Soaring Guidance
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
423
UXUS97 KPUB 181239
SRGPUB
Soaring Forecast
National Weather Service Pueblo, Colorado
0639 MDT Friday, April 18, 2025
This forecast is for the Air Force Academy for Friday, April 18, 2025:
If the trigger temperature of 42.6 F/5.9 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 10976 ft MSL (3348 ft AGL)
Forecast maximum temperature................... 37.0 F/3.2 C
Time of trigger temperature.................... None
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 9958 ft MSL (2330 ft AGL)
Thermal soaring outlook for Saturday 04/19..... Poor
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:17:28 / 19:39:31 MDT
Total possible sunshine........... 13 hr 22 min 3 sec (802 min 3 sec)
Altitude of sun at 12:58:30 MDT... 62.13 degrees
Upper air data from numerical model forecast valid on 04/18/2025 at 0600 MDT
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 13974 ft MSL (6346 ft AGL)
Lifted condensation level....... 11690 ft MSL (4063 ft AGL)
Lifted index.................... +6.1
K index......................... +3.7
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 -55.0 -67.0 230 54 28 -0.2 -0.1 M M M M M
45000 -55.4 -67.7 225 70 36 -0.4 -0.2 M M M M M
40000 -52.8 -63.0 230 76 39 1.8 1.0 M M M M M
38000 -51.7 -61.1 230 81 42 1.7 0.9 M M M M M
36000 -50.7 -59.3 225 91 47 1.7 0.9 M M M M M
34000 -49.7 -57.5 225 101 52 2.1 1.2 M M M M M
32000 -47.8 -54.0 225 98 50 3.1 1.7 M M M M M
30000 -45.9 -50.6 225 94 48 4.1 2.2 M M M M M
29000 -44.2 -47.6 225 89 46 6.2 3.4 21.8 71.3 14.8 M M
28000 -42.3 -44.1 225 83 43 6.2 3.4 20.4 68.7 13.9 M M
27000 -40.5 -40.9 225 78 40 6.2 3.4 19.1 66.5 13.0 M M
26000 -38.4 -37.1 225 75 38 7.6 4.2 18.1 64.5 12.3 M M
25000 -36.1 -33.0 225 73 37 7.6 4.2 17.2 63.0 11.8 M M
24000 -33.3 -27.9 225 70 36 7.6 4.2 16.3 61.4 11.2 M M
23000 -30.9 -23.6 230 67 34 8.0 4.4 15.6 60.1 10.7 M M
22000 -28.5 -19.3 230 63 33 8.0 4.4 14.9 58.9 10.3 M M
21000 -26.2 -15.2 230 59 31 7.9 4.4 14.4 57.9 10.0 M M
20000 -23.9 -11.0 230 57 29 7.5 4.1 13.6 56.5 9.4 M M
19500 -22.8 -9.0 230 56 29 7.5 4.1 13.2 55.8 9.1 M M
19000 -21.6 -6.9 235 55 29 7.5 4.1 12.8 55.1 8.8 M M
18500 -20.5 -4.9 235 54 28 7.7 4.2 12.5 54.5 8.6 M M
