@TrentMWeather yeah that's why I didn't even try, way too steep.
10
Aug
2011 Now hottest feeling year on record?
There is little doubt that this has been a very hot summer, likely an understatement for many. On a strictly temperature stand point though it’s only currently the 5th hottest on record since 1939 and the 7th hottest since 1878. There’s a split there because from 1878-1939 the temperatures in Charlotte were taken uptown at the post office. Then in 1939 the temperature observations were moved to their current location at the airport.
Though based on another metric this has now become the hottest feeling summer ever. I’m talking about the heat index, or the “feels like” reading. Which if you remember is a calculation of the heat and humidity together and how it makes a human being feel. Remember this post about the heat index back in July. (The Heat Index & Records for Charlotte)
This year so far we have officially surpassed the most number of hours with a heat Index of 100° or higher since these records have been kept. Which only started back in 1972 which is 39 years ago.
Today we stand at 131 hours of 100° Heat Indices or higher
You should note that 1999 and 1983 had more hours of 105° plus which made them feel likely even hotter. This summer has had the most combined hours above 100°. If you like you can see the complete rundown of data below. Remember, we still have over a month left in astronomical summer!
Heat Index Counts for KCLT from 1972 through 2011
Year
100-104
105-109
110-114
≥115
Total
1972
5
0
0
0
5
1973
11
0
0
0
11
1974
3
0
0
0
3
1975
12
0
0
0
12
1976
4
0
0
0
4
1977
98
5
0
0
103
1978
40
8
0
0
48
1979
34
0
0
0
34
1980
80
10
0
0
90
1981
31
1
0
0
32
1982
2
0
0
0
2
1983
52
25
4
0
81
1984
2
0
0
0
2
1985
10
0
0
0
10
1986
73
0
0
0
73
1987
64
0
0
0
64
1988
46
5
0
0
51
1989
13
0
0
0
13
1990
37
0
0
0
37
1991
76
2
0
0
78
1992
29
0
0
0
29
1993
100
4
0
0
104
1994
3
0
0
0
3
1995
44
0
0
0
44
1996
9
0
0
0
9
1997
0
0
0
0
0
1998
24
0
0
0
24
1999
56
31
5
0
92
2000
26
0
0
0
26
2001
26
3
0
0
29
2002
47
1
0
0
48
2003
11
0
0
0
11
2004
0
0
0
0
0
2005
40
6
0
0
46
2006
29
1
0
0
30
2007
44
3
1
0
48
2008
17
0
0
0
17
2009
10
0
0
0
10
2010
111
18
1
0
130
2011
105
26
0
0
131
Sum
Avg1424
36149
411
00
01584
40
25
Jul
Heat Index Counts
The heat has been big news for the past few weeks as much of the country has baked under a large ridge of high pressure. While the temperatures and those records have been impressive.
I have been impressive at the Heat Index or how it feels to you and I and how that has been abnormally high. Remember I blogged about the Heat Index before and what it actually means. In this post I thought I’d look at the climatology of the Heat Index at locations that have been keeping such records since 1972. The following are all graphs of the number of hours the Heat Index value was above 100° or more at selected large cities in the Carolinas. This does include this year up through Sunday 7/24/11.
Charlotte, NC
Greensboro, NC
Raleigh, NC
Asheville, NC (Proving once again the mountains are awesome, 
)
Greer, SC (GSP)
Columbia, SC
Charleston, SC
18
Jul
The Heat Index & Records for Charlotte
With another impeding heat wave bearing down on the Carolinas. I thought I’d help explain what the Heat Index really is. In it’s purely mathematical form the calculation is as follows.
Heat Index = 16.923 + ((1.85212 x 10-1) x T)
+ (5.37941 x RH)
- ((1.00254 x 10-1) x T x RH)
+ ((9.41695 x 10-3) x T2)
+ ((7.28898 x 10-3) x RH2)
+ ((3.45372 x 10-4) x T2 x RH)
- ((8.14971 x 10-4) x T x RH2)
+ ((1.02102 x 10-5) x T2 x RH2)
- ((3.8646 x 10-5) x T3)
+ ((2.91583 x 10-5) x RH3)
+ ((1.42721 x 10-6) x T3 x RH)
+ ((1.97483 x 10-7) x T x RH3)
- ((2.18429 x 10-8) x T3 x RH2)
+ ((8.43296 x 10-10) x T2 x RH3)
- ((4.81975 x 10-11) x T3 x RH3)
where T is the dry bulb temperature (°F) and RH is relative humidity (%)
Looks crazy doesn’t it? Well it is when you think about it the Heat Index is really a measure of how the human body reacts to the combination of heat and humidity. More to the point how efficiently or in this case inefficiently it cools itself. So to calculate that you need lots of data besides the temperature and relative humidity. You need to know things like the surface area of an average human, rate of heat loss through skin, evaporative cooling, sweating…etc. So you can see lots of biology is in this as well as meteorology. This calculation is about how your body cools itself and the more humidity the less evaporation of sweat from your skin. This inefficiency makes you feel hotter, thus the Heat Index.
