Soaring Guidance
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
946
UXUS97 KPUB 171220
SRGPUB
Soaring Forecast
National Weather Service Pueblo, Colorado
0620 MDT Thursday, April 17, 2025
This forecast is for the Air Force Academy for Thursday, April 17, 2025:
If the trigger temperature of 57.7 F/14.3 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 1176 ft/min (6.0 m/s)
Maximum height of thermals.................. 20385 ft MSL (12775 ft AGL)
Forecast maximum temperature................... 72.0 F/22.7 C
Time of trigger temperature.................... 0900 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ Between 20 mph and 30 mph
Height of the -3 thermal index................. 17836 ft MSL (10226 ft AGL)
Thermal soaring outlook for Friday 04/18....... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:18:53 / 19:38:33 MDT
Total possible sunshine........... 13 hr 19 min 40 sec (799 min 40 sec)
Altitude of sun at 12:58:43 MDT... 61.79 degrees
Upper air data from numerical model forecast valid on 04/17/2025 at 0600 MDT
Freezing level.................. 12826 ft MSL (5216 ft AGL)
Convective condensation level... 21850 ft MSL (14240 ft AGL)
Lifted condensation level....... 21753 ft MSL (14143 ft AGL)
Lifted index.................... +0.0
K index......................... -2.9
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 -61.2 -78.2 245 62 32 -1.6 -0.9 M M M M M
45000 -63.6 -82.5 245 76 39 1.4 0.8 M M M M M
40000 -60.7 -77.3 245 91 47 1.9 1.1 M M M M M
38000 -57.8 -72.0 245 91 47 6.7 3.7 M M M M M
36000 -53.8 -64.8 245 88 45 6.7 3.7 M M M M M
34000 -49.2 -56.6 240 84 43 7.6 4.2 M M M M M
32000 -44.6 -48.3 245 80 41 7.6 4.2 M M M M M
30000 -40.0 -40.0 245 77 39 8.0 4.4 28.2 82.8 4.6 M M
29000 -37.6 -35.7 245 75 39 8.0 4.4 27.4 81.4 4.1 M M
28000 -35.2 -31.4 245 73 38 8.0 4.4 26.8 80.3 3.6 M M
27000 -32.9 -27.2 245 72 37 7.7 4.2 26.3 79.3 3.2 M M
26000 -30.6 -23.1 245 69 36 7.7 4.2 25.4 77.6 2.5 M M
25000 -28.3 -18.9 245 67 35 7.7 4.2 24.6 76.3 1.9 M M
24000 -26.0 -14.8 245 65 33 8.1 4.5 24.0 75.1 1.4 M M
23000 -23.3 -9.9 240 61 31 9.0 4.9 23.6 74.4 1.1 M M
22000 -20.6 -5.1 240 57 29 9.0 4.9 23.3 74.0 0.9 M M
21000 -18.0 -0.4 240 53 27 7.6 4.2 23.1 73.6 0.7 M M
20000 -15.4 4.3 240 54 28 6.7 3.7 21.7 71.1 -0.5 1130 5.7
