Soaring Guidance
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
946
UXUS97 KPUB 181234
SRGPUB
Soaring Forecast
National Weather Service Pueblo, Colorado
0634 MDT Wednesday, September 18, 2024
This forecast is for the Air Force Academy for Wednesday, September 18, 2024:
If the trigger temperature of 61.9 F/16.6 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 945 ft/min (4.8 m/s)
Maximum height of thermals.................. 18829 ft MSL (11237 ft AGL)
Forecast maximum temperature................... 79.0 F/26.6 C
Time of trigger temperature.................... 0930 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................. 15303 ft MSL (7711 ft AGL)
Thermal soaring outlook for Thursday 09/19..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:44:11 / 19:02:09 MDT
Total possible sunshine........... 12 hr 17 min 59 sec (737 min 59 sec)
Altitude of sun at 12:53:10 MDT... 52.44 degrees
Upper air data from numerical model forecast valid on 09/18/2024 at 0600 MDT
Freezing level.................. 15051 ft MSL (7459 ft AGL)
Convective condensation level... 21921 ft MSL (14329 ft AGL)
Lifted condensation level....... 20742 ft MSL (13150 ft AGL)
Lifted index.................... +2.0
K index......................... -24.3
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 -59.9 -75.8 250 60 31 2.3 1.3 M M M M M
45000 -56.1 -69.0 255 82 42 3.4 1.9 M M M M M
40000 -50.7 -59.3 255 97 50 3.2 1.7 M M M M M
38000 -48.7 -55.7 255 86 44 3.2 1.7 M M M M M
36000 -46.8 -52.2 255 74 38 3.3 1.8 M M M M M
34000 -42.8 -45.0 255 67 35 8.3 4.6 M M M M M
32000 -37.7 -35.9 250 63 32 8.4 4.6 M M M M M
30000 -32.7 -26.9 250 59 31 8.4 4.6 36.2 97.2 7.8 M M
29000 -30.2 -22.4 250 58 30 8.4 4.6 35.7 96.2 7.5 M M
28000 -27.7 -17.9 250 56 29 8.4 4.6 35.3 95.5 7.3 M M
27000 -25.3 -13.5 245 55 28 7.6 4.2 34.5 94.1 6.7 M M
26000 -23.1 -9.6 245 53 27 7.6 4.2 33.7 92.6 6.1 M M
25000 -20.8 -5.4 245 51 26 7.6 4.2 33.0 91.4 5.6 M M
24000 -18.5 -1.3 245 49 25 7.2 4.0 32.2 89.9 5.0 M M
23000 -15.8 3.6 245 47 24 7.3 4.0 31.0 87.8 4.1 M M
22000 -13.6 7.5 245 45 23 7.4 4.1 30.2 86.4 3.5 M M
21000 -11.7 10.9 245 43 22 5.7 3.1 28.9 84.1 2.4 M M
20000 -10.0 14.0 245 42 22 5.7 3.1 27.5 81.5 1.2 M M
19500 -9.1 15.6 245 41 21 5.8 3.2 26.9 80.4 0.6 M M
