Soaring Guidance
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
858
UXUS97 KPUB 171311
SRGPUB
Soaring Forecast
National Weather Service Pueblo, Colorado
0710 MDT Thursday, July 17, 2025
This forecast is for Thursday, July 17, 2025:
If the trigger temperature of 70.6 F/21.4 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 585 ft/min (3.0 m/s)
Maximum height of thermals.................. 16374 ft MSL (8767 ft AGL)
Forecast maximum temperature................... 79.0 F/26.6 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ 1300 MDT
Middle/high clouds during soaring window....... Overcast opaque high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 12172 ft MSL (4565 ft AGL)
Thermal soaring outlook for Friday 07/18....... Good
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:48:05 / 20:22:57 MDT
Total possible sunshine........... 14 hr 34 min 52 sec (874 min 52 sec)
Altitude of sun at 13:05:31 MDT... 72.03 degrees
Upper air data from numerical model forecast valid on 07/17/2025 at 0600 MDT
Freezing level.................. 16255 ft MSL (8648 ft AGL)
Convective condensation level... 13656 ft MSL (6049 ft AGL)
Lifted condensation level....... 14438 ft MSL (6831 ft AGL)
Lifted index.................... -5.5
K index......................... +23.4
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 -65.9 -86.6 260 27 14 0.3 0.2 M M M M M
45000 -62.5 -80.5 250 43 22 6.6 3.6 M M M M M
40000 -52.4 -62.3 240 49 25 7.8 4.3 M M M M M
38000 -47.2 -53.0 240 47 24 7.8 4.3 M M M M M
36000 -42.5 -44.5 240 45 23 7.8 4.3 M M M M M
34000 -37.8 -36.0 245 42 22 7.8 4.3 M M M M M
32000 -33.1 -27.6 255 41 21 8.5 4.7 M M M M M
30000 -28.3 -18.9 255 37 19 8.0 4.4 40.8 105.5 11.4 M M
29000 -25.9 -14.6 255 35 18 8.0 4.4 40.2 104.4 11.1 M M
28000 -23.6 -10.5 255 33 17 7.1 3.9 39.7 103.4 10.7 M M
27000 -21.6 -6.9 260 31 16 6.7 3.7 38.4 101.1 9.8 M M
26000 -19.6 -3.3 260 29 15 6.7 3.7 37.3 99.1 9.0 M M
25000 -17.6 0.3 260 27 14 6.8 3.7 36.3 97.3 8.2 M M
24000 -16.0 3.2 260 25 13 5.2 2.9 34.7 94.4 7.0 M M
23000 -14.5 5.9 265 23 12 5.2 2.9 33.1 91.5 5.6 M M
22000 -12.5 9.5 275 20 10 6.5 3.6 31.2 88.2 4.1 M M
21000 -10.4 13.3 275 19 10 7.1 3.9 30.2 86.4 3.2 M M
20000 -8.3 17.1 280 17 9 7.1 3.9 29.4 84.8 2.4 M M
