Soaring Guidance
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
008
UXUS97 KPUB 201210
SRGPUB
Soaring Forecast
National Weather Service Pueblo, Colorado
0610 MDT Friday, September 20, 2024
This forecast is for the Air Force Academy for Friday, September 20, 2024:
If the trigger temperature of 69.6 F/20.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1023 ft/min (5.2 m/s)
Maximum height of thermals.................. 19097 ft MSL (11491 ft AGL)
Forecast maximum temperature................... 84.0 F/29.3 C
Time of trigger temperature.................... 0945 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 17316 ft MSL (9709 ft AGL)
Thermal soaring outlook for Saturday 09/21..... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:45:59 / 18:58:55 MDT
Total possible sunshine........... 12 hr 12 min 56 sec (732 min 56 sec)
Altitude of sun at 12:52:27 MDT... 51.66 degrees
Upper air data from numerical model forecast valid on 09/20/2024 at 0600 MDT
Freezing level.................. 15070 ft MSL (7464 ft AGL)
Convective condensation level... 20258 ft MSL (12652 ft AGL)
Lifted condensation level....... 20083 ft MSL (12477 ft AGL)
Lifted index.................... -0.7
K index......................... +3.4
Height Temperature Wind Wind Spd Lapse Rate ConvectionT Thermal Lift Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft deg C deg F Index fpm m/s
--------------------------------------------------------------------------------
50000 -65.2 -85.4 250 58 30 3.1 1.7 M M M M M
45000 -59.1 -74.4 250 75 39 6.1 3.3 M M M M M
40000 -50.0 -58.0 245 84 43 6.4 3.5 M M M M M
38000 -46.1 -51.0 245 84 43 6.4 3.5 M M M M M
36000 -41.8 -43.2 245 84 43 6.4 3.5 M M M M M
34000 -38.1 -36.6 245 78 40 6.2 3.4 M M M M M
32000 -34.4 -29.9 240 72 37 6.0 3.3 M M M M M
30000 -30.3 -22.5 240 63 32 6.9 3.8 38.4 101.1 7.4 M M
29000 -28.2 -18.8 235 58 30 6.9 3.8 37.4 99.2 6.6 M M
28000 -26.1 -15.0 235 53 27 7.3 4.0 36.4 97.6 6.0 M M
27000 -23.8 -10.8 235 51 26 7.9 4.3 35.6 96.1 5.4 M M
26000 -21.5 -6.7 235 48 25 8.0 4.4 34.9 94.9 4.8 M M
25000 -19.1 -2.4 235 46 24 8.1 4.4 34.4 93.8 4.4 M M
24000 -16.8 1.8 235 44 23 7.3 4.0 33.5 92.3 3.8 M M
23000 -14.6 5.7 235 41 21 7.4 4.1 32.7 90.8 3.2 M M
22000 -12.3 9.9 235 39 20 7.6 4.2 31.9 89.5 2.6 M M
21000 -9.7 14.5 235 35 18 6.8 3.7 30.7 87.2 1.6 M M
20000 -7.6 18.3 230 31 16 6.8 3.7 29.7 85.4 0.7 M M
19500 -6.6 20.1 230 29 15 7.1 3.9 29.2 84.6 0.3 M M
