El Niño Puts Israel’s Needed Winter Rain on a Flood Clock

The Israel Meteorological Service has put three El Niño flood cases on the books for winter 2026/27, including 150 km/h gusts and hailstones 5 to 7 cm across. Its own seasonal map, issued later, still only locks in a wet October, not a winter of record rain.

Lake Kinneret opened late September below the lower red line, so the country needs the water. The planning problem is the hour, not the season, because coastal bursts have already gotten heavier than the drains were built for.

The Pacific Heat Has Outrun the June Brief

In June 2026 the IMS wrote a set of reference storms for an extreme El Niño and sent them to ministries and cities as planning tools. By early July the three cases were public: a short coastal burst, a one- to two-day soaking, and a Mediterranean cyclone. NOAA’s Climate Prediction Center, in its greater than 90 percent chance of a very strong event note dated 10 September 2026, said the Pacific event had kept strengthening and was on track for Northern Hemisphere fall and winter 2026-27.

August sea-surface departures in the agency’s relative Niño indices reached +1.8°C in Niño-3.4, +2.5°C in Niño-3, and +3.4°C in Niño-1+2, while Niño-4 slipped to +0.1°C. Anomalies in the eastern equatorial Pacific exceeded +3.0°C at the surface, and subsurface readings stayed more than +10.0°C above average at depth. For October-December 2026, CPC put a 75 percent chance on a historic event, defined as a three-month relative Oceanic Niño Index of +2.5°C or more, which would exceed every El Niño in that record back to 1950. The next monthly discussion is due 8 October 2026.

Columbia University’s International Research Institute, in a 21 September 2026 brief, had all 22 models keeping a very strong winter through 2026-27. That is the Pacific state. It is not, by itself, a rainfall total for Tel Aviv.

HOW THE FILE MOVED FROM A BRIEF TO A LIVE EVENT

1. June 2026: The IMS issues meteorological reference scenarios for rain season 2026-27 under extreme El Niño, with Dr. Amir Givati among the authors of the companion 156-year study.
2. 5 July 2026: The three cases, labelled low probability with severe potential impact, are presented to help national and local authorities prepare.
3. 1 September 2026: Seasonal models used in the IMS outlook are initialized; Dr. Yitzhak Carmona and Givati later sign the October-to-January map.
4. 10 September 2026: NOAA keeps an El Niño Advisory and raises the historic-event odds for October-December.
5. 23 September 2026: Israel Water Authority readings put Lake Kinneret at 213.53 meters below sea level, 0.53 meters under the lower red line.
6. 29 September 2026: The Israel Academy of Sciences and Humanities climate committee publishes a position paper on the same winter.
7. 2 October 2026: The IMS seasonal page still carries yellow warnings for high Mediterranean seas and heat in the southern Judean Desert and Dead Sea basin.

A weather-hobbyist map that circulated in June treated a super El Niño as a slightly better snow bet for the hills. That is a fair side reading of old composites. It is not what the emergency file is for.

October Looks Wet, and Still Too Warm

Carmona and Givati’s seasonal outlook, built from the 1 September 2026 model suite, is the document that actually forecasts totals. It is milder than the June horror cases, and it is not dry.

The service’s own table puts October rainfall at 170 to 200 percent of average across most of the country, and above 200 percent in the Judean hills, the Arava, and the southern Negev, against the 1993-2016 mean. November stays above average, mostly 110 to 130 percent depending on the region. December is the fade: 100 to 110 percent in the north and center, 95 to 100 percent in the southern Negev.

Stacked as seasons, October-December 2026 lands at 120 to 130 percent of the long-term mean in most districts and 130 to 150 percent in the southern Negev. November-January 2026/27 is only 105 to 110 percent in the north and center and 100 to 105 percent in the south. That is a wet opening month inside a winter that is only a little above normal, not a six-month flood.

IMS SEASONAL MAP FOR EARLY WINTER 2026/27

The same map keeps the country warm. Evaporation in October runs 105 to 200 percent of the old mean, highest in the south. More rain in a hotter, thirstier air mass is how you get both a useful month for the reservoirs and a dangerous hour for a street that cannot shed water.