19500 -7.3 18.9 285 16 8 7.2 4.0 29.0 84.1 2.0 M M
19000 -6.2 20.8 285 14 7 7.8 4.3 28.6 83.5 1.7 M M
18500 -5.0 23.0 285 12 6 7.8 4.3 28.2 82.8 1.4 M M
18000 -3.9 25.0 285 11 5 7.6 4.2 27.9 82.2 1.1 M M
17500 -2.8 27.0 290 10 5 7.5 4.1 27.5 81.5 0.7 M M
17000 -1.6 29.1 295 9 4 7.6 4.2 27.2 80.9 0.4 M M
16500 -0.5 31.1 295 8 4 7.8 4.3 26.8 80.3 0.1 M M
16000 0.6 33.1 295 8 4 7.9 4.3 26.5 79.7 -0.3 746 3.8
15500 1.8 35.2 290 8 4 7.7 4.3 26.2 79.1 -0.6 697 3.5
15000 2.9 37.2 285 9 4 7.8 4.3 25.8 78.5 -1.0 649 3.3
14500 4.0 39.2 280 9 5 8.6 4.7 25.5 78.0 -1.3 601 3.1
14000 5.3 41.5 275 9 5 9.0 4.9 25.4 77.7 -1.5 547 2.8
13500 6.5 43.7 275 10 5 8.7 4.8 25.3 77.6 -1.7 494 2.5
13000 7.7 45.9 265 9 5 8.0 4.4 25.1 77.1 -2.0 445 2.3
12500 8.9 48.0 265 9 5 7.4 4.0 24.8 76.7 -2.3 395 2.0
12000 9.3 48.7 250 10 5 1.7 0.9 23.9 74.9 -3.3 366 1.9
11750 9.4 48.9 245 10 5 2.2 1.2 23.3 73.9 -4.0 356 1.8
11500 9.5 49.1 240 11 6 2.0 1.1 22.7 72.8 -4.6 346 1.8
11250 9.6 49.3 235 11 6 0.7 0.4 22.0 71.6 -5.3 336 1.7
11000 9.5 49.1 230 12 6 -0.3 -0.2 21.3 70.3 -6.1 331 1.7
10750 9.5 49.1 225 13 7 0.7 0.4 20.5 68.9 -6.9 325 1.7
10500 9.4 48.9 220 14 7 -2.0 -1.1 19.8 67.6 -7.7 319 1.6
10250 9.2 48.6 215 16 8 1.5 0.8 18.9 66.0 -8.7 318 1.6
10000 9.6 49.3 210 17 9 6.8 3.7 18.6 65.4 -9.1 300 1.5
9750 9.9 49.8 210 17 9 5.6 3.0 18.3 64.9 -9.4 282 1.4
9500 10.3 50.5 205 18 9 5.5 3.0 18.0 64.3 -9.8 263 1.3
9250 10.6 51.1 200 18 9 5.6 3.1 17.6 63.7 -10.2 246 1.2
9000 11.1 52.0 200 19 10 6.9 3.8 17.4 63.3 -10.5 226 1.1
8750 11.6 52.9 195 19 10 7.4 4.0 17.2 62.9 -10.8 203 1.0
8500 12.1 53.8 190 20 10 6.9 3.8 17.0 62.6 -11.1 181 0.9
8250 12.5 54.5 190 19 10 5.9 3.2 16.8 62.2 -11.4 161 0.8
8000 12.9 55.2 185 17 9 5.8 3.2 16.4 61.6 -11.7 142 0.7
7750 13.3 55.9 185 13 6 6.6 3.6 16.2 61.1 -12.1 122 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 * * * * * *
07/17/2025 at 0900 MDT | 07/17/2025 at 1200 MDT
|
CAPE... +370.6 LI... -2.8 | CAPE... +1385.8 LI... -4.9
CINH... -100.0 K Index... +22.1 | CINH... -7.0 K Index... +21.5
|
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 -66.0 -86.8 260 23 12 1.1 0.6 | -66.4 -87.5 245 25 13 0.8 0.5
45000 -62.1 -79.8 250 35 18 5.9 3.2 | -62.4 -80.3 240 37 19 6.4 3.5
