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.
Square 161 (SE England / Greater London area). Deciduous tree SMD* is the primary tracking metric for shrinkable clay subsidence risk.
* 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.
‡ Timing matters as much as the marker itself. Crossing 218mm only carries predictive weight if it happens early in the season — historically before around week 26. In the confirmed surge years of 2018 and 2022, the marker was crossed by weeks 23–26. In 2024, a year that saw elevated but not surge-level subsidence activity, the marker wasn't crossed until week 33 — too late in the season to drive the same sustained drying through summer. An early crossing indicates advanced soil moisture deficit building ahead of peak summer evapotranspiration, which increases the likelihood — but does not guarantee — that conditions progress to a confirmed surge year.
| Year | Week 218mm crossed | Within early-warning window (< wk 26)? | Outcome |
|---|---|---|---|
| 2018 | Wk 1 (then re-crossed Wk 26) | Yes | Surge year |
| 2022 | Wk 23 | Yes | Surge year |
| 2024 | Wk 33 | No | Elevated, not surge |
| 2025 | Wk 25 | Yes | Surge confirmed |
| 2026 | Wk 26 | Yes | Elevated risk — monitoring continues |
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 |
|---|
Sources: MORECS Square 161 week ending 7 Jul 2026; Met Office third heatwave advisory 6 Jul 2026; NOAA El Niño Advisory 6 Jul 2026.
2026 context: England had its warmest spring on record, its warmest June on record, and has now experienced three consecutive heatwaves. The June record was broken with 37.7°C at Lingwood, Norfolk. The June heatwave is estimated to have caused around 20,000 deaths across Europe.
| Year | Profile | First above 218mm | First above 320mm | Peak SMD | Notes |
|---|
In May 2025, Geobear published an early-warning analysis identifying conditions consistent with a surge year — before the summer drying peaked. SMD crossed the 218mm elevated-risk threshold in Week 25 and the 320mm extreme threshold in Week 30. Geobear subsidence case reports rose by almost 200% between July and October 2025.
Sources: NOAA CPC El Niño Advisory (6 Jul 2026), IRI ENSO Quick Look (mid-Jun 2026 update), WMO Global Seasonal Climate Update.
| Layer | Role | Current status |
|---|---|---|
| ENSO / El Niño | Global context signal | Advisory maintained (6 Jul). Strengthening — most models forecast Niño 3.4 >+2.0°C by Jul–Sep |
| North Atlantic Oscillation | Jet stream / blocking driver | 3rd heatwave driven by high pressure. Brief easing Sat 12 Jul then rebuilding mid-July |
| UK pressure pattern | Regional driver | Third heatwave. 34–35°C Thu–Fri. UKHSA amber alert. England warmest June on record. |
| MORECS SMD | Ground condition evidence | 304.8mm — 320mm extreme marker just 15.2mm away |
| Case reports | Impact validation | 2025 confirmed +200% Jul–Oct. 2026 case report monitoring active. |
London used as a proxy for clay-rich South East England.
A surge-risk hypothesis strengthens only when multiple signals align and MORECS confirms ground drying.
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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