Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
493
UXUS97 KBOU 300115
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1913 MDT Monday, April 29, 2024
This forecast is for Tuesday, April 30, 2024:
If the trigger temperature of 62.1 F/16.7 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 753 ft/min (3.8 m/s)
Maximum height of thermals.................. 16363 ft MSL (11054 ft AGL)
Forecast maximum temperature................... 73.0 F/23.2 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 13258 ft MSL (7949 ft AGL)
Thermal soaring outlook for Wednesday 05/01.... Good
Wave Soaring Index............................. Good
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....................... 44734 ft MSL (39425 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.................. 11406 ft MSL (6097 ft AGL)
Convective condensation level... 14656 ft MSL (9347 ft AGL)
Lifted condensation level....... 15551 ft MSL (10242 ft AGL)
Lifted index.................... -0.2
K index......................... +11.5
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 -56.8 -70.2 255 41 21 0.7 0.4 M M M M M
45000 -55.8 -68.4 255 73 37 -1.4 -0.7 M M M M M
40000 -58.3 -72.9 255 76 39 -1.6 -0.9 M M M M M
38000 -57.2 -71.0 255 75 39 4.7 2.6 M M M M M
36000 -54.3 -65.7 255 72 37 4.7 2.6 M M M M M
34000 -50.7 -59.3 250 69 36 7.1 3.9 M M M M M
32000 -46.4 -51.5 250 69 36 7.2 3.9 M M M M M
30000 -41.8 -43.2 250 69 35 8.2 4.5 33.6 92.5 8.2 M M
29000 -39.4 -38.9 250 68 35 8.2 4.5 33.0 91.3 7.8 M M
28000 -36.9 -34.4 250 67 34 8.2 4.5 32.4 90.4 7.4 M M
27000 -34.4 -29.9 250 66 34 8.4 4.6 32.0 89.6 7.2 M M
26000 -31.9 -25.4 250 63 32 8.5 4.7 31.4 88.5 6.8 M M
25000 -29.3 -20.7 250 60 31 8.5 4.7 30.9 87.7 6.5 M M
24000 -26.7 -16.1 250 58 30 8.2 4.5 30.6 87.1 6.3 M M
23000 -24.5 -12.1 255 56 29 7.5 4.1 29.7 85.5 5.7 M M
22000 -22.2 -8.0 255 54 28 7.5 4.1 28.9 84.0 5.1 M M
21000 -20.0 -4.0 255 52 27 7.0 3.8 28.2 82.7 4.5 M M
20000 -18.0 -0.4 255 50 26 6.7 3.7 27.0 80.6 3.6 M M
19500 -17.0 1.4 255 50 26 6.7 3.7 26.5 79.6 3.1 M M
19000 -15.9 3.4 260 49 25 6.7 3.7 26.0 78.7 2.7 M M
18500 -14.9 5.2 260 48 25 6.6 3.6 25.5 77.9 2.3 M M
18000 -14.0 6.8 260 47 24 6.5 3.6 24.9 76.9 1.8 M M
