Soaring Guidance Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 171420
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0820 MDT Wednesday, April 17, 2024
This forecast is for Wednesday, April 17, 2024:
If the trigger temperature of 63.1 F/17.3 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 475 ft/min (2.4 m/s)
Maximum height of thermals.................. 15094 ft MSL (9773 ft AGL)
Forecast maximum temperature................... 69.0 F/21.0 C
Time of trigger temperature.................... 1030 MDT
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................. 10246 ft MSL (4925 ft AGL)
Thermal soaring outlook for Thursday 04/18..... 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)................ Weak NVA
Potential height of wave....................... 53589 ft MSL (48268 ft AGL)
Wave soaring outlook for Thursday 04/18........ Poor
Remarks...
Sunrise/Sunset.................... 06:17:40 / 19:40:04 MDT
Total possible sunshine........... 13 hr 22 min 24 sec (802 min 24 sec)
Altitude of sun at 12:58:52 MDT... 61.08 degrees
Upper air data from numerical model forecast valid on 04/17/2024 at 0600 MDT
Freezing level.................. 11434 ft MSL (6113 ft AGL)
Convective condensation level... 16368 ft MSL (11047 ft AGL)
Lifted condensation level....... 16008 ft MSL (10688 ft AGL)
Lifted index.................... +1.4
K index......................... +8.1
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 -57.2 -71.0 275 49 25 3.8 2.1 M M M M M
45000 -52.0 -61.6 275 54 28 -4.2 -2.3 M M M M M
40000 -57.5 -71.5 275 54 28 -3.7 -2.0 M M M M M
38000 -57.2 -71.0 275 53 27 4.0 2.2 M M M M M
36000 -54.8 -66.6 275 51 26 4.0 2.2 M M M M M
34000 -51.5 -60.7 275 49 25 7.4 4.1 M M M M M
32000 -47.0 -52.6 270 47 24 7.4 4.1 M M M M M
30000 -42.4 -44.3 270 46 23 8.3 4.5 33.2 91.7 9.5 M M
29000 -39.9 -39.8 265 44 23 8.3 4.5 32.5 90.5 9.1 M M
28000 -37.4 -35.3 265 43 22 8.3 4.5 32.0 89.6 8.8 M M
27000 -35.0 -31.0 265 42 22 7.6 4.2 31.5 88.7 8.5 M M
26000 -32.7 -26.9 265 42 21 7.5 4.1 30.5 86.9 7.8 M M
25000 -30.5 -22.9 260 41 21 7.5 4.1 29.7 85.4 7.2 M M
24000 -28.3 -18.9 260 40 21 7.2 3.9 29.0 84.2 6.7 M M
23000 -26.2 -15.2 260 38 20 6.8 3.7 27.8 82.0 5.8 M M
22000 -24.2 -11.6 260 37 19 6.8 3.7 26.7 80.1 5.0 M M
21000 -22.1 -7.8 255 35 18 7.7 4.2 25.8 78.4 4.2 M M
20000 -19.8 -3.6 260 33 17 7.8 4.3 25.0 77.1 3.6 M M
19500 -18.6 -1.5 260 32 17 7.8 4.3 24.7 76.4 3.4 M M
19000 -17.5 0.5 260 31 16 7.8 4.3 24.4 75.9 3.1 M M
