Midweek Post 09/28/2017...September Projection

What a comeback! After nearly 2 weeks of Fall-like temperatures earlier this month, the longest stretch of 90 degree heat ends today in Louisville. Eight consecutive days in the 90's beat out the previous streak of 7 in July. In addition, the entire state's average temperatures increased. What was once expected to be an impressive below normal month now shows several reporting stations (at least NWS offices) going to be near normal or even above normal.

Here is a look at the NWS offices in Kentucky and their temperature departure from average as of this morning, the 28th...

Louisville..........+0.3
Lexington..........+0.1
Bowling Green...-0.5
Frankfort............+0.6
Jackson...............-0.2
London...............-1.2
Paducah.............+1.7

However, we have transitioned again to our Fall-like pattern, but maybe only for a few days. Yet, it may be enough to help offset these averages just a bit for the rest of this month.

So, what did I come up?

Projection time....

My information is taken from the F-6 form at weather.gov, a preliminary form of the monthly climatic data. If you look just below the last calendar day entry, on the left hand side, you will note a sum (SM) with a couple sets of 4 digit numbers like this...

SM 2216  1646

This represents the sum of the high temperatures from the one column and the sum of the low temperatures from the next column.

I total these together.

Next, find the average temperature for the month then multiply by 30 days and multiply again by 2 for another total sum.

Now, compare the total sum for 'average' with the current total sum in the sample above.

Subtract the current sum from the monthly 'average' sum.

Look at the area forecast for the rest of the month and add the forecast high and low temperatures through midnight of the last day of the month.

How does this compare with the 'average'? Is it higher? Lower?

Sounds complicated, but not really.

Let me walk you through Louisville's F-6 sheet...

SM  2211  1669......Current Sum = 3880
Average temperature for September is 71.0 degrees (found on another page)
Multiply 71.0 by 30 days = 2130
Multiply by 2 (for combining high and low)
Average September Total Sum = 4260
Subtract Current Sum from 'Average' Sum = 380
Expected Forecast temperatures total...
   low temp from this morning = est. 60
   high temp 28th = 75
   low temp 29th = 53
   high temp 29th = 76
   low temp 30th = 51
   high temp 30th = 71

Add those numbers to get 386
This number is greater than the 380 just to reach normal
Therefore, the forecast or projection is for a total of 3880+386=4266
Divide 4266/30 days to get combined high/low 142.2
Divide by 2 to get overall average of 71.1
71.1 is greater than the 'average' for September of 71.0
Therefore, projection is Louisville to finish the month 0.1 degrees above normal

Lexington should finish at normal or 0.1 degrees above normal depending on how they round the numbers.

Jackson looks to finish right at normal, even slightly above but not enough for rounding up.

Frankfort and Paducah should finish above normal.

Bowling Green and London should finish the month below normal

There you go. Only 2 out of the 7 forecast centers that I follow are projected to be below normal. Oh, by the way, the Louisville Bowman Field area, the WFO, the one with less concrete than the official site, may actually finish at least 0.3 degrees above normal, kind of surprising compared to the official site.

MS