What can we expect for fall?

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By Charles Roop
September 22, 2016

TALLAHASSEE, Fla. (WCTV) - It’s that time of year where pumpkin-flavored everything starts creeping out at coffee shops and stores, college football season ramps up, women pull out the sweaters and Ugg boots, and my allergies start going haywire.

Autumnal equinox, or the first day of fall, begins at 10:21 am ET Thursday in the northern hemisphere. This is when the direct angle of the sun is on the Earth’s equator. The Earth is on a 23.5-degree tilt, so twice a year (spring and fall), the earth will get roughly equal amounts of sunshine as the third rock from the sun we reside on revolves around our nearest star. It also means that we will have about 12 hours of daylight and 12 hours of darkness.

As we move closer to December, the Southern Hemisphere will see more of the direct sunlight. This will put us on the path towards winter solstice in late December and summer in the Southern Hemisphere.

So, yes, we will move away from the balmy, humid cesspool into a more comfortable, open-window weather pattern. Or will we?

I’ve read discussions and dug into the data to see what will the season could hold. So, throw away that Old Farmer's Almanac and get ready to read up on some real science. (Chief Meteorologist Mike McCall told me I should have been harsher with the Almanac).

What’s normal?

Typically in Tallahassee on Sept. 24, we normally see highs near 86 and the low near 64 (Winsberg 2003 ). The average high temperature drops to near 77 with a low near 53 by Halloween. By time mid December rolls around and “Santa” does his last-minute shopping at the mall, we normally see the high near 64 and the low near 39.

We start to leave the rainy season as fall arrives. The average rainfall in Tallahassee between late September and mid December is a little over 11 inches (Winsberg 2003). That’s under 20 percent of the rainfall we get year round. We see less afternoon thunderstorms, and rely more on large-scale weather systems to deliver our rainfall.

Global influences on our area.

You might remember last winter’s chatter about El Ni‎ño, the cyclical phenomenon where the water temperatures off the Pacific coast of South America are above normal. Generally speaking, El Ni‎ño usually helps make the Southeast U.S. a little wetter and colder. It can also aid in increasing the risk of severe weather in the winter.

We left the El NI‎ño phase during the summer and we are beginning to enter the a more neutral phase. It’s not quite El Ni‎ño, but it’s not quite La Ni‎ña. It’s somewhere in the middle.

For the next three months, there is a good chance we will see neutral conditions in the equatorial Pacific; therefore, no El Ni‎ño or La Ni‎ña. The Climate Prediction Center gives between a 55 to 60 percent chance of encountering neutral conditions, while having nearly a 40 percent chance of La Ni‎ña conditions (cooler waters off the South American coast).

What to expect: Rainfall.

If you like getting caught in the rain and/or piña coladas, I might have some bad news for you. You can still consume the aforementioned drink, but the likelihood recording below average rain amounts will be increased, according to the Climate Prediction Center’s forecast for the next three months.

As water temps in the Pacific are expected to be above normal, we could see the tracks for storms farther north. This pattern would leave us high and dry. Some portions of the northern U.S. Rockies and Alaska could see a better chance of above normal rainfall.

What to expect: Temperatures.

It could be warmer. It could be colder. It could be just right.

The CPC is calling for equal chances for seeing above normal, below normal, or average conditions from October to December.

The CPC noted “uncertainty” in their forecast for their reasoning with equal chances for the three-month period. However, some long-range models are hinting at the warmth for much of the U.S. - including our viewing area - during the next month. The CPC's October outlook has higher chances of above normal temps for our region. If you like the cooler temps, chances are greater that will not get as cool as it could be.

Keep in mind that this will not mean will never see rain or cooler weather. Weather patterns at any given moment could change things in the short term. These seasonal predictions encompass an entire season.

We’ll have another outlook for winter 2016-17 when we get close to that time.