17500 -12.5 9.5 265 46 24 6.5 3.6 24.1 75.4 1.1 M M
17000 -11.6 11.1 265 45 23 6.4 3.5 23.5 74.3 0.6 M M
16500 -10.6 12.9 265 44 23 6.5 3.6 23.0 73.3 0.0 M M
16000 -9.7 14.5 265 43 22 6.6 3.6 22.4 72.3 -0.5 913 4.6
15500 -8.7 16.3 265 42 22 6.6 3.6 21.9 71.4 -1.0 869 4.4
15000 -7.8 18.0 265 41 21 6.7 3.7 21.4 70.5 -1.5 826 4.2
14500 -6.8 19.8 265 39 20 6.7 3.7 20.8 69.5 -2.0 782 4.0
14000 -5.9 21.4 265 36 19 7.4 4.0 20.4 68.7 -2.5 738 3.7
13500 -4.7 23.5 265 34 18 7.8 4.3 20.0 68.1 -2.9 689 3.5
13000 -3.6 25.5 265 32 16 7.8 4.3 19.7 67.5 -3.2 640 3.3
12500 -2.4 27.7 265 29 15 7.8 4.3 19.4 66.9 -3.6 592 3.0
12000 -1.3 29.7 270 26 13 7.8 4.3 19.1 66.4 -3.9 543 2.8
11500 -0.1 31.8 270 27 14 7.9 4.3 18.8 65.8 -4.2 493 2.5
11000 1.0 33.8 275 28 14 7.4 4.1 18.5 65.3 -4.5 443 2.3
10500 2.0 35.6 280 26 13 5.8 3.2 18.0 64.4 -5.1 400 2.0
10250 2.4 36.3 280 25 13 7.9 4.4 17.7 63.9 -5.4 379 1.9
10000 3.1 37.6 285 23 12 9.9 5.4 17.7 63.9 -5.4 350 1.8
9750 3.8 38.8 285 22 11 8.3 4.6 17.6 63.8 -5.5 323 1.6
9500 4.4 39.9 290 21 11 7.7 4.2 17.5 63.5 -5.7 298 1.5
9250 5.0 41.0 290 20 10 8.1 4.5 17.4 63.2 -5.8 273 1.4
9000 5.5 41.9 295 19 10 7.0 3.9 17.2 63.0 -6.0 249 1.3
8750 6.0 42.8 300 18 9 7.4 4.1 17.0 62.5 -6.2 226 1.1
8500 6.7 44.1 300 17 9 8.8 4.8 16.9 62.4 -6.4 200 1.0
8250 7.3 45.1 305 16 8 8.2 4.5 16.8 62.2 -6.5 174 0.9
8000 7.9 46.2 310 15 8 6.9 3.8 16.6 61.9 -6.7 149 0.8
7750 8.4 47.1 315 15 7 7.4 4.1 16.4 61.5 -6.9 127 0.6
7500 9.0 48.2 315 14 7 8.7 4.8 16.3 61.3 -7.0 101 0.5
7250 9.6 49.3 320 13 7 7.7 4.2 16.2 61.1 -7.1 75 0.4
7000 10.1 50.2 325 13 7 6.6 3.6 16.0 60.7 -7.4 52 0.3
6750 10.6 51.1 325 13 6 5.6 3.1 15.7 60.3 -7.7 30 0.2
6500 11.0 51.8 325 12 6 5.9 3.3 15.4 59.7 -8.0 11 0.1
6250 11.3 52.3 320 11 6 -0.1 -0.1 15.0 58.9 -8.4 M M
6000 11.0 51.8 315 9 5 -4.1 -2.2 13.9 57.1 -9.5 M M
5750 10.7 51.3 310 8 4 -7.3 -4.0 12.9 55.2 -10.6 M M
5500 9.4 48.9 295 5 3 -26.1 -14.3 11.0 51.7 -12.6 30 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/30/2024 at 0900 MDT | 04/30/2024 at 1200 MDT
|
CAPE... +1.9 LI... +3.4 | CAPE... +4.1 LI... +2.8
CINH... -5.7 K Index... +7.5 | CINH... -1.3 K Index... +2.4
|
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 -56.7 -70.1 255 43 22 0.7 0.4 | -56.6 -69.9 255 46 24 0.5 0.3