40000 -52.2 -62.0 225 45 23 8.2 4.5 | -51.8 -61.2 235 47 24 8.2 4.5
38000 -47.3 -53.1 225 44 23 8.2 4.5 | -46.9 -52.4 235 46 24 8.2 4.5
36000 -42.3 -44.1 230 44 23 8.1 4.4 | -42.0 -43.6 235 45 23 7.8 4.3
34000 -37.6 -35.7 235 39 20 7.9 4.3 | -37.5 -35.5 235 42 21 7.5 4.1
32000 -32.8 -27.0 250 36 18 8.5 4.7 | -33.0 -27.4 235 38 20 8.2 4.5
30000 -28.2 -18.8 255 34 17 7.7 4.2 | -28.3 -18.9 245 31 16 7.8 4.3
29000 -25.9 -14.6 255 33 17 7.7 4.2 | -26.0 -14.8 250 28 14 7.8 4.3
28000 -23.6 -10.5 260 32 16 7.4 4.1 | -23.7 -10.7 260 26 13 7.0 3.8
27000 -21.4 -6.5 260 31 16 7.4 4.0 | -21.7 -7.1 255 26 13 6.9 3.8
26000 -19.2 -2.6 260 30 15 7.4 4.0 | -19.6 -3.3 255 25 13 6.9 3.8
25000 -17.0 1.4 260 29 15 7.3 4.0 | -17.6 0.3 250 25 13 6.9 3.8
24000 -15.1 4.8 265 26 13 6.4 3.5 | -15.6 3.9 255 26 13 6.7 3.7
23000 -12.7 9.1 265 22 11 6.4 3.5 | -13.1 8.4 255 27 14 6.7 3.7
22000 -10.9 12.4 265 19 10 5.0 2.7 | -11.1 12.0 260 27 14 5.6 3.1
21000 -9.5 14.9 265 16 8 4.6 2.5 | -9.6 14.7 260 22 12 5.5 3.0
20000 -8.2 17.2 265 13 7 4.7 2.6 | -8.0 17.6 260 18 9 5.5 3.0
19500 -7.6 18.3 270 12 6 4.8 2.7 | -7.2 19.0 260 16 8 5.4 3.0
19000 -6.8 19.8 270 11 5 5.2 2.9 | -6.4 20.5 260 15 7 5.0 2.8
18500 -6.1 21.0 270 9 5 5.1 2.8 | -5.7 21.7 260 13 7 4.9 2.7
18000 -5.2 22.6 270 8 4 7.5 4.1 | -4.9 23.2 260 11 6 7.6 4.1
17500 -4.1 24.6 270 6 3 8.0 4.4 | -3.8 25.2 265 10 5 8.0 4.4
17000 -3.0 26.6 270 5 3 8.1 4.5 | -2.6 27.3 265 8 4 8.2 4.5
16500 -1.8 28.8 280 5 2 8.3 4.6 | -1.4 29.5 270 7 4 8.6 4.7
16000 -0.5 31.1 285 5 2 8.3 4.5 | -0.1 31.8 280 7 4 8.6 4.7
15500 0.7 33.3 290 5 3 8.6 4.7 | 1.1 34.0 290 7 3 8.5 4.6
15000 2.0 35.6 295 6 3 8.6 4.7 | 2.4 36.3 295 7 3 8.5 4.7
14500 3.2 37.8 295 6 3 8.4 4.6 | 3.7 38.7 305 6 3 8.5 4.7
14000 4.5 40.1 290 7 4 8.3 4.6 | 4.9 40.8 315 6 3 8.5 4.7
13500 5.7 42.3 290 8 4 8.4 4.6 | 6.2 43.2 320 7 3 8.5 4.7
13000 6.9 44.4 290 8 4 8.5 4.7 | 7.4 45.3 325 7 4 8.4 4.6
12500 8.2 46.8 290 8 4 8.7 4.8 | 8.6 47.5 330 7 4 8.1 4.4
12000 9.4 48.9 290 8 4 8.3 4.5 | 9.8 49.6 330 8 4 8.8 4.8
11750 10.0 50.0 290 8 4 8.1 4.5 | 10.4 50.7 335 8 4 8.1 4.4
11500 10.6 51.1 290 8 4 7.2 4.0 | 10.9 51.6 335 8 4 6.7 3.7
11250 11.0 51.8 290 8 4 6.2 3.4 | 11.4 52.5 335 7 4 7.4 4.1
11000 11.5 52.7 285 8 4 6.2 3.4 | 11.9 53.4 330 7 3 8.2 4.5
