heraklion-Lasithi), where stations reported 200-400 mm while the forecasts gave mostly 50-150 mm. Stations on the south coast also had more rain (30-80 mm) than the forecast rain-shadow minimum (mostly 10-30 mm).
• IFS versus AIFS: AIFS-single and the AIFS ensemble were consistently drier than IFS. In the shortest-range forecast AIFS-single gave 109 mm in the box, against 213 mm for HRES. In the last two runs the AIFS-ENS median was 116-125 mm, against 160-196 mm for ENS, and only 28-38% of AIFS-ENS members exceeded 150 mm, against 66-90% of ENS members. The AIFS fields are smoother and lack the orographic detail of IFS, but the band of heavy rain was in a similar position.
• Run-to-run consistency: HRES jumped between consecutive runs (for example 102 mm from 28 September 00UTC, then 183 mm and 259 mm from the next two runs), while the ENS median increased steadily over the last 4-5 days before the event.

6.2 Experience from general performance/other cases

7. Additional material