19000 -5.8 21.6 230 27 14 4.2 2.3 28.5 83.4 -0.3 1010 5.1
18500 -5.1 22.8 230 24 12 4.5 2.5 27.6 81.7 -1.1 976 5.0
18000 -4.5 23.9 230 22 11 4.7 2.6 26.8 80.2 -1.9 942 4.8
17500 -3.8 25.2 235 21 11 4.7 2.6 25.9 78.7 -2.8 908 4.6
17000 -3.2 26.2 240 21 11 4.7 2.6 25.1 77.2 -3.6 874 4.4
16500 -2.5 27.5 240 21 11 6.0 3.3 24.4 75.9 -4.4 837 4.3
16000 -1.6 29.1 245 22 11 6.1 3.3 23.7 74.7 -5.1 798 4.1
15500 -0.8 30.6 245 23 12 6.8 3.7 23.2 73.7 -5.7 758 3.9
15000 0.2 32.4 250 23 12 7.1 3.9 22.7 72.9 -6.2 714 3.6
14500 1.2 34.2 250 24 12 7.6 4.2 22.3 72.2 -6.7 670 3.4
14000 2.3 36.1 250 24 13 8.6 4.7 22.1 71.8 -7.1 619 3.1
13500 3.6 38.5 250 25 13 8.7 4.8 21.9 71.5 -7.3 568 2.9
13000 5.0 41.0 255 24 13 10.6 5.8 22.0 71.5 -7.4 510 2.6
12500 6.4 43.5 255 24 12 9.2 5.0 21.9 71.5 -7.5 453 2.3
12000 7.8 46.0 255 24 12 9.0 4.9 21.8 71.3 -7.6 397 2.0
11750 8.5 47.3 255 24 12 9.2 5.1 21.8 71.2 -7.7 370 1.9
11500 9.2 48.6 255 24 12 10.6 5.8 21.8 71.2 -7.7 340 1.7
11250 10.0 50.0 255 24 12 9.7 5.3 21.8 71.3 -7.6 309 1.6
11000 10.6 51.1 255 23 12 8.2 4.5 21.8 71.2 -7.7 282 1.4
10750 11.2 52.2 255 23 12 7.5 4.1 21.6 70.9 -7.9 257 1.3
10500 11.9 53.4 255 23 12 10.2 5.6 21.5 70.7 -8.0 231 1.2
10250 12.8 55.0 255 22 11 11.4 6.2 21.7 71.0 -7.9 197 1.0
10000 13.5 56.3 255 21 11 8.2 4.5 21.6 70.9 -7.9 167 0.9
9750 14.1 57.4 260 20 10 7.6 4.2 21.5 70.7 -8.0 142 0.7
9500 14.7 58.5 260 19 10 7.9 4.4 21.3 70.4 -8.2 116 0.6
9250 15.3 59.5 260 18 9 7.2 3.9 21.2 70.1 -8.3 91 0.5
9000 15.8 60.4 260 17 9 6.6 3.6 20.9 69.7 -8.6 69 0.3
8750 16.3 61.3 265 16 8 5.8 3.2 20.7 69.2 -8.8 47 0.2
8500 16.8 62.2 265 15 8 8.9 4.9 20.4 68.8 -9.1 25 0.1
8250 17.2 63.0 270 14 7 -2.6 -1.4 20.2 68.4 -9.4 3 0.0
8000 15.9 60.6 270 12 6 -32.7 -18.0 18.1 64.6 -11.5 36 0.2
7750 12.6 54.7 270 10 5 -48.0 -26.4 14.2 57.5 -15.5 126 0.6
7500 M M M M M M M M M M M M
7250 M M M M M M M M M M M M
7000 M M M M M M M M M M M M
6750 M M M M M M M M M M M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/20/2024 at 0900 MDT | 09/20/2024 at 1200 MDT
|
CAPE... 0.0 LI... +3.3 | CAPE... 0.0 LI... +1.8
CINH... 0.0 K Index... -13.0 | CINH... 0.0 K Index... -16.1
|
Height Temperature Wnd WndSpd Lapse Rate | Temperature Wnd WndSpd Lapse Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft | deg C deg F Dir kt m/s C/km F/kft
--------------------------------------------------------------------------------
50000 -64.4 -83.9 250 56 29 1.9 1.0 | -62.9 -81.2 250 49 25 1.0 0.5
