Meteorological Fall Begins Today

Even though astronomical fall does not begin until September 22, today is the beginning of meteorological fall. What’s the difference? The seasons we are accustomed to seeing on calendars are known as the astronomical seasons, which are based on the Earth’s orbit of the Sun. Astronomical fall marks the day that both the northern and southern hemispheres see an equal amount of daylight.

The-Astronomical-Seasons
Courtesy: NOAA

Meteorological seasons are based on our annual temperature cycle. Winter includes the coldest months, summer includes the hottest months, with spring and fall falling in between the two.

Winter – December, January, February

Spring – March, April, May

Summer – June, July, August

Fall – September, October, November

So now that it is officially meteorological fall in Bowling Green, we can take a look at how our summer fared. The folks from NWS Louisville released a summer summary for Kentucky today. Bowling Green had an average temperature of 76.5° this summer which is 0.6º below normal. Our total rainfall was 15.58″ which is 4″ above normal.

Most of our rainfall occurred during the Month of August when the Bowling Green Airport picked up a record 11.33″ of precipitation. Temperatures were a bit on the warm side during August, our average monthly temperature was 0.6º above normal. For more info, check out this August summary from NWS Louisville.

So how are things looking now that we have entered fall? In the latest outlook from the CPC, temperatures are forecast to remain near normal during the month of September. Temperatures are expected to be warmer than normal across the eastern and western coasts, with temperatures expected to be below normal in portions of the upper Midwest.

Courtesy: CPC
Courtesy: CPC

In the monthly precipitation outlook, September is forecast to be near normal in Kentucky with a large portion of the Midwest expected to be wetter than normal. Things look to stay dry in the Pacific Northwest where some areas really need rain to aid in drought relief.

off15_prcp
Courtesy: CPC

Just for grins, below is the GFS precipitation forecast for the first half of the month. This model forecasts 1.5-1.75″ of rainfall in southern Kentucky which is near-normal. One interesting note is that the axis of highest precipitation amounts lines up well with the CPC’s forecast.

gfs_namer_384_precip_ptot
12Z GFS Total Precipitation Amounts valid from today until 7am September 17 (Courtesy: NOAA)

It is important to remember that long range-forecasts are not very accurate. The outlooks from the CPC are meant to be used as guidance and are not produced to be taken as a forecast that is set in stone. Additionally, model guidance is not very accurate beyond four or five days, and this precipitation forecast from the GFS will likely change many times over the next few runs.

In reality, we will just have to see what September has in store for us. It will be interesting to see if the rainy pattern we saw in August rolls over into the start of Fall.