19500 -14.4 6.1 245 55 28 6.7 3.7 21.2 70.2 -0.9 1085 5.5
19000 -13.4 7.9 245 55 28 6.9 3.8 20.7 69.3 -1.3 1040 5.3
18500 -12.5 9.5 245 56 29 4.3 2.3 20.1 68.2 -1.9 999 5.1
18000 -12.0 10.4 245 56 29 4.0 2.2 19.1 66.4 -2.8 968 4.9
17500 -11.5 11.3 245 56 29 4.7 2.6 18.2 64.7 -3.8 937 4.8
17000 -10.5 13.1 245 54 28 7.1 3.9 17.6 63.7 -4.3 895 4.5
16500 -9.5 14.9 245 52 27 6.8 3.8 17.1 62.9 -4.8 850 4.3
16000 -8.4 16.9 245 47 24 9.3 5.1 16.9 62.3 -5.1 800 4.1
15500 -7.0 19.4 240 39 20 9.3 5.1 16.8 62.2 -5.2 743 3.8
15000 -5.6 21.9 235 31 16 9.2 5.0 16.7 62.1 -5.3 686 3.5
14500 -4.2 24.4 235 27 14 9.1 5.0 16.6 61.9 -5.4 630 3.2
14000 -2.8 27.0 230 23 12 8.6 4.7 16.5 61.7 -5.5 574 2.9
13500 -1.7 28.9 235 24 12 7.4 4.0 16.1 61.1 -5.9 526 2.7
13000 -0.6 30.9 240 25 13 10.0 5.5 15.7 60.3 -6.3 479 2.4
12500 0.6 33.1 245 28 14 4.4 2.4 15.5 59.9 -6.6 428 2.2
12000 1.4 34.5 250 32 16 5.0 2.7 14.8 58.7 -7.3 390 2.0
11750 1.8 35.2 250 34 18 8.5 4.7 14.5 58.2 -7.6 369 1.9
11500 2.6 36.7 250 36 18 9.4 5.2 14.6 58.2 -7.6 340 1.7
11250 3.1 37.6 250 37 19 7.2 4.0 14.4 57.9 -7.8 315 1.6
11000 3.7 38.7 250 39 20 7.8 4.3 14.2 57.6 -8.0 291 1.5
10750 4.2 39.6 250 40 21 7.7 4.2 14.1 57.3 -8.2 267 1.4
10500 4.8 40.6 250 40 21 8.2 4.5 13.9 57.1 -8.3 242 1.2
10250 5.5 41.9 250 41 21 9.4 5.1 13.8 56.9 -8.4 215 1.1
10000 6.2 43.2 255 41 21 10.1 5.5 13.9 56.9 -8.5 185 0.9
9750 7.0 44.6 255 42 21 9.1 5.0 13.9 56.9 -8.5 156 0.8
9500 7.6 45.7 255 41 21 8.6 4.7 13.8 56.8 -8.6 129 0.7
9250 8.3 46.9 255 41 21 8.3 4.6 13.7 56.6 -8.7 102 0.5
9000 8.8 47.8 250 40 21 7.5 4.1 13.5 56.4 -8.9 78 0.4
8750 9.3 48.7 250 39 20 3.6 2.0 13.3 55.9 -9.2 57 0.3
8500 9.3 48.7 250 36 18 -0.0 -0.0 12.6 54.7 -9.9 48 0.2
8250 9.4 48.9 250 32 17 3.5 1.9 12.0 53.5 -10.6 39 0.2
8000 9.5 49.1 250 28 15 -2.2 -1.2 11.4 52.6 -11.2 27 0.1
7750 8.5 47.3 250 20 10 -28.2 -15.5 9.7 49.4 -13.0 52 0.3
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 * * * * * *
04/17/2025 at 0900 MDT | 04/17/2025 at 1200 MDT
|
CAPE... 0.0 LI... +3.3 | CAPE... 0.0 LI... +3.4
CINH... 0.0 K Index... -5.1 | CINH... 0.0 K Index... -6.7
|
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 -61.2 -78.2 245 69 35 -1.7 -0.9 | -59.9 -75.8 245 68 35 -2.2 -1.2
45000 -63.7 -82.7 245 80 41 1.3 0.7 | -63.2 -81.8 240 81 42 -1.2 -0.6