18500 -16.3 2.7 260 30 16 7.5 4.1 24.1 75.3 2.9 M M
18000 -14.7 5.5 265 29 15 7.3 4.0 23.4 74.2 2.3 M M
17500 -13.6 7.5 265 28 14 7.1 3.9 23.0 73.4 2.0 M M
17000 -12.5 9.5 265 27 14 7.0 3.8 22.5 72.5 1.6 M M
16500 -11.5 11.3 265 25 13 6.9 3.8 22.1 71.7 1.2 M M
16000 -10.5 13.1 270 24 12 6.8 3.8 21.6 70.8 0.7 M M
15500 -9.5 14.9 270 23 12 6.8 3.7 21.1 69.9 0.3 M M
15000 -8.4 16.9 270 22 11 7.4 4.1 20.6 69.1 -0.1 859 4.4
14500 -7.3 18.9 270 20 10 7.3 4.0 20.2 68.4 -0.5 812 4.1
14000 -6.2 20.8 270 19 10 7.9 4.3 19.9 67.8 -0.9 764 3.9
13500 -5.0 23.0 270 17 9 8.0 4.4 19.6 67.2 -1.2 714 3.6
13000 -3.8 25.2 270 16 8 8.2 4.5 19.3 66.7 -1.4 663 3.4
12500 -2.6 27.3 270 15 8 8.3 4.6 19.1 66.3 -1.7 611 3.1
12000 -1.4 29.5 270 14 7 8.5 4.6 18.9 65.9 -1.9 560 2.8
11500 -0.1 31.8 265 14 7 8.5 4.7 18.6 65.6 -2.1 507 2.6
11000 1.1 34.0 265 14 7 7.5 4.1 18.4 65.2 -2.3 455 2.3
10500 2.2 36.0 270 14 7 6.0 3.3 18.0 64.4 -2.8 409 2.1
10250 2.7 36.9 270 14 7 11.0 6.0 17.8 64.0 -3.0 386 2.0
10000 3.7 38.7 270 15 8 11.6 6.4 18.1 64.6 -2.7 348 1.8
9750 4.3 39.7 270 15 8 6.9 3.8 17.9 64.3 -2.9 323 1.6
9500 4.9 40.8 270 15 8 8.4 4.6 17.8 64.0 -3.1 298 1.5
9250 5.4 41.7 275 16 8 7.2 3.9 17.7 63.8 -3.2 274 1.4
9000 5.9 42.6 275 16 8 6.9 3.8 17.4 63.4 -3.4 251 1.3
8750 6.5 43.7 275 15 8 7.8 4.3 17.3 63.1 -3.6 228 1.2
8500 7.1 44.8 275 15 8 8.0 4.4 17.1 62.8 -3.8 203 1.0
8250 7.6 45.7 275 14 7 7.5 4.1 17.0 62.5 -4.0 179 0.9
8000 8.2 46.8 275 13 7 6.9 3.8 16.8 62.2 -4.2 156 0.8
7750 8.7 47.7 275 12 6 7.3 4.0 16.5 61.8 -4.4 133 0.7
7500 9.2 48.6 270 11 5 7.6 4.1 16.4 61.5 -4.6 109 0.6
7250 9.7 49.5 270 9 5 6.3 3.5 16.2 61.1 -4.8 86 0.4
7000 10.2 50.4 265 9 4 5.1 2.8 15.8 60.5 -5.2 66 0.3
6750 10.6 51.1 260 8 4 6.8 3.7 15.5 60.0 -5.5 46 0.2
6500 11.1 52.0 250 7 3 5.3 2.9 15.3 59.6 -5.7 24 0.1
6250 11.3 52.3 240 6 3 1.1 0.6 14.8 58.6 -6.3 10 0.1
6000 11.3 52.3 230 6 3 1.1 0.6 14.1 57.4 -7.0 2 0.0
5750 11.4 52.5 220 6 3 -1.4 -0.8 13.4 56.2 -7.7 M M
5500 10.7 51.3 205 7 3 -18.0 -9.9 12.1 53.7 -9.1 5 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/17/2024 at 0900 MDT | 04/17/2024 at 1200 MDT
|
CAPE... +5.4 LI... +2.6 | CAPE... +0.2 LI... +1.1
CINH... -9.8 K Index... +13.2 | CINH... -0.7 K Index... +19.0
|
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 -56.4 -69.5 270 54 28 3.6 2.0 | -56.8 -70.2 265 59 30 2.9 1.6
45000 -51.4 -60.5 275 66 34 -4.3 -2.4 | -52.8 -63.0 270 72 37 -3.2 -1.8
40000 -58.4 -73.1 270 62 32 -4.6 -2.5 | -58.3 -72.9 275 69 35 -3.6 -2.0
