Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
503
UXUS97 KBOU 200004
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1803 MDT Thursday, September 19, 2024
This forecast is for Friday, September 20, 2024:
If the trigger temperature of 78.5 F/25.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1064 ft/min (5.4 m/s)
Maximum height of thermals.................. 17216 ft MSL (11931 ft AGL)
Forecast maximum temperature................... 89.0 F/32.1 C
Time of trigger temperature.................... 1130 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................. 14243 ft MSL (8958 ft AGL)
Thermal soaring outlook for Saturday 09/21..... Poor
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 18334 ft MSL (13049 ft AGL)
Wave soaring outlook for Saturday 09/21........ Poor
Remarks...
Sunrise/Sunset.................... 06:46:04 / 18:59:14 MDT
Total possible sunshine........... 12 hr 13 min 10 sec (733 min 10 sec)
Altitude of sun at 12:52:39 MDT... 50.87 degrees
Upper air data from numerical model forecast valid on 09/20/2024 at 0600 MDT
Freezing level.................. 14977 ft MSL (9692 ft AGL)
Convective condensation level... 19574 ft MSL (14289 ft AGL)
Lifted condensation level....... 18593 ft MSL (13308 ft AGL)
Lifted index.................... +2.0
K index......................... +10.4
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 -64.6 -84.3 255 62 32 2.6 1.4 M M M M M
45000 -59.1 -74.4 250 76 39 5.6 3.1 M M M M M
40000 -50.5 -58.9 250 88 45 6.6 3.6 M M M M M
38000 -46.5 -51.7 245 87 45 6.6 3.6 M M M M M
36000 -42.5 -44.5 245 87 45 6.6 3.6 M M M M M
34000 -38.8 -37.8 245 83 43 6.2 3.4 M M M M M
32000 -35.1 -31.2 245 78 40 6.2 3.4 M M M M M
30000 -30.5 -22.9 240 68 35 7.0 3.8 45.5 114.0 10.5 M M
29000 -28.4 -19.1 240 63 32 7.0 3.8 44.5 112.1 9.8 M M
28000 -26.4 -15.5 240 58 30 7.3 4.0 43.6 110.5 9.2 M M
27000 -24.1 -11.4 240 56 29 7.6 4.2 42.6 108.8 8.5 M M
26000 -21.8 -7.2 240 54 28 7.6 4.2 41.8 107.3 7.9 M M
25000 -19.5 -3.1 240 52 27 7.7 4.2 41.1 106.0 7.4 M M
24000 -17.2 1.0 240 49 25 7.6 4.2 40.3 104.5 6.9 M M
23000 -14.8 5.4 240 44 23 7.7 4.2 39.5 103.1 6.4 M M
22000 -12.5 9.5 235 40 21 8.2 4.5 38.9 101.9 6.0 M M
21000 -10.7 12.7 235 36 19 5.1 2.8 37.4 99.3 4.8 M M
20000 -9.2 15.4 235 32 17 5.1 2.8 35.8 96.4 3.5 M M
19500 -8.4 16.9 230 30 16 5.2 2.8 35.0 95.0 2.8 M M
19000 -7.7 18.1 230 28 15 5.4 3.0 34.2 93.6 2.2 M M
18500 -6.8 19.8 230 26 14 5.6 3.1 33.5 92.3 1.6 M M
