Remainder of July, Rain or Shine?

Written on: 08th Jul 2021

July has started off with a bit of a north/south split in terms of temperature. Across the south temperatures have been largely below average for the time of year, further north they've been a little above, especially across parts of Scotland. 

In terms of rainfall, it's been a very wet start in the south with some areas already recording more than 100% of their monthly average rainfall.

Looking ahead to the remainder of July, I'm not overly confident we're going to see summer set in properly, however towards the middle of the month there is good support for high pressure to build in across the UK turning things increasingly settled, and perhaps a little warmer. The GEFS and EPS are in agreement for this scenario.

Into the second half of July though, there is some evidence within the background signals that high pressure is less likely to stick around and could be replaced by low pressure again in the final third of the month. 

The AAM (Atmospheric Angular Momentum) is currently in the negative phase, and this generally supports a more cyclonic (low pressure) outlook. There was some suggestion from the GFS that the MJO would become more active, perhaps helping to recover the AAM into a more positive state and allowing for high pressure, though the GFS has somewhat backed away from that signal. 

There is one saving grace, and that's frictional torques are currently moving into a positive phase which could help recover the AAM, though given the lag, without the MJO it's likely this wont have a big enough impact to support high pressure for the rest of the month. 

The forecast then, the weather should turn increasingly settled as we approach the mid month period as the Azores high extends north-eastwards across the country, however it is likely low pressure will become an increasing player in our weather as we go through the second half of July, I'm not expecting things to be quite as poor as the first half, but I don't think we're looking at days of wall to wall sunshine and hot weather, either.