38000 -58.1 -72.6 270 59 31 4.7 2.6 | -57.2 -71.0 280 67 34 5.0 2.8
36000 -55.3 -67.5 270 55 29 4.7 2.6 | -54.2 -65.6 285 64 33 5.0 2.8
34000 -51.5 -60.7 270 52 27 8.0 4.4 | -50.6 -59.1 285 61 31 7.8 4.3
32000 -46.7 -52.1 270 51 26 8.1 4.4 | -45.9 -50.6 275 55 28 7.9 4.3
30000 -41.8 -43.2 270 49 25 8.0 4.4 | -41.1 -42.0 270 51 26 8.0 4.4
29000 -39.5 -39.1 270 48 25 8.0 4.4 | -38.7 -37.7 270 51 26 8.0 4.4
28000 -37.1 -34.8 270 47 24 8.0 4.4 | -36.4 -33.5 270 50 26 8.0 4.4
27000 -34.7 -30.5 270 47 24 7.8 4.3 | -34.0 -29.2 270 50 26 7.6 4.2
26000 -32.4 -26.3 270 46 24 7.7 4.2 | -31.7 -25.1 270 48 25 7.5 4.1
25000 -30.1 -22.2 270 45 23 7.7 4.2 | -29.5 -21.1 270 47 24 7.5 4.1
24000 -27.8 -18.0 270 44 23 7.2 4.0 | -27.2 -17.0 270 46 24 7.4 4.1
23000 -25.8 -14.4 270 43 22 6.6 3.6 | -25.1 -13.2 270 45 23 7.2 4.0
22000 -23.9 -11.0 270 42 22 6.6 3.6 | -22.9 -9.2 270 44 22 7.2 4.0
21000 -21.9 -7.4 270 41 21 6.8 3.8 | -20.8 -5.4 270 43 22 6.1 3.3
20000 -19.9 -3.8 265 39 20 6.9 3.8 | -18.7 -1.7 265 40 21 5.7 3.2
19500 -18.9 -2.0 265 37 19 6.9 3.8 | -17.9 -0.2 265 39 20 5.7 3.2
19000 -17.8 -0.0 265 36 19 6.9 3.8 | -17.0 1.4 265 38 20 5.6 3.1
18500 -16.3 2.7 265 34 18 7.0 3.9 | -16.1 3.0 260 38 19 7.4 4.0
18000 -15.2 4.6 265 33 17 7.0 3.9 | -15.0 5.0 260 37 19 7.2 3.9
17500 -14.2 6.4 265 31 16 7.0 3.9 | -14.0 6.8 260 36 19 7.0 3.9
17000 -13.1 8.4 260 29 15 7.0 3.9 | -12.9 8.8 260 35 18 7.0 3.8
16500 -12.1 10.2 260 27 14 7.1 3.9 | -11.9 10.6 260 34 18 6.9 3.8
16000 -11.0 12.2 260 25 13 7.2 3.9 | -10.9 12.4 260 33 17 6.3 3.4
15500 -9.9 14.2 260 23 12 7.2 3.9 | -10.0 14.0 265 31 16 6.2 3.4
15000 -8.9 16.0 260 22 11 7.4 4.0 | -9.0 15.8 265 29 15 7.7 4.2
14500 -7.8 18.0 260 20 10 7.3 4.0 | -7.9 17.8 265 27 14 7.6 4.2
14000 -6.7 19.9 260 18 9 7.9 4.4 | -6.7 19.9 260 25 13 8.4 4.6
13500 -5.5 22.1 260 17 9 8.1 4.4 | -5.4 22.3 260 24 12 8.7 4.8
13000 -4.3 24.3 260 16 8 8.3 4.5 | -4.1 24.6 260 23 12 8.9 4.9
12500 -3.0 26.6 265 16 8 8.4 4.6 | -2.8 27.0 260 22 11 9.0 4.9
12000 -1.8 28.8 265 16 8 8.4 4.6 | -1.4 29.5 255 20 10 9.0 5.0
11500 -0.5 31.1 270 17 9 8.4 4.6 | -0.1 31.8 255 19 10 9.0 5.0
11000 0.7 33.3 275 18 9 7.3 4.0 | 1.3 34.3 255 17 9 8.4 4.6
10500 1.7 35.1 275 19 10 5.7 3.1 | 2.4 36.3 255 16 8 7.1 3.9
10250 2.2 36.0 275 19 10 10.3 5.7 | 3.0 37.4 250 15 8 10.7 5.9
10000 3.1 37.6 275 18 9 11.2 6.1 | 4.0 39.2 250 14 7 11.6 6.4
9750 3.7 38.7 270 17 9 6.9 3.8 | 4.7 40.5 250 13 7 8.6 4.7
9500 4.3 39.7 270 17 9 8.5 4.7 | 5.4 41.7 250 12 6 9.8 5.4
9250 4.9 40.8 270 16 8 6.2 3.4 | 6.1 43.0 245 11 6 8.1 4.4
