Camelot Climate Index

CAMELOT

It's true! It's true!
The crown has made it clear:
The climate must be perfect all the year.

A law was made a distant moon ago here,
June, July and August cannot be too hot;
And there's a legal limit to the snow here...
In Camelot.

The winter is forbidden till December...
And exits March the second on the dot.
By order summer lingers through September...
In Camelot.

I know it sounds a bit bizarre.
But in Camelot, Camelot,
That's how conditions are.

The rain may never fall till after sundown,
By eight the morning fog must disappear.
In short, there's simply not,
A more congenial spot
for happy everaftering than here
In Camelot.

~Alan Jay Lerner (1960)

click map to enlarge

CAMELOT CLIMATE INDEX

In this1960's musical King Arthur professes that Camelot has a perfect climate all the year; and by royal decree at that! But actually an "ideal" climate is extremely subjective, with one person's idea of perfection being met with disdain by others. Some individuals may want warm beach weather all year round, while four distinct seasons are most desirable for others. What follows is just one person's (the author's) idea that an ideal climate is sunny and relatively mild with few extremes in temperature, humidity or precipitation.

Dataset
Data for this project was extracted from the Comparative Climatic Data for the United States (NCDC, 1998). Nine different weather elements were used in constructing an index of ideal weather; a Camelot Climate Index (CCI). These parameters are: maximum temperatures, minimum temperatures, mean number of days with minimum temperatures less than 32º F, mean number of days with maximum temperatures greater than 90º F, mean annual rainfall, mean number of days with precipitation, mean annual snowfall, average percent of sunshine, and average relative humidity. The average monthly maximum temperature and corresponding afternoon relative humidity were combined to derive a monthly temperature humidity index (THI) which is a measure of "discomfort".

The initial Comparative Climatic Data (CCC) analyzed has approximately 300 locations from all fifty states, Puerto Rico and 10 Pacific island stations. This represents ninety major urban areas by stations within thirty miles. Unfortunately, not all of the meteorological parameters are available for all of the stations. In particular, some stations do not regularly record relative humidity and sunshine. The most limiting factor was the lack of data for the percent of possible sunshine data, with only 158 stations having all the requisite parameters.

Maximum Temperature
Because of the strong relationship between discomfort due to high temperature and high humidity, it was decided combine these factors using the temperature-humidity index (THI) using THI = Td-(0.55-0.55RH)(Td-58) where Td is the dry bulb temperature and RH is the relative humidity. A THI value was calculated for each month using the average maximum temperature and the average afternoon relative humidity. If the monthly THI was less than 75 degrees, then a value of 0 was assigned to the month. This threshold was chosen because statistically at least half of people feel uncomfortable with a THI greater than 75. If the THI was between 75 and 85 it was given a value of 1, between 85 and 95 a 2, between 95 and 105 a 3 and if it was 105 or greater a value of 4 was assigned to that month. The assigned monthly values were then summed to get an annual Temperature Humidity Index (THI). Additionally, the average annual number of days when the maximum was above 90 degrees (MAX90).

Minimum Temperature
The average monthly minimum temperatures were handled similarly. If the monthly minimum (MIN) was greater than 45 degrees, then a value of 0 was assigned to the month. If the monthly minimum was between 45 and 35 it was given a 1, between 35 and 25 a 2, between 25 and 15 a 3 and if it was 15 or less a value of 4 was assigned to that month. The assigned monthly values were then summed to get an annual minimum value (MIN). Data was also used for the average annual number of days when the minimum was below 32 degrees (MIN32).

Precipitation Data
The precipitation data set included several types of data. The annual average rainfall (RAIN) for each station was the primary data. Also the average number of days when measurable rain (i.e., greater than or equal to .01 inch) fell was used (RAIN01). The final precipitation parameter was the annual average snowfall expressed inches (SNOW).

Sunshine Data
The final data subset used was the annual percentage of possible sunshine (SUN). These values are derived by calculating the total time that sunshine reaches the station as a percentage of the maximum amount of possible from sunrise to sunset.

Index Calculation
Equal weight was given to each of the data categories in calculating the Camelot Climate Index (CCI). Thus the combination of maximum temperature, minimum temperature, precipitation and sunshine each account for 25% of the total index. Within the maximum temperature category, The THI was weighted as 10% and MAX90 as 15% of the total CCI. The minimum temperature group was weighted with MIN32 as 20% and MIN as 5%. In the precipitation group RAIN was weighted as 15%, RAIN32 as 5% and SNOW as 5%.