45000 -59.7 -75.5 245 77 40 6.1 3.3 | -59.4 -74.9 245 78 40 5.6 3.1
40000 -50.5 -58.9 240 83 43 6.6 3.6 | -50.9 -59.6 240 87 45 6.9 3.8
38000 -46.6 -51.9 240 83 43 6.6 3.6 | -46.8 -52.2 240 86 44 6.8 3.8
36000 -42.6 -44.7 240 82 42 6.6 3.6 | -42.2 -44.0 240 84 43 6.9 3.8
34000 -38.6 -37.5 240 75 39 5.9 3.2 | -38.5 -37.3 235 78 40 6.0 3.3
32000 -35.0 -31.0 240 68 35 5.7 3.1 | -34.9 -30.8 235 71 37 5.8 3.2
30000 -30.8 -23.4 235 61 31 7.3 4.0 | -30.9 -23.6 235 63 32 6.9 3.8
29000 -28.6 -19.5 235 57 29 7.3 4.0 | -28.8 -19.8 230 59 30 6.9 3.8
28000 -26.4 -15.5 235 53 27 7.5 4.1 | -26.8 -16.2 230 54 28 7.1 3.9
27000 -24.1 -11.4 235 51 26 7.9 4.4 | -24.5 -12.1 230 52 27 7.8 4.3
26000 -21.7 -7.1 235 49 25 8.0 4.4 | -22.1 -7.8 230 50 26 7.9 4.3
25000 -19.4 -2.9 235 46 24 8.1 4.4 | -19.8 -3.6 230 48 25 7.9 4.3
24000 -17.1 1.2 235 44 23 7.5 4.1 | -17.6 0.3 230 47 24 7.2 3.9
23000 -14.8 5.4 235 42 22 7.6 4.1 | -15.4 4.3 230 45 23 7.2 4.0
22000 -12.5 9.5 230 41 21 7.8 4.3 | -13.2 8.2 230 43 22 7.4 4.1
21000 -10.0 14.0 230 38 19 6.3 3.4 | -10.9 12.4 235 41 21 5.7 3.2
20000 -8.1 17.4 230 35 18 6.3 3.4 | -9.1 15.6 235 39 20 5.7 3.2
19500 -7.2 19.0 230 34 18 6.3 3.5 | -8.3 17.1 235 37 19 5.6 3.1
19000 -6.3 20.7 230 33 17 5.8 3.2 | -7.3 18.9 235 36 19 6.9 3.8
18500 -5.4 22.3 230 32 16 5.8 3.2 | -6.3 20.7 240 35 18 6.8 3.7
18000 -4.5 23.9 230 30 16 5.0 2.7 | -5.3 22.5 240 34 17 7.0 3.8
17500 -3.9 25.0 230 29 15 4.0 2.2 | -4.2 24.4 240 32 16 7.3 4.0
17000 -3.4 25.9 230 27 14 4.2 2.3 | -3.1 26.4 240 30 16 7.6 4.2
16500 -2.8 27.0 230 25 13 4.3 2.3 | -2.3 27.9 240 28 14 4.0 2.2
16000 -2.3 27.9 230 23 12 4.6 2.5 | -1.7 28.9 240 25 13 4.7 2.6
15500 -1.6 29.1 230 21 11 7.9 4.4 | -1.1 30.0 240 22 11 6.4 3.5
15000 -0.3 31.5 230 19 10 9.2 5.1 | -0.2 31.6 235 18 9 7.2 3.9
14500 1.1 34.0 225 18 9 9.4 5.2 | 0.7 33.3 235 14 7 8.1 4.5
14000 2.5 36.5 225 17 9 9.5 5.2 | 2.1 35.8 235 13 7 9.3 5.1
13500 3.9 39.0 225 17 9 9.5 5.2 | 3.5 38.3 235 12 6 9.3 5.1
13000 5.4 41.7 225 16 8 10.1 5.5 | 5.0 41.0 235 11 6 10.4 5.7
12500 6.7 44.1 225 15 8 8.4 4.6 | 6.3 43.3 230 10 5 8.5 4.7
12000 7.9 46.2 225 14 7 9.2 5.1 | 7.6 45.7 225 8 4 8.7 4.8
11750 8.6 47.5 230 13 7 9.1 5.0 | 8.2 46.8 220 8 4 9.2 5.0
11500 9.2 48.6 230 13 7 9.0 4.9 | 9.0 48.2 215 7 4 10.9 6.0
11250 9.9 49.8 230 12 6 8.6 4.7 | 9.8 49.6 210 6 3 10.1 5.5
11000 10.5 50.9 230 11 6 8.3 4.6 | 10.4 50.7 205 6 3 8.6 4.7
10750 11.1 52.0 235 11 6 8.1 4.5 | 11.1 52.0 200 6 3 8.1 4.4
10500 11.7 53.1 235 10 5 9.0 4.9 | 11.7 53.1 195 6 3 10.5 5.8