18000 -19.5 -3.1 235 53 27 5.9 3.2 12.0 53.6 8.2 M M
17500 -18.6 -1.5 235 52 27 6.1 3.3 11.4 52.5 7.6 M M
17000 -17.7 0.1 235 50 26 6.4 3.5 10.8 51.4 7.1 M M
16500 -16.7 1.9 235 49 25 6.6 3.6 10.2 50.4 6.7 M M
16000 -15.8 3.6 235 48 25 7.0 3.8 9.7 49.5 6.2 M M
15500 -14.6 5.7 235 46 24 8.5 4.7 9.4 49.0 5.9 M M
15000 -13.3 8.1 235 44 23 8.5 4.6 9.2 48.6 5.7 M M
14500 -12.0 10.4 235 42 22 9.7 5.3 9.1 48.4 5.6 M M
14000 -10.6 12.9 235 40 21 9.6 5.3 9.1 48.4 5.6 M M
13500 -9.2 15.4 230 39 20 9.4 5.1 9.1 48.3 5.6 M M
13000 -7.8 18.0 230 38 20 9.3 5.1 9.0 48.2 5.5 M M
12500 -6.5 20.3 230 37 19 5.4 3.0 8.9 48.0 5.4 M M
12000 -6.2 20.8 225 35 18 3.3 1.8 7.7 45.9 4.3 M M
11750 -6.0 21.2 225 34 17 0.3 0.2 7.2 44.9 3.8 M M
11500 -6.3 20.7 220 31 16 -7.1 -3.9 6.1 43.0 2.8 M M
11250 -6.9 19.6 215 27 14 -6.0 -3.3 4.7 40.5 1.4 M M
11000 -7.2 19.0 210 23 12 -2.9 -1.6 3.7 38.7 0.4 M M
10750 -7.5 18.5 200 21 11 -2.5 -1.3 2.7 36.8 -0.6 361 1.8
10500 -7.5 18.5 190 18 9 2.6 1.4 1.9 35.5 -1.3 354 1.8
10250 -7.2 19.0 175 15 8 2.1 1.1 1.4 34.6 -1.8 340 1.7
10000 -7.2 19.0 165 12 6 -1.4 -0.8 0.7 33.2 -2.6 332 1.7
9750 -7.3 18.9 145 11 6 -0.2 -0.1 -0.2 31.7 -3.4 327 1.7
9500 -7.2 19.0 135 9 5 1.2 0.7 -0.9 30.5 -4.1 318 1.6
9250 -7.1 19.2 115 7 4 1.8 1.0 -1.5 29.3 -4.7 308 1.6
9000 -7.0 19.4 090 6 3 2.6 1.4 -2.1 28.3 -5.3 295 1.5
8750 -6.7 19.9 070 7 3 6.1 3.4 -2.5 27.5 -5.7 279 1.4
8500 -6.1 21.0 070 6 3 8.6 4.7 -2.7 27.2 -5.9 254 1.3
8250 -5.5 22.1 065 6 3 7.6 4.2 -2.8 27.0 -6.1 229 1.2
8000 -4.9 23.2 055 5 3 9.1 5.0 -2.9 26.8 -6.2 204 1.0
7750 -3.0 26.6 060 5 2 14.8 8.1 -2.4 27.7 -5.8 131 0.7
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 * * * * * *
04/18/2025 at 0900 MDT | 04/18/2025 at 1200 MDT
|
CAPE... +17.3 LI... +2.0 | CAPE... +41.1 LI... +0.9
CINH... 0.0 K Index... +2.8 | CINH... 0.0 K Index... +10.1
|
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 -53.7 -64.7 230 45 23 0.1 0.1 | -53.1 -63.6 230 38 20 0.1 0.0
45000 -53.5 -64.3 225 71 37 0.1 0.1 | -52.9 -63.2 225 65 34 0.1 0.0
40000 -52.3 -62.1 225 77 39 0.8 0.4 | -52.4 -62.3 220 76 39 0.3 0.2
38000 -51.7 -61.1 225 81 41 1.5 0.8 | -52.0 -61.6 220 80 41 1.9 1.0
36000 -50.8 -59.4 225 90 46 1.5 0.8 | -50.9 -59.6 220 87 45 1.9 1.0
