That is the typical signature of the cold ENSO phase. The main feature is a strong high-pressure system in the North Pacific and low pressure over Canada. They form as the surface water is being pushed west by the trade winds, bringing deeper colder water to the surface.īelow we have an image that shows the average winter pressure pattern from multiple La Nina winters. You can see new cooling starting in July, as the cold “waveforms” develop across the equatorial Pacific. The high-resolution video animation below shows the ocean temperature anomalies from Summer to late Fall. Overall, the current event is marked as a moderately-strong La Nina. The strongest cold anomalies are reaching below 3☌ colder than the long-term average. That is the currently active La Nina phase. We can clearly see the strong cold anomalies in the tropical Pacific Ocean. We usually observe a global shift in pressure patterns during the emergence of an ENSO phase but it is usually most influential during the peak of the phase and its decay.īelow we have the latest global ocean temperature anomaly from NOAA.

This way, ENSO has a major impact on the tropical rainfall and pressure patterns and impacts the ocean-atmosphere feedback system. Air is descending in the eastern Pacific, causing stable and dry weather, while lower pressure and rising air cause frequent thunderstorms and a lot of rainfall over the western Pacific. The image below from NOAA Climate shows the typical circulation during a cold ENSO phase that we are currently in. This directly translates into the global circulation, affecting the jet stream on both Hemispheres over time. During an El Nino, the pressure over the tropical Pacific is lower, with more rainfall and storms and westerly winds.īut during a La Nina, the pressure over the equatorial Pacific is high, creating stable conditions and less precipitation. Their names literally translate to “the girl” (La Nina), and “the boy” (El Nino), indicating an opposite dynamic between the two phases.īut besides the ocean temperatures, one of the more important differences is also in the pressure pattern. The cold ENSO phase is called La Nina and the warm phase is called El Nino. Some stronger events can last even up to two years. A specific phase (cold/warm) usually develops between late summer and fall and typically lasts into next Spring. Over time, this translates to the overall global circulation, impacting the weather worldwide differently. Region 3 covers the eastern tropical Pacific, while region 4 covers the central and most of the western tropical Pacific.Įach ENSO phase has a different effect on the pressure and weather in the tropics. Main analysis (and forecast) is done for a combination of regions 3 and 4, seen on the image as the Nino 3.4 region. The image below shows the ENSO regions in the tropical Pacific. With some delay, these changes directly affect the circulation over the rest of the world. We can observe large-scale pressure changes in the tropics as ENSO shifts between warm and cold phases. It has a major impact on the tropical convection patterns (storms), pressure patterns, and thus on the interaction between the ocean and the atmosphere.

This is a large oceanic region in the tropical Pacific, that is regularly changing between warm and cold phases. Winter is still ongoing and driven largely by a cold ENSO phase.ĮNSO is short for “El Niño Southern Oscillation”. We are starting off with the current weather conditions, brought on from the 2021 cold season. You will see how and why these global changes occur, and what is going to be different in 2022, compared to the last few years. From there we will go into the atmosphere and the oceans, to observe what is changing already, and what is yet to come. We will go on a weather journey through 2022, starting with a seasonal weather pattern forecast for late winter and early parts of the Spring. The changes will start slowly, but the main shift will start to occur during the 2022 warm season.īut what exactly is changing this year, and what weather patterns resulted from such changes in the past? Major changes are coming in 2022 across the atmosphere and the oceans, creating different weather patterns into the second half of the year, and especially in the cold season later in the year.

Temperature anomaly