45000 -55.8 -68.4 260 69 35 -1.1 -0.6 | -55.9 -68.6 260 70 36 -1.1 -0.6
40000 -57.7 -71.9 255 73 38 -1.3 -0.7 | -58.1 -72.6 260 75 38 -1.4 -0.8
38000 -56.4 -69.5 250 72 37 4.9 2.7 | -57.1 -70.8 260 74 38 4.3 2.3
36000 -53.4 -64.1 250 69 35 4.9 2.7 | -54.2 -65.6 260 72 37 4.3 2.3
34000 -49.8 -57.6 255 67 34 6.6 3.6 | -51.0 -59.8 260 71 36 7.4 4.0
32000 -45.8 -50.4 255 71 36 6.6 3.6 | -46.6 -51.9 265 71 37 7.4 4.1
30000 -41.5 -42.7 260 73 38 7.9 4.3 | -41.9 -43.4 270 71 37 8.6 4.7
29000 -39.2 -38.6 260 73 37 7.9 4.4 | -39.3 -38.7 270 71 37 8.7 4.8
28000 -36.8 -34.2 260 72 37 7.9 4.4 | -36.7 -34.1 270 71 36 8.7 4.8
27000 -34.4 -29.9 260 72 37 7.9 4.4 | -34.1 -29.4 270 70 36 7.8 4.3
26000 -32.0 -25.6 260 71 37 7.9 4.4 | -31.9 -25.4 270 69 36 7.6 4.2
25000 -29.6 -21.3 260 71 36 7.9 4.4 | -29.6 -21.3 270 68 35 7.6 4.2
24000 -27.2 -17.0 260 70 36 7.9 4.3 | -27.3 -17.1 270 68 35 7.3 4.0
23000 -24.9 -12.8 260 70 36 7.7 4.2 | -25.2 -13.4 270 66 34 7.0 3.8
22000 -22.6 -8.7 260 69 35 7.7 4.2 | -23.1 -9.6 270 64 33 7.0 3.8
21000 -20.3 -4.5 260 68 35 7.2 3.9 | -21.0 -5.8 270 62 32 7.5 4.1
20000 -18.2 -0.8 260 65 34 6.9 3.8 | -18.7 -1.7 275 57 30 7.6 4.2
19500 -17.2 1.0 260 64 33 6.9 3.8 | -17.6 0.3 275 55 28 7.6 4.2
19000 -15.7 3.7 260 62 32 7.0 3.8 | -16.4 2.5 275 53 27 7.6 4.2
18500 -14.7 5.5 260 61 31 6.2 3.4 | -14.7 5.5 275 50 26 6.7 3.7
18000 -13.7 7.3 260 60 31 6.2 3.4 | -13.7 7.3 280 51 26 6.7 3.7
17500 -12.8 9.0 260 59 30 6.0 3.3 | -12.7 9.1 280 52 27 6.4 3.5
17000 -12.0 10.4 260 58 30 5.6 3.0 | -11.8 10.8 280 51 26 6.1 3.4
16500 -11.2 11.8 260 57 29 5.6 3.1 | -10.9 12.4 280 50 26 6.1 3.4
16000 -10.4 13.3 265 55 28 5.2 2.9 | -10.1 13.8 275 49 25 5.5 3.0
15500 -9.6 14.7 265 53 27 5.3 2.9 | -9.2 15.4 275 47 24 5.6 3.1
15000 -8.8 16.2 265 51 26 5.6 3.1 | -8.4 16.9 275 45 23 5.7 3.1
14500 -8.0 17.6 265 49 25 5.7 3.1 | -7.6 18.3 270 43 22 5.8 3.2
14000 -7.2 19.0 265 46 24 6.3 3.4 | -6.7 19.9 270 41 21 6.3 3.5
13500 -6.3 20.7 265 44 23 6.7 3.7 | -5.8 21.6 270 38 20 6.5 3.6
13000 -5.3 22.5 265 42 21 7.1 3.9 | -4.8 23.4 265 36 18 7.1 3.9
12500 -4.2 24.4 265 39 20 7.7 4.2 | -3.8 25.2 265 33 17 7.5 4.1
12000 -3.1 26.4 265 36 19 7.7 4.2 | -2.7 27.1 265 30 16 8.0 4.4
11500 -2.0 28.4 265 33 17 7.7 4.2 | -1.5 29.3 265 28 14 8.3 4.6