Three Low-Odds Storms Now on the Planning Books

The June file is not that seasonal map. It is a set of reference storms the IMS says are low probability and would have severe potential impact if they hit between September 2026 and January 2027. Climate warming, the service wrote, has widened the physical range beyond extremes already in the Israeli record, so planners should not lean on old return periods alone.

IMS REFERENCE STORMS FOR EL NIÑO WINTER 2026/27

Lead time on the longer two cases is five to seven days, with sharper detail one to three days out. That is enough for a city to move pumps and close a road. It is not enough to rebuild a drain.

Short Bursts, 150 km/h Gusts, and 7 cm Hail

The first case is the one drawn on the cities. Wind, hail, and lightning ride with a rain that is over in four hours, which is exactly the window that fills underpasses and knocks out power lines before a reservoir feels a thing.

COASTAL CITIES NAMED IN THE SHORT-BURST CASE

• Southern coast: Ashkelon and Ashdod take the first hit off the sea.
• Central coast: Rishon LeZion, Tel Aviv, and Netanya sit on the same packed strip of asphalt and storm pipe.
• Northern coast: Haifa and Nahariya close the line up to the Lebanese border.

Transport, power, and farms are the damage list the service attached to that burst. Hail at 5 to 7 cm is large enough to break greenhouse glass and dent bodywork. It is also large enough that a driver treats it as a wreck, not weather.

Two Days of Rain at 270 to 400 mm

The second case is volume. Two hundred and seventy to 400 mm in 24 to 48 hours, spread over the coastal plain, the low hills, and the central and northern ranges, is enough to put rivers out of bank and to stall rail. The IMS listed serious urban flooding, flash floods in basins, road closures, and pressure on critical sites, including military airfields. That is the file’s quiet extra reader: bases and runways on the same coastal and lowland ground as the apartment blocks.

A Mediterranean Cyclone on the Southern Coast

The third case is a medicane, a compact Mediterranean cyclone with some hurricane-like traits, smaller and shorter-lived than a tropical hurricane. The IMS puts winds at 120 km/h, hundreds of millimeters of rain, and rough seas, mainly on the central and southern coast. For scale, Medicane Ianos in September 2020 hit Greece with gusts to 54 meters per second, about 194 km/h, and killed four people. The Israeli planning wind is far below that. It is still enough to close a port and throw sea over a promenade.

Ashkelon Drowned in an Hour the Last Time

The last very strong El Niño winter, 2015/16, is the specimen the seasonal desk now cites as the previous peak, and it did not refill the lake. It did flood a coastal city in an hour.

On 17 December 2015 the IMS Ashkelon station logged 112 mm between 7 a.m. and noon. An automated gauge run by the local towns association logged 118 mm. Of that fall, 92 mm arrived in 60 minutes, beating the national hourly mark of 88 mm set at the University of Haifa in October 2008. Ashkelon also took the half-hour mark at 67 mm. Schools and kindergartens flooded, roads seized up, and Barzilai hospital staff mopped water and kept working. The Sea of Galilee rose 1.5 centimeters that day.

By late January 2016 the Hydrological Service still called the north dry. Givati, then in that service, said the main systems had been sitting on the center and south, and that unless February and March turned wet in the north, it would be a third straight dry year for the Kinneret. A strong Pacific event had delivered a record hour to Ashkelon and a poor winter to the lake. That split is the planning problem again.

Colin Price and colleagues at Tel Aviv University, writing in 1998 in Geophysical Research Letters, had already found wetter Israeli winters, fuller streams, more snow, and higher lake levels in El Niño years, with the statistical link showing up clearly only in the then-recent 25 years. The 156-year IMS review, covering 1870/1 through 2025/6 and listing Noam Halfon, Eyal Ilotovitz, Yitzhak Carmona, Yitzhak Yosef, and Givati as authors, still finds a tilt toward wet years in extreme El Niño seasons. It does not, the researchers have stressed, let anyone call winter 2026/27 wet in advance, because other Mediterranean systems can add to the signal or wipe it out.

Why the IMS Says History Is a Poor Guide

The doctrine change sits in one line of the June file. Warming and a wider envelope of extremes, the service said, mean historical statistics alone may not cover preparedness, because the physical range now runs past events already written down in Israel.

