Wednesday, September 04, 2013

The Fall Outlook


Once again, I want to congratulate Linda Bissell for winning the 2013 Summer Contest.  Look for the winter contest to crank up in a couple of months. 

Now onto the outlook this fall.  Many of you are shaking your heads right now wondering what I'm doing.  As you know, I don't like long range forecasting.  I have seen more wrong than right over the years.  I know there is great interest in this so I'll try to shed some light on what to expect.

Let's first look at the past year so far in terms of temperature.  With the exception of January and June, EVERY month has been at or below average.  The only month we ended exactly on average was February.  March, April, May, July, and August have all had below average temperatures.

How about precipitation?  That water is a little muddy here (pun intended).  So far this year, 4 months have had above average precipitation amounts and 4 months have had below average amounts.

This time of year we look to the tropics for our rainfall, especially in September.  By October, our pattern becomes more dominated by fronts coming out of the north and we rely more on mid latitude extratropical systems for our rainfall.  The hurricane season peaks in about a week when we look at climatology and so far it has been very quiet.  Looking at the long range models (7-10 days), there does appear to be a weak tropical feature that may affect the Texas coast next week.  This will bring excessive rains to that area, but it's likely to stay south of us.  That takes us into the middle to end of September with our best chance for tropical rainfall.  While some rain sounds nice, especially since many counties in southern Arkansas are under a burn ban and the wildfire danger is elevated, tropical rains can do more harm than good.  They usually produce significant flooding and tornadoes. 

At this point, I would say this fall has a better chance temperatures will end up below average.  That's considering the months of September, October, and November.  This is primarily based on trends over the past 8 months.   In terms of rainfall, NOAA says there's a higher than average confidence level for above average rainfall and I'll show you that map below.

Looks like my kids went crazy with the crayons. LOL.  Each line represents a tropical system in September from 1980 to 2008.  You can see several tracks near or right through Arkansas.  If we get remnant tropical systems, this is the peak month for that.
This shows you tropical systems in October from 1980 through 2008.  Notice there are fewer storms and fewer tracks across our region of the country.  The storms mainly affect Florida up the east coast and out in the Atlantic Ocean.  This is primarily due to a more active jet stream moving south as we go deeper into fall and towards the winter months.  These troughs help steer much of the activity away from us in October.  While tropical systems are possible, the chance decreases in October.
NOAA says there are "Equal Chances" for average, below average, and above average temperatures for September, October, and November.  I cringe every time they do this!!!!!!!!!  If I went out and said there was a 50/50 chance for precipitation everyday, I would never be wrong, right?  At least take an educated guess! LOL.  Anyway, as I stated above, I would say there's a better chance for temperatures to end the fall below average.
NOAA precipitation chances through the fall indicates a higher confidence for above average precipitation.  The area outlined from AR to the Great Lakes makes me believe they are banking on an increase in fronts diving out of Canada in October and November to produce these results.  We'll see.

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