Contrasting weather across Europe – Tuesday 18 July 2023
Extreme and dangerous heat has been impacting many parts of the northern hemisphere, including Mediterranean countries where air temperatures are 10 to 15 degrees Celsius above average. The heatwave is set to continue this week with record breaking temperatures forecast. In contrast, Ireland is experiencing unsettled weather with temperatures on the cool side, near or below the July average.
Why is there such a difference? Met Éireann meteorologist Linda Hughes explains “The main contributing factor is the position of the jet stream relative to Ireland. The jet stream is a band of very strong winds located around 9 or 10km above the surface of the earth which can meander to the north or south of Ireland. At the moment the jet stream is positioned to the south (Fig.1), which is placing Ireland in a cool airmass and a mainly west to northwest airflow (Fig.2)”.
Fig1: Jet stream at 12Z 18th July 2023 (ECMWF)
Fig 2: Wet-bulb potential temperature at 12Z 18th July 2023 (ECMWF)
A blocking area of high pressure is affecting southern Europe, which is inhibiting cloud formation and allowing heat to build day on day. A marine heatwave is occurring in the Mediterranean Sea with sea surface temperatures in the mid to high twenties (Fig.3). Nighttime temperatures are also remaining very high. Red high temperature warnings have been issued in some Mediterranean countries. For any holidaymakers heading in that direction check www.meteoalarm.org for all active warnings.
Fig 3: Sea surface temperatures (degrees Celsius)
Linda Hughes continues, “In contrast, Ireland is currently under the influence of Atlantic low pressure systems, bringing changeable weather with spells of heavy rain at times. Looking at the extended range forecast, there is no clear signal for any long-settled periods”.
Contrasting weather across Europe – Tuesday 18 July 2023
Extreme and dangerous heat has been impacting many parts of the northern hemisphere, including Mediterranean countries where air temperatures are 10 to 15 degrees Celsius above average. The heatwave is set to continue this week with record breaking temperatures forecast. In contrast, Ireland is experiencing unsettled weather with temperatures on the cool side, near or below the July average.
Why is there such a difference? Met Éireann meteorologist Linda Hughes explains “The main contributing factor is the position of the jet stream relative to Ireland. The jet stream is a band of very strong winds located around 9 or 10km above the surface of the earth which can meander to the north or south of Ireland. At the moment the jet stream is positioned to the south (Fig.1), which is placing Ireland in a cool airmass and a mainly west to northwest airflow (Fig.2)”.
Fig1: Jet stream at 12Z 18th July 2023 (ECMWF)
Fig 2: Wet-bulb potential temperature at 12Z 18th July 2023 (ECMWF)
A blocking area of high pressure is affecting southern Europe, which is inhibiting cloud formation and allowing heat to build day on day. A marine heatwave is occurring in the Mediterranean Sea with sea surface temperatures in the mid to high twenties (Fig.3). Nighttime temperatures are also remaining very high. Red high temperature warnings have been issued in some Mediterranean countries. For any holidaymakers heading in that direction check www.meteoalarm.org for all active warnings.
Fig 3: Sea surface temperatures (degrees Celsius)
Linda Hughes continues, “In contrast, Ireland is currently under the influence of Atlantic low pressure systems, bringing changeable weather with spells of heavy rain at times. Looking at the extended range forecast, there is no clear signal for any long-settled periods”.
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