10750 11.9 53.4 285 8 4 5.8 3.2 | 12.4 54.3 325 6 3 8.2 4.5
10500 12.3 54.1 280 8 4 7.6 4.2 | 12.9 55.2 320 5 3 7.8 4.3
10250 12.8 55.0 275 8 4 5.2 2.8 | 13.5 56.3 315 4 2 7.7 4.2
10000 13.0 55.4 270 9 4 1.6 0.9 | 14.0 57.2 295 3 1 7.9 4.3
9750 13.1 55.6 265 9 5 2.5 1.4 | 14.5 58.1 260 2 1 8.5 4.6
9500 13.2 55.8 265 10 5 2.7 1.5 | 15.0 59.0 225 3 1 6.4 3.5
9250 13.3 55.9 260 10 5 1.8 1.0 | 15.3 59.5 200 4 2 7.3 4.0
9000 13.3 55.9 255 10 5 0.3 0.2 | 16.0 60.8 190 4 2 11.0 6.0
8750 13.2 55.8 245 11 6 -0.4 -0.2 | 16.8 62.2 180 5 2 11.1 6.1
8500 13.1 55.6 240 12 6 2.2 1.2 | 17.6 63.7 175 5 3 10.7 5.9
8250 13.5 56.3 240 12 6 8.2 4.5 | 18.4 65.1 170 6 3 10.9 6.0
8000 14.2 57.6 235 11 6 13.9 7.6 | 19.4 66.9 165 6 3 17.9 9.8
7750 15.4 59.7 225 9 5 18.5 10.1 | 21.1 70.0 165 6 3 27.3 15.0
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
07/17/2025 at 1500 MDT | 07/17/2025 at 1800 MDT
|
CAPE... +2176.8 LI... -5.6 | CAPE... +1661.0 LI... -5.6
CINH... -0.4 K Index... +25.0 | CINH... -1.2 K Index... +31.3
|
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 -65.6 -86.1 240 29 15 0.8 0.4 | -65.5 -85.9 235 31 16 0.7 0.4
45000 -61.7 -79.1 235 42 22 5.8 3.2 | -62.0 -79.6 225 41 21 5.3 2.9
40000 -52.3 -62.1 230 50 26 8.8 4.8 | -53.1 -63.6 225 36 18 9.5 5.2
38000 -47.0 -52.6 230 50 26 8.8 4.8 | -47.4 -53.3 235 35 18 9.4 5.2
36000 -41.7 -43.1 230 50 26 8.6 4.7 | -41.7 -43.1 245 36 18 9.1 5.0
34000 -36.2 -33.2 230 45 23 8.2 4.5 | -36.6 -33.9 250 34 18 8.5 4.7
32000 -31.3 -24.3 235 41 21 8.7 4.8 | -31.5 -24.7 250 33 17 8.4 4.6
30000 -26.8 -16.2 245 33 17 7.5 4.1 | -26.5 -15.7 250 28 14 7.4 4.0
29000 -24.6 -12.3 250 30 15 7.6 4.2 | -24.3 -11.7 250 25 13 7.4 4.0
28000 -22.4 -8.3 255 27 14 6.5 3.5 | -22.2 -8.0 250 22 11 6.7 3.7
27000 -20.5 -4.9 255 26 13 6.5 3.6 | -20.2 -4.4 250 19 10 6.8 3.7
26000 -18.5 -1.3 255 25 13 6.6 3.6 | -18.2 -0.8 250 16 8 6.8 3.7
25000 -16.6 2.1 255 23 12 6.4 3.5 | -16.2 2.8 250 13 7 6.5 3.6
24000 -14.8 5.4 255 23 12 6.0 3.3 | -14.4 6.1 250 10 5 6.1 3.3
23000 -13.0 8.6 260 22 11 6.0 3.3 | -12.7 9.1 250 8 4 6.1 3.3
22000 -11.3 11.7 270 22 11 5.9 3.3 | -10.9 12.4 250 6 3 5.7 3.1
21000 -9.5 14.9 270 20 10 5.9 3.2 | -9.4 15.1 240 4 2 5.3 2.9
20000 -7.3 18.9 275 17 9 5.9 3.2 | -7.8 18.0 225 2 1 5.3 2.9
