Justin, I have two weather questions for you, both in relation to your weekly weather
forecast every week. I understand climate figures into weather forecasting, what is
climate? And second, every week I see in your forecast the terms “Partly Cloudy”
and “Mostly Cloudy.” What are the differences in the various weather terms you use
on a weekly basis?
-Susan, Sapphire
Answered by Justin Caudell
Susan, you have provided me with two very good questions. While there are many factors
in generating a weather forecast every week, climate is certainly an important persona I have
to take in consideration. Climate plays a vital role in any town or city’s geographic weather.
Climate refers to the average, or typical, weather conditions observed over a long period
of time for a given area. For instance, the climate of Cashiers in the winter is on average,
rather cold with occasional snow. On the contrast, the climate of the tropical oceans is warm
and humid all year long, with occasional showers or thunderstorms and no winter. On an island
in December, you can still find 80 degree temperatures.
There is a lot of uncertainty about what causes climate variations though between say here
and Bermuda. Some of the factors most attributed to climate are variations in the sun, changes
in ocean circulation, changes in land cover types, the production of greenhouse gases by
mankind's burning of fossil fuels, and the role of man-made aerosols on cloud formation.
Climate variations can occur from year to year, one decade to another, one century to
another or any longer time scale. The biggest uncertainty in predicting future climate change
for the United States and abroad is not knowing what part of observed climate change in the
past century is natural and what part is man-made. Since climate change occurs naturally,
meteorologists don't know how much of the one degree warming in the last century is due to
mankind pumping greenhouse gases into the atmosphere versus the Earth simply coming out
of a “Little Ice Age”.
What is the difference between Partly and Mostly Cloudy?
Susan, I thoroughly enjoyed this part of your e-mail because I think it is important for
readers to know every week what exactly it is I am forecasting. You are the first person thus far
to ask me what specific terms mean.
In weather forecasting, there are certain sky conditions a meteorologist must decipher on a
map and predict what type of cloud cover, if any, an area will have in a pro long time period.
The following is a break down of what each sky condition term means: Sunny is when the sky
will be 0 - 10% obscured (covered by clouds), Mostly Sunny 10 - 30% obscured, Partly Cloudy
30 - 60% obscured, Mostly Cloudy 60 - 90% obscured and Overcast is when the sky will be
100% obscured.