40000 -60.9 -77.6 235 90 46 1.8 1.0 | -59.8 -75.6 230 91 47 2.3 1.2
38000 -57.7 -71.9 235 90 46 7.4 4.1 | -57.0 -70.6 230 92 47 6.2 3.4
36000 -53.3 -63.9 235 87 45 7.4 4.1 | -53.2 -63.8 230 91 47 6.2 3.4
34000 -48.9 -56.0 230 84 43 7.3 4.0 | -49.3 -56.7 230 90 46 7.1 3.9
32000 -43.9 -47.0 235 81 41 7.3 4.0 | -45.0 -49.0 230 89 46 7.2 3.9
30000 -39.5 -39.1 235 77 40 7.6 4.2 | -40.6 -41.1 235 87 45 7.8 4.3
29000 -37.2 -35.0 235 76 39 7.6 4.2 | -38.3 -36.9 235 86 44 7.8 4.3
28000 -34.9 -30.8 235 75 38 7.6 4.2 | -36.0 -32.8 235 85 44 7.8 4.3
27000 -32.7 -26.9 235 73 38 7.9 4.3 | -33.6 -28.5 235 83 43 7.8 4.3
26000 -30.3 -22.5 235 73 37 8.0 4.4 | -31.3 -24.3 235 82 42 7.9 4.3
25000 -27.9 -18.2 240 72 37 8.0 4.4 | -28.3 -18.9 235 80 41 7.9 4.3
24000 -25.5 -13.9 240 71 37 8.1 4.4 | -25.9 -14.6 235 78 40 8.0 4.4
23000 -23.1 -9.6 240 71 36 8.3 4.5 | -23.5 -10.3 235 77 40 8.0 4.4
22000 -20.6 -5.1 240 70 36 8.3 4.5 | -21.1 -6.0 235 77 40 8.1 4.4
21000 -18.1 -0.6 240 69 35 7.5 4.1 | -18.8 -1.8 235 76 39 7.1 3.9
20000 -15.6 3.9 240 67 35 6.8 3.8 | -16.7 1.9 235 74 38 7.0 3.8
19500 -14.6 5.7 240 67 34 6.9 3.8 | -15.7 3.7 235 73 38 7.0 3.8
19000 -13.6 7.5 240 66 34 6.9 3.8 | -14.6 5.7 235 72 37 6.9 3.8
18500 -12.6 9.3 240 65 34 6.2 3.4 | -13.6 7.5 235 71 37 6.6 3.6
18000 -11.7 10.9 240 63 33 6.0 3.3 | -12.6 9.3 240 70 36 6.4 3.5
17500 -10.8 12.6 240 61 32 5.9 3.2 | -11.6 11.1 240 68 35 6.7 3.7
17000 -10.0 14.0 240 59 31 5.6 3.0 | -10.8 12.6 240 64 33 4.0 2.2
16500 -9.1 15.6 240 57 29 5.5 3.0 | -10.2 13.6 240 58 30 4.3 2.3
16000 -8.2 17.2 245 54 28 7.0 3.8 | -9.5 14.9 240 53 27 5.5 3.0
15500 -7.2 19.0 240 49 25 7.2 4.0 | -8.7 16.3 240 47 24 6.1 3.3
15000 -6.1 21.0 240 43 22 8.1 4.4 | -7.8 18.0 240 41 21 6.8 3.7
14500 -4.8 23.4 235 36 19 8.9 4.9 | -6.7 19.9 245 35 18 8.3 4.6
14000 -3.4 25.9 230 30 15 8.8 4.9 | -5.5 22.1 245 28 15 8.5 4.7
13500 -2.1 28.2 225 27 14 8.3 4.6 | -3.9 25.0 245 25 13 11.8 6.5
13000 -0.9 30.4 225 26 13 6.3 3.4 | -2.1 28.2 245 24 12 5.5 3.0
12500 -0.2 31.6 230 28 14 5.4 3.0 | -1.2 29.8 245 22 12 11.6 6.4
12000 0.6 33.1 240 31 16 4.9 2.7 | 0.3 32.5 245 22 11 9.8 5.4
11750 1.0 33.8 240 32 17 6.1 3.4 | 1.0 33.8 245 22 11 11.7 6.4
11500 1.5 34.7 245 34 17 6.8 3.7 | 2.0 35.6 245 22 11 11.2 6.2
11250 1.9 35.4 250 36 18 6.1 3.4 | 2.7 36.9 245 22 11 8.7 4.8