34000 -49.9 -57.8 220 99 51 1.6 0.9 | -49.7 -57.5 220 93 48 1.9 1.0
32000 -48.4 -55.1 220 98 50 2.6 1.4 | -48.2 -54.8 220 92 47 2.2 1.2
30000 -46.9 -52.4 220 96 49 3.2 1.8 | -46.9 -52.4 220 89 46 3.5 1.9
29000 -45.1 -49.2 220 90 47 6.2 3.4 | -45.2 -49.4 220 84 43 5.8 3.2
28000 -43.3 -45.9 220 84 43 6.2 3.4 | -43.5 -46.3 220 78 40 5.8 3.2
27000 -41.4 -42.5 220 78 40 6.2 3.4 | -41.8 -43.2 220 72 37 5.9 3.2
26000 -39.3 -38.7 220 73 37 8.2 4.5 | -39.8 -39.6 220 66 34 7.4 4.1
25000 -36.9 -34.4 220 69 35 8.1 4.5 | -37.6 -35.7 220 61 31 7.4 4.1
24000 -33.8 -28.8 220 63 33 8.1 4.5 | -35.4 -31.7 220 55 28 7.5 4.1
23000 -31.4 -24.5 220 59 31 8.0 4.4 | -33.0 -27.4 225 51 26 8.4 4.6
22000 -29.0 -20.2 225 56 29 8.0 4.4 | -30.5 -22.9 225 50 26 8.4 4.6
21000 -26.6 -15.9 225 52 27 8.0 4.4 | -28.0 -18.4 225 48 25 8.4 4.6
20000 -24.3 -11.7 225 49 25 7.5 4.1 | -25.6 -14.1 225 47 24 7.8 4.3
19500 -23.2 -9.8 225 47 24 7.5 4.1 | -23.9 -11.0 225 46 24 7.8 4.3
19000 -22.0 -7.6 230 45 23 7.6 4.1 | -22.7 -8.9 225 46 24 7.8 4.3
18500 -20.9 -5.6 230 44 22 7.6 4.2 | -21.5 -6.7 225 45 23 7.8 4.3
18000 -19.8 -3.6 230 42 22 7.1 3.9 | -20.5 -4.9 225 45 23 6.9 3.8
17500 -18.7 -1.7 230 41 21 7.2 3.9 | -19.4 -2.9 225 44 23 7.0 3.8
17000 -17.7 0.1 230 41 21 7.0 3.8 | -18.4 -1.1 225 44 23 6.8 3.7
16500 -16.6 2.1 230 40 21 6.9 3.8 | -17.4 0.7 225 43 22 6.8 3.7
16000 -15.6 3.9 235 40 20 6.8 3.7 | -16.4 2.5 225 42 22 6.7 3.7
15500 -14.6 5.7 235 40 20 6.7 3.7 | -15.5 4.1 220 42 21 6.6 3.6
15000 -13.6 7.5 235 39 20 6.6 3.6 | -14.5 5.9 220 41 21 6.6 3.6
14500 -12.6 9.3 230 39 20 7.9 4.4 | -13.4 7.9 220 39 20 8.5 4.7
14000 -11.4 11.5 230 38 20 7.8 4.3 | -12.2 10.0 215 36 19 8.5 4.7
13500 -10.2 13.6 230 37 19 8.9 4.9 | -11.0 12.2 215 33 17 7.7 4.2
13000 -8.9 16.0 225 36 18 9.2 5.1 | -9.9 14.2 210 30 16 8.5 4.7
12500 -7.9 17.8 225 34 18 3.3 1.8 | -9.3 15.3 210 28 14 -1.6 -0.9
12000 -7.7 18.1 225 31 16 2.3 1.3 | -9.6 14.7 215 22 11 -2.2 -1.2
11750 -7.6 18.3 225 29 15 -0.6 -0.3 | -9.8 14.4 215 19 10 -3.9 -2.2
11500 -7.9 17.8 220 26 13 -6.9 -3.8 | -10.2 13.6 215 15 8 -5.1 -2.8
11250 -8.4 16.9 215 22 11 -5.4 -3.0 | -10.4 13.3 210 10 5 -0.6 -0.3
11000 -8.7 16.3 210 18 9 -2.9 -1.6 | -10.4 13.3 195 6 3 1.3 0.7
10750 -8.9 16.0 200 14 7 -2.1 -1.2 | -10.3 13.5 140 3 2 2.5 1.3
