Rain/Snowfall during Very strong El Niño in the UK

 

While the direct atmospheric Teleconnections between the tropical Pacific Ocean and Western Europe are significantly weaker and more variable than those in the Americas, a very strong El Niño (often termed a "Super El Niño" when sea surface temperatures exceed +2.0^\circ\text{C} above average) does exert a measurable, split-phase influence on UK weather patterns.

​Rather than creating a single uniform weather regime throughout the winter, a strong El Niño typically alters the path of the North Atlantic Jet Stream in two distinct phases between early and late winter.

1.     Early Winter (Late October – December): Wet, Stormy, and Mild

During the initial phase of a strong El Niño, the enhanced atmospheric heating in the tropics tends to strengthen the North Atlantic jet stream and steer it directly across the UK.

Rainfall: Increased frequency of low-pressure systems moving off the Atlantic. This often brings above-average rainfall, persistent frontal rain belts, and higher risks of localized river and surface-water flooding across western and southern Britain.

Snowfall: Snowfall is generally below average during early winter during a strong El Niño, restricted mostly to high ground (e.g., the Scottish Highlands, the Pennines) due to dominant mild, maritime air masses.

2.     Late Winter (January – March): Colder, Drier, and Increased Snow Risk

As the event reaches and passes its tropical peak around mid-winter, atmospheric teleconnections shift. Strong El Niño events transfer energy higher into the stratosphere, which significantly increases the statistical probability of a Sudden Stratospheric Warming (SSW) event.

An SSW event weakens or disrupts the Polar Vortex, which can weaken the prevailing westerly Atlantic winds and set up high-pressure blocking patterns over Greenland or Scandinavia. 

Rainfall: Overall precipitation levels tend to drop below average as drier continental air masses take over.

Snowfall: The probability of cold snaps and organized snowfall increases. When moist Atlantic air interacts with continental easterly or northerly Arctic blasts around high-pressure blocks, it can generate significant lowland snow events across the UK.

Key Modulating Factors

While a strong El Niño sets up these background probabilities, local winter precipitation and snowfall in the UK are also heavily modulated by competing North Atlantic climate drivers:

North Atlantic Oscillation (NAO): A positive NAO index reinforces mild, wet Atlantic storms (amplifying early winter trends), whereas a negative NAO index promotes high-pressure blocking and colder, snowier continental easterlies.

Indian Ocean Dipole (IOD) & Quasi-Biennial Oscillation (QBO): The phase of tropical stratospheric winds (QBO) and Indian Ocean sea temperatures can either reinforce or offset the El Niño signal propagating toward northern Europe.

Global Ocean Temperatures: Baseline climate warming elevates moisture content in Atlantic air masses. Even during cold snaps, warmer surrounding seas can mean that marginal temperature drops lead to heavy rainfall near coastal regions rather than widespread lowland snow.

2026 Atlantic Hurricane season downgraded

               Why Downgrade?

The 2026 Atlantic hurricane season is projected to be well below average, a major shift from the highly active seasons of recent years.

Two powerful, large-scale climate drivers are responsible for this quiet forecast.

1. A Powerful, Strengthening El Niño:

The primary culprit behind the expected quiet season is the rapid intensification of El Niño in the tropical Pacific.  

While El Niño is centered in the Pacific, it has a massive global ripple effect on atmospheric circulation. In the Atlantic basin, El Niño drives exceptionally high levels of vertical wind shear (the change in wind speed and direction at different altitudes).

Why wind shear kills storms:

 Hurricanes are tall, vertically stacked heat engines that need a symmetrical, upright structure to grow. When strong upper-level winds blow in a different direction or speed than low-level winds, they tilt the storm's core and blow the heat and moisture away from its center, effectively ripping the developing storm apart before it can organize.

2. Average to Cooler Sea Surface Temperatures (SSTs)

In previous hyper-active years, record-shattering ocean warmth acted as high-octane fuel for storms, sometimes overpowering suppressing atmospheric factors. For 2026, the thermal profile of the Atlantic is much more modest:

Sea surface temperatures across the Caribbean and the Main Development Region (MDR) of the tropical Atlantic are sitting much closer to their long-term historical averages.

Key areas in the central Atlantic (the Cape Verde region, where many major storms originate) are actually experiencing below-average sea surface temperatures. Without extreme ocean heat, developing systems lack the thermodynamic boost required to easily overcome the strong El Niño wind shear.

The Crucial Warning: "It Only Takes One"

While we project one of the quietest seasons in over a decade, they emphasize that a quiet overall season does not guarantee safety.  

