Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
022
UXUS97 KBOU 301327
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0726 MDT Tuesday, April 30, 2024
This forecast is for Tuesday, April 30, 2024:
If the trigger temperature of 63.0 F/17.2 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 651 ft/min (3.3 m/s)
Maximum height of thermals.................. 13588 ft MSL (8309 ft AGL)
Forecast maximum temperature................... 72.0 F/22.7 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................. 10898 ft MSL (5618 ft AGL)
Thermal soaring outlook for Wednesday 05/01.... 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 PVA
Potential height of wave....................... 14402 ft MSL (9123 ft AGL)
Wave soaring outlook for Wednesday 05/01....... Poor
Remarks...
Sunrise/Sunset.................... 06:00:05 / 19:53:08 MDT
Total possible sunshine........... 13 hr 53 min 3 sec (833 min 3 sec)
Altitude of sun at 12:56:36 MDT... 65.32 degrees
Upper air data from numerical model forecast valid on 04/30/2024 at 0600 MDT
Freezing level.................. 12160 ft MSL (6881 ft AGL)
Convective condensation level... 15920 ft MSL (10641 ft AGL)
Lifted condensation level....... 15368 ft MSL (10088 ft AGL)
Lifted index.................... -0.6
K index......................... +6.4
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 -57.0 -70.6 255 46 23 1.9 1.1 M M M M M
45000 -54.3 -65.7 255 69 36 -1.3 -0.7 M M M M M
40000 -56.6 -69.9 255 78 40 -1.5 -0.8 M M M M M
38000 -56.1 -69.0 260 78 40 2.8 1.5 M M M M M
36000 -54.4 -65.9 260 75 39 2.8 1.5 M M M M M
34000 -51.7 -61.1 260 72 37 7.6 4.2 M M M M M
32000 -47.1 -52.8 260 73 37 7.7 4.2 M M M M M
30000 -42.3 -44.1 255 72 37 8.6 4.7 33.0 91.4 8.1 M M
29000 -39.7 -39.5 255 71 36 8.6 4.7 32.5 90.4 7.8 M M
28000 -37.1 -34.8 255 69 36 8.6 4.7 32.1 89.7 7.6 M M
27000 -34.6 -30.3 260 67 35 8.0 4.4 31.7 89.0 7.4 M M
26000 -32.2 -26.0 260 64 33 7.9 4.3 30.9 87.5 6.8 M M
25000 -29.9 -21.8 260 60 31 7.9 4.3 30.2 86.3 6.4 M M
24000 -27.5 -17.5 260 56 29 7.8 4.3 29.6 85.2 6.0 M M
23000 -25.2 -13.4 260 51 26 7.6 4.2 28.7 83.6 5.3 M M
22000 -22.9 -9.2 260 45 23 7.6 4.2 27.9 82.2 4.7 M M
21000 -20.7 -5.3 255 39 20 7.8 4.3 27.2 81.0 4.2 M M
20000 -18.3 -0.9 255 34 17 7.9 4.3 26.5 79.6 3.6 M M
19500 -17.1 1.2 255 31 16 7.9 4.3 26.1 79.0 3.3 M M
19000 -16.0 3.2 255 28 15 7.9 4.3 25.8 78.5 3.1 M M
18500 -14.8 5.4 250 26 13 8.2 4.5 25.6 78.0 2.8 M M
18000 -13.5 7.7 250 26 13 8.5 4.7 25.3 77.6 2.6 M M