18000 -6.0 21.2 235 25 13 5.6 3.1 32.8 91.0 1.0 M M
17500 -5.1 22.8 235 23 12 6.6 3.6 32.2 89.9 0.4 M M
17000 -4.1 24.6 240 21 11 6.5 3.6 31.6 88.9 -0.1 1054 5.4
16500 -3.2 26.2 240 19 10 6.5 3.6 31.1 87.9 -0.6 1011 5.1
16000 -2.2 28.0 245 18 9 6.7 3.7 30.5 86.9 -1.2 968 4.9
15500 -0.8 30.6 250 16 8 7.2 3.9 29.8 85.6 -2.0 904 4.6
15000 0.2 32.4 255 15 8 7.3 4.0 29.4 84.9 -2.5 858 4.4
14500 1.2 34.2 260 14 7 7.9 4.3 29.0 84.2 -2.9 813 4.1
14000 2.4 36.3 260 13 7 8.3 4.6 28.7 83.7 -3.2 763 3.9
13500 3.6 38.5 270 12 6 8.3 4.6 28.5 83.4 -3.5 713 3.6
13000 4.8 40.6 275 11 5 8.2 4.5 28.3 82.9 -3.8 662 3.4
12500 5.9 42.6 285 10 5 8.2 4.5 28.0 82.4 -4.1 612 3.1
12000 7.1 44.8 290 9 5 8.2 4.5 27.8 82.0 -4.4 561 2.8
11500 8.4 47.1 300 8 4 8.2 4.5 27.5 81.5 -4.6 510 2.6
11000 9.6 49.3 310 9 4 8.5 4.6 27.3 81.2 -4.9 457 2.3
10500 10.9 51.6 315 9 5 5.8 3.2 27.1 80.9 -5.0 403 2.0
10250 11.2 52.2 320 10 5 5.3 2.9 26.7 80.0 -5.5 387 2.0
10000 11.9 53.4 320 10 5 10.2 5.6 26.6 79.9 -5.6 361 1.8
9750 12.6 54.7 325 10 5 10.5 5.7 26.6 79.9 -5.6 330 1.7
9500 13.4 56.1 325 11 5 10.1 5.6 26.7 80.0 -5.5 299 1.5
9250 14.1 57.4 325 11 6 6.8 3.7 26.6 79.9 -5.6 272 1.4
9000 14.5 58.1 325 11 6 6.8 3.7 26.3 79.4 -5.9 251 1.3
8750 15.2 59.4 330 11 6 9.2 5.0 26.2 79.2 -6.0 224 1.1
8500 15.8 60.4 330 11 6 8.2 4.5 26.1 79.1 -6.1 197 1.0
8250 16.4 61.5 330 11 6 7.1 3.9 26.0 78.8 -6.2 172 0.9
8000 16.9 62.4 330 11 6 6.4 3.5 25.7 78.3 -6.5 150 0.8
7750 17.4 63.3 330 11 6 6.6 3.6 25.5 77.9 -6.7 128 0.6
7500 17.9 64.2 330 11 5 5.9 3.2 25.2 77.4 -7.0 106 0.5
7250 18.3 64.9 330 10 5 4.8 2.6 24.9 76.8 -7.4 87 0.4
7000 18.6 65.5 330 10 5 4.5 2.5 24.5 76.1 -7.8 70 0.4
6750 18.9 66.0 330 9 5 5.1 2.8 24.1 75.4 -8.2 52 0.3
6500 19.2 66.6 330 8 4 -0.0 -0.0 23.7 74.6 -8.7 37 0.2
6250 18.9 66.0 320 7 4 -5.0 -2.7 22.6 72.7 -9.8 39 0.2
6000 18.6 65.5 310 6 3 -2.2 -1.2 21.6 70.9 -10.8 40 0.2
5750 18.3 64.9 300 6 3 -7.1 -3.9 20.6 69.2 -11.8 41 0.2
5500 17.2 63.0 275 4 2 -23.6 -13.0 18.8 65.8 -13.7 68 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/20/2024 at 0900 MDT | 09/20/2024 at 1200 MDT
|
CAPE... 0.0 LI... +3.4 | CAPE... 0.0 LI... +3.9
CINH... -0.2 K Index... +13.6 | CINH... -0.2 K Index... +5.6
|
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 -64.3 -83.7 250 57 29 2.0 1.1 | -63.2 -81.8 250 52 27 0.7 0.4
45000 -59.4 -74.9 245 76 39 5.9 3.2 | -59.8 -75.6 245 80 41 5.8 3.2
40000 -50.4 -58.7 245 87 45 6.7 3.7 | -51.0 -59.8 240 90 46 6.6 3.6
38000 -46.4 -51.5 245 87 45 6.8 3.7 | -47.0 -52.6 240 88 45 6.6 3.6
