Researchers think they can predict a heat wave 9 months in advance

The meteorologists believe that the weather forecast can be really reliable and precise, over 4 to 5 days, with a more or less clear trend over 10 to 15 days. Beyond that, it is only possible to identify global seasonal trends based on the influence of the ocean, sea ice and major action centers in theatmosphere. This means that beyond 15 days, an event (rain, snow, storm…) is not reliably predictable, currently.

But, concerning the temperatures, it is all the same possible to have a general idea of ​​the evolution over the month to come: it is often possible to envisage a anomaly thermal over the next 3 to 4 weeks, i.e. simply warmer or colder than normal.

A team of researchers from the National Oceanic and Atmospheric Administration (NOAA), the United States Oceanic and Atmospheric Administration, has just published a study on his progress in matter forecasting heat waves on the North American continent. By studying the waves of heat between 1992 and 2019, and the atmospheric and oceanic parameters that preceded these events, the researchers believe they can predict the probability of a summer heat wave 9 months before, unheard of!

Three decisive weather parameters from the end of summer

Three settings weather report are analyzed from September to determine this risk of temperatures above seasonal averages during the following summer: radiative forcing, the surface temperature of the North Pacific Ocean and the North Atlantic, which influences the heat and humidity of the central United States, and finally, the occurrence of the phenomenon El Nino or not, which is reliably predictable at least 4 months in advance.

Radiative forcing is the balance between the solar radiation who enters, and emissions radiation infrared coming out: if the sum of these two types of radiation is positive, then the Earth warms up, as it does now. Ocean temperature also plays a very important role in regulating the climate on land: the ocean absorbs solar radiation, and then redistributes this heat and humidity across the globe, directly influencing weather conditions. The water of the ocean is indeed in constant evaporation and theair which escapes is therefore warmer and more humid: it then travels inland with the currents, influencing the risk of heat andthunderstorms in the central and southern United States.

The climate of the United States is also largely determined by La Niña and El Niño, two climatic phenomena characterized by a temperature anomaly part of the waters of the Pacific Ocean. They occur in phases of one to three years, and influence weather conditions in part of the world. We speak of an “El Niño year” when the water in a specific area of ​​the Pacific is warmer than average. In this case, warm air is regularly locked over the northern United States and western Canada, greatly increasing the likelihood of severe and long-lasting heat waves.

The NOAA team uses two models to determine the probability of a heat wave between June and August, starting in September of the previous year: the GFDL (Geophysical Fluid Dynamics Laboratory) and the Spear (Seamless system for Prediction and Earth system Research). These two models are statistical tools, they issue a probability of a heat wave, and not a forecast: in other words, with the parameters of the atmosphere and the oceans currently visible, the risk of a heat wave is statistically low or high for the following summer.