17500 -12.3 9.9 255 26 13 8.5 4.7 25.1 77.2 2.4 M M
17000 -11.0 12.2 255 27 14 8.3 4.6 24.9 76.8 2.2 M M
16500 -9.8 14.4 260 30 15 8.3 4.6 24.6 76.3 2.0 M M
16000 -8.0 17.6 260 32 16 7.4 4.0 24.2 75.5 1.6 M M
15500 -6.9 19.6 265 31 16 7.4 4.1 23.8 74.8 1.3 M M
15000 -5.8 21.6 265 31 16 7.7 4.2 23.4 74.2 0.9 M M
14500 -4.6 23.7 265 33 17 7.7 4.2 23.1 73.5 0.6 M M
14000 -3.5 25.7 270 35 18 7.5 4.1 22.7 72.9 0.3 M M
13500 -2.4 27.7 270 38 20 7.4 4.0 22.3 72.2 -0.1 634 3.2
13000 -1.4 29.5 270 41 21 6.9 3.8 22.0 71.5 -0.5 587 3.0
12500 -0.5 31.1 270 43 22 6.1 3.3 21.4 70.5 -1.1 546 2.8
12000 0.4 32.7 275 46 24 6.1 3.3 20.8 69.4 -1.7 505 2.6
11500 1.3 34.3 275 46 23 6.1 3.3 20.2 68.3 -2.3 464 2.4
11000 2.1 35.8 275 45 23 6.0 3.3 19.6 67.3 -2.9 423 2.1
10500 2.9 37.2 280 43 22 5.6 3.1 19.0 66.1 -3.6 384 1.9
10250 3.3 37.9 280 42 22 5.9 3.2 18.6 65.6 -3.9 364 1.9
10000 3.8 38.8 280 41 21 6.9 3.8 18.4 65.1 -4.2 343 1.7
9750 4.3 39.7 280 41 21 7.4 4.0 18.2 64.7 -4.4 320 1.6
9500 4.9 40.8 285 41 21 7.4 4.0 18.0 64.4 -4.7 297 1.5
9250 5.4 41.7 285 42 21 7.2 3.9 17.8 64.0 -4.9 273 1.4
9000 5.9 42.6 285 42 21 8.0 4.4 17.6 63.7 -5.1 250 1.3
8750 6.6 43.9 285 38 20 8.1 4.5 17.5 63.5 -5.2 223 1.1
8500 7.1 44.8 285 37 19 7.4 4.1 17.3 63.2 -5.4 199 1.0
8250 7.7 45.9 290 36 18 7.7 4.2 17.2 62.9 -5.6 175 0.9
8000 8.3 46.9 290 34 17 8.1 4.5 17.0 62.6 -5.7 150 0.8
7750 8.9 48.0 290 31 16 7.8 4.3 16.9 62.4 -5.9 125 0.6
7500 9.4 48.9 295 29 15 7.2 4.0 16.7 62.1 -6.1 101 0.5
7250 10.0 50.0 295 27 14 7.6 4.1 16.5 61.8 -6.2 77 0.4
7000 10.6 51.1 295 26 13 8.1 4.4 16.4 61.5 -6.4 52 0.3
6750 11.2 52.2 300 24 12 7.7 4.2 16.3 61.3 -6.5 26 0.1
6500 11.7 53.1 300 21 11 9.3 5.1 16.1 61.0 -6.7 1 0.0
6250 12.2 54.0 300 19 10 -2.1 -1.1 15.8 60.5 -7.0 M M
6000 11.5 52.7 295 15 8 -9.5 -5.2 14.4 57.9 -8.5 M M
5750 10.8 51.4 285 11 6 -15.3 -8.4 13.0 55.4 -10.0 9 0.0
5500 8.4 47.1 255 7 4 -45.3 -24.8 10.0 50.1 -13.0 71 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/30/2024 at 0900 MDT | 04/30/2024 at 1200 MDT
|
CAPE... 0.0 LI... +4.4 | CAPE... 0.0 LI... +3.0
CINH... 0.0 K Index... -6.3 | CINH... 0.0 K Index... -17.5
|
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 -55.8 -68.4 250 41 21 1.6 0.9 | -55.9 -68.6 245 42 22 1.0 0.5
45000 -53.5 -64.3 255 70 36 -1.8 -1.0 | -54.6 -66.3 260 71 37 -2.0 -1.1
40000 -57.1 -70.8 255 78 40 -2.4 -1.3 | -58.4 -73.1 260 73 38 -2.5 -1.4
38000 -56.7 -70.1 255 79 41 3.4 1.9 | -57.7 -71.9 260 73 38 4.3 2.4
