August has been a mixed period of weather with outbreaks of rain interspersed with a period of very warm weather, but what does September have in store for us?

Lets start by taking a look at a couple of teleconnections, we’ll start with the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO)

North Atlantic Oscillation Forecast
Arctic Oscillation


These have both been positive/neutral recently but are forecasted to return negative through September which is indicative of High Pressure re-building in the Atlantic and across Greenland, this pattern is generally quite pour for prolonged warm weather.

The next chart we’re going to look at is the 500MB Anomaly Chart for the ECM and GFS, this will take us up until around the 7th-8th September

Height Anomaly Comparison

As you can see, both the ECM and GFS are forecasting High Pressure to be over the United Kingdom for the first part of September bringing settled, sunny and warm weather, a setup like this at this time of year is likely to see temperatures in the low-mid 20’s.

Moving onto some Longer Range Models, we’ll take a look at the CFS Model to see what thats predicting. Here’s the CFS Pressure Anomaly Chart

CFS Pressure Anomaly

This model is predicting lower heights to our North-East giving us Northerly/North Easterly winds, it’s also indicating a weak signal for High Pressure out in the Western Atlantic though not so much over Greenland. Below is the CFS Precipitation Anomaly Chart

CFS Precipitation Anomaly

The precipitation chart is predicting slightly above average rainfall across Northern areas and around average rainfall for Southern areas, we can also see above average rainfall being forecasted across Scandinavia which reflects the pressure chart for Low Pressure to be sitting here, if we look towards Greenland however we can see below average precipitation being forecasted, perhaps an indication of High Pressure being over this area. Now lets take a look at the CFS Temperature Anomaly Chart

CFS Temperature Anomaly

The temperature chart is predicting slightly below average temperatures overall this month which again would tend to fit in with the models forecast for low pressure positioning.

Forecast Conclusion:

Based on the models talked about above, September will start off on a rather dry and settled note with High Pressure dominating, temperatures responding quite nicely sitting comfortably in the low-mid 20’s, as we move through into the second week of September however High Pressure will begin to be replaced by Low Pressure bringing in cooler air along with wet weather returning to the forecast, the wettest weather looks likely to be across more North parts with High Pressure perhaps extending into Southern England from time to time, keeping it slightly drier here. Temperatures on the whole are expected to be slightly below average with rainfall close to, or above average for the time of year.