10250 12.4 54.3 235 9 5 9.2 5.1 | 12.6 54.7 190 6 3 12.0 6.6
10000 13.1 55.6 235 8 4 8.3 4.6 | 13.4 56.1 190 6 3 9.7 5.3
9750 13.7 56.7 235 7 4 8.1 4.5 | 14.1 57.4 185 6 3 9.6 5.3
9500 14.3 57.7 235 6 3 8.9 4.9 | 14.8 58.6 180 6 3 9.4 5.2
9250 15.0 59.0 235 5 3 6.0 3.3 | 15.5 59.9 180 6 3 10.2 5.6
9000 15.3 59.5 235 5 2 5.1 2.8 | 16.3 61.3 175 6 3 10.6 5.8
8750 15.8 60.4 235 4 2 7.1 3.9 | 17.1 62.8 175 6 3 10.2 5.6
8500 16.3 61.3 235 3 1 7.1 3.9 | 17.9 64.2 170 6 3 10.0 5.5
8250 16.8 62.2 240 2 1 4.3 2.4 | 18.6 65.5 170 6 3 11.0 6.0
8000 16.9 62.4 260 2 1 3.0 1.7 | 19.6 67.3 165 6 3 17.3 9.5
7750 17.3 63.1 265 2 1 9.2 5.1 | 21.2 70.2 165 6 3 24.4 13.4
7500 M M M M M M M | M M M M M M M
7250 M M M M M M M | M M M M M M M
7000 M M M M M M M | M M M M M M M
6750 M M M M M M M | M M M M M M M
09/20/2024 at 1500 MDT | 09/20/2024 at 1800 MDT
|
CAPE... +0.6 LI... +1.3 | CAPE... 0.0 LI... +1.1
CINH... 0.0 K Index... +13.8 | CINH... 0.0 K Index... +10.7
|
Height Temperature Wnd WndSpd Lapse Rate | Temperature Wnd WndSpd Lapse Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft | deg C deg F Dir kt m/s C/km F/kft
--------------------------------------------------------------------------------
50000 -63.3 -81.9 245 50 26 2.1 1.1 | -64.2 -83.6 245 49 25 2.9 1.6
45000 -58.8 -73.8 245 80 41 5.1 2.8 | -58.8 -73.8 250 80 41 4.9 2.7
40000 -51.0 -59.8 240 91 47 6.7 3.7 | -51.2 -60.2 240 95 49 6.6 3.6
38000 -46.9 -52.4 235 90 46 6.7 3.7 | -47.3 -53.1 240 93 48 6.6 3.6
36000 -42.4 -44.3 235 88 45 6.7 3.7 | -43.3 -45.9 235 91 47 6.6 3.6
34000 -38.5 -37.3 235 83 43 6.5 3.5 | -38.8 -37.8 235 85 44 6.7 3.7
32000 -34.7 -30.5 235 78 40 6.3 3.5 | -34.8 -30.6 235 79 41 6.6 3.6
30000 -30.8 -23.4 235 69 36 6.5 3.6 | -31.1 -24.0 235 71 36 6.3 3.5
29000 -28.9 -20.0 235 65 33 6.5 3.6 | -29.2 -20.6 235 66 34 6.3 3.5
28000 -26.9 -16.4 235 60 31 6.7 3.7 | -27.3 -17.1 235 61 31 6.7 3.7
27000 -24.7 -12.5 230 57 29 7.5 4.1 | -25.1 -13.2 235 58 30 7.6 4.2
26000 -22.5 -8.5 230 55 28 7.5 4.1 | -22.8 -9.0 235 54 28 7.6 4.2
25000 -20.2 -4.4 230 52 27 7.5 4.1 | -20.5 -4.9 235 51 26 7.6 4.2
24000 -18.1 -0.6 230 50 26 6.9 3.8 | -18.3 -0.9 235 48 25 7.2 4.0
23000 -16.0 3.2 230 48 25 7.0 3.8 | -16.1 3.0 235 46 24 7.3 4.0
22000 -13.9 7.0 230 47 24 7.1 3.9 | -13.9 7.0 240 44 23 7.4 4.1
21000 -11.5 11.3 235 44 22 5.9 3.3 | -11.8 10.8 240 41 21 6.6 3.6
20000 -9.8 14.4 240 41 21 6.0 3.3 | -9.3 15.3 245 37 19 6.7 3.7