9000 5.3 41.5 270 15 8 6.2 3.4 | 6.6 43.9 245 10 5 8.4 4.6
8750 5.9 42.6 270 14 7 8.9 4.9 | 7.3 45.1 240 10 5 10.1 5.5
8500 6.5 43.7 270 12 6 9.3 5.1 | 8.1 46.6 240 9 5 9.7 5.3
8250 7.2 45.0 265 11 6 7.9 4.3 | 8.8 47.8 240 9 4 9.7 5.3
8000 7.7 45.9 265 9 5 6.6 3.6 | 9.5 49.1 240 8 4 9.7 5.3
7750 8.3 46.9 260 8 4 8.1 4.5 | 10.3 50.5 235 8 4 10.0 5.5
7500 8.9 48.0 260 7 3 9.3 5.1 | 11.0 51.8 235 8 4 10.4 5.7
7250 9.5 49.1 255 6 3 6.7 3.7 | 11.8 53.2 235 7 4 9.4 5.1
7000 9.9 49.8 245 5 2 4.5 2.5 | 12.4 54.3 235 7 4 8.4 4.6
6750 10.3 50.5 230 4 2 6.9 3.8 | 13.1 55.6 235 7 4 10.6 5.8
6500 10.9 51.6 225 5 2 7.3 4.0 | 14.0 57.2 230 7 3 11.7 6.4
6250 11.3 52.3 215 5 2 5.5 3.0 | 14.8 58.6 230 6 3 10.7 5.9
6000 11.7 53.1 205 5 2 5.2 2.8 | 15.6 60.1 230 6 3 10.9 6.0
5750 12.1 53.8 195 5 2 5.3 2.9 | 16.4 61.5 230 6 3 9.4 5.2
5500 12.5 54.5 205 5 3 7.5 4.1 | 17.2 63.0 230 5 3 14.3 7.9
04/17/2024 at 1500 MDT | 04/17/2024 at 1800 MDT
|
CAPE... +36.0 LI... -0.4 | CAPE... +44.3 LI... -0.5
CINH... -15.1 K Index... +23.4 | CINH... -7.4 K Index... +23.3
|
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 -57.5 -71.5 265 60 31 2.4 1.3 | -57.2 -71.0 265 63 32 1.5 0.8
45000 -54.2 -65.6 265 78 40 -2.8 -1.5 | -55.2 -67.4 265 82 42 -1.9 -1.0
40000 -58.2 -72.8 275 77 39 -2.7 -1.5 | -59.1 -74.4 270 77 40 -2.4 -1.3
38000 -57.1 -70.8 275 76 39 5.2 2.9 | -57.3 -71.1 270 75 39 5.7 3.1
36000 -53.5 -64.3 280 74 38 5.2 2.9 | -53.8 -64.8 275 73 38 5.7 3.1
34000 -49.9 -57.8 280 72 37 7.6 4.2 | -50.0 -58.0 275 70 36 7.8 4.3
32000 -45.3 -49.5 280 67 34 7.6 4.2 | -45.3 -49.5 270 67 34 7.9 4.3
30000 -40.7 -41.3 275 62 32 7.8 4.3 | -40.7 -41.3 270 63 32 7.4 4.1
29000 -38.3 -36.9 270 60 31 7.8 4.3 | -37.9 -36.2 270 60 31 7.4 4.1
28000 -36.0 -32.8 270 59 30 7.8 4.3 | -35.7 -32.3 270 58 30 7.4 4.1
27000 -33.7 -28.7 265 57 29 7.5 4.1 | -33.5 -28.3 270 56 29 6.9 3.8
26000 -31.5 -24.7 265 55 28 7.4 4.1 | -31.5 -24.7 270 53 27 6.9 3.8
25000 -29.2 -20.6 270 54 28 7.4 4.1 | -29.4 -20.9 270 51 26 6.9 3.8
24000 -27.0 -16.6 270 52 27 7.1 3.9 | -27.3 -17.1 270 48 25 7.1 3.9
23000 -25.0 -13.0 270 48 25 6.7 3.7 | -25.2 -13.4 270 44 23 7.1 3.9
22000 -23.0 -9.4 270 45 23 6.8 3.7 | -23.1 -9.6 270 41 21 7.2 3.9
21000 -21.0 -5.8 270 41 21 6.5 3.6 | -21.0 -5.8 270 37 19 7.1 3.9
20000 -19.1 -2.4 265 38 20 6.5 3.6 | -18.9 -2.0 265 34 18 7.1 3.9
19500 -18.2 -0.8 265 36 19 6.5 3.6 | -17.8 -0.0 265 33 17 7.1 3.9
19000 -16.7 1.9 260 34 18 6.5 3.6 | -16.8 1.8 265 31 16 7.1 3.9