Even during quiet, El Niño-dominated years, individual powerful storms can still form and make devastating landfalls. A classic historical example is 1992—a highly suppressed El Niño year that produced only six named storms, but one of them was Hurricane Andrew, a Category 5 monster that devastated South Florida.  

How does El Niño affect pacific hurricane and typhoon season?

While El Niño is a "buzzkill" for Atlantic hurricanes, it acts as high-octane fuel for the Pacific. Because El Niño physically shifts heat and wind patterns across the globe, the two oceans behave like a atmospheric seesaw—when the Atlantic goes quiet, the Pacific usually gets wild.

The diagram below shows this exact atmospheric see-saw: as warm water pools in the central/eastern Pacific, it triggers rising air and favorable storm conditions there, while sending strong upper-level winds eastward to suppress the Atlantic.

The El Niño atmospheric seesaw

1. The Eastern Pacific: Highly Active

In the Eastern Pacific (off the west coast of Mexico), El Niño creates the perfect storm of ingredients.

Warm Water Fuel: The warmer-than-average ocean temperatures characteristic of El Niño extend right into this basin, giving storms plenty of thermal energy.

Low Wind Shear: Unlike the Atlantic, wind shear in the Eastern Pacific decreases during El Niño.

The Result: Eastern Pacific hurricane seasons during El Niño are typically well above average, featuring more named storms, stronger major hurricanes, and a higher chance of storms tracking far enough north to affect Baja California or bring tropical moisture into the southwestern United States.

2. The Western Pacific (Typhoons): A Shift in Location

In the Western Pacific—where tropical cyclones are called typhoons—El Niño doesn’t necessarily increase the total number of storms, but it drastically changes where they form and how strong they get.

The Eastward Shift: Normally, the warmest water is pooled in the far western Pacific (near Indonesia). During El Niño, that warm water sloshes eastward toward the Central Pacific. Typhoons start forming much further east than usual.

Longer Lifespans & Monsters: Because they form further east, these storms have thousands of miles of open, warm ocean to travel across before they ever hit land. This gives them significantly more time to feed, organize, and intensify.

The Result: El Niño years typically produce more super typhoons (Category 4 and 5 equivalents). While places like Australia and Indonesia tend to experience drought, islands in the central Pacific (like Hawaii) and East Asia (Japan and Korea) often face a heightened threat of highly intense storms.

            The comparison at a glance:

David I Birch 

15th July 2026

Credits to graphics as per pictures bottom.

      

Adding water to ice

 What happens when water   is added to ice.

When you mix water and ice, what happens depends entirely on the initial temperatures of both the ice and the water, the amount of each you have, and the environment they are in. Over time, the mixture will always move toward a state of thermal equilibrium (where everything reaches the same temperature). Here is a breakdown of what happens during this process under different conditions:

1. The Ideal Equilibrium:          Exactly 0°c (32F).

If you have a mixture of ice and water in a perfectly insulated container (like a high-quality thermos) and it has stabilized, a fascinating dynamic occurs:

Dynamic Equilibrium: 

The temperature of both the water and the ice will rest at exactly 0°c. At this temperature, water molecules are freezing onto the ice at the exact same rate that ice molecules are melting into the liquid.  

No Net Change: 

To the naked eye, nothing changes—the ice stops melting, and the water stops freezing.

2. When the Water Wins            (Melting): 

If you add ice to a glass of room-temperature water:

The Process: 

Heat from the warmer water flows into the colder ice.  

Latent Heat of Fusion: 

As the ice reaches 0°c, it begins to melt. Interestingly, while the ice is melting, the temperature of the water-ice mixture will stay right around 0°c because all the absorbed heat energy is being used to break the hydrogen bonds holding the ice together, rather than raising the temperature.

The Result: 

Once all the ice has melted, any remaining heat from the room will begin to warm the liquid water back up to room temperature.  

3. When the Ice Wins                 (Freezing):

If you add a small amount of liquid water to a massive, deeply frozen block of ice (say, straight out of a deep freezer at -18°c:

The Process: 

The sub-zero ice will rapidly absorb heat from the liquid water.  

The Result: 

The liquid water will quickly cool down to 0°c and then freeze solid, joining the ice block. The overall temperature of the system will remain below freezing.

4. What Happens to the Water Level?

A classic physics question is: If you have a glass of water with ice floating in it, does the water level rise as the ice melts?

