Jacob's weather forecasts

I remember last summer and late spring, where dreaded breakdowns of warm weather patterns to persistently cool, wet weather in weather models kept being downgraded to what was closer to average conditions. It relates to how weather models often incorrectly predict or underestimate the impact of SSTs on atmospheric circulation at 3+ days out and correct themselves closer to the time. An implication for this is that the longevity of "heat domes" can be underestimated by weather models in the context of global warming. The first reason for SSTs causing warm, dry weather is that a weaker AMOC, freshwater in the North Atlantic and cold blob are linked to a stronger Icelandic Low, causing southerly, anticyclonic conditions to dominate in late spring and early summer, when the cold SSTs in the North Atlantic are more pronounced from melting retreating ice in summer. Last spring, we saw some very stark, cold SST anomalies, which lead to a heatwave in April and May. These southerly wi...

In the shorter term, a more imminent potential tipping point could be an SPG convection collapse:   Abrupt Climate Change in the Subpolar North Atlantic: Drivers and Impacts In this study, climate models show that this tipping point is not a matter of if it happens, but when it happens. It may suggest that the tipping point may have already been reached, and the SPG convection is already in terminal decline, or it may be as a result of climate model biases, not including Greenland freshwater runoff, and resolution, which isn't high enough to properly represent eddies, though the model used (CESM2-LENS) is still fairly skillful. The timing of the collapse is uncertain, but the risk raises significantly in the 2030s, and into mid-century. The collapse would cause a significant drop in SSTs in the subpolar gyre, so it essentially strengthens the NAWH/cold blob, and is a more minor, abrupt version of an AMOC collapse, that would occur before it. The ensemble mean for the timing of this...

The impacts of an AMOC collapse on Europe Introduction As the Earth has warmed, one section of the Atlantic Ocean has been cooling. This has been attributed to an ocean current, known as the Atlantic Meridional Overturning Circulation (AMOC) weakening. This ocean current regulates the climate worldwide by transporting waters at different temperatures, but this is expected to continue to weaken with climate change, bringing worrying consequences on the climate. However, a more extreme, but still a very plausible scenario of the current collapsing may occur as early as mid-century, where the climate may rapidly change within a few decades. In this summary, I'll focus on Europe. Source: High-resolution ‘fingerprint’ images reveal a weakening Atlantic Ocean circulation (AMOC) The AMOC brings warmer water from the Gulf of Mexico to Europe, contributing to keeping its climate mild in comparison to areas such as Canada. Under a collapse, a lot of the warmer water is shut off, shown by the...