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Posted by Karl Eggestad on Jul 21, 2016 8:19:21 AM
Karl Eggestad

In the northern hemisphere, we are now enjoying summer. And although summer and summer holidays are strongly associated with lazy days at the beach or walking through the mountains on sunny days, the typical definition of “summer weather” is not as clear.

Why Summer Can Mean More Rain Than Usual

Summer is by definition warmer than winter. At least that yields true for most locations. A few locations experience microclimate* conditions that actually counteract the large scale heating effects of the improved angle between the sun and the surface of the earth, caused by the Earth’s rotation around the sun. In places like San Francisco, for example, the marine layer** around the San Francisco Bay and just offshore from the Bay, is propelled closer to land by the rising air from the strong heating of the inland areas by the sun. As a result, the temperature in San Francisco may, for several days running, be lower in July than in October-December. That is, however, a microclimate effect which is unfortunate for visitors and tourists, but very predictable and normal.

What is less obvious is that although the temperature is higher, and the term, “Warm Summer Day” yields true, the actual rainfall and more significantly, the rain rate (often measured or estimated as rainfall per 1 or 6 hours) is higher in major tourist areas during the summer months of June through August. So, as many have experienced, the impact of severe rainfall is more often felt in the summer than at other times of the year.

An example of this is the recent flooding of the River Seine in May/June 2016. The river rose well above flood guards and into the streets surrounding the river, changing the river walk around the river, into actual river, and tragically, this rain event caused fatalities in Germany and France. The flooding was caused by extreme rainfall from strong convection***, and both the immediate surface (often street) flooding and the subsequent river flooding caused material damage, as well as fatalities.


Beware of Lightning Strikes – They Are More Frequent Than You Think

Another severe weather effect of summer weather is lightning strike damage. The saying that something has less chance of happening than being hit by lightning is a dangerous misconception since lightning strikes cause multiple fatalities every year, even in countries with advanced weather prediction capability.

In fact, so far this year, 14 people have been killed by lightning strikes in the US alone. On a global scale, more than 10,000 - 20,000 people are killed and several hundred thousand people are injured every year by lightning strikes. For many years, due to urbanization of the population, the statistics showed improvement in lowering the number of injuries and deaths, but outdoor activities have caused a recent increase in the numbers.

Expertise in Communicating Forecasts Can Prevent Deaths

Most lighting-related fatalities are preventable since lightning probability (but not actual location) is a well forecasted parameter. If the public were better informed about the dangers of lightning and would heed the warnings from meteorologists, as often communicated by broadcasters, many lives would be saved.

Knowledge of the weather forecast and expertise in communicating the forecast to the public makes a big difference, so this becomes our mission.

Until next time, stay weather aware and weather prepared!

Karl Eggestad, Global Sales Director for Metacast, ChyronHego

A microclimate is the climate of a small area that is different from the area around it

** A marine layer is the lower part of the atmosphere where the cooling effect from the cold waters causes temperature inversion - colder air closer to the surface

***Convection is the circular motion that happens when warmer air or liquid — which has faster moving molecules, making it less dense — rises while the cooler air or liquid drops down

Contact Karl Eggestad

Topics: Weather, Metacast