10500 -9.0 15.8 185 11 6 1.1 0.6 | -10.0 14.0 100 5 2 4.6 2.5
10250 -8.8 16.2 165 10 5 2.1 1.1 | -9.6 14.7 085 6 3 6.4 3.5
10000 -8.7 16.3 145 9 5 1.5 0.8 | -9.0 15.8 075 8 4 8.8 4.8
9750 -8.6 16.5 130 8 4 3.6 2.0 | -8.4 16.9 065 9 5 8.2 4.5
9500 -8.2 17.2 115 7 4 6.1 3.3 | -7.8 18.0 060 10 5 7.5 4.1
9250 -7.7 18.1 100 7 4 6.3 3.5 | -7.3 18.9 050 12 6 8.3 4.6
9000 -7.2 19.0 085 7 4 8.9 4.9 | -6.6 20.1 050 13 7 10.6 5.8
8750 -6.5 20.3 080 8 4 9.6 5.3 | -5.8 21.6 045 13 7 10.1 5.5
8500 -5.8 21.6 075 8 4 8.9 4.9 | -5.1 22.8 045 13 7 9.1 5.0
8250 -5.2 22.6 075 7 4 8.6 4.7 | -4.5 23.9 040 13 6 8.5 4.7
8000 -4.5 23.9 075 7 4 10.5 5.7 | -3.8 25.2 040 12 6 10.4 5.7
7750 -3.5 25.7 075 6 3 16.1 8.8 | -2.8 27.0 040 11 5 17.2 9.5
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
04/18/2025 at 1500 MDT | 04/18/2025 at 1800 MDT
|
CAPE... +35.5 LI... -0.8 | CAPE... +23.6 LI... +1.3
CINH... 0.0 K Index... +15.1 | CINH... 0.0 K Index... +15.6
|
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 -52.4 -62.3 225 43 22 1.2 0.6 | -53.4 -64.1 230 47 24 1.2 0.7
45000 -50.6 -59.1 225 56 29 1.4 0.7 | -51.6 -60.9 235 58 30 1.2 0.7
40000 -51.1 -60.0 225 70 36 -0.4 -0.2 | -51.0 -59.8 225 63 32 0.2 0.1
38000 -51.3 -60.3 220 76 39 0.5 0.3 | -51.0 -59.8 225 65 33 -0.7 -0.4
36000 -50.9 -59.6 225 79 41 0.5 0.3 | -51.5 -60.7 225 67 34 -0.7 -0.4
34000 -50.6 -59.1 225 83 43 0.5 0.3 | -51.9 -61.4 230 69 35 -0.9 -0.5
32000 -50.1 -58.2 225 75 38 0.8 0.4 | -51.5 -60.7 230 62 32 0.8 0.4
30000 -49.7 -57.5 230 65 34 2.6 1.4 | -51.1 -60.0 235 55 28 1.3 0.7
29000 -47.8 -54.0 230 58 30 7.0 3.8 | -49.1 -56.4 235 51 26 8.0 4.4
28000 -45.7 -50.3 235 51 26 7.0 3.8 | -46.7 -52.1 235 47 24 7.9 4.3
27000 -43.6 -46.5 240 43 22 7.0 3.9 | -44.3 -47.7 235 42 22 8.0 4.4
26000 -41.2 -42.2 240 39 20 9.1 5.0 | -41.7 -43.1 235 40 21 9.5 5.2
25000 -38.5 -37.3 245 38 20 9.1 5.0 | -38.9 -38.0 235 41 21 9.5 5.2
24000 -35.7 -32.3 245 37 19 9.1 5.0 | -35.3 -31.5 230 41 21 9.6 5.3
23000 -33.1 -27.6 240 37 19 8.8 4.8 | -32.7 -26.9 230 42 22 8.3 4.6
22000 -30.4 -22.7 235 39 20 8.8 4.8 | -30.2 -22.4 230 43 22 8.3 4.6
21000 -27.8 -18.0 235 42 21 8.9 4.9 | -27.7 -17.9 225 44 23 8.4 4.6
20000 -25.6 -14.1 230 45 23 6.7 3.7 | -25.1 -13.2 225 43 22 8.7 4.8