36000 -54.7 -66.5 255 76 39 3.4 1.9 | -55.1 -67.2 265 73 37 4.3 2.4
34000 -51.6 -60.9 255 74 38 7.5 4.1 | -51.4 -60.5 265 72 37 8.4 4.6
32000 -47.1 -52.8 255 74 38 7.5 4.1 | -46.3 -51.3 265 72 37 8.4 4.6
30000 -42.4 -44.3 255 73 38 8.3 4.5 | -41.3 -42.3 265 72 37 8.3 4.5
29000 -40.0 -40.0 255 73 37 8.3 4.5 | -38.8 -37.8 265 73 37 8.3 4.5
28000 -37.5 -35.5 255 72 37 8.3 4.5 | -36.3 -33.3 265 73 38 8.3 4.5
27000 -35.0 -31.0 255 71 36 8.2 4.5 | -33.8 -28.8 265 73 38 8.2 4.5
26000 -32.6 -26.7 255 69 36 8.1 4.5 | -31.4 -24.5 265 72 37 8.2 4.5
25000 -30.1 -22.2 255 67 35 8.1 4.5 | -28.9 -20.0 265 72 37 8.2 4.5
24000 -27.7 -17.9 255 66 34 7.9 4.3 | -26.4 -15.5 265 71 37 7.6 4.2
23000 -25.4 -13.7 255 63 32 7.4 4.1 | -24.3 -11.7 265 69 35 6.8 3.8
22000 -23.2 -9.8 255 60 31 7.4 4.1 | -22.3 -8.1 270 66 34 6.8 3.8
21000 -20.9 -5.6 250 57 29 8.2 4.5 | -20.2 -4.4 270 64 33 7.3 4.0
20000 -18.4 -1.1 250 55 28 8.5 4.6 | -18.0 -0.4 275 62 32 7.4 4.1
19500 -17.1 1.2 245 54 28 8.5 4.6 | -16.8 1.8 275 61 31 7.4 4.1
19000 -15.8 3.6 245 53 27 8.5 4.7 | -15.7 3.7 275 60 31 7.4 4.1
18500 -14.6 5.7 245 52 27 8.8 4.8 | -14.6 5.7 280 60 31 6.6 3.6
18000 -13.2 8.2 245 50 26 9.2 5.0 | -13.7 7.3 280 59 30 5.9 3.2
17500 -11.8 10.8 240 48 25 9.4 5.2 | -12.8 9.0 275 58 30 5.8 3.2
17000 -10.0 14.0 245 47 24 7.4 4.0 | -11.5 11.3 275 56 29 6.2 3.4
16500 -8.9 16.0 250 47 24 7.3 4.0 | -10.5 13.1 275 55 28 6.2 3.4
16000 -7.9 17.8 250 46 24 6.9 3.8 | -9.6 14.7 270 54 28 6.4 3.5
15500 -6.9 19.6 250 45 23 7.1 3.9 | -8.6 16.5 270 52 27 6.4 3.5
15000 -5.9 21.4 250 43 22 5.5 3.0 | -7.7 18.1 270 51 26 6.3 3.5
14500 -5.1 22.8 255 44 22 5.4 3.0 | -6.7 19.9 270 48 25 6.3 3.5
14000 -4.3 24.3 260 44 23 5.8 3.2 | -5.8 21.6 270 46 24 6.7 3.7
13500 -3.5 25.7 260 46 24 6.0 3.3 | -4.8 23.4 270 47 24 6.8 3.7
13000 -2.6 27.3 265 47 24 5.5 3.0 | -3.8 25.2 270 47 24 5.9 3.2
12500 -1.9 28.6 265 47 24 4.9 2.7 | -3.1 26.4 270 44 23 5.3 2.9
12000 -1.3 29.7 265 47 24 5.1 2.8 | -2.4 27.7 270 40 21 6.4 3.5
11500 -0.5 31.1 270 48 25 5.2 2.9 | -1.4 29.5 270 35 18 7.3 4.0
11000 0.2 32.4 270 49 25 5.1 2.8 | -0.4 31.3 270 31 16 7.3 4.0
10500 0.8 33.4 270 45 23 4.4 2.4 | 0.7 33.3 270 27 14 6.6 3.6
10250 1.2 34.2 275 42 22 5.3 2.9 | 1.2 34.2 270 25 13 10.2 5.6
10000 1.6 34.9 275 41 21 6.4 3.5 | 2.1 35.8 275 22 11 10.6 5.8
9750 2.0 35.6 275 39 20 5.9 3.2 | 2.7 36.9 275 20 10 7.3 4.0
9500 2.4 36.3 280 37 19 5.5 3.0 | 3.3 37.9 275 17 9 8.2 4.5
9250 2.8 37.0 280 34 18 5.6 3.1 | 3.8 38.8 275 15 8 7.7 4.2