19000 -8.3 17.1 245 41 21 6.5 3.6 26.2 79.2 0.1 M M
18500 -7.2 19.0 245 40 21 7.2 3.9 25.8 78.4 -0.3 908 4.6
18000 -6.1 21.0 245 40 20 7.2 4.0 25.4 77.7 -0.7 861 4.4
17500 -5.0 23.0 245 39 20 7.3 4.0 24.9 76.9 -1.1 813 4.1
17000 -3.9 25.0 240 37 19 7.3 4.0 24.5 76.2 -1.5 766 3.9
16500 -2.8 27.0 240 35 18 6.9 3.8 24.1 75.4 -1.8 718 3.6
16000 -1.9 28.6 235 32 16 6.7 3.7 23.6 74.5 -2.3 674 3.4
15500 -0.9 30.4 230 28 15 6.7 3.7 23.1 73.6 -2.8 629 3.2
15000 0.1 32.2 235 26 14 6.7 3.7 22.6 72.7 -3.3 585 3.0
14500 1.1 34.0 245 26 13 6.9 3.8 22.1 71.8 -3.8 540 2.7
14000 2.0 35.6 250 25 13 4.8 2.6 21.5 70.7 -4.4 499 2.5
13500 2.7 36.9 255 26 13 4.9 2.7 20.7 69.3 -5.2 464 2.4
13000 3.4 38.1 255 26 14 5.4 2.9 20.0 67.9 -6.0 428 2.2
12500 3.9 39.0 265 27 14 1.7 0.9 18.9 66.1 -7.0 399 2.0
12000 4.2 39.6 270 28 14 3.2 1.8 17.8 64.0 -8.2 375 1.9
11750 4.4 39.9 270 27 14 4.1 2.3 17.3 63.2 -8.7 360 1.8
11500 4.7 40.5 270 26 14 3.7 2.1 16.8 62.3 -9.2 344 1.7
11250 4.9 40.8 275 26 13 3.5 1.9 16.4 61.5 -9.8 330 1.7
11000 5.2 41.4 275 26 13 5.3 2.9 15.9 60.7 -10.3 315 1.6
10750 5.6 42.1 280 25 13 6.6 3.6 15.7 60.2 -10.6 293 1.5
10500 6.1 43.0 280 25 13 6.5 3.6 15.4 59.7 -10.9 272 1.4
10250 6.6 43.9 280 24 12 8.4 4.6 15.2 59.4 -11.1 249 1.3
10000 7.3 45.1 285 22 11 8.8 4.8 15.1 59.3 -11.2 223 1.1
9750 7.9 46.2 280 21 11 8.2 4.5 15.0 59.0 -11.4 197 1.0
9500 8.5 47.3 280 19 10 8.1 4.4 14.9 58.8 -11.5 172 0.9
9250 9.1 48.4 280 18 9 9.1 5.0 14.8 58.6 -11.7 146 0.7
9000 9.8 49.6 280 16 8 8.9 4.9 14.8 58.6 -11.8 118 0.6
8750 10.3 50.5 275 15 8 7.3 4.0 14.6 58.3 -12.0 94 0.5
8500 10.9 51.6 270 15 8 8.7 4.8 14.5 58.1 -12.2 69 0.4
8250 11.5 52.7 265 14 7 4.7 2.6 14.3 57.8 -12.4 45 0.2
8000 11.2 52.2 265 13 7 -13.3 -7.3 13.4 56.1 -13.4 46 0.2
7750 9.4 48.9 265 10 5 -30.9 -17.0 10.9 51.6 -16.0 92 0.5
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 * * * * * *
09/18/2024 at 0900 MDT | 09/18/2024 at 1200 MDT
|
CAPE... 0.0 LI... +4.3 | CAPE... 0.0 LI... +4.6
CINH... 0.0 K Index... -27.7 | CINH... 0.0 K Index... -26.5
|
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 -61.2 -78.2 255 63 32 1.7 0.9 | -61.3 -78.3 255 60 31 0.8 0.4
45000 -57.7 -71.9 260 88 45 4.3 2.3 | -58.4 -73.1 260 92 47 4.7 2.6