36000 -42.3 -44.1 245 87 45 6.8 3.7 | -43.0 -45.4 240 86 44 6.6 3.6
34000 -38.8 -37.8 240 82 42 5.6 3.1 | -39.4 -38.9 240 80 41 5.9 3.2
32000 -35.4 -31.7 240 75 39 5.7 3.1 | -35.8 -32.4 240 73 37 6.0 3.3
30000 -30.9 -23.6 240 66 34 7.1 3.9 | -31.1 -24.0 240 64 33 7.4 4.1
29000 -28.8 -19.8 240 61 32 7.1 3.9 | -28.9 -20.0 240 60 31 7.4 4.1
28000 -26.7 -16.1 240 57 29 7.1 3.9 | -26.7 -16.1 240 56 29 7.3 4.0
27000 -24.6 -12.3 240 54 28 7.1 3.9 | -24.6 -12.3 240 54 28 7.0 3.9
26000 -22.5 -8.5 240 52 27 7.1 3.9 | -22.5 -8.5 240 51 26 7.0 3.9
25000 -20.4 -4.7 240 49 25 7.1 3.9 | -20.4 -4.7 235 49 25 7.1 3.9
24000 -18.2 -0.8 240 47 24 7.1 3.9 | -18.3 -0.9 235 47 24 6.9 3.8
23000 -16.0 3.2 240 44 22 7.2 3.9 | -16.1 3.0 235 45 23 7.0 3.9
22000 -13.8 7.2 240 40 21 7.3 4.0 | -14.0 6.8 235 42 22 7.1 3.9
21000 -11.9 10.6 240 37 19 6.3 3.4 | -12.0 10.4 235 40 21 6.6 3.6
20000 -10.0 14.0 235 34 18 6.3 3.4 | -10.0 14.0 240 38 20 6.6 3.6
19500 -9.1 15.6 235 33 17 6.3 3.5 | -9.0 15.8 240 37 19 6.6 3.6
19000 -8.2 17.2 235 31 16 6.4 3.5 | -8.0 17.6 240 36 19 6.7 3.7
18500 -7.2 19.0 235 30 15 6.4 3.5 | -7.0 19.4 240 35 18 6.8 3.7
18000 -6.3 20.7 235 29 15 6.5 3.6 | -6.0 21.2 240 34 17 6.8 3.7
17500 -5.4 22.3 235 27 14 5.7 3.1 | -5.0 23.0 240 32 17 6.7 3.7
17000 -4.6 23.7 235 26 13 5.8 3.2 | -4.0 24.8 240 30 16 6.7 3.7
16500 -3.3 26.1 235 24 12 6.9 3.8 | -2.5 27.5 240 27 14 6.6 3.6
16000 -2.3 27.9 235 23 12 6.9 3.8 | -1.5 29.3 240 25 13 6.7 3.7
15500 -1.3 29.7 235 21 11 7.7 4.3 | -0.6 30.9 235 23 12 6.6 3.6
15000 -0.2 31.6 235 20 10 7.9 4.3 | 0.3 32.5 235 20 10 6.8 3.7
14500 0.9 33.6 235 19 10 8.2 4.5 | 1.2 34.2 235 18 9 7.5 4.1
14000 2.2 36.0 240 17 9 8.4 4.6 | 2.4 36.3 230 16 8 8.1 4.4
13500 3.4 38.1 240 16 8 8.4 4.6 | 3.5 38.3 225 14 7 8.2 4.5
13000 4.7 40.5 240 14 7 8.4 4.6 | 4.8 40.6 220 13 7 8.4 4.6
12500 5.9 42.6 240 12 6 8.4 4.6 | 6.0 42.8 215 12 6 8.4 4.6
12000 7.2 45.0 240 11 5 8.3 4.6 | 7.2 45.0 210 11 6 8.5 4.7
11500 8.4 47.1 245 9 5 8.3 4.5 | 8.5 47.3 200 10 5 8.5 4.6
11000 9.6 49.3 245 8 4 7.8 4.3 | 9.8 49.6 195 10 5 8.3 4.5
10500 10.8 51.4 245 6 3 5.1 2.8 | 11.1 52.0 185 9 5 3.8 2.1
10250 11.1 52.0 245 6 3 5.3 2.9 | 11.2 52.2 180 9 5 5.0 2.7
10000 11.7 53.1 250 5 3 10.0 5.5 | 12.0 53.6 180 9 5 12.0 6.6
9750 12.5 54.5 250 5 3 9.7 5.3 | 12.7 54.9 175 9 5 10.2 5.6
9500 13.2 55.8 255 5 2 9.6 5.2 | 13.5 56.3 175 9 4 10.5 5.8
9250 13.8 56.8 260 4 2 7.1 3.9 | 14.2 57.6 170 8 4 6.8 3.7
9000 14.3 57.7 265 4 2 7.1 3.9 | 14.6 58.3 165 8 4 7.3 4.0