9000 3.2 37.8 285 32 16 5.2 2.9 | 4.4 39.9 275 13 7 8.4 4.6
8750 3.6 38.5 285 29 15 5.2 2.9 | 5.1 41.2 275 12 6 9.3 5.1
8500 4.0 39.2 290 27 14 5.4 3.0 | 5.7 42.3 275 11 6 9.1 5.0
8250 4.4 39.9 290 25 13 5.5 3.0 | 6.4 43.5 275 10 5 9.7 5.3
8000 4.8 40.6 295 23 12 6.0 3.3 | 7.1 44.8 275 10 5 10.2 5.6
7750 5.2 41.4 300 21 11 6.2 3.4 | 7.9 46.2 275 10 5 9.2 5.1
7500 5.7 42.3 300 19 10 6.3 3.4 | 8.5 47.3 275 10 5 8.2 4.5
7250 6.2 43.2 305 17 9 6.2 3.4 | 9.2 48.6 275 9 5 10.0 5.5
7000 6.6 43.9 310 14 7 6.1 3.4 | 10.0 50.0 275 9 5 11.6 6.4
6750 7.0 44.6 315 11 6 5.7 3.1 | 10.8 51.4 275 9 5 10.0 5.5
6500 7.4 45.3 325 9 5 5.4 3.0 | 11.5 52.7 275 9 4 9.6 5.3
6250 7.8 46.0 335 7 3 6.1 3.3 | 12.3 54.1 275 8 4 10.7 5.9
6000 8.3 46.9 355 5 3 6.4 3.5 | 13.1 55.6 275 8 4 11.4 6.3
5750 8.7 47.7 025 4 2 6.3 3.4 | 13.9 57.0 275 8 4 9.8 5.4
5500 9.3 48.7 040 4 2 11.9 6.5 | 14.8 58.6 275 7 4 14.7 8.0
04/30/2024 at 1500 MDT | 04/30/2024 at 1800 MDT
|
CAPE... 0.0 LI... +2.9 | CAPE... 0.0 LI... +1.6
CINH... 0.0 K Index... -11.6 | CINH... 0.0 K Index... +8.3
|
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 -56.8 -70.2 250 47 24 0.8 0.4 | -57.6 -71.7 260 40 21 0.8 0.4
45000 -55.8 -68.4 265 70 36 -2.4 -1.3 | -56.6 -69.9 265 71 36 -2.5 -1.4
40000 -60.0 -76.0 260 77 39 -2.8 -1.5 | -60.8 -77.4 270 75 39 -2.9 -1.6
38000 -58.7 -73.7 265 77 39 5.7 3.2 | -59.3 -74.7 270 76 39 6.4 3.5
36000 -55.2 -67.4 265 75 39 5.7 3.2 | -55.5 -67.9 270 76 39 6.4 3.5
34000 -50.9 -59.6 265 73 38 8.1 4.4 | -50.7 -59.3 270 75 39 8.3 4.6
32000 -46.0 -50.8 265 72 37 8.1 4.4 | -45.7 -50.3 265 73 37 8.3 4.5
30000 -41.1 -42.0 265 70 36 8.4 4.6 | -40.7 -41.3 265 71 36 8.5 4.7
29000 -38.6 -37.5 265 70 36 8.4 4.6 | -38.2 -36.8 265 70 36 8.5 4.7
28000 -36.0 -32.8 265 69 36 8.4 4.6 | -35.6 -32.1 265 69 35 8.5 4.7
27000 -33.6 -28.5 260 68 35 7.6 4.2 | -33.2 -27.8 265 68 35 6.9 3.8
26000 -31.3 -24.3 260 66 34 7.6 4.2 | -31.1 -24.0 265 66 34 6.9 3.8
25000 -29.0 -20.2 265 64 33 7.6 4.2 | -29.1 -20.4 265 63 33 6.9 3.8
24000 -26.8 -16.2 265 62 32 7.0 3.9 | -27.0 -16.6 260 61 31 6.4 3.5
23000 -24.8 -12.6 260 60 31 6.6 3.6 | -25.2 -13.4 260 58 30 6.0 3.3
22000 -22.8 -9.0 260 58 30 6.6 3.6 | -23.4 -10.1 260 55 28 6.0 3.3
21000 -20.8 -5.4 260 55 29 7.1 3.9 | -21.5 -6.7 260 52 27 7.6 4.2
20000 -18.6 -1.5 265 52 27 7.2 3.9 | -19.2 -2.6 255 48 25 7.7 4.2
19500 -17.5 0.5 265 50 26 7.2 3.9 | -18.0 -0.4 255 46 23 7.7 4.2
19000 -16.4 2.5 265 49 25 7.2 3.9 | -16.9 1.6 255 44 22 7.7 4.2
