Met office predicts normal summer temps, admits forecast failures

Using computer modelling, the met office’s three-month forecast is predicting normal seasonal temperatures until the end of August but the model failed to predict higher-than-normal temperatures that occurred in March, April and May.

The forecasts are issued monthly looking three months ahead with the latest being for June, July and August. The computer modelling is then looked at in terms of each previous month to gauge how it performed in comparison with real-world data.

For instance, the latest report up until the end of August looks back on how the computer model performed in May.

In terms of June, which is seeing extremely high temperatures well above normal for an extended period, the model predicted that temperatures would be between 1C and 2C above normal over most of the island except in the east and southeast.

Specifically the model predicts normal temperatures for the three months with a smattering of thunderstorms inland and on the mountains.

“Normal temperatures but also drought is the general feature for these three months,” the report says.  “That means that the mean temperature will be around normal and does not exclude days with temperatures well above normal.”

Also, it said, any precipitation would be a result of thermal instability, in the form of a thunderstorm, with very local and temporal characteristics.

There might be a bit more rain from thunderstorms in August, it added but the expectation was low and would be confined to the northwest coast and the mountains.

The same report goes on to evaluate its previous forecast for May, saying the model had predicted temperatures would be 1C to 2C warmer than normal “across almost the entire island, except in the east where temperatures were expected to be at normal levels”.

In relation to rain the model predicted this would be 50 per cent of normal for Cyprus when it fact it was 148 per cent of normal for the month.

“Concerning the models’ evaluation for May, a general judgment is that it performed relatively well regarding the mean monthly temperature,” the report said.

“However, regarding the accumulated precipitation the model did not perform well since it underestimated the expected accumulated monthly precipitation amounts”.

In a more detailed evaluation of the recorded temperatures, both the mean daily maximum and minimum temperatures were in some of the weather stations above normal with the average daily minimum temperature being in some cases up to even 2.9C above normal.

A number of extremes were recorded during the month, it added, some with a deviation of 4C above normal.  

As far as the model’s underestimation of the amount of rain expected, the report said this was “something that shows us the uncertainty of the seasonal forecast model which must always be taken into account with reservations.”

Similarly, the evaluation for April prompted the met office to say the model had not performed well. It had suggested temperatures would be above normal by 1C to 2C with rain a disappointing 50 per cent of the usual for the month.

“A general judgment is that the model did not perform well concerning both the mean daily temperatures and even more concerning the accumulated monthly precipitation,” the report said.

The recorded data showed that the mean daily maximum and the mean daily minimum temperatures were well above normal for the month, “which the seasonal forecast model did not support very well”. In the end temperatures were 3.3C to 4.8C above normal, not 1C to 2C.

“Extremes (deviating by 4C or more from normal) were recorded in all of the selected meteorological stations,” it added.

As far as the rain was concerned, the report said that although the prediction was for 50 per cent or less of the normal, April’s precipitation came in at 125 per cent of normal.

A similar forecast had been made for March with the same results. March was overall warmer than predicted but the model did accurately predict the rainfall for the month.