19500 -6.5 20.3 275 16 8 5.9 3.2 | -7.1 19.2 200 2 1 5.3 2.9
19000 -5.7 21.7 275 15 8 5.8 3.2 | -6.3 20.7 165 1 1 5.4 3.0
18500 -4.9 23.2 275 13 7 5.7 3.1 | -5.5 22.1 135 2 1 5.4 3.0
18000 -4.0 24.8 280 12 6 7.3 4.0 | -4.8 23.4 120 2 1 5.6 3.0
17500 -2.9 26.8 280 11 5 7.4 4.1 | -4.0 24.8 105 3 2 5.7 3.1
17000 -1.9 28.6 285 9 5 7.7 4.2 | -3.1 26.4 095 4 2 5.6 3.1
16500 -0.7 30.7 290 8 4 8.4 4.6 | -2.2 28.0 090 5 2 7.1 3.9
16000 0.5 32.9 300 6 3 8.5 4.6 | -0.8 30.6 085 5 3 7.1 3.9
15500 1.7 35.1 310 5 3 7.7 4.2 | 0.4 32.7 080 6 3 9.2 5.0
15000 2.8 37.0 330 4 2 7.8 4.3 | 1.7 35.1 080 6 3 9.0 5.0
14500 4.0 39.2 350 4 2 8.3 4.5 | 3.0 37.4 080 7 3 9.3 5.1
14000 5.2 41.4 010 4 2 8.5 4.6 | 4.3 39.7 080 7 3 9.4 5.1
13500 6.4 43.5 030 4 2 8.5 4.7 | 5.7 42.3 080 7 3 8.6 4.7
13000 7.6 45.7 035 4 2 8.6 4.7 | 6.8 44.2 085 6 3 8.5 4.7
12500 8.8 47.8 045 4 2 8.5 4.7 | 8.3 46.9 085 6 3 9.4 5.2
12000 10.0 50.0 055 4 2 8.9 4.9 | 9.4 48.9 095 5 2 7.0 3.8
11750 10.6 51.1 060 4 2 8.2 4.5 | 9.9 49.8 100 4 2 8.5 4.7
11500 11.1 52.0 065 4 2 6.8 3.7 | 10.5 50.9 105 4 2 8.2 4.5
11250 11.6 52.9 075 4 2 7.2 4.0 | 11.0 51.8 110 4 2 5.0 2.8
11000 12.0 53.6 095 4 2 8.1 4.5 | 11.3 52.3 115 4 2 4.6 2.5
10750 12.5 54.5 110 4 2 7.4 4.0 | 11.6 52.9 125 3 2 5.2 2.9
10500 13.0 55.4 125 5 3 10.3 5.7 | 12.0 53.6 135 3 2 3.0 1.6
10250 13.7 56.7 125 6 3 7.6 4.2 | 12.2 54.0 165 3 2 4.9 2.7
10000 14.0 57.2 130 7 4 2.8 1.5 | 12.7 54.9 180 3 2 8.3 4.6
9750 14.3 57.7 135 8 4 4.3 2.3 | 13.2 55.8 195 4 2 8.0 4.4
9500 14.5 58.1 140 9 4 3.1 1.7 | 13.7 56.7 205 4 2 6.2 3.4
9250 14.8 58.6 140 9 5 7.0 3.8 | 14.1 57.4 220 6 3 8.7 4.8
9000 15.5 59.9 140 10 5 11.2 6.2 | 14.9 58.8 230 8 4 13.6 7.5
8750 16.3 61.3 140 10 5 10.8 5.9 | 15.8 60.4 235 9 5 14.5 7.9
8500 17.1 62.8 140 10 5 10.6 5.8 | 16.7 62.1 240 11 6 11.4 6.2
8250 17.9 64.2 140 10 5 10.2 5.6 | 17.2 63.0 245 13 7 8.3 4.6
8000 18.8 65.8 140 10 5 13.8 7.6 | 17.8 64.0 250 16 8 11.9 6.5
7750 20.0 68.0 140 10 5 19.0 10.4 | 18.6 65.5 255 18 9 14.6 8.0
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) and again by approximately 1830 MST/1930 MDT (0130 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.
CINH (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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