The maximum value for each category was used to set the "best possible" for that category. This was divided by the weight given that parameter to derive an overall rating factor. For example: the highest value of MAX90 was 170 days (at Yuma, AZ), and MAX90 has a weight of 15%, giving a weighting factor of 11.3, which is expressed as MAX90wf. The only exception to this was with the sunshine data, where the "ideal" condition would be 100% sunshine, thus the percent of sunshine received is subtracted from 100 initially, then divided by the given weight.

The total CCI for each station was derived by subtracting the weighted value for each parameter from a value of 100, which would be "perfect" weather. It takes the form:
CCI=100-(THI/THIwf)-(MAX90/MAX90wf)-(MIN/MINwf)-
(MIN32/MIN32wf)-(RAIN/RAINwf)-(RAIN01/RAIN01wf)-
(SNOW/SNOWwf)-((100-SUN)/SUNwf)

CCI Map
The accompanying iso-analysis (isocams?) is rudimentary at best given the limited dataset. Especially given the fact that no effort was made to draw for topography and there are undoubtedly areas, mostly in and around mountainous terrain, where an intermediate point would vary greatly from the rather crude analysis.

Conclusions
A project like this sort is by nature extremely subjective, as everyone's "ideal" climate is different. Even by quantifying a relatively small climatic dataset, numerous subjective choices had to be made, including which climatic factors to choose and how much weight to give to each.

And remember the primary assumptions for this study are based upon a 1960's musical about a mythical land with a mild dry "perfect" climate as expressed by mythical King Arthur! Consequently, cities with dry, mild and temperate climates ended up at the top of the Camelot Climate Indices. If a similar project was done by a storm chaser it might be called the Oz Climate Index with a bias towards the number of thunderstorm days, hail and tornadoes.