The Answer: No, the water level stays exactly the same.  The Physics: 

According to Archimedes' Principle, a floating object displaces a volume of water equal to its own mass. Because ice is less dense than liquid water, it expands by about 10% when it freezes and floats. When that ice melts, it shrinks back down, perfectly filling the exact volume of water it was previously displacing.

Written on 1st October 2011

Author David I Birch 

Comparing the climate of 2026 to 1976

 Should we really make comparisons 

Comparing the climate of 2026 to 1976 is an incredibly compelling exercise, but because of that ~90 ppm gap in atmospheric carbon dioxide ~{CO}_2), we have to change how we make the comparison.

​In 1976, global ~{CO}_2 levels were hovering around 332 ppm; today in 2026, we are sitting near 422 ppm. Because of this massive shift in the global baseline, a direct "apples-to-apples" comparison of absolute temperatures or specific weather anomalies can be misleading. Instead, we look at 1976 through two distinct lenses: forced climate trends versus internal climate variability.

​Here is how to approach the comparison effectively:

​1. Establishing the New Baseline (Forced Trend)

​The 90 ppm difference represents a massive increase in radiative forcing. The primary consequence is that the "normal" background temperature has shifted dramatically.

• ​The Temperature Floor has Risen: A severe heatwave or drought in 1976 occurred on a cooler planet. If you took the exact same atmospheric pressure patterns from 1976 and superimposed them onto 2026's atmosphere, the resulting heatwave would be significantly more intense today purely because the baseline tropospheric temperature is higher.
• ​Ocean Heat Content: The oceans have absorbed over 90% of the excess heat trapped by that extra 90 ppm of {CO}_2. Comparing current Sea Surface Temperatures (SSTs) to 1976 requires accounting for this global marine warming, which alters everything from hurricane potential intensity to marine heatwaves.

2. Comparing Synoptic Dynamics (Internal Variability):

Where a comparison to 1976 remains highly valuable is in analyzing atmospheric circulation patterns. The extra ~{CO}_2 changes the energy balance, but it doesn't completely rewrite the laws of fluid dynamics or erase natural cycles like El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), or jet stream behavior.

You can effectively compare 1976 to 2026 by looking at:

• ​Jet Stream Behavior: 1976 was famous for a prolonged, deeply blocked jet stream that led to the historic UK/European drought. Comparing the wavelength and persistence of 2026’s jet stream to 1976 helps scientists understand if climate change is making these stagnant atmospheric blocks more frequent or persistent.
• ​Relative Anomalies: Instead of comparing absolute temperatures, compare how far 1976 departed from its local 30-year climatological norm against how far 2026 departs from its current norm. This isolates the structural efficiency of the weather patterns themselves.

3. The "Non-Linear" Complication:

We also cannot assume the climate responds in a perfectly linear fashion to that 90 ppm increase. The climate system has feedback loops and thresholds. For instance, the loss of Arctic sea ice over the last 50 years has altered the latitudinal temperature gradient between the equator and the pole. This potentially impacts jet stream waviness in ways that wouldn't have been captured in the 1976 data.

Summary:

Don't directly compare absolute temperatures or SSTs without adjusting for the modern warming trend.

Do compare the synoptic setups—like pressure anomalies, omega blocks, and planetary wave setups—to see how effectively the atmosphere is transporting heat and moisture under two very different thermodynamic regimes.

Written on the 9th July 2026

Author David I Birch 

Is a reversal of AMO imminent

 

Whether the Atlantic Multidecadal Oscillation (AMO)—also referred to as Atlantic Multidecadal Variability (AMV)—is due to flip from its current warm phase to a cool phase is one of the most heavily debated topics in modern climatology.

Because the AMO operates on long timescales, a shift is statistically "due" soon, but an increase in Global temperaturea is making predicting the exact timing highly complex.

​Historical Timing Between Phases:

​Based on historical instrumental records, a full AMO cycle spans roughly 60 to 80 years, meaning each individual warm or cool phase typically lasts between 30 and 40 years. 

Historical phases of the AMO - warm/cool

As shown in the historical data above, the shifts follow a distinct multidecadal rhythm:

1880–1900: Warm Phase (~20 years                           recorded)

1900–1930: Cool Phase (~30 years)  

1930–1965: Warm Phase (~35 years)  

1965–1995: Cool Phase (~30 years)  

1995–Present: Warm Phase (Currently at              31 years)

Because the current warm phase has been active since roughly 1995, the North Atlantic has spent over three decades in a warm state. Statistically, this puts the climate system near the typical window for a reversal.