Here’s an easier way to understand it by just using this simple chart.
So lets look at some of the climatology of the Heat Index in Charlotte. Last week South Carolina set a state record for the highest Heat Index in the 20 years of record keeping at 124°. This was in Mount Pleasant, SC.
For Charlotte our worst year of Heat Indices was last summer which actually wasn’t our hottest ever for air temperatures. We’ve never gone above 114°. 2010 was more about the high heat Index values though it was plenty hot out there.
Notice last year we heat a Heat Index of 100°-104° or more for 130 hours.
We hit 105°-109° for 18 hours
We had 1 hour of a Heat Index of 110°-114°
We are way behind last years pace but we still have half the summer to go. Here’s a look at every year since these types of records have been kept. (Via The NC state Climate Office)
Heat Index Counts for KCLT from 1972 through 2011
Heat Index Climatology: Output
Year
100-104
105-109
110-114
≥115
Total
1972
5
0
0
0
5
1973
11
0
0
0
11
1974
3
0
0
0
3
1975
12
0
0
0
12
1976
4
0
0
0
4
1977
98
5
0
0
103
1978
40
8
0
0
48
1979
34
0
0
0
34
1980
80
10
0
0
90
1981
31
1
0
0
32
1982
2
0
0
0
2
1983
52
25
4
0
81
1984
2
0
0
0
2
1985
10
0
0
0
10
1986
73
0
0
0
73
1987
64
0
0
0
64
1988
46
5
0
0
51
1989
13
0
0
0
13
1990
37
0
0
0
37
1991
76
2
0
0
78
1992
29
0
0
0
29
1993
100
4
0
0
104
1994
3
0
0
0
3
1995
44
0
0
0
44
1996
9
0
0
0
9
1997
0
0
0
0
0
1998
24
0
0
0
24
1999
56
31
5
0
92
2000
26
0
0
0
26
2001
26
3
0
0
29
2002
47
1
0
0
48
2003
11
0
0
0
11
2004
0
0
0
0
0
2005
40
6
0
0
46
2006
29
1
0
0
30
2007
44
3
1
0
48
2008
17
0
0
0
17
2009
10
0
0
0
10
2010
111
18
1
0
130
2011
30
10
0
0
40
Sum
Avg1349
34133
311
00
01493
37
31
May
The First Warn Outdoor Index
Here’s today’s First Warn Outdoor Index for Tuesday May 31, 2011
Here’s what it means:
Earlier this year I starting thinking about a way to help people to understand and deal with summer time weather. In particular kids going to the YMCA of Greater Charlotte summer camps. They had approached me about doing some summer heat education and safety talks. So I started to develop what I call the Outdoor Index. It takes 3 widely used indicies that are used most often during the summer months. The Heat Index, the Air Quality Index and the UV index. Now all of these can have significant impacts on your outdoor activities, but not equally in my onion. So I weighted them based on the biggest impacts to everyone.
The first is the Heat Index, which many people are already all too familiar with. This is your basic “Feels Like” temperature based on the combination of heat and humidity. This is the most important factor in the Outdoor Index because it affects everyone and really impacts your bodies ability to cool itself. Using the scale below I assign a numeric value from 1-10.
Next is the Air Quality index and a common problem when we get stagnate air masses during the summer months in the Carolinas. While I certainly don’t want to diminish the impacts of poor air quality. It most often only impacts those with poor respiratory health or the very young and old. On very rare occasions when it’s quite high it impacts us all. It gets the second highest weight in the Outdoor Index. Same as above a 1-10 scale is used to assign a value.
Last but not least in the UV index. Now everyone should be protecting their skin from the sun due to the increased risk of skin cancer. With that said the UV index on any given day during the summer is above 8 an often 10+. If it’s sunny you need to protect yourself. So not to constantly skew the Outdoor Index it was given the lowest weight. Plus no matter the number on the Outdoor Index you should always be safe and protect yourself form UV. It will be something I’ll try always mention in my forecast.
So after getting all those values above you use the formula below and you end up with our exclusive Frist Warn Outdoor Index.
So today is Tuesday and today’s Outdoor Index is a 6.4. This was based on taking a 106 AQI = 4 , Heat index 102 = 7 and UV index of 10=1. Plugging those number into the formula and getting a number that then will fall in the scale above. I will always round to the nearest whole number to simplify this.
Now this index is not to discourage people from doing outdoor activities. Just the opposite it’s to inform you so you can prepare and do it safely. Most people know what they can tolerate so knowing what to expect can help make a decision how what and how you do your outdoor activities this summer.
