The weather in September spoils us. Even though autumn will begin in a few days, the temperature is like in the middle of summer, and the sun never stops shining. How long will we be able to enjoy the warmth and what can be seen in the long-term forecasts for autumn and winter 2023/2024? Our weather forecaster Arleta Unton-Pyziołek checked it.
An exceptionally warm half of September is behind us. And although the thermal summer has ended with the average daily temperature above 15 degrees Celsius, no major changes in nature can be seen yet. In the charming Barycz Valley, in the protected bird sanctuary at the Milicz Ponds, all winged creatures still live noisily, and swans calmly lead the grey-brown young swans. Wild geese fly into the air and after a short flight they land on the water. The birds’ preparations for their overseas journey are going slowly.
Does this mean that the warm autumn will last for a long time? This year we will welcome the astronomical and calendar variation of this season on the same day, Saturday, September 23.
Fall and winter weather. Preliminary forecasts
For now, the forecast for the next few days shows a heat dome over Europe. This week, the temperature is expected to rise at an altitude of 1.5 kilometers to about 15 degrees Celsius, which will result in heat waves at the ground and temperature increases at times up to 28-30 degrees Celsius, especially in the east and south of the country. And although it will get colder later, there is no significant break in the weather. The heat shows no signs of giving up, with heat wedges visible in the temperature field forecasts every few days, at least until the first week of October.
However, the sun is sinking lower and lower over the horizon and the day is getting shorter. With its apparent migration towards the equator, a slow reconstruction of the thermal field in the Northern Hemisphere begins, from the summer system (north-south) to the winter system (east-west). While in summer it is generally warmest in the south and coldest in the north, in winter it is warmest in the west and coldest in the east. In the autumn and winter period, the Atlantic Ocean acts as a radiator, accumulating heat in summer and releasing it in winter, thanks to which the air masses above it maintain the temperature above 0 degrees Celsius. Therefore, winter in western Europe, and increasingly in the center, is generally cloudy, rainy and windy. Meanwhile, the rapidly cooling large landmass of Asia favors the formation of a large frosty high pressure.
This year, the Atlantic has warmed up exceptionally in the area of Labrador in Canada, where low-pressure air vortices are born. There, the surface water temperature ranges from 15 to 20 degrees Celsius, and such values favor the formation of cyclones, which favor the inflow of mild air masses over our continent from the west and south, in successful cooperation with warm, autumn high pressures over eastern Europe. This year, the Atlantic Ocean has a lot of potential, because the average temperature of surface waters in its north-western part is higher than the norm by about 5 degrees Celsius, which is a significant value.
The lows forming over the ocean and the sunny highs remaining in the eastern part of the continent give hope for a warm autumn and the beginning of winter. It is supported by calculations of the long-term model of the US National Oceanic and Atmospheric Administration (NOAA). The average air temperature over the next three months (October, November and December) is expected to be above the long-term norm, by about 2 degrees Celsius.
El Nino on the horizon
But there is a cloud in the otherwise sunny sky of these forecasts. For now it is harmless Cumulus humiliswhich has a chance of turning into a dangerous one Cumulonimbus capillatus. Because not only the Atlantic, but also the great Pacific Ocean has warmed up. There, far along the equator, a phenomenon is unfolding El Niñowhich means not only future downpours and floods in the Andes, but also the heating of the atmosphere of the entire globe.
This will cause great instability of the atmosphere and is very likely to disturb the normal, predominantly western air circulation in Europe. The activity of powerful cyclones over the Atlantic may increase, which brings with it large temperature fluctuations and the inflow of warm air masses from the south, sometimes frosty ones from the north. But above all, it may generate heavy snowfall and storms, which will ultimately result in a snowy and frosty winter. The forecast for the deviation of the average temperature of surface waters in the northern part of the Atlantic Ocean and the equatorial Pacific Ocean assumes an increase in temperature above normal by 2-3 degrees C in winter. Such a disturbance will cause nature to have a strong need to strive for balance and clean up, which is usually associated with extreme phenomena.
What about the polar vortex?
There are voices among meteorologists that the extremely warm atmosphere of the Earth this year will be reflected in the circulation over the North Pole. The Arctic Oscillation blog, run by Dr. Judah Cohen and the AER (Atmospheric and Environmental Research within Verisk Analytisk) seasonal forecasting team, has just announced that they are “welcoming the return of the polar vortex like a good friend.” Because solar radiation is weakening, the temperature of the atmosphere over the pole begins to drop and a cold cap is slowly forming. However, researchers ask themselves whether he will actually turn out to be a friend later? This is because possible large heat inputs into the stratosphere (at an altitude of 10 km) in the upcoming winter may disturb the polar vortex from its stable rhythm from time to time. Statistically speaking, the El Nino phenomenon has a positive correlation with the disruption of the polar vortex, which means there is a high probability of the vortex breaking up in the coming winter.
Sudden stratospheric warming, an otherwise very interesting and spectacular phenomenon, causes the vortex to shake and break up. This means a dive of severe cold into lower temperate latitudes. Who will it fall on, North America, Europe, Asia? We don’t know it today, but we have to take into account that the heavy waves of wet snow will be followed by waves of bitter frost. And according to the Japan Meteorological Agency (JMA), which conducts constant monitoring over the Arctic, the temperature in the stratosphere is expected to drop to about -80 degrees Celsius. Last winter, such cold sliding from the higher parts of the atmosphere near the ground in Siberia resulted in frost below -60 degrees Celsius.
Forecasts for late autumn and winter are, of course, still speculations. But meteorological data from various parts of the globe now collected by researchers paint an interesting scenario. No one knows yet how the polar vortex will behave in the coming months, not even the best scientists, but fears arise that after a warm and pleasant autumn, we may find a large bill in the mailbox.
Main photo source: Shutterstock/NOAA