40000 -51.0 -59.8 260 97 50 4.1 2.3 | -51.3 -60.3 260 97 50 5.1 2.8
38000 -48.5 -55.3 260 84 43 4.1 2.3 | -48.3 -54.9 260 87 45 5.1 2.8
36000 -46.0 -50.8 255 71 37 4.3 2.3 | -45.2 -49.4 260 77 40 5.1 2.8
34000 -41.7 -43.1 255 63 32 8.1 4.5 | -41.2 -42.2 255 67 34 7.3 4.0
32000 -36.8 -34.2 250 57 29 8.2 4.5 | -36.3 -33.3 250 55 28 7.3 4.0
30000 -31.9 -25.4 245 54 28 8.2 4.5 | -31.5 -24.7 250 52 27 8.2 4.5
29000 -29.5 -21.1 245 53 27 8.2 4.5 | -29.1 -20.4 250 52 27 8.2 4.5
28000 -27.0 -16.6 245 52 27 8.3 4.5 | -26.6 -15.9 250 51 26 8.2 4.5
27000 -24.6 -12.3 245 50 26 7.7 4.2 | -24.2 -11.6 250 50 26 7.9 4.3
26000 -22.3 -8.1 245 49 25 7.7 4.2 | -21.9 -7.4 250 49 25 7.9 4.3
25000 -20.0 -4.0 245 47 24 7.7 4.2 | -19.5 -3.1 250 48 25 7.9 4.3
24000 -17.3 0.9 245 45 23 6.8 3.7 | -17.2 1.0 250 46 24 7.5 4.1
23000 -15.3 4.5 245 43 22 6.8 3.7 | -15.0 5.0 245 44 23 7.5 4.1
22000 -13.2 8.2 240 41 21 6.9 3.8 | -12.8 9.0 245 43 22 7.6 4.2
21000 -11.3 11.7 245 40 20 6.1 3.3 | -10.8 12.6 245 41 21 6.1 3.3
20000 -9.5 14.9 245 38 19 6.1 3.3 | -8.9 16.0 245 40 20 6.1 3.3
19500 -8.6 16.5 245 37 19 6.1 3.3 | -8.0 17.6 245 39 20 6.1 3.3
19000 -7.6 18.3 245 36 18 6.3 3.4 | -6.6 20.1 245 38 20 5.2 2.8
18500 -6.7 19.9 245 35 18 6.4 3.5 | -5.9 21.4 250 38 19 5.0 2.7
18000 -5.7 21.7 250 34 18 6.3 3.5 | -5.1 22.8 250 37 19 5.2 2.9
17500 -4.7 23.5 250 34 17 6.8 3.7 | -4.2 24.4 250 37 19 7.1 3.9
17000 -3.7 25.3 245 33 17 6.8 3.7 | -3.1 26.4 250 36 19 7.0 3.9
16500 -2.7 27.1 245 32 17 6.5 3.6 | -2.1 28.2 250 35 18 6.8 3.8
16000 -1.7 28.9 245 31 16 6.3 3.5 | -1.1 30.0 250 35 18 6.8 3.7
15500 -0.8 30.6 250 30 16 6.4 3.5 | -0.1 31.8 250 34 18 6.7 3.7
15000 0.2 32.4 250 30 15 6.9 3.8 | 0.9 33.6 250 32 17 6.6 3.6
14500 1.2 34.2 255 30 15 7.1 3.9 | 1.9 35.4 250 31 16 6.6 3.6
14000 2.1 35.8 255 29 15 5.1 2.8 | 2.6 36.7 250 28 14 3.9 2.2
13500 2.9 37.2 255 27 14 5.3 2.9 | 3.2 37.8 245 24 12 4.3 2.4
13000 3.7 38.7 255 24 12 6.3 3.5 | 3.8 38.8 240 20 10 3.6 2.0
12500 4.6 40.3 255 22 11 6.0 3.3 | 4.5 40.1 235 15 8 6.2 3.4
12000 5.5 41.9 260 20 10 6.4 3.5 | 5.4 41.7 235 13 7 6.0 3.3
11750 6.0 42.8 265 20 10 6.7 3.7 | 5.8 42.4 240 14 7 6.0 3.3
11500 6.5 43.7 265 21 11 4.5 2.5 | 6.2 43.2 240 14 7 6.1 3.3
11250 6.7 44.1 265 21 11 2.8 1.5 | 6.6 43.9 245 13 7 6.5 3.6