Rank	CITY	CCI	THI	MAX90	MIN	MIN32	RAIN	RAIN01	SNOW	SUN
1	SAN DIEGO CA	88	3	3	0	0	9	42	0	68
2	SAN FRANCISCO CA	86	0	1	4	0	19	68	0	66
3	SAN JOSE CA	86	3	9	0	5	14	42	0	68
4	LOS ANGELES CA	85	7	20	0	0	15	36	0	73
5	EUREKA CA	78	0	0	5	5	39	118	0	50
6	HONOLULU HI	78	19	9	0	0	23	100	0	68
7	SACRAMENTO CA	78	10	77	5	16	17	58	0	77
8	KEY WEST FL	76	17	43	0	0	39	109	0	75
9	GALVESTON TX	75	10	35	0	4	40	96	0	62
10	APALACHICOLA FL	75	11	23	0	7	55	105	0	67
11	FRESNO CA	75	12	110	5	21	11	45	0	78
12	LAS VEGAS NV	74	13	132	7	33	4	26	1	85
13	SEATTLE WA	74	0	2	6	17	39	157	16	43
14	CAPE HATTERAS NC	74	6	4	4	33	56	119	2	59
15	YUMA AZ	74	18	170	2	1	3	17	0	90
16	SEATTLE AP WA	74	0	3	7	31	39	152	8	46
17	RED BLUFF CA	74	11	103	5	20	21	72	2	77
18	EL PASO TX	73	11	103	8	63	8	48	5	83
19	MIAMI FL	73	17	32	0	0	58	129	0	72
20	TUCSON AZ	73	15	139	4	18	11	53	1	86
21	WALLA WALLA WA	72	2	37	10	65	16	107	20	54
22	PHOENIX AZ	72	17	165	3	8	7	36	0	85
23	PORTLAND OR	72	2	10	8	43	37	153	7	47
24	ROSWELL NM	70	9	85	9	89	10	55	11	74
25	ATLANTA GA	70	8	19	8	57	49	115	2	61
26	ALBUQUERQUE NM	70	8	61	14	120	8	60	11	76
27	NORFOLK VA	70	8	30	8	55	45	114	8	62
28	LAKE CHARLES LA	70	14	69	3	15	53	99	0	70
29	CHARLESTON AP SC	70	11	48	4	36	52	113	1	65
30	CHARLOTTE NC	70	8	34	8	70	43	111	6	64
31	WILMINGTON NC	69	10	43	5	44	53	116	2	63
32	MIDLAND-ODESSA TX	69	15	97	8	63	14	52	4	74
33	AMARILLO TX	69	8	64	13	110	19	69	15	73
34	GREENVILLE SC	68	8	31	8	67	51	118	6	62
35	RALEIGH NC	68	8	23	8	80	42	111	7	59
36	NEW YORK CITY NY	68	6	16	10	80	44	121	29	58
37	LUBBOCK TX	68	10	79	10	95	18	62	11	72
38	TAMPA FL	68	17	85	0	4	47	107	0	66
39	GREENSBORO NC	68	8	28	8	84	42	116	9	61
40	BOSTON MA	68	3	11	12	98	44	127	41	58
41	OKLAHOMA CITY OK	68	11	64	8	80	31	82	9	68
42	BOISE ID	68	6	43	15	124	12	92	22	64
43	SAVANNAH GA	68	14	56	3	32	50	111	0	62
44	LYNCHBURG VA	68	7	22	9	92	40	119	18	59
45	WASHINGTON DC	67	8	37	8	71	39	112	17	57
46	ABILENE TX	67	15	97	7	54	23	66	5	70
47	PENSACOLA FL	67	14	55	3	17	61	109	0	60
48	GRAND JUNCTION CO	67	7	64	15	132	8	72	26	70
49	SAN JUAN P.R.	67	24	37	0	0	54	196	0	65
50	KNOXVILLE TN	67	8	19	8	74	47	127	12	55
51	CAIRO IL	67	8	48	8	67	48	112	10	61
52	CORPUS CHRISTI TX	67	19	102	0	7	30	77	0	62
53	ASHEVILLE NC	67	7	5	12	101	48	124	17	59
54	JACKSONVILLE FL	67	14	81	0	15	53	116	0	62
55	RENO NV	67	6	51	21	180	7	51	25	79
56	KANSAS CITY AP MO	67	8	45	11	98	29	98	20	62
57	RICHMOND VA	67	8	41	8	85	44	113	14	62
58	DALLAS-F WORTH TX	67	15	88	6	41	29	78	3	64
59	CHEYENNE WY	67	2	10	22	172	13	98	54	65
60	PHILADELPHIA PA	66	6	19	12	98	41	117	22	56
61	NEW ORLEANS LA	66	14	67	3	14	60	114	0	59
62	PUEBLO CO	66	7	65	17	155	11	69	31	76
63	BIRMINGHM AP AL	66	10	40	6	61	55	117	1	58
64	BROWNSVILLE TX	66	19	118	0	2	25	73	0	60
65	MEMPHIS TN	66	10	65	8	58	52	106	6	64
66	DENVER CO	66	6	32	18	158	15	88	60	70
67	PROVIDENCE RI	66	3	8	15	119	45	125	36	58
68	AUSTIN TX	66	15	105	3	22	32	83	1	60
69	BALTIMORE MD	66	6	31	11	98	42	113	21	57
70	OMAHA (NORTH) NE	66	3	24	16	138	30	103	33	60
71	LOUISVILLE KY	66	8	25	9	91	44	125	17	56
72	SALT LAKE CITY UT	66	6	59	15	125	15	91	59	66
73	CONCORDIA KS	66	7	49	16	128	27	90	23	68
74	GREAT FALLS MT	66	2	20	21	158	15	101	59	61
75	MACON GA	66	14	80	5	47	45	110	1	65
76	POCATELLO ID	65	4	33	12	170	11	96	43	63
77	ATLANTIC CITY NJ	65	5	17	13	109	42	112	16	54
78	SAN ANTONIO TX	65	15	113	3	23	29	82	1	60
79	HAVRE MT	65	2	27	24	179	11	90	45	67
80	FLAGSTAFF AZ	65	2	3	24	211	21	81	96	76
81	HARRISBURG PA	65	6	25	13	106	39	128	35	58