18500 -15.4 4.3 265 47 24 7.2 4.0 | -15.7 3.7 250 42 21 7.3 4.0
18000 -14.3 6.3 270 45 23 7.3 4.0 | -14.7 5.5 250 40 20 7.2 4.0
17500 -13.2 8.2 270 42 22 7.3 4.0 | -13.6 7.5 250 37 19 7.2 4.0
17000 -11.6 11.1 270 38 20 7.0 3.9 | -12.0 10.4 245 34 18 7.3 4.0
16500 -10.5 13.1 270 35 18 7.0 3.9 | -10.9 12.4 245 32 16 7.7 4.2
16000 -9.5 14.9 270 34 17 7.1 3.9 | -9.7 14.5 240 30 15 8.7 4.8
15500 -8.4 16.9 270 32 17 7.0 3.9 | -8.4 16.9 235 28 14 8.7 4.8
15000 -7.3 18.9 270 32 16 7.7 4.2 | -7.2 19.0 235 26 13 8.4 4.6
14500 -6.2 20.8 270 31 16 7.7 4.2 | -5.9 21.4 235 24 13 8.4 4.6
14000 -5.0 23.0 270 31 16 7.6 4.1 | -4.7 23.5 230 23 12 8.9 4.9
13500 -3.9 25.0 270 32 16 7.6 4.2 | -3.3 26.1 230 21 11 9.0 4.9
13000 -2.9 26.8 270 31 16 6.7 3.7 | -2.0 28.4 225 19 10 9.2 5.0
12500 -2.0 28.4 265 26 13 6.3 3.5 | -0.6 30.9 220 18 9 9.2 5.0
12000 -1.1 30.0 265 21 11 7.9 4.4 | 0.8 33.4 215 16 8 8.7 4.8
11500 0.3 32.5 265 18 9 9.0 4.9 | 2.0 35.6 215 14 7 8.5 4.6
11000 1.6 34.9 260 15 8 8.2 4.5 | 3.3 37.9 210 12 6 7.7 4.2
10500 2.7 36.9 260 12 6 6.9 3.8 | 4.4 39.9 200 10 5 6.5 3.5
10250 3.2 37.8 260 11 5 10.5 5.8 | 4.9 40.8 195 9 4 10.3 5.6
10000 4.2 39.6 265 10 5 11.9 6.5 | 5.8 42.4 190 7 4 10.4 5.7
9750 4.9 40.8 265 10 5 9.2 5.1 | 6.4 43.5 190 6 3 6.7 3.7
9500 5.6 42.1 265 10 5 10.0 5.5 | 6.9 44.4 185 4 2 7.6 4.2
9250 6.4 43.5 265 9 5 9.5 5.2 | 7.4 45.3 175 3 2 7.7 4.2
9000 7.1 44.8 265 9 5 9.7 5.3 | 8.0 46.4 160 2 1 8.6 4.7
8750 7.8 46.0 265 9 5 10.2 5.6 | 8.7 47.7 145 1 1 9.0 4.9
8500 8.6 47.5 265 9 5 9.9 5.4 | 9.3 48.7 125 1 1 8.6 4.7
8250 9.3 48.7 265 9 5 10.8 5.9 | 10.0 50.0 085 1 1 10.0 5.5
8000 10.2 50.4 265 9 4 11.1 6.1 | 10.8 51.4 065 1 1 11.0 6.0
7750 10.9 51.6 265 9 4 9.7 5.3 | 11.5 52.7 060 1 1 9.4 5.2
7500 11.6 52.9 265 8 4 9.1 5.0 | 12.2 54.0 055 1 1 8.5 4.6
7250 12.3 54.1 265 8 4 10.1 5.6 | 12.9 55.2 045 1 1 10.2 5.6
7000 13.1 55.6 265 8 4 10.9 6.0 | 13.7 56.7 045 2 1 11.5 6.3
6750 13.9 57.0 270 8 4 9.7 5.3 | 14.5 58.1 040 2 1 9.3 5.1
6500 14.6 58.3 270 8 4 9.6 5.3 | 15.2 59.4 035 2 1 8.7 4.7
6250 15.4 59.7 270 8 4 10.9 6.0 | 15.9 60.6 030 2 1 9.9 5.4
6000 16.2 61.2 270 7 4 11.9 6.5 | 16.6 61.9 030 2 1 10.5 5.8
5750 17.1 62.8 270 7 4 9.4 5.2 | 17.4 63.3 025 2 1 9.4 5.2
5500 17.8 64.0 270 7 4 12.2 6.7 | 18.1 64.6 025 2 1 10.1 5.5
________________________________________________________________________________
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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