SMD comparison — surge years vs 2026

2026 shown against confirmed surge years 2018 and 2022, plus 2024 (no surge) and 2025 (confirmed surge). Dashed lines mark the 218mm and 320mm risk markers.

 
 
Soil moisture deficit — current position

Square 161 (SE England / Greater London area). Deciduous tree SMD* is the primary tracking metric for shrinkable clay subsidence risk.

 
Deciduous SMD vs trigger thresholds
 
 
 
218mm 320mm
 

* Soil moisture deficit (SMD) is a measure of how dry the soil is relative to its maximum water-holding capacity. A high SMD means the ground has lost significant moisture. In areas underlain by shrinkable clay, high SMD causes the clay to contract and crack — the principal mechanism behind subsidence damage to buildings and infrastructure.

† The 218mm and 320mm risk markers are Geobear-defined thresholds derived from analysis of historic subsidence case report data and previous surge years. They are not official Met Office or industry-standard figures. The 218mm level represents the SMD at which Geobear's historic data shows a material increase in subsidence activity on shrinkable clay soils; the 320mm level is associated with extreme and sustained surge conditions.

MORECS data — latest four weeks

Most recent four weeks of Square 161 data. Week-on-week SMD change shows the direction of travel.

Week ending Sun (hrs) Rain (mm) SMD grass SMD deciduous Wk change
 
Did you know?
Why deciduous trees — not grass — are the key indicator

Soil moisture is lost through evapotranspiration — the combined process of water evaporating from the soil surface and transpiring through plant leaves. In summer, this is the primary mechanism driving soil drying. Large deciduous trees such as oak, willow, poplar and elm extract water from deep within shrinkable clay layers via extensive root systems, even when the surface appears dry. Their evapotranspiration rates are substantially higher than grass, which is why deciduous SMD diverges from grass SMD as the season progresses — and why heatwaves, which dramatically accelerate transpiration rates, cause such rapid SMD jumps.

This is why this dashboard tracks deciduous tree SMD rather than grass SMD. It better reflects the deep moisture extraction in clay soils that causes shrinkage and ground movement beneath buildings. MORECS deciduous SMD is modelled using canopy resistance and available water capacity parameters calibrated specifically for tree-covered soils, based on the Hough & Jones (1997) methodology.

⚠ Week 9 above 320mm — El Niño now at +3.0°C, EA Gold Command active

Sources: MORECS Square 161 week ending 22 Sep 2026; Gov.uk drought report 11–17 Sep 2026; IRI ENSO Quick Look mid-Sep 2026; NOAA CPC update 21 Sep 2026; Met Office autumn outlook.

SMD deciduous remains at 332.4mm — the MORECS model ceiling — for week 9 above the 320mm extreme-risk marker. Just 2.2mm of rain and 46.9 sunshine hours in the week to 22 September. Settled, warm conditions are returning to southern England. The brief dip to 324.6mm in the week of 8 September has now been fully negated by two subsequent dry weeks. Total September rainfall in Square 161 to date: approximately 24mm — far short of the sustained recharge required.

Two significant developments this week. First, the IRI mid-September objective outlook confirms Niño 3.4 has reached +3.0°C — all 22 forecast models agree the event will remain firmly established through end of 2026. Second, the Environment Agency has activated Gold Command drought incident response arrangements, with the Environment Agency and Natural Resources Wales having applied for a River Severn Drought Order on 17 August 2026. Summer 2026 has been confirmed as setting a new UK mean temperature record of 16.5°C.
The Met Office SON 2026 outlook (issued 1 Sep) now leans wet overall, but explicitly states: “it is too early to say whether rainfall this autumn will provide meaningful drought relief in the areas that have experienced the driest conditions.” The wet signal in the outlook sits in late autumn — October and November — not September. The short-range forecast (14–15 Sep) shows a changeable but near-normal pattern, with showers interspersed with drier and brighter spells, especially in the south and east.
Note on missing data: the MORECS reading for the week ending 29 August 2026 is unavailable and cannot be recovered. The chart and table skip directly from 25 August to 8 September.

The Met Office (14 Sep) confirms a changeable September continues: occasional rain and showers most frequent across northern and western UK, with reasonably dry and more settled periods especially across southern areas. There is a chance settled weather may expand further northwards during the final week of September.
The September outlook confirms the pattern likely to continue. September is unlikely to settle into one dominant weather pattern, with Atlantic systems expected to keep parts of the UK wet while drier spells develop elsewhere. Northern and western areas are likely to see more frequent rain, while the south and east should have better opportunities for dry weather. The Met Office identifies the south and east — the clay belt — as likely to see the driest and sunniest weather in September. A warmer, relatively dry start to September, with drought conditions easing slowly and increasingly unsettled, wetter and windier spells from late October into November.
Meanwhile, the ENSO situation has escalated dramatically. NOAA CPC (13 Aug 2026): El Niño is strengthening, with a greater than 90% chance of a very strong event during NH fall and winter 2026–27 — upgraded from 81% in July. The IRI mid-August assessment describes OND 2026 as truly off the charts: 15 forecast models show Niño 3.4 reaching or exceeding +3.0°C, well beyond the highest defined intensity category. The NOAA median OND 2026 forecast places Niño 3.4 at +2.66°C, with a 69% chance of exceeding every El Niño on record since 1950.
Speculative outlook
How long might the 2026 surge last?