11000 6.9 44.4 265 21 11 3.6 1.9 | 7.1 44.8 245 12 6 7.7 4.2
10750 7.2 45.0 270 21 11 3.6 2.0 | 7.6 45.7 235 11 6 7.7 4.2
10500 7.4 45.3 275 21 11 3.7 2.0 | 8.2 46.8 230 9 5 9.2 5.0
10250 7.7 45.9 280 21 11 4.5 2.5 | 9.0 48.2 225 9 4 12.0 6.6
10000 8.0 46.4 285 21 11 5.5 3.0 | 9.9 49.8 220 8 4 10.4 5.7
9750 8.5 47.3 285 20 10 5.9 3.2 | 10.6 51.1 220 8 4 8.9 4.9
9500 8.9 48.0 285 19 10 5.4 2.9 | 11.3 52.3 220 8 4 8.9 4.9
9250 9.3 48.7 285 18 9 7.1 3.9 | 11.9 53.4 220 8 4 10.3 5.7
9000 9.9 49.8 285 15 8 7.3 4.0 | 12.8 55.0 215 8 4 11.3 6.2
8750 10.3 50.5 285 14 7 5.7 3.2 | 13.6 56.5 215 8 4 10.4 5.7
8500 10.7 51.3 285 12 6 6.2 3.4 | 14.4 57.9 215 8 4 10.7 5.9
8250 11.2 52.2 285 10 5 6.2 3.4 | 15.1 59.2 210 7 4 10.4 5.7
8000 11.6 52.9 280 11 6 8.8 4.8 | 16.1 61.0 210 7 4 16.8 9.2
7750 12.3 54.1 275 8 4 12.6 6.9 | 17.8 64.0 210 7 4 27.9 15.3
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
09/18/2024 at 1500 MDT | 09/18/2024 at 1800 MDT
|
CAPE... 0.0 LI... +6.2 | CAPE... 0.0 LI... +6.0
CINH... 0.0 K Index... -8.6 | CINH... 0.0 K Index... -10.2
|
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 -62.8 -81.0 250 61 32 1.6 0.9 | -62.8 -81.0 250 59 30 1.8 1.0
45000 -58.8 -73.8 255 86 44 5.2 2.9 | -58.6 -73.5 255 83 43 5.0 2.7
40000 -50.9 -59.6 255 89 46 5.9 3.2 | -51.0 -59.8 255 91 47 6.3 3.4
38000 -47.3 -53.1 255 87 45 5.9 3.2 | -47.3 -53.1 255 89 46 6.2 3.4
36000 -43.8 -46.8 255 84 43 5.9 3.2 | -43.6 -46.5 255 88 45 6.2 3.4
34000 -40.1 -40.2 255 76 39 6.3 3.5 | -39.6 -39.3 255 80 41 5.9 3.2
32000 -35.9 -32.6 255 66 34 6.3 3.5 | -36.0 -32.8 250 72 37 5.9 3.3
30000 -31.5 -24.7 255 60 31 7.5 4.1 | -31.9 -25.4 250 64 33 7.2 3.9
29000 -29.3 -20.7 255 57 29 7.5 4.1 | -29.8 -21.6 245 60 31 7.2 3.9
28000 -27.1 -16.8 255 55 28 7.8 4.3 | -27.6 -17.7 245 56 29 7.5 4.1
27000 -24.4 -11.9 255 51 26 9.0 4.9 | -25.0 -13.0 245 53 27 9.1 5.0
26000 -21.7 -7.1 250 48 24 9.0 4.9 | -22.2 -8.0 245 50 26 9.1 5.0
25000 -19.0 -2.2 250 44 23 9.0 5.0 | -19.5 -3.1 240 47 24 9.1 5.0
24000 -16.6 2.1 250 42 22 7.5 4.1 | -16.9 1.6 240 47 24 8.7 4.8
23000 -14.4 6.1 250 42 21 7.5 4.1 | -14.3 6.3 245 48 25 8.7 4.7
22000 -12.1 10.2 245 41 21 7.6 4.1 | -11.7 10.9 245 49 25 8.8 4.8
21000 -10.0 14.0 245 41 21 6.8 3.7 | -9.5 14.9 250 48 25 6.6 3.6