19500 -8.9 16.0 240 40 20 6.0 3.3 | -8.3 17.1 245 35 18 6.8 3.7
19000 -8.0 17.6 245 38 19 5.5 3.0 | -7.4 18.7 245 32 17 5.6 3.1
18500 -7.2 19.0 245 35 18 5.8 3.2 | -6.6 20.1 245 28 15 5.9 3.2
18000 -6.5 20.3 245 33 17 6.9 3.8 | -5.8 21.6 245 25 13 6.8 3.7
17500 -5.3 22.5 245 29 15 8.4 4.6 | -4.7 23.5 245 23 12 7.9 4.4
17000 -4.2 24.4 245 25 13 8.5 4.7 | -3.6 25.5 245 21 11 8.0 4.4
16500 -2.9 26.8 245 23 12 9.2 5.0 | -2.3 27.9 240 20 10 9.0 5.0
16000 -1.5 29.3 245 21 11 9.2 5.0 | -1.0 30.2 240 21 11 9.0 4.9
15500 -0.2 31.6 245 19 10 9.5 5.2 | 0.3 32.5 240 22 11 8.9 4.9
15000 1.2 34.2 240 18 9 9.7 5.3 | 1.6 34.9 235 22 11 8.9 4.9
14500 2.7 36.9 240 17 8 9.6 5.3 | 2.8 37.0 235 22 12 9.0 4.9
14000 4.1 39.4 235 16 8 9.5 5.2 | 4.2 39.6 235 22 12 9.5 5.2
13500 5.5 41.9 235 15 8 9.4 5.2 | 5.6 42.1 235 22 11 9.4 5.2
13000 7.1 44.8 230 15 8 10.7 5.8 | 7.1 44.8 235 22 11 10.2 5.6
12500 8.5 47.3 225 14 7 9.0 4.9 | 8.4 47.1 230 22 11 8.8 4.8
12000 9.8 49.6 215 14 7 8.7 4.8 | 9.7 49.5 230 21 11 9.6 5.2
11750 10.4 50.7 210 14 7 9.2 5.1 | 10.4 50.7 230 21 11 9.6 5.3
11500 11.2 52.2 210 14 7 10.3 5.7 | 11.2 52.2 230 21 11 9.9 5.4
11250 12.0 53.6 205 13 7 9.9 5.5 | 11.9 53.4 230 21 11 9.6 5.3
11000 12.7 54.9 205 13 7 9.2 5.0 | 12.6 54.7 230 21 11 9.3 5.1
10750 13.3 55.9 205 13 7 8.8 4.8 | 13.3 55.9 225 20 11 8.9 4.9
10500 14.0 57.2 200 14 7 10.1 5.5 | 14.0 57.2 225 20 10 10.1 5.5
10250 14.8 58.6 200 13 7 10.9 6.0 | 14.8 58.6 225 20 10 10.8 5.9
10000 15.6 60.1 200 13 7 9.7 5.3 | 15.5 59.9 225 20 10 9.5 5.2
9750 16.3 61.3 200 13 7 9.6 5.3 | 16.2 61.2 220 19 10 9.4 5.1
9500 17.0 62.6 195 13 7 8.9 4.9 | 16.9 62.4 220 19 10 8.9 4.9
9250 17.7 63.9 195 13 7 11.8 6.5 | 17.6 63.7 215 19 10 10.8 5.9
9000 18.7 65.7 195 13 7 11.9 6.5 | 18.5 65.3 215 18 9 10.6 5.8
8750 19.4 66.9 195 13 7 9.1 5.0 | 19.1 66.4 215 18 9 8.8 4.8
8500 20.1 68.2 190 13 7 9.6 5.3 | 19.8 67.6 210 17 9 9.1 5.0
8250 20.9 69.6 190 13 7 10.4 5.7 | 20.5 68.9 210 17 9 9.7 5.3
8000 21.8 71.2 190 13 7 17.1 9.4 | 21.2 70.2 205 16 8 9.8 5.4
7750 23.4 74.1 190 12 6 25.2 13.8 | 21.9 71.4 205 13 7 7.9 4.3
7500 M M M M M M M | M M M M M M M
7250 M M M M M M M | M M M M M M M
7000 M M M M M M M | M M M M M M M
6750 M M M M M M M | M M M M M M M
________________________________________________________________________________
This product is issued twice per day, once by approximately 0630 MST/0730 MDT
(1330 UTC). It is not continuously monitored nor updated after its initial
issuance.