19500 -24.1 -11.4 225 47 24 6.7 3.7 | -23.8 -10.8 225 42 22 8.7 4.8
19000 -23.1 -9.6 225 49 25 6.7 3.7 | -22.5 -8.5 225 42 21 8.8 4.8
18500 -22.1 -7.8 220 51 26 6.8 3.7 | -21.2 -6.2 225 41 21 8.8 4.8
18000 -21.0 -5.8 220 51 26 8.6 4.7 | -20.0 -4.0 225 40 21 8.1 4.4
17500 -19.7 -3.5 220 50 26 8.5 4.7 | -18.8 -1.8 225 38 20 8.2 4.5
17000 -18.5 -1.3 215 49 25 8.0 4.4 | -17.6 0.3 225 37 19 7.4 4.0
16500 -17.4 0.7 215 47 24 7.9 4.3 | -16.6 2.1 225 35 18 7.1 3.9
16000 -16.3 2.7 215 45 23 8.3 4.5 | -15.5 4.1 220 34 17 6.8 3.7
15500 -15.0 5.0 210 43 22 9.0 4.9 | -14.6 5.7 220 32 17 6.3 3.4
15000 -13.7 7.3 210 41 21 8.9 4.9 | -13.7 7.3 220 31 16 6.2 3.4
14500 -12.5 9.5 205 39 20 7.0 3.8 | -12.9 8.8 220 29 15 4.7 2.6
14000 -11.5 11.3 205 38 19 7.8 4.3 | -12.2 10.0 215 27 14 5.1 2.8
13500 -10.8 12.6 205 34 18 1.0 0.5 | -11.7 10.9 215 24 12 2.0 1.1
13000 -10.6 12.9 205 29 15 2.1 1.2 | -11.3 11.7 220 20 10 2.5 1.4
12500 -10.8 12.6 205 25 13 -4.8 -2.7 | -11.1 12.0 225 16 8 -0.6 -0.3
12000 -11.4 11.5 215 14 7 -4.8 -2.6 | -11.2 11.8 240 9 5 -0.8 -0.4
11750 -11.7 10.9 230 9 4 -2.8 -1.5 | -11.3 11.7 265 7 3 -0.2 -0.1
11500 -11.8 10.8 225 6 3 0.7 0.4 | -11.2 11.8 280 5 3 0.6 0.3
11250 -11.6 11.1 205 3 2 3.4 1.8 | -11.2 11.8 295 4 2 1.0 0.5
11000 -11.3 11.7 145 2 1 4.7 2.6 | -11.1 12.0 320 3 2 0.8 0.4
10750 -11.0 12.2 105 4 2 3.9 2.2 | -11.0 12.2 355 4 2 2.2 1.2
10500 -10.7 12.7 085 7 4 2.9 1.6 | -10.8 12.6 035 4 2 3.6 2.0
10250 -10.5 13.1 075 11 6 4.5 2.5 | -10.5 13.1 060 5 3 4.2 2.3
10000 -10.1 13.8 070 13 7 6.7 3.7 | -10.2 13.6 065 8 4 5.7 3.1
9750 -9.6 14.7 065 15 8 7.4 4.1 | -9.7 14.5 065 10 5 6.4 3.5
9500 -9.0 15.8 055 15 8 7.7 4.2 | -9.2 15.4 065 12 6 6.6 3.6
9250 -8.4 16.9 050 16 8 8.3 4.5 | -8.7 16.3 065 13 7 6.8 3.7
9000 -7.7 18.1 045 16 8 10.5 5.8 | -8.2 17.2 060 15 8 8.6 4.7
8750 -7.0 19.4 045 16 8 10.2 5.6 | -7.5 18.5 060 15 8 9.5 5.2
8500 -6.3 20.7 040 15 8 9.4 5.2 | -6.8 19.8 055 14 7 9.3 5.1
8250 -5.6 21.9 040 15 8 9.0 4.9 | -6.2 20.8 050 14 7 9.0 5.0
8000 -4.9 23.2 035 14 7 11.4 6.3 | -5.5 22.1 050 13 7 11.2 6.1
7750 -3.8 25.2 035 12 6 17.9 9.8 | -4.5 23.9 045 11 6 15.8 8.7
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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