11000 2.4 36.3 250 38 20 6.1 3.3 | 3.4 38.1 245 21 11 9.4 5.1
10750 2.8 37.0 255 40 21 6.9 3.8 | 4.1 39.4 245 21 11 9.1 5.0
10500 3.4 38.1 255 41 21 8.4 4.6 | 4.7 40.5 245 21 11 9.4 5.2
10250 4.0 39.2 255 41 21 9.3 5.1 | 5.5 41.9 245 21 11 10.2 5.6
10000 4.8 40.6 255 40 21 10.0 5.5 | 6.3 43.3 245 21 11 10.6 5.8
9750 5.5 41.9 255 40 20 9.2 5.0 | 7.1 44.8 245 21 11 10.1 5.6
9500 6.1 43.0 255 38 20 8.2 4.5 | 7.8 46.0 245 20 10 9.4 5.2
9250 6.7 44.1 255 36 19 9.2 5.0 | 8.5 47.3 245 20 10 10.0 5.5
9000 7.5 45.5 255 34 18 10.2 5.6 | 9.3 48.7 245 20 10 10.7 5.9
8750 8.2 46.8 255 32 16 10.1 5.6 | 10.1 50.2 245 20 10 10.9 6.0
8500 9.0 48.2 255 29 15 10.2 5.6 | 10.9 51.6 245 19 10 11.3 6.2
8250 9.7 49.5 255 26 13 9.7 5.3 | 11.8 53.2 245 19 10 10.6 5.8
8000 10.4 50.7 255 23 12 10.5 5.8 | 12.5 54.5 245 18 9 9.9 5.5
7750 11.4 52.5 255 19 10 15.6 8.6 | 13.5 56.3 245 17 9 20.2 11.1
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
04/17/2025 at 1500 MDT | 04/17/2025 at 1800 MDT
|
CAPE... +1.2 LI... +1.2 | CAPE... +20.8 LI... -0.5
CINH... 0.0 K Index... +9.0 | CINH... 0.0 K Index... +16.4
|
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 -59.2 -74.6 245 66 34 -1.0 -0.6 | -57.3 -71.1 240 56 29 -1.6 -0.9
45000 -60.8 -77.4 240 81 42 1.0 0.5 | -59.7 -75.5 240 74 38 -0.2 -0.1
40000 -58.2 -72.8 235 92 48 1.7 0.9 | -57.5 -71.5 240 90 46 1.5 0.8
38000 -56.1 -69.0 235 96 50 4.9 2.7 | -55.9 -68.6 240 95 49 4.3 2.3
36000 -53.2 -63.8 235 99 51 4.9 2.7 | -53.3 -63.9 240 99 51 4.3 2.3
34000 -50.0 -58.0 235 101 52 6.6 3.6 | -50.1 -58.2 240 102 53 6.5 3.5
32000 -46.1 -51.0 235 99 51 6.6 3.6 | -46.3 -51.3 240 100 51 6.5 3.5
30000 -42.1 -43.8 235 96 50 7.3 4.0 | -42.3 -44.1 240 97 50 7.2 3.9
29000 -39.9 -39.8 240 93 48 7.3 4.0 | -40.2 -40.4 240 93 48 7.2 3.9
28000 -37.7 -35.9 240 90 46 7.3 4.0 | -38.0 -36.4 240 89 46 7.2 3.9
27000 -35.5 -31.9 240 87 45 7.4 4.1 | -35.9 -32.6 240 86 44 7.3 4.0
26000 -32.4 -26.3 240 76 39 8.4 4.6 | -33.6 -28.5 240 81 42 7.6 4.2
25000 -29.8 -21.6 240 67 34 8.4 4.6 | -31.3 -24.3 235 76 39 7.6 4.2
24000 -27.3 -17.1 235 57 29 8.5 4.7 | -29.0 -20.2 235 70 36 7.6 4.2
23000 -24.7 -12.5 235 58 30 8.7 4.8 | -26.6 -15.9 235 68 35 8.2 4.5
22000 -22.1 -7.8 240 59 31 8.7 4.8 | -24.2 -11.6 240 66 34 8.2 4.5
21000 -19.5 -3.1 240 60 31 6.9 3.8 | -21.2 -6.2 240 63 33 6.6 3.6