18500 -15.7 3.7 260 33 17 7.5 4.1 | -15.7 3.7 265 30 15 7.4 4.0
18000 -14.6 5.7 260 33 17 7.4 4.1 | -14.7 5.5 265 30 15 7.4 4.1
17500 -13.6 7.5 255 32 16 7.7 4.2 | -13.6 7.5 265 29 15 7.5 4.1
17000 -12.4 9.7 255 31 16 7.9 4.3 | -12.5 9.5 260 29 15 7.4 4.1
16500 -11.2 11.8 255 30 15 7.9 4.3 | -11.4 11.5 260 29 15 7.4 4.1
16000 -10.1 13.8 255 29 15 7.7 4.2 | -10.3 13.5 260 28 14 7.9 4.3
15500 -9.0 15.8 255 27 14 7.6 4.2 | -8.6 16.5 260 26 13 7.9 4.3
15000 -7.8 18.0 255 26 13 8.5 4.7 | -7.3 18.9 260 25 13 9.1 5.0
14500 -6.5 20.3 255 24 13 8.4 4.6 | -6.0 21.2 260 24 12 8.9 4.9
14000 -5.2 22.6 255 23 12 8.9 4.9 | -4.7 23.5 260 23 12 9.4 5.1
13500 -3.9 25.0 255 22 11 9.0 4.9 | -3.3 26.1 260 23 12 9.4 5.2
13000 -2.6 27.3 255 21 11 9.2 5.0 | -1.9 28.6 260 22 11 9.3 5.1
12500 -1.2 29.8 255 19 10 9.3 5.1 | -0.5 31.1 265 21 11 9.3 5.1
12000 0.2 32.4 255 18 9 9.2 5.1 | 0.9 33.6 265 20 10 9.4 5.2
11500 1.6 34.9 255 17 9 9.1 5.0 | 2.3 36.1 265 19 10 9.5 5.2
11000 3.0 37.4 255 15 8 8.4 4.6 | 3.7 38.7 270 18 9 8.5 4.7
10500 4.1 39.4 255 14 7 6.8 3.7 | 4.9 40.8 270 17 9 6.9 3.8
10250 4.7 40.5 255 14 7 11.4 6.2 | 5.5 41.9 270 16 8 12.1 6.7
10000 5.7 42.3 260 13 7 12.8 7.0 | 6.6 43.9 270 16 8 13.2 7.2
9750 6.5 43.7 260 13 6 8.9 4.9 | 7.3 45.1 275 16 8 8.5 4.7
9500 7.2 45.0 260 12 6 10.4 5.7 | 8.0 46.4 275 15 8 10.2 5.6
9250 7.9 46.2 260 12 6 8.2 4.5 | 8.7 47.7 275 15 8 8.3 4.5
9000 8.5 47.3 260 12 6 8.7 4.8 | 9.3 48.7 275 15 8 8.8 4.8
8750 9.3 48.7 260 11 6 10.9 6.0 | 10.1 50.2 275 14 7 10.6 5.8
8500 10.1 50.2 265 11 6 10.5 5.8 | 10.8 51.4 275 14 7 10.4 5.7
8250 10.8 51.4 265 11 6 9.8 5.4 | 11.6 52.9 275 14 7 9.4 5.2
8000 11.5 52.7 265 11 5 9.1 5.0 | 12.2 54.0 275 14 7 8.9 4.9
7750 12.2 54.0 265 10 5 10.1 5.6 | 13.0 55.4 280 13 7 10.1 5.5
7500 13.0 55.4 265 10 5 11.0 6.0 | 13.7 56.7 280 13 7 10.8 5.9
7250 13.8 56.8 265 10 5 9.2 5.0 | 14.5 58.1 280 13 7 9.0 4.9
7000 14.4 57.9 265 9 5 7.6 4.2 | 15.1 59.2 280 13 7 7.6 4.1
6750 15.1 59.2 265 9 5 10.7 5.9 | 15.7 60.3 280 12 6 10.7 5.8
6500 16.0 60.8 265 9 5 12.3 6.8 | 16.6 61.9 280 12 6 12.0 6.6
6250 16.8 62.2 270 8 4 10.4 5.7 | 17.4 63.3 280 12 6 9.9 5.4
6000 17.6 63.7 270 8 4 9.7 5.3 | 18.1 64.6 285 11 6 8.9 4.9
5750 18.3 64.9 270 8 4 10.0 5.5 | 18.8 65.8 285 11 6 9.7 5.3
5500 19.2 66.6 270 7 4 16.1 8.8 | 19.6 67.3 285 10 5 12.1 6.6
________________________________________________________________________________
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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