82	KANSAS CITY MO	65	7	38	14	110	35	107	20	61
83	SPOKANE WA	65	2	21	16	140	17	114	52	53
84	DODGE CITY KS	65	9	68	15	124	21	78	20	70
85	BILLINGS MT	65	3	30	19	149	15	96	57	60
86	PORT ARTHUR TX	65	15	80	3	16	53	104	0	58
87	SHREVEPORT LA	65	14	89	4	37	44	97	2	62
88	NASHVILLE TN	65	9	38	8	77	48	119	11	56
89	FORT WAYNE IN	65	5	14	15	130	34	131	33	58
90	ST. LOUIS MO	65	8	37	11	103	34	111	19	57
91	MONTGOMERY AL	65	14	71	4	40	49	108	0	59
92	LANDER WY	65	2	20	24	186	13	72	105	69
93	ELY NV	65	2	17	26	219	9	74	50	73
94	HOUSTON TX	65	15	83	3	22	45	106	0	56
95	EVANSVILLE IN	65	8	41	12	99	42	116	14	60
96	DAYTON OH	65	6	16	15	117	35	132	29	55
97	SPRINGFIELD IL	65	7	28	15	117	34	115	24	58
98	WICHITA KS	65	9	62	14	112	29	86	16	65
99	DES MOINES IA	64	6	21	16	135	31	107	35	59
100	SPRINGFIELD MO	64	8	44	12	103	39	108	17	60
101	COLUMBIA SC	64	14	66	8	63	49	109	2	65
102	INDIANAPOLIS IN	64	6	15	15	119	39	125	23	55
103	SIOUX CITY IA	64	6	24	19	149	25	99	32	62
104	CHATTANOOGA TN	64	9	48	8	75	53	120	4	57
105	LITTLE ROCK AR	64	12	71	8	62	49	104	6	62
106	TULSA OK	64	11	70	9	80	39	90	9	61
107	PEORIA IL	64	6	17	16	129	35	114	25	56
108	CINCINNATI AP OH	64	3	28	14	109	40	129	24	51
109	DETROIT MI	64	3	15	15	137	31	134	41	53
110	MILWAUKEE WI	64	3	9	18	142	31	125	47	54
111	TOPEKA KS	64	8	36	15	120	33	97	21	59
112	FORT SMITH AR	64	12	68	8	80	40	96	7	61
113	QUILLAYUTE WA	64	2	1	11	67	51	163	18	32
114	COLUMBIA MO	64	7	39	14	108	36	112	23	56
115	WILKES-BARRE PA	64	3	8	15	129	35	140	49	50
116	HELENA MT	64	2	18	23	184	11	96	48	59
117	CLEVELAND OH	63	3	8	15	124	35	156	54	49
118	MINNEAPOLIS MN	63	4	14	19	156	26	115	50	57
119	LINCOLN NE	63	7	44	16	143	27	93	29	62
120	RAPID CITY SD	63	5	31	22	168	16	97	39	62
121	HURON SD	63	5	31	22	170	19	93	39	63
122	COLUMBUS OH	63	6	13	15	119	37	137	29	49
123	TOLEDO OH	63	5	13	15	143	32	137	38	53
124	JACKSON MS	63	14	80	6	51	53	109	1	60
125	HARTFORD CT	63	4	20	15	136	44	127	49	57
126	TUPELO MS	63	12	79	8	61	56	104	6	62
127	CHICAGO IL	63	5	21	16	133	33	127	40	53
128	MILFORD UT	63	6	57	23	181	9	67	45	70
129	NORTH PLATTE NE	63	6	31	23	177	19	84	31	65
130	ROCHESTER NY	63	3	11	15	134	31	158	89	51
131	WILLISTON ND	63	3	23	25	188	14	93	40	61
132	MOLINE IL	63	6	22	16	135	37	114	31	55
133	GREEN BAY WI	62	3	6	21	161	28	122	46	53
134	VALENTINE NE	62	6	41	23	176	17	83	32	66
135	FARGO ND	62	3	14	24	180	20	100	36	57
136	PITTSBURGH PA	62	3	16	15	124	36	154	44	47
137	LANSING MI	62	3	11	18	149	30	140	49	51
138	PORTLAND ME	62	2	5	20	158	44	128	71	57
139	BISMARCK ND	62	4	21	24	185	15	97	41	59
140	BUFFALO NY	62	3	2	15	134	38	169	93	49
141	WINNEMUCCA NV	62	6	56	21	190	8	69	25	66
142	SHERIDAN WY	62	3	26	24	189	15	107	71	62
143	MADISON WI	61	4	11	21	163	31	119	42	54
144	ALBANY NY	61	4	8	18	150	36	135	65	52
145	BINGHAMTON NY	61	2	2	17	146	37	162	83	48
146	MISSOULA MT	61	2	21	22	184	13	124	48	53
147	GRAND RAPIDS MI	60	4	10	17	145	34	145	73	46
148	DULUTH MN	60	1	2	24	184	30	135	78	52
149	BURLINGTON VT	60	3	5	21	157	34	154	78	49
150	CONCORD NH	60	3	11	21	174	37	125	64	54
151	SYRACUSE NY	60	3	7	16	137	39	170	110	46
152	ALPENA MI	59	2	6	21	178	29	147	86	49
153	ANCHORAGE AK	59	0	11	24	191	15	115	68	44
154	ELKINS WV	58	3	2	16	143	43	171	72	41
155	SAULT ST MARIE MI	57	1	1	21	181	33	166	115	47
156	HILO HII	56	17	1	0	0	128	278	0	41
157	MARQUETTE MI	54	0	5	24	195	37	170	122	44
158	JUNEAU AK	52	0	19	20	145	53	220	102	30

	MAX	88	24	170	26	219	61	278	122	90
	MIN	52	0	0	0	0	3	17	0	30
	AVG	66	7	40	12	98	32	107	27	61