Weatherwatch: It may feel like spring, but we are not out of the winter woods yet

http://www.theguardian.com/news/2015/mar/23/weather-spring-oceans-snow

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Last Friday was the spring equinox, and for those of us in the northern hemisphere the days started to become longer than the nights.

The extra minutes of sunshine (when the sun manages to break through the cloud) do bring a spring-like feel to the air, but we are not out of the winter woods yet.

In the UK, a blast of snow in March or April is not unusual, and in fact snow is more likely to fall at Easter than it is at Christmas. One of the reasons for this seasonal delay is that the oceans take significantly longer to respond to the warming effects of the sun.

Air and land heat up quickly, but water has a very high heat capacity, meaning that it takes a lot of heat energy and, therefore, a long time to heat the oceans up.

Equally water is good at holding on to energy, meaning that it takes a long time for warm oceans to cool at the other end of the year. Since more than 70% of Earth is covered by ocean, most locations experience some seasonal lag.

In the UK our seasons lag behind the sun’s heat input by around one month, which explains why our warmest months tend to be July and August, rather than midsummer, and our coldest months are January and February rather than midwinter.

Temperature-wise, March has more in common with December than its equinox equivalent month – September.

So if you are impatient for warmth, hang on in there: it is on the way, but we just have to wait for the oceans to catch up …