8750 14.9 58.8 270 4 2 8.7 4.8 | 15.4 59.7 165 7 4 10.2 5.6
8500 15.6 60.1 280 4 2 7.9 4.3 | 16.1 61.0 165 6 3 9.2 5.0
8250 16.1 61.0 290 3 2 6.6 3.6 | 16.7 62.1 160 6 3 7.3 4.0
8000 16.6 61.9 300 3 2 6.1 3.4 | 17.2 63.0 150 5 3 7.9 4.3
7750 17.1 62.8 305 3 2 7.0 3.8 | 17.9 64.2 150 5 2 10.3 5.6
7500 17.6 63.7 310 3 2 5.7 3.1 | 18.7 65.7 150 4 2 9.1 5.0
7250 17.9 64.2 315 3 2 3.6 2.0 | 19.3 66.7 145 4 2 7.2 3.9
7000 18.2 64.8 315 3 1 3.6 2.0 | 19.8 67.6 145 4 2 7.7 4.2
6750 18.5 65.3 315 2 1 6.5 3.6 | 20.5 68.9 140 4 2 12.5 6.9
6500 19.0 66.2 305 2 1 3.7 2.0 | 21.5 70.7 145 3 2 11.9 6.5
6250 19.0 66.2 270 2 1 -0.2 -0.1 | 22.2 72.0 140 3 2 9.1 5.0
6000 19.0 66.2 230 2 1 0.6 0.3 | 22.9 73.2 135 3 2 9.2 5.0
5750 19.1 66.4 210 3 1 1.9 1.0 | 23.7 74.7 135 3 2 12.3 6.7
5500 19.3 66.7 220 3 2 5.5 3.0 | 25.0 77.0 135 3 1 22.7 12.4
09/20/2024 at 1500 MDT | 09/20/2024 at 1800 MDT
|
CAPE... 0.0 LI... +4.1 | CAPE... 0.0 LI... +2.4
CINH... 0.0 K Index... +17.6 | CINH... 0.0 K Index... +14.7
|
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 -63.1 -81.6 250 53 27 0.4 0.2 | -63.9 -83.0 250 50 26 1.3 0.7
45000 -60.1 -76.2 250 84 43 5.8 3.2 | -59.9 -75.8 250 81 42 5.6 3.1
40000 -51.2 -60.2 240 90 46 6.9 3.8 | -51.4 -60.5 240 89 46 6.9 3.8
38000 -47.1 -52.8 240 89 46 6.9 3.8 | -47.2 -53.0 240 87 45 6.9 3.8
36000 -42.9 -45.2 240 88 45 6.9 3.8 | -43.0 -45.4 240 86 44 6.9 3.8
34000 -39.1 -38.4 240 82 42 6.3 3.5 | -38.9 -38.0 240 81 42 6.8 3.7
32000 -34.8 -30.6 240 75 38 6.1 3.4 | -34.8 -30.6 240 76 39 6.8 3.7
30000 -30.7 -23.3 240 66 34 7.0 3.9 | -30.5 -22.9 240 68 35 6.4 3.5
29000 -28.6 -19.5 240 62 32 7.0 3.9 | -28.6 -19.5 240 64 33 6.4 3.5
28000 -26.5 -15.7 240 57 29 7.4 4.1 | -26.7 -16.1 240 60 31 7.1 3.9
27000 -24.2 -11.6 240 55 28 7.8 4.3 | -24.3 -11.7 240 58 30 8.0 4.4
26000 -21.9 -7.4 240 53 27 7.8 4.3 | -21.9 -7.4 240 55 28 8.0 4.4
25000 -19.5 -3.1 240 51 26 7.9 4.3 | -19.5 -3.1 245 52 27 8.0 4.4
24000 -17.2 1.0 240 50 26 7.5 4.1 | -17.1 1.2 245 50 26 7.8 4.3
23000 -14.9 5.2 240 49 25 7.6 4.2 | -14.8 5.4 245 48 25 7.9 4.3
22000 -12.5 9.5 240 47 24 7.8 4.3 | -12.4 9.7 250 47 24 8.2 4.5
21000 -10.5 13.1 240 45 23 6.6 3.6 | -10.8 12.6 250 42 22 4.7 2.6
20000 -8.5 16.7 240 42 22 6.6 3.6 | -9.4 15.1 255 37 19 4.8 2.6
19500 -7.5 18.5 240 41 21 6.6 3.6 | -8.7 16.3 260 34 18 4.9 2.7
19000 -6.5 20.3 245 39 20 5.8 3.2 | -8.0 17.6 260 32 16 6.0 3.3
18500 -5.7 21.7 245 38 19 5.5 3.0 | -7.1 19.2 260 27 14 6.6 3.6
