A Summer's Day Sea Breeze

Sea breezes are a regular feature of the weather here in the Otter Valley. The breeze is common on calm, hot sunny days in late spring and early summer and will arrive on such days as early as 10am or even as late as 2pm.

A hot early July day on Jacob's Ladder Beach in nearby Sidmouth.

The Arrival of the Sea Breeze:

A typical sea breeze day will dawn warm, calm and sunny. The temperature rises quickly in the strong sunshine and is soon in the mid to high 20s Celsius by mid-morning. It is now, under these conditions that the sea breeze may arrive and with it a relief from what would be a scorching afternoon. Figure 1 shows the arrival of a sea breeze on what turned out to be one of the hottest days of the year when temperatures were as high as 35oC across parts southern England. The temperature rose rapidly after a warm night and by 11:00am it was already 28oC, the air was humid and oppressive with just a slight, variable wind of around 1 mph. Patchy cumulus cloud was developing in the sky but by 12:30 there was a clearance moving up from the south, this heralds the start of the sea breeze as it moves inland suppressing cloud formation and bringing crystal clear, deep blue skies with a welcome drop in temperature and humidity.

Figure 1. Temperature and Wind Speed (with wind direction) for the 19th July 2006 demonstrating the arrival of the sea breeze at 12:45.

The temperature drop associated with the sea breeze on the 19th of July was not as great as it would have been earlier in the summer and spring time. This is because the sea was already quite warm by mid-July with sea surface temperatures approaching 20oC. The drop in relative humidity as the sea breeze arrives with the associated temperature drop, wind speed increase and change of direction is shown in the data set in Table 1.

Table 1. 15 minute data set from AWS for July 19th, 2006.

Time hPa oC RH% MPH Direction
11:30 1014.2 28.3 48 0.9 ESE
11:45 1014.1 29.1 46 1.2 ENE
12:00 1013.9 29.5 47 0.3 NE
12:15 1013.9 29.8 48 0.6 NE
12:30 1014.0 30.3 49 0.4 NE
12:45 1014.0 30.8 50 0.9 SSE
13:00 1014.0 29.1 46 7.6 SSE
13:15 1013.8 27.7 47 5.3 SSE
13:30 1013.8 27.3 47 5.1 S
13:45 1013.7 27.3 46 4.9 SSE
14:00 1013.7 27.2 47 4.6 SSE

This is a satellite picture taken on 15th April 2008. It shows a convergence over the spine of the Devon & Cornwall peninsula. On this day a slack south easterly air stream was present. Note the way how the cumulus clouds had been pushed very far inland around Lyme Bay. This picture was taken from Bernard Burton's website at Wokingham Weather.