Likelihood of a Reversal:

​Predicting the likelihood of an imminent flip involves tracking two competing forces: internal ocean dynamics and external atmospheric forcing.

1. Signs of Potential Cooling (The Case for a Flip)

​Oceanographers closely monitor the Atlantic Meridional Overturning Circulation (AMOC)—the deep ocean conveyor belt that pumps warm water north. Subsurface observations in the North Atlantic subpolar gyre have periodically shown cooling trends and a weakening AMOC. When the AMOC slows down, it delivers less heat northward, which is historically the primary trigger for a negative (cool) AMO phase. Some decadal forecasting models suggest a transition toward a cooler North Atlantic state could materialize within the coming decade.

Even if the internal ocean circulation shifts to a cooling mode, it may manifest as a "pause" or a deceleration in rapid warming rather than a dramatic drop into historical cold anomalies.

Summary: While a shift toward the cooler ocean mechanisms of a negative AMO is moderately likely to build momentum over the next decade due to natural internal cycles, background global SST's warming may blunt or mask the actual cooling effects traditionally associated with past negative phases.

Written on the 2nd July 2026

Author - David I Birch 

Reference - Wikipedia - NCAR climate data -                        guide, NOAA GFDL.

Physics behind why El Niño suppresses the Asian monsoon

The suppression of the Asian monsoon during an El Niño event is a direct consequence of a fundamental reconfiguration in the Walker Circulation—a massive east-west atmospheric overturning cell driven by sea surface temperature (SST) gradients across the Pacific.

The walker circulation pivot: Shifting Trade winds.

1. The Normal State: Strong Zonal            Gradient:

In a non-El Niño year, the tropical Pacific maintains a strong zonal pressure gradient.

Thermal Engine: Intense solar radiation keeps the Western Pacific (the "Warm Pool" near Indonesia) significantly warmer than the Eastern Pacific.

Convection: This temperature contrast drives deep convection. Air rises over the warm Maritime Continent, travels eastward in the upper troposphere, sinks over the cool Eastern Pacific, and returns westward at the surface as the Trade Winds.

Monsoon Coupling: The rising limb of this circulation over the Maritime Continent creates a vast low-pressure area that anchors the Asian monsoon, pulling moisture-laden air into the Asian landmass.

2. The El Niño Pivot: Convective              Dislocation:

​During El Niño, the Pacific undergoes a positive SST anomaly in the central and eastern basin.

​The Eastward Shift: As the warm pool spreads eastward, the center of deep convection follows. The primary rising limb of the Walker Circulation is no longer anchored over Indonesia/Southeast Asia but pivots toward the Central or Eastern Pacific.

​Physics of Suppression (Subsidence):The atmosphere must conserve mass. Because the primary convective engine has "moved" east, the air that was previously rising over Southeast Asia is replaced by anomalous subsidence (sinking air).

​Pressure Inversion: Subsiding air creates a local high-pressure anomaly. In fluid dynamics, this effectively "caps" the region. It inhibits cloud formation and suppresses the low-level cyclonic moisture transport that the Asian monsoon relies on.

3. The Thermal Inertia Problem:

The Asian monsoon is essentially a giant thermal engine driven by the land-sea temperature contrast: 

T_{land} - T_{ocean} > 0.

By disrupting the Walker Circulation, El Niño alters the large-scale moisture convergence. When the convective branch shifts away:

Reduced Latent Heat Release: The massive release of latent heat (which usually fuels the upper-level monsoon flow) is reduced over the Maritime Continent.

Weakened Jet Stream: The weakening of this tropical heating source leads to a downstream perturbation of the jet stream, often altering the timing and intensity of the monsoon's "burst" phases.

In short, the monsoon mechanism is starved of its primary convective "pump," and the local high-pressure anomalies created by the shift in the Walker Circulation act as a physical barrier to the typical moisture flux needed for heavy rains.

Written on the 1st July 2026

Author - David I Birch 

Interbasin connections of ENSO and Hurricane season

There is a substantial inverse correlation between tropical Pacific Sea Surface Temperatures (SSTs) and tropical Atlantic activity, which directly modulates conditions in the Atlantic Main Development Region (MDR). This interbasin connection is primarily driven by the El Niño-Southern Oscillation (ENSO) cycle via atmospheric teleconnections.

1. The ENSO Teleconnection Mechanism:

The relationship is not driven by a direct mixing of water, but rather by changes in the global atmospheric circulation (specifically the Walker Circulation) triggered by Pacific SST anomalies.  

When Pacific SSTs are Warm (El Niño):

When the central and eastern equatorial Pacific experiences anomalously warm SSTs (+ENSO), it triggers intense atmospheric convection over the Pacific.

