# The polar vortex and cold weather in Romania: what the data show El Niño is strengthening in the Pacific. For that signal to become a cold week in Romania, it must connect with the stratosphere, the polar jet and a regional pattern close to the event. The polar vortex circulates high in the stratosphere. The polar jet sits closer to the weather we feel. This page follows how upper-air circulation can shape surface weather. > NOAA is describing the odds for El Niño in the Pacific. For Romania, the answer depends on the jet configuration and forecasts closer to the event. ## The number describes the Pacific. A Romania forecast comes later. The question and the evidence change between those two points. Follow the same transition in four steps. ### 01. PACIFIC: El Niño raises ocean temperatures Equatorial Pacific surface waters are warmer than average. NOAA estimates a greater than 90% chance of a very strong episode during Northern Hemisphere autumn and winter. _Status: SEASONAL FORECAST. Source: NOAA CPC._ ### 02. STRATOSPHERE: Upper-air circulation can be disturbed Atmospheric waves can change the vortex above the North Pole. Historical data show a link between ENSO and sudden stratospheric warmings, and that relationship changes between winters. _Status: STATISTICAL LINK. Source: Butler et al. 2011._ ### 03. POLAR JET: The jet changes which region is affected After a major stratospheric event, surface effects vary by place and time. NOAA maps show regional averages, not the temperature of one country. _Status: OBSERVED CONTEXT. Source: NOAA Climate.gov._ ### 04. ROMANIA: The local forecast arrives close to the event A week of frost or snow requires a specific pattern in the jet, the Atlantic and pressure fields. The useful answer comes from updated regional forecasts. _Status: LOCAL FORECAST. Source: regional data._ ## What changes when the vortex weakens The slider shows two simplified configurations. Follow the same scene: the vortex above, the jet in the middle and cold air that can move south in some regions. A more stable vortex: Stratospheric winds remain stronger and more circular. Cold air is more contained in the Arctic, while the jet tends to stay farther north. A weakened or disturbed vortex: Stratospheric warming or a shift in the vortex can make the jet more wavy. Arctic air can move south in some regions. Explanatory diagram. It is not a forecast or a live measurement. ## NOAA estimates the chance of a strong El Niño On 13 August 2026, NOAA estimated a greater than 90% chance of the "very strong" category during Northern Hemisphere autumn and winter. For October-December, the chance of a historic event was 69%, at a RONI threshold of at least +2.5°C. - >90% · very strong category: Northern Hemisphere autumn and winter 2026-2027. Source: NOAA CPC. - 69% · historic event: October-December 2026, RONI at least +2.5°C. Source: NOAA CPC. ### What these percentages cannot tell you Both percentages refer to El Niño in the Pacific. They do not give a temperature for Europe on their own. That requires the stratosphere, the polar jet and regional forecasts. ### In 2021, tropospheric circulation mattered more at the surface After the major sudden stratospheric warming in 2021, one study found limited surface impacts in North America. Tropospheric circulation mattered more for the cold that was observed. [Read the Nature Communications study](https://www.nature.com/articles/s41467-022-28836-1) ## What should you watch next? For one specific week, three things matter more than the El Niño headline. - The stratosphere: Is there a major sudden stratospheric warming or a displaced vortex? - The polar jet: Is it bending south over Europe? - The local forecast: What do the models show for Romania in the near-term window? A seasonal signal tells you where to look. A local forecast answers for one specific week. ## Sources you can check NOAA is the source for the percentages and the vortex explanation. Research tests the relationship between ENSO and the stratosphere. The Libertatea article is the starting point for the public question. ### The number, the mechanism and the forecast do different jobs The number comes from the NOAA bulletin. The mechanism comes from NOAA Climate.gov and research. A Romania forecast stays tied to regional evidence close to the event. - NUMBER: a probability for El Niño with a window and threshold - MECHANISM: a documented relationship between atmospheric layers - FORECAST: a regional estimate for a specific time window ### NOAA CPC: ENSO Diagnostic Discussion, 13 August 2026 The discussion estimates a greater than 90% chance of a very strong El Niño during the Northern Hemisphere autumn and winter of 2026–2027. For October–December 2026, the chance of a historic event is 69% at a RONI threshold of at least +2.5°C. NOAA says El Niño-consistent impacts become more likely without becoming guaranteed. [ENSO Diagnostic Discussion, 13 August 2026](https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html) ### NOAA CPC: Long-Lead Seasonal Outlook, 16 July 2026 The 16 July seasonal outlook gave an 81% chance of a very strong El Niño in OND 2026. The 13 August diagnostic uses an update and two different thresholds. The product remains U.S.-focused and does not provide a Romania forecast on its own. [Long-Lead Seasonal Outlook, 16 July 2026](https://www.cpc.ncep.noaa.gov/products/predictions/long_range/lead14/fxus05.html) ### NOAA Climate.gov: Understanding the Arctic polar vortex It describes the polar vortex as stratospheric circulation and separates it from the tropospheric polar jet, which sits closer to day-to-day surface weather. [Understanding the Arctic polar vortex](https://www.climate.gov/news-features/understanding-climate/understanding-arctic-polar-vortex) ### NOAA Climate.gov: But what does a polar vortex breakdown look like down here? It shows that surface cold signals after major sudden stratospheric warmings vary by region and time. NOAA's maps average 42 observed events between 1958 and 2023, around 30 days after each event; they describe patterns, not local forecasts. [But what does a polar vortex breakdown look like down here?](https://www.climate.gov/news-features/blogs/enso/what-does-polar-vortex-breakdown-look-down-here) ### Butler et al.: El Niño, La Niña, and stratospheric sudden warmings: a reevaluation The 53-year reanalysis finds a statistical relationship between ENSO and sudden stratospheric warmings, with higher frequency in ENSO winters. The relationship does not become a required sequence for every El Niño event. [El Niño, La Niña, and stratospheric sudden warmings: a reevaluation](https://doi.org/10.1029/2011GL048084) ### Nature Communications: Limited surface impacts of the January 2021 sudden stratospheric warming The study finds limited surface impacts from the 2021 stratospheric warming in North America; tropospheric circulation mattered more for the cold that was observed. [Limited surface impacts of the January 2021 sudden stratospheric warming](https://www.nature.com/articles/s41467-022-28836-1) ### Libertatea: Super El Niño and its possible influence on Romania in 2026-2027 The article is the public-media starting point for the question. It is used here as context, not as the source for meteorological figures or mechanisms. [Super El Niño and its possible influence on Romania in 2026-2027](https://www.libertatea.ro/stiri/fenomenul-super-el-nino-si-influenta-asupra-romaniei-in-2026-2027-seceta-severa-si-canicula-extrema-5780910) Checked 16 August 2026. Revisit when NOAA issues a new ENSO discussion, a major sudden stratospheric warming occurs, or forecasts for Europe and Romania change the relevant evidence. --- A public object by Marius Comper. [Marius Comper](https://mariuscomper.uk/en/).