20000 -8.0 17.6 250 41 21 6.9 3.8 | -7.1 19.2 245 45 23 6.6 3.6
19500 -6.5 20.3 250 41 21 7.1 3.9 | -6.1 21.0 245 44 23 6.9 3.8
19000 -5.6 21.9 250 41 21 4.9 2.7 | -5.3 22.5 250 43 22 3.2 1.8
18500 -4.9 23.2 250 40 21 4.6 2.5 | -4.8 23.4 250 41 21 2.8 1.5
18000 -4.2 24.4 250 39 20 4.6 2.5 | -4.4 24.1 255 39 20 3.1 1.7
17500 -3.5 25.7 250 38 20 4.2 2.3 | -3.8 25.2 260 37 19 4.5 2.5
17000 -2.8 27.0 255 37 19 4.2 2.3 | -3.2 26.2 265 35 18 4.5 2.5
16500 -2.1 28.2 255 37 19 5.2 2.9 | -2.6 27.3 265 32 16 4.3 2.4
16000 -1.3 29.7 255 36 18 5.4 3.0 | -2.0 28.4 265 28 14 4.6 2.5
15500 -0.6 30.9 255 35 18 5.4 2.9 | -1.4 29.5 270 24 12 6.5 3.6
15000 0.2 32.4 260 31 16 5.4 3.0 | -0.2 31.6 265 21 11 8.7 4.8
14500 0.9 33.6 260 27 14 5.9 3.3 | 1.0 33.8 265 18 9 8.9 4.9
14000 1.9 35.4 255 23 12 8.9 4.9 | 2.4 36.3 265 17 9 9.7 5.3
13500 3.2 37.8 255 19 10 8.5 4.7 | 3.9 39.0 260 17 9 9.4 5.2
13000 4.5 40.1 250 17 9 10.0 5.5 | 5.4 41.7 260 16 8 10.8 5.9
12500 5.8 42.4 245 15 8 8.3 4.6 | 6.8 44.2 260 16 8 9.1 5.0
12000 7.1 44.8 235 13 7 8.1 4.4 | 8.1 46.6 255 16 8 8.3 4.5
11750 7.7 45.9 230 12 6 8.7 4.8 | 8.7 47.7 255 15 8 8.7 4.8
11500 8.4 47.1 225 12 6 10.3 5.7 | 9.4 48.9 250 15 8 9.9 5.4
11250 9.2 48.6 220 11 6 10.3 5.6 | 10.2 50.4 250 15 8 9.7 5.3
11000 9.9 49.8 210 11 6 8.8 4.8 | 10.8 51.4 245 14 7 8.6 4.7
10750 10.5 50.9 205 11 6 7.6 4.2 | 11.4 52.5 240 14 7 7.7 4.2
10500 11.1 52.0 200 11 6 9.6 5.3 | 12.0 53.6 235 14 7 9.4 5.2
10250 11.9 53.4 195 11 6 12.1 6.7 | 12.8 55.0 235 13 7 11.4 6.2
10000 12.8 55.0 195 11 6 10.4 5.7 | 13.6 56.5 230 13 7 9.4 5.1
9750 13.5 56.3 195 11 6 9.2 5.1 | 14.3 57.7 225 13 7 8.3 4.5
9500 14.2 57.6 190 11 6 9.1 5.0 | 14.9 58.8 220 13 6 8.0 4.4
9250 14.9 58.8 190 11 6 10.6 5.8 | 15.5 59.9 215 13 6 10.1 5.5
9000 15.8 60.4 185 11 6 11.0 6.0 | 16.3 61.3 210 12 6 10.5 5.7
8750 16.5 61.7 185 11 6 9.8 5.4 | 17.0 62.6 205 12 6 8.7 4.8
8500 17.2 63.0 185 11 6 9.7 5.3 | 17.7 63.9 200 12 6 9.0 5.0
8250 18.0 64.4 180 11 6 11.4 6.3 | 18.3 64.9 195 12 6 9.4 5.1
8000 19.1 66.4 180 11 6 18.1 9.9 | 19.0 66.2 190 12 6 10.0 5.5
7750 20.6 69.1 180 10 5 23.3 12.8 | 19.8 67.6 190 10 5 9.6 5.3
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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