Increased vertical wind sheer:

This shifts the upper-level wind patterns, sending strong westerly winds across the Caribbean and into the tropical Atlantic MDR. These strong winds clash with the low-level easterly trade winds, creating high vertical wind shear. High shear literally rips developing tropical disturbances apart.

Atmospheric Stability:

El Niño induces broad anomalous sinking motion (subsidence) and warmer upper-tropospheric temperatures over the Atlantic basin, which stabilizes the atmosphere and suppresses deep convection. 

MDR Response:

Even if local Atlantic MDR waters are warm, an active El Niño act as a powerful "brake" on hurricane development.

When Pacific SSTs are cool: 

Cool (La Niña) Conversely, when Pacific SSTs are below average (-ENSO), the opposite occurs.

Reduced Vertical Wind Shear: 

Convection shifts to the far western Pacific, causing the upper-level westerlies over the Atlantic to weaken. Increased Instability: The atmosphere over the MDR becomes much more unstable, with enhanced rising motion and deep tropical moisture pushed into the region. MDR Response: This creates an environment highly conducive to tropical genesis and intensification.

2. The "Relative SST" Concept

​In modern climate science, researchers look closely at Relative SSTs—the temperature of the Atlantic MDR relative to the rest of the global tropical oceans.

​If the tropical Pacific warms faster or is warmer than the Atlantic, the global tropical troposphere warms, raising the thermodynamic threshold required for convection in the Atlantic. Therefore, even if the MDR is technically warmer than its historical average, it may underperform if the Pacific is significantly warmer. Conversely, if the Pacific cools (La Niña) while the Atlantic MDR remains exceptionally warm, the two factors work in tandem to create hyper-conducive conditions for extreme development.

               Current conditions.

Right now, we are seeing a fascinating, textbook setup of this exact interbasin relationship playing out in real time. The ocean-atmosphere setup has changed dramatically over the last few months, shifting the outlook for the hurricane season.

Here is exactly how the anomalies look across both basins as of June 2026:

1. The Tropical Pacific: A Rapidly Intensifying El Niño

The tropical Pacific is undergoing a confident warming trend. NOAA and the Met Office officially declared the start of an El Niño event, and it is ramping up incredibly fast, we spotted this back in April when subsurface temperatures were romping eastward. The Core Anomalies: In the central equatorial Pacific (the critical Niño 3.4 region), weekly SST anomalies have surged to +1.7^\circ\text{C}.  

Subsurface Heat:

Beneath the surface (at depths of 50–150 meters), a massive reservoir of warm water is packed into the central-eastern Pacific, with localized anomalies hitting up to +6^\circ\text{C}. This acts as a massive engine room, guaranteeing that this El Niño will continue to intensify through the summer and autumn.  

Atmospheric Response: 

The atmosphere has fully coupled with the ocean. The Southern Oscillation Index (SOI) is strongly negative (sitting at -21.9), and the easterly trade winds have severely weakened or even flipped to westerlies.

Current climate models are highly aligned, predicting this will peak as a strong to very strong El Niño later this year, potentially ranking among the most intense events observed since 1950.  

2. The Atlantic MDR: Robust Anomalous Cooling

While global sea surface temperatures as a whole remain exceptionally warm, the tropical Atlantic Main Development Region (MDR) is presenting a very stark contrast to the record-breaking warmth seen over the last couple of years.

The Local Anomalies:

The eastern and central tropical Atlantic MDR have actually experienced significant anomalous cooling, dropping below average for this time of year. Only the far western tropical Atlantic (near the Caribbean) is holding onto near-average temperatures.  

The "Relative SST" Trap: Because the Pacific is warming at a near-historic pace while the central/eastern Atlantic MDR has cooled below climatological norms, the Relative SST values for the Atlantic are deeply negative.

3. The Real-World Impact on the Seasonal Outlook

Because the anomalies have lined up this way, major meteorological institutions (like Colorado State University) have notably reduced their 2026 seasonal hurricane forecasts to below-normal levels.  

Normally, a warm global ocean provides plenty of background thermal energy, but the combination of a potent, rapidly growing Pacific El Niño and cooler-than-normal local MDR waters is expected to unleash exceptionally high vertical wind shear straight across the Caribbean and tropical Atlantic. This atmospheric "shear wall" is anticipated to act as a major suppressor, keeping a lid on deep tropical organization and storm track development through the peak of the season.

Written by David I Birch 

28th June 2026