The following is an interpretive assessment based on historical MORECS patterns and current climate signals. It is speculative and should not be treated as a forecast.

SMD will remain at or near the model ceiling until sustained and repeated rainfall events drive meaningful recharge into the deep clay root zone. This is not triggered by a single shower — it requires the kind of persistent Atlantic low-pressure systems that typically establish themselves from late September onwards as the jet stream shifts southward for autumn. Based on the two most recent confirmed surge years, that process looks like this:

Year 320mm crossed Recharge began Weeks above 320mm Peak claims activity
2018 Wk 29 (mid-Jul) Late Oct (wk 43) ~14 weeks Aug–Oct 2018
2022 Wk 26 (late Jun) Early Oct (wk 40) ~14 weeks Jul–Oct 2022
2025 Wk 30 (late Jul) Mid-Oct (wk 42) ~12 weeks Aug–Oct 2025
2026 (projected) Wk 28 (mid-Jul) Late Sep–Oct (wk 39–43)? ~11–15 weeks (speculative) Aug–Oct–Nov 2026?

Applying the same pattern to 2026: SMD crossed 320mm in week 28. If recharge follows the same late-September to mid-October timeline as 2022 and 2025, the surge would remain active for approximately 11–15 weeks — meaning SMD would remain above 320mm until around late September or mid-October 2026.

There is one factor that could extend this: a very strong El Niño. During strong El Niño winters, the UK tends to see wetter and stormier conditions — but this typically becomes the dominant pattern from November onwards, not September or October. The autumn transition period (September–October) tends to be less reliably wet in El Niño years than mid-winter. This means the surge may not benefit from early El Niño-driven autumn rainfall; the recharge signal is more likely to come from the return of normal Atlantic westerly flow in late September.

Speculative summary: Based on historical patterns, the 2026 surge is most likely to remain active — with SMD at or near the model ceiling and subsidence claims elevated — through August, September and into October 2026. The peak window for claims activity aligns with August–October, consistent with 2022 and 2025. Meaningful recharge is unlikely before late September, and sustained recharge probably not until October or November. This assessment would change materially if a significant Atlantic low-pressure system delivered 30mm+ of rainfall across multiple days in a short window — something that cannot be ruled out but is not currently signalled.
The insurance picture — what ABI data tells us

Sources: ABI "Sinking UK" press release (21 Mar 2023); ABI written evidence to House of Lords Environment and Climate Change Committee (Nov 2025); ABI Q2 2026 property claims data (3 Aug 2026); Insurance Times. All figures are directly published by the ABI unless stated.

Year / Period ABI claims Total payout Avg claim
2022 (full year) 23,000 total
18,000 in H2 — 1 every 15 mins		 £219m £9,600
H1 2025 ~9,000 households £153m £17,264
2025 (full year) — £307m (record) —
Q2 2026 (Apr–Jun only) — £72m £20,000 (record)

The Q2 2026 ABI data (published 3 Aug 2026) covers April to June — before either Geobear risk threshold was crossed and before the bulk of the summer heatwave season. The £72m payout and £20,000 average are therefore pre-peak figures.

Why claim volumes may appear lower despite more intense conditions

The headline numbers from earlier surge years (2003: ~55,000 claims; 2006: ~40,000+) appear higher than 2022 (23,000) despite comparable or more severe ground conditions. Several structural factors explain this:

Rising excesses & exclusions

After each surge year, insurers raise subsidence excesses, tighten acceptance criteria and in some cases add natural peril exclusions. Many homeowners discover the gap only when they try to claim.

Underinsurance

Around 7 in 10 UK properties are estimated to carry only ~66% of the cover needed for a full rebuild. Underinsured properties generate lower-value claims or none at all.

Claim cost rising sharply

Fewer claims does not mean lower total cost. Average claims rose from £9,600 in 2022 to £17,264 in H1 2025 to £20,000 in Q2 2026 — a near-tripling in four years driven by construction inflation and more complex damage.

Cumulative ground damage

Three surge years in eight (2018, 2022, 2025) mean ground damaged in 2025 had not recovered before 2026 began — a compounding dynamic that is extending claim lifecycles and complicating loss adjustment.

2026 projection: The ABI confirmed £72m in Q2 2026 (April–June) at a record £20,000 average — before either Geobear threshold was crossed. In 2022, 78% of annual claims fell in H2. Applying the same seasonal distribution to 2026, and accounting for more severe conditions and a higher average claim cost, Geobear estimates August–November 2026 insured losses in the range of £200m or more — with a full-year total likely to match or exceed 2025’s record £307m. This is an estimate based on ABI historical data, not an industry forecast.
Annual surge comparison
Year Profile First above 218mm First above 320mm Peak SMD Notes
ENSO / El Niño and NAO — forward watch

Sources: NOAA CPC El Niño Advisory, ENSO Recent Evolution and Status (10 Aug 2026), full ENSO Diagnostic Discussion due 13 Aug 2026.