The information contained herein is based on rawinsonde observation and/or
numerical weather prediction model data taken near the Air Force Academy
in Colorado Springs, Colorado at
North Latitude: 38 deg 58 min 48.000 sec
West Longitude: 104 deg 49 min 12.000 sec
Elevation: 6572 feet (2003 meters)
and may not be representative of other areas along the Front Range of the
Colorado Rocky Mountains. Note that some elevations in numerical weather
prediction models differ from actual station elevations, which can lead to
data which appear to be below ground. Erroneous data such as these should
not be used.
The content and format of this report as well as the issuance times are subject
to change without prior notice. Comments and suggestions are welcome and should
be directed to one of the addresses or phone numbers shown at the bottom of this
page. To expedite a response to comments, be sure to mention your interest in
the soaring forecast.
DEFINITIONS:
CAPE (Convective Available Potential Energy) - An integrated measure of the
energy available for convective development, also known as the positive
area on a thermodynamic diagram. Units are Joules per kilogram. Larger
values are indicative of greater instability and the possibility of
stronger convective activity, including thunderstorms. Values around or
greater than 1000 suggest the possibility of severe weather should
convective activity develop.
CIN (Convective Inhibition) - An integrated measure of the amount of energy
needed to initiate convective activity, also known as the negative area on
a thermodynamic diagram. Units are Joules per kilogram. The more negative
this number, the more energy is required to initiate convection. This
inhibitive energy can be overcome through surface heating, cooling aloft,
lifting mechanisms (orographic, frontal, gravity waves, etc.)
Convective Condensation Level - The height to which an air parcel possessing the
average saturation mixing ratio in the lowest 4000 feet of the airmass,
if heated sufficiently from below, will rise dry adiabatically until it
just becomes saturated. It estimates the base of cumulus clouds that are
produced by surface heating only.
Convection Temperature (ConvectionT) - The surface temperature required to make
the airmass dry adiabatic up to the given level. It can be considered a
"trigger temperature" for that level.
Freezing Level - The height where the temperature is zero degrees Celsius.
Height of Stable Layer - The height (between 12,000 and 18,000 feet above
mean sea level) where the smallest lapse rate exists. The location and
existence of this feature is important in the generation of mountain
waves.
K Index - A measure of stability which combines the temperature difference
between approximately 5,000 and 18,000 feet above the surface, the amount
of moisture at approximately 5,000 feet above the surface, and a measure
of the dryness at approximately 10,000 feet above the surface. Larger
positive numbers indicate more instability and a greater likelihood of
thunderstorm development. One interpretation of K index values regarding
soaring in the western United States is given in WMO Technical Note 158
and is reproduced in the following table:
below -10 no or weak thermals
-10 to 5 dry thermals or 1/8 cumulus with moderate thermals
5 to 15 good soaring conditions
15 to 20 good soaring conditions with occasional showers
20 to 30 excellent soaring conditions, but increasing
probability of showers and thunderstorms
above 30 more than 60 percent probability of thunderstorms
Lapse Rate - The change with height of the temperature. Negative values indicate
inversions.