Relying on historical statistics alone may not be enough for preparedness needs. This is especially true when processes of warming and climatic extreme expansion broaden the range of physical possibilities beyond extreme events that have been documented in the past.

Israel Meteorological Service, June 2026 reference scenarios

That is why a 270 to 400 mm, two-day case is in the book even if the seasonal mean for November-January is only a little above normal. The mean can hold while one storm uses up the extra in a single catchment.

WHAT HAS ALREADY CHANGED ON THE COAST

• Short-period intensity: IMS analyses behind a 31 December 2025 government preparedness report find an increase of up to 40 percent in short-period rain in parts of the coastal strip, with a severe-case rise of about 26 percent to 40 percent in 60-minute totals.
• Fewer rain days: The same report says the number of rain days and the seasonal total are expected to fall over time, while the short, hard bursts become more common, mainly on the Coastal Plain and in the center.
• Old return periods: Events once treated as 1-in-50 or 1-in-100 year rains are arriving more often, which is the exact reason a city drain sized on the old tables fails in a four-hour burst.

Givati has put the 40 percent figure on 30- to 60-minute rains, the window that actually drowns a street. Seasonal totals can still look ordinary on a chart while an underpass fills. That is the gap between the October-December 120 to 130 percent mean and a 150 km/h, 7 cm hail afternoon on the Ashkelon-to-Nahariya strip.

NOAA’S SEPTEMBER SNAPSHOT

• Alert: El Niño Advisory, issued 10 September 2026, with the next update due 8 October 2026.
• Strength odds: Greater than 90 percent for a very strong event in fall and winter 2026-27; 75 percent for a historic October-December, +2.5°C or more on the three-month relative index, above every event since 1950.
• August indices: Niño-3.4 at +1.8°C, Niño-3 at +2.5°C, Niño-1+2 at +3.4°C, Niño-4 at +0.1°C, with eastern Pacific surface anomalies above +3.0°C and subsurface anomalies above +10.0°C at depth.

Those Pacific numbers raise the chance of an El Niño-type winter. They do not write the rain gauge in Netanya.

Lake Kinneret Opens the Season Below the Red Line

Israel Water Authority readings for 23 September 2026 put the lake at 213.53 meters below sea level. Full is 208.8 meters below sea level, 4.73 meters above that day’s level. The lower red line is 213.0 meters below sea level, so the lake was 0.53 meters under the mark where salinity and the food web start to suffer. Fullness was 22.1 percent. Among late-September readings in a 61-year series, it ranked ninth lowest. On 23 September 2025 the lake stood at 213.00 meters below sea level, half a meter higher than this year’s cut.

That is the other half of the same winter. A 170 to 200 percent October would help the lake. A four-hour, 150 km/h burst on the coast would not, and it would hit the same week the seasonal models say the rain is most likely to arrive. The 2015/16 pattern, wet on the southern coast and thin on the Kinneret, is still available.

On 29 September 2026 the Israel Academy of Sciences and Humanities climate committee put the caution in public language. Committee member Prof. Daniel Rosenfeld’s group said El Niño does not guarantee a wet winter, though it can raise the odds of hard rain, urban flooding, and flash floods, which is why they want the country ready anyway.

אל ניניו מתחזק, ומה זה עשוי לומר על החורף בישראל?
כתבה בידיעות ו-ynet על נייר עמדה חדש של ועדת האקלים של האקדמיה הלאומית הישראלית למדעים.
המסר המרכזי: אל ניניו אינו מבטיח חורף גשום, אך הוא עשוי להגביר את הסיכון לגשמים עוצמתיים, להצפות ולשיטפונות. לכן, מדגישים מחברי נייר העמדה,… pic.twitter.com/cFqCACcFnC

— The Israel Academy of Sciences and Humanities (@IsraelAcademy) September 29, 2026

The June book and the September map can both be right. October can come in heavy and warm, the lake can still need every millimeter, and a low-odds burst can still be the event a coastal city actually has to survive. The IMS is not forecasting 7 cm hail. It is telling anyone who still sizes a drain on the 1990s that the Pacific heat now in the record is a reason to plan past it.