20000 -17.7 0.1 240 59 30 6.3 3.5 | -19.4 -2.9 240 55 28 6.4 3.5
19500 -16.7 1.9 240 58 30 6.3 3.5 | -18.4 -1.1 240 50 26 6.5 3.6
19000 -15.8 3.6 245 57 29 6.3 3.5 | -17.5 0.5 245 46 24 6.7 3.7
18500 -14.8 5.4 245 56 29 5.7 3.1 | -16.5 2.3 245 42 21 8.1 4.4
18000 -14.1 6.6 245 48 25 4.9 2.7 | -15.2 4.6 245 36 19 9.1 5.0
17500 -13.5 7.7 245 39 20 4.7 2.6 | -13.9 7.0 245 31 16 9.2 5.0
17000 -12.4 9.7 245 33 17 9.5 5.2 | -12.5 9.5 245 28 14 9.5 5.2
16500 -11.1 12.0 245 30 15 9.1 5.0 | -11.1 12.0 245 26 13 9.5 5.2
16000 -9.8 14.4 245 27 14 9.5 5.2 | -9.7 14.5 245 24 13 9.7 5.3
15500 -8.3 17.1 245 26 14 9.8 5.4 | -8.2 17.2 245 24 12 9.8 5.4
15000 -6.8 19.8 240 25 13 9.8 5.4 | -6.8 19.8 245 24 12 9.7 5.3
14500 -5.4 22.3 240 25 13 9.8 5.4 | -5.4 22.3 245 23 12 9.4 5.2
14000 -3.9 25.0 240 24 13 9.7 5.3 | -4.0 24.8 245 23 12 9.6 5.3
13500 -2.2 28.0 240 24 12 12.4 6.8 | -2.3 27.9 240 23 12 12.2 6.7
13000 -0.3 31.5 240 23 12 7.2 4.0 | -0.4 31.3 240 23 12 5.8 3.2
12500 0.5 32.9 240 23 12 9.6 5.3 | 0.4 32.7 240 22 11 11.2 6.1
12000 2.0 35.6 235 23 12 9.1 5.0 | 1.9 35.4 240 22 11 9.5 5.2
11750 2.7 36.9 235 23 12 12.1 6.7 | 2.6 36.7 240 22 11 11.4 6.2
11500 3.7 38.7 235 22 12 11.6 6.4 | 3.5 38.3 240 22 11 11.0 6.0
11250 4.4 39.9 235 22 11 8.3 4.6 | 4.2 39.6 240 21 11 8.5 4.7
11000 5.0 41.0 235 22 11 9.1 5.0 | 4.9 40.8 240 21 11 9.3 5.1
10750 5.7 42.3 235 22 11 9.2 5.0 | 5.6 42.1 240 21 11 8.7 4.8
10500 6.4 43.5 235 22 11 9.8 5.4 | 6.2 43.2 235 21 11 9.0 4.9
10250 7.2 45.0 235 22 11 9.9 5.4 | 6.9 44.4 235 21 11 10.1 5.5
10000 7.9 46.2 235 21 11 9.8 5.4 | 7.7 45.9 235 21 11 10.4 5.7
9750 8.7 47.7 235 21 11 10.0 5.5 | 8.5 47.3 235 20 10 10.2 5.6
9500 9.4 48.9 235 21 11 10.3 5.7 | 9.2 48.6 235 20 10 10.0 5.5
9250 10.2 50.4 235 21 11 10.4 5.7 | 10.0 50.0 235 20 10 10.2 5.6
9000 11.0 51.8 235 21 11 10.2 5.6 | 10.8 51.4 235 20 10 10.7 5.9
8750 11.7 53.1 230 20 10 10.5 5.8 | 11.5 52.7 235 19 10 10.3 5.6
8500 12.5 54.5 230 20 10 10.7 5.9 | 12.3 54.1 235 19 10 9.7 5.3
8250 13.3 55.9 230 20 10 11.2 6.1 | 13.0 55.4 230 19 10 9.8 5.4
8000 14.8 58.6 230 18 9 14.3 7.8 | 13.7 56.7 230 18 9 8.8 4.8
7750 17.9 64.2 230 16 8 89.5 49.1 | 14.4 57.9 230 17 9 11.3 6.2
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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