Lifted Condensation Level - The height to which an air parcel possessing the
average dew point in the lowest 4000 feet of the airmass and the forecast
maximum temperature must be lifted dry adiabatically to attain saturation.
Lifted Index (LI) - The difference between the environmental temperature at a
level approximately 18,000 feet above the surface and the temperature of
an air parcel lifted dry adiabatically from the surface to its lifted
condensation level and then pseudoadiabatically thereafter to this same
level. The parcel`s initial temperature is the forecast maximum
temperature and its dew point is the average dew point in the lowest 4000
feet of the airmass. Negative values are indicative of instability with
positive values showing stable conditions.
Lift Rate - An experimental estimate of the strength of thermals. It is
computed the same way as the maximum rate of lift but uses the actual
level rather than the maximum height of thermals in the calculation.
Also, none of the empirical adjustments based on cloudiness and K-index
are applied to these calculations.
Maximum Height of Thermals - The height where the dry adiabat through the
forecast maximum temperature intersects the environmental temperature.
Maximum Rate of Lift - An estimate of the maximum strength of thermals. It
is computed from an empirical formula which combines the expected maximum
height of thermals with the difference in the environmental temperatures
between the maximum height of thermals and the temperature 4,000 feet
above the ground. After this computation, further empirical adjustments
are made based on the value of the K-index and the amount and opacity of
middle and high level cloudiness expected between the time of trigger
temperature and the time of overdevelopment.
Middle/High Clouds - The amount and opacity of middle (altostratus, altocumulus)
or high (cirrus, cirrostratus, cirrocumulus) clouds. Broken means that
between 60% and 90% of the sky is covered by the cloud, with overcast
conditions occurring when more than 90% of the sky is covered by the cloud.
Thin implies that the clouds are predominantly transparent, meaning that
some sunlight is reaching the ground, in contrast to opaque which suggests
that little sunlight is reaching the ground.
Potential Height of Wave - The minimum of the following two heights:
1. Level above the height of stable layer (or 14,000 feet if none exists)
where the wind direction changes by 30 degrees or more
2. Level above the height of stable layer (or 14,000 feet if none exists)
where the wind speed no longer increases with height
PVA/NVA - Positive vorticity advection (PVA)/negative vorticity advection (NVA)
on the 500 millibar isobaric surface (approximately 18,000 feet above mean
sea level). Weak PVA has been shown to assist in mountain wave soaring.
Soaring Window - The time between the time the trigger temperature is reached
and the time of overdevelopment.
Thermal Index - The difference between the environmental temperature and the
temperature at a particular level determined by following the dry adiabat
through the forecast maximum temperature up to that level. Negative values
are indicative of thermal lift.
Thermal Soaring Index - An adjective rating (for sailplanes) based on the
computed maximum rate of lift, and the wind speed and middle and high
cloud cover expected during the soaring window (the time of the trigger
temperature and the time of overdevelopment) according to the following:
Maximum rate of lift Adjective Rating
>= 800 fpm Excellent
>= 400 and < 800 fpm Good
>= 200 and < 400 fpm Fair
< 200 fpm Poor
Time of Overdevelopment - The time one or more of the following phenomena,
which essentially shut off thermal lift, is expected to occur:
1. formation of broken to overcast convective cloud cover
2. formation of scattered to numerous downbursts
3. initiation of widespread precipitation
Time of Trigger Temperature - The time the surface temperature is expected to
reach the trigger temperature.
Trigger Temperature - The surface temperature required to make the first 4000
feet of the atmosphere dry adiabatic.
Wave Soaring Index - An empirical, adjective rating (for sailplanes) which
attempts to combine a variety of phenomena important in mountain wave
soaring into a single index number. Objective points are assigned to
these phenomena: wind speed and direction at 14,000 ft MSL, the static
stability in the 12,000-18,000 ft MSL layer, the wind speed gradient above
the stable layer, jet stream location and frontal and upper trough
movements.
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