18000 -4.9 23.2 245 36 19 5.6 3.1 | -6.2 20.8 260 23 12 6.8 3.7
17500 -4.2 24.4 250 34 17 5.0 2.7 | -5.1 22.8 255 20 10 9.1 5.0
17000 -3.5 25.7 250 31 16 5.3 2.9 | -3.7 25.3 250 19 10 8.9 4.9
16500 -2.8 27.0 250 28 15 6.5 3.6 | -2.4 27.7 245 17 9 9.0 5.0
16000 -1.8 28.8 250 25 13 7.1 3.9 | -1.1 30.0 240 17 9 9.1 5.0
15500 -0.8 30.6 250 22 12 7.5 4.1 | 0.3 32.5 235 17 9 9.0 4.9
15000 0.3 32.5 250 21 11 8.3 4.6 | 1.6 34.9 230 17 9 8.7 4.8
14500 2.1 35.8 240 18 9 8.3 4.6 | 3.6 38.5 220 17 9 8.8 4.8
14000 3.4 38.1 235 17 9 8.4 4.6 | 4.9 40.8 215 17 9 8.9 4.9
13500 4.7 40.5 225 16 8 8.3 4.6 | 6.2 43.2 215 17 9 8.9 4.9
13000 6.0 42.8 215 16 8 8.0 4.4 | 7.6 45.7 210 17 9 9.0 4.9
12500 7.2 45.0 210 15 8 8.1 4.4 | 8.9 48.0 205 17 9 9.0 4.9
12000 8.5 47.3 200 14 7 8.7 4.8 | 10.3 50.5 200 16 8 8.8 4.8
11500 9.8 49.6 195 12 6 8.7 4.8 | 11.6 52.9 195 16 8 9.0 4.9
11000 11.0 51.8 190 11 6 7.8 4.3 | 12.8 55.0 190 14 7 7.5 4.1
10500 12.1 53.8 185 10 5 10.5 5.8 | 13.9 57.0 185 13 7 11.6 6.3
10250 13.1 55.6 185 10 5 11.6 6.3 | 15.0 59.0 180 12 6 12.2 6.7
10000 13.7 56.7 185 9 5 8.7 4.8 | 15.6 60.1 180 11 6 7.3 4.0
9750 14.4 57.9 185 9 5 9.5 5.2 | 16.2 61.2 175 10 5 8.6 4.7
9500 15.1 59.2 180 8 4 9.2 5.1 | 16.8 62.2 175 9 5 8.3 4.6
9250 15.8 60.4 180 8 4 8.6 4.7 | 17.5 63.5 170 8 4 8.0 4.4
9000 16.4 61.5 180 8 4 9.4 5.2 | 18.1 64.6 170 7 4 8.8 4.8
8750 17.2 63.0 180 7 4 10.4 5.7 | 18.8 65.8 165 6 3 9.6 5.3
8500 18.0 64.4 180 7 4 10.1 5.5 | 19.5 67.1 165 5 3 9.4 5.1
8250 18.7 65.7 180 7 3 9.7 5.3 | 20.2 68.4 160 4 2 9.8 5.4
8000 19.4 66.9 180 7 3 9.8 5.4 | 20.9 69.6 160 4 2 9.6 5.3
7750 20.2 68.4 180 6 3 10.3 5.6 | 21.6 70.9 160 3 2 9.2 5.1
7500 20.9 69.6 180 6 3 10.2 5.6 | 22.3 72.1 160 2 1 9.3 5.1
7250 21.7 71.1 180 6 3 10.2 5.6 | 23.0 73.4 155 2 1 9.1 5.0
7000 22.5 72.5 185 6 3 10.2 5.6 | 23.7 74.7 160 1 1 9.2 5.0
6750 23.2 73.8 185 6 3 10.0 5.5 | 24.4 75.9 160 1 0 9.3 5.1
6500 24.0 75.2 185 5 3 10.0 5.5 | 25.1 77.2 000 0 0 9.6 5.3
6250 24.7 76.5 185 5 3 10.3 5.7 | 25.8 78.4 000 0 0 10.1 5.5
6000 25.5 77.9 185 5 3 9.8 5.4 | 26.6 79.9 000 0 0 10.1 5.6
5750 26.3 79.3 185 5 2 12.5 6.8 | 27.3 81.1 325 1 0 10.1 5.5
5500 27.5 81.5 185 4 2 21.3 11.7 | 28.1 82.6 325 1 1 9.8 5.4
________________________________________________________________________________
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 old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 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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