Most of you must know what an old curmudgeon I can be in this blog of mine. So I was just wondering about the term ‘hot’ and what exactly it meant in forecaster parlance. In the last couple of days it seems to be tripping of the tongue of just about every weather presenter on the TV. There was a pamphlet issued by the Meteorological Office ‘Your Weather Service’ which did list the terminology in a table used by presenters when forecasting the temperature and frost in the 1950’s, and which you can find if you do a search the archives of the Weather Magazine (page 138 in the 1964 volume). As far as I can see from the table, which in itself is a little ambiguous about each range, the definition for hot for the summer period, is a temperature that’s between +6°C and +7°C above the long-term average, and very hot when its >+7°C, i.e. +8°C or higher.
As you can see for yesterday’s maximum temperature anomalies [06-18] for large parts of the countries that weren’t affected by an onshore sea breeze where in the hot category, and many parts in the north and northwest were in the very hot range, with Aboyne +12.4°C above the long-term average for that day. Generally along the south coast and the southeast temperatures were in the very warm category (fig 1).
Here’s a more detailed analysis of yesterday’s highest anomalies from across WMO block 03 (fig 2). So it may have felt hot at Heathrow yesterday, and it certainly was with an anomaly of +7.8°C, but a temperature that was just one degree higher produced an even larger anomaly in the Highlands where it was very hot.
I think it would be a good idea if the Met Office could update and reissue the original pamphlet ‘Your Weather Service’ on their website. They produce may helpful factsheets, but none of them cover forecast terminology used in their forecasts or by their presenters, as far as I can see. I am sure it would help the general public to standardising terminology used to describe just how cold or warm it was expected to be, how severe a frost was expected to be, or how windy it would be tonight. Until they do, we will never really know exactly what they mean when then say there’ll be a sharp frost or it will be blustery day, or it’ll be hot, when what they really mean is that it’ll be very hot in the northwest.