 
El Niño Advisory — IRI mid-Sep: Niño 3.4 at +3.0°C. All 22 models agree. NOAA: >90% very strong fall/winter.
NOAA CPC / IRI update (mid-to-late Sep 2026): Niño 3.4 has reached +3.0°C as of mid-September — a historic milestone. (cite index="4-1">All 22 forecast models agree the event will remain firmly established through the end of 2026 and persist into spring 2027. NOAA CPC (21 Sep 2026): El Niño is strengthening, with a greater than 90% chance of a very strong event during Northern Hemisphere fall and winter 2026–27. Positive SST anomalies have remained steady since late July. (cite index="1-1">During the October–December 2026 season, there is a 75% chance of a historic event exceeding the strength of every previous El Niño dating back to 1950 (+2.5°C or more for a three-month RONI value). GFDL SPEAR (Sep): slightly weaker peak than August forecast but still high confidence in a historically strong event this fall and early winter.
North Atlantic Oscillation (NAO): (cite index="11-1">Settled conditions are expected to continue into next week with increasingly warmer temperatures and humid conditions forecast across England, with the south likely to see the warmest and driest weather. Independent forecasters (Mark Vogan Weather) flag a potential last warm spell for SE England in late September, possibly with temperatures again approaching 28–30°C. The longer-range outlook signals a shift to more sustained Atlantic conditions from late October, with (cite index="10-1">increasingly unsettled, wetter and windier spells from late October into November, raising the risk of localised flooding especially across Scotland, Northern Ireland, northern England and Wales.
El Niño and UK subsidence risk: El Niño is best treated as a background risk modifier, not a direct trigger for UK subsidence conditions. A 2024 Met Office study found the primary ENSO teleconnection to UK/European summer climate is statistically weak (correlation skill 0.2–0.3) and non-stationary. The North Atlantic circulation patterns, jet stream position and blocking events that actually determine UK summer conditions — and that drove the six heatwaves of 2026 — can operate independently of the Pacific ENSO state. Summer 2026 was primarily driven by human-induced climate change and a persistent blocking pattern; El Niño only formally developed in June 2026. The more defensible forward-looking statement is this: the Met Office expects 2027 to very likely challenge the global annual temperature record due to the lagged effect of this El Niño on global temperatures — but higher global mean temperature does not automatically translate to a hot, dry UK summer, which depends far more heavily on North Atlantic pressure patterns, jet stream position and antecedent soil moisture conditions.
North Atlantic Oscillation (NAO): Mid-August Atlantic intrusions brought rain widely across the UK, particularly Scotland, Wales and north-west England. However, SE England — where Square 161 sits — received just 1.0mm and 2.7mm in the two MORECS weeks respectively. England recorded just 43% of August’s long-term average rainfall for the whole month, with southern England receiving far less. The summer blocking pattern that drove six heatwaves has eased, but the deficit is of such a scale that individual Atlantic intrusions make no meaningful impact on root-zone soil moisture. September begins unsettled but high pressure may reassert mid-month.
Layer Current status
ENSO / El Niño Global context signal 10 Aug: Niño 3.4 +1.8°C, Niño 1+2 +3.3°C. 81% chance very strong OND 2026.
North Atlantic Oscillation Jet stream / blocking driver Warm/dry late-Sept in south. Atlantic pattern from late Oct. Flooding risk Nov.
UK pressure pattern Regional driver EA Gold Command active. River Severn Drought Order pending. UK temp record 16.5°C.
MORECS SMD Ground condition evidence 332.4mm — back at ceiling. Brief dip (324.6mm, wk to 8 Sep) reversed. Wk 8 above 320mm.
Case reports Impact validation 2022 rose from 18 Jul. 2025 from 11 Aug. 2026 active monitoring.
London 10-day forecast — subsidence drying lens

London used as a proxy for clay-rich South East England.

Loading live forecast…
 
Speculative weather signal watch

A surge-risk hypothesis strengthens only when multiple signals align and MORECS confirms ground drying.

 
Current assessment: 2026 is a confirmed surge year, now in week 9 above the 320mm extreme-risk marker. SMD remains at the model ceiling. The September dip-and-recovery has played out exactly as the 2025 analogue predicted. El Niño has crossed +3.0°C — all 22 models agree. The Environment Agency has activated Gold Command drought response. Summer 2026 set a new UK mean temperature record. Meaningful recharge is most likely from October–November 2026, when the Met Office signals increasingly unsettled Atlantic conditions.

Learn more: What is subsidence?

Last updated:  ·  MORECS week ending:

Sources: MORECS Square 161 weekly data (Met Office Hadley Centre), Met Office UK weather summaries and ENSO commentary, NOAA Climate Prediction Center, WMO El Niño/La Niña Update (2 Jun 2026), Geobear internal subsidence case report trends.

This dashboard is an operational early-warning framework, not a property-level diagnosis. It should not be used as a basis for insurance or engineering decisions without professional assessment.

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