11000 -0.9 30.4 265 30 16 7.3 4.0 | -0.2 31.6 265 25 13 7.8 4.3
10500 0.1 32.2 265 28 14 5.9 3.2 | 0.8 33.4 265 23 12 6.3 3.5
10250 0.6 33.1 265 26 14 8.4 4.6 | 1.4 34.5 270 22 11 11.0 6.0
10000 1.3 34.3 270 24 13 10.5 5.8 | 2.4 36.3 270 21 11 11.9 6.5
9750 2.0 35.6 270 23 12 8.2 4.5 | 3.0 37.4 270 20 10 7.8 4.3
9500 2.6 36.7 270 21 11 7.5 4.1 | 3.6 38.5 270 18 9 9.2 5.1
9250 3.1 37.6 270 19 10 7.7 4.2 | 4.3 39.7 270 17 9 7.7 4.2
9000 3.6 38.5 270 18 9 5.7 3.1 | 4.8 40.6 270 16 8 7.9 4.3
8750 4.0 39.2 275 16 8 5.9 3.3 | 5.5 41.9 270 15 8 9.5 5.2
8500 4.5 40.1 275 15 8 7.5 4.1 | 6.2 43.2 270 14 7 9.7 5.3
8250 5.1 41.2 275 13 7 6.8 3.7 | 6.9 44.4 270 13 6 8.8 4.9
8000 5.5 41.9 280 11 6 5.6 3.1 | 7.5 45.5 270 12 6 8.2 4.5
7750 5.9 42.6 280 9 5 5.2 2.8 | 8.1 46.6 270 11 6 9.7 5.3
7500 6.3 43.3 285 7 4 5.6 3.1 | 8.9 48.0 270 11 6 11.0 6.1
7250 6.7 44.1 290 6 3 5.3 2.9 | 9.7 49.5 270 10 5 9.1 5.0
7000 7.0 44.6 295 4 2 5.0 2.8 | 10.3 50.5 270 10 5 7.5 4.1
6750 7.4 45.3 310 3 2 6.0 3.3 | 10.9 51.6 270 10 5 11.0 6.0
6500 7.9 46.2 325 3 1 6.3 3.5 | 11.9 53.4 275 9 5 12.5 6.9
6250 8.3 46.9 350 2 1 4.1 2.2 | 12.7 54.9 275 8 4 10.2 5.6
6000 8.5 47.3 020 2 1 2.5 1.4 | 13.4 56.1 275 8 4 9.8 5.4
5750 8.7 47.7 040 3 1 4.4 2.4 | 14.2 57.6 275 8 4 9.8 5.4
5500 9.1 48.4 050 2 1 11.6 6.4 | 15.0 59.0 275 7 4 16.4 9.0
04/30/2024 at 1500 MDT | 04/30/2024 at 1800 MDT
|
CAPE... 0.0 LI... +2.5 | CAPE... +2.9 LI... +1.0
CINH... 0.0 K Index... +1.5 | CINH... -3.1 K Index... +10.6
|
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 -55.9 -68.6 255 46 24 -0.8 -0.5 | -56.1 -69.0 260 42 22 0.1 0.1
45000 -57.3 -71.1 260 72 37 -1.7 -0.9 | -56.0 -68.8 265 73 38 -2.3 -1.3
40000 -60.0 -76.0 260 75 39 -1.9 -1.0 | -60.4 -76.7 265 76 39 -3.0 -1.6
38000 -58.6 -73.5 260 74 38 5.5 3.0 | -59.1 -74.4 265 76 39 6.0 3.3
36000 -54.9 -66.8 265 71 37 5.5 3.0 | -55.1 -67.2 265 74 38 6.0 3.3
34000 -51.1 -60.0 265 69 36 8.3 4.6 | -51.0 -59.8 265 72 37 8.4 4.6
32000 -46.1 -51.0 270 69 35 8.3 4.6 | -45.9 -50.6 265 71 37 8.4 4.6
30000 -41.1 -42.0 265 68 35 8.4 4.6 | -40.8 -41.4 265 69 36 8.3 4.6
29000 -38.6 -37.5 265 67 35 8.4 4.6 | -38.3 -36.9 265 68 35 8.3 4.6
28000 -36.1 -33.0 265 67 35 8.4 4.6 | -35.9 -32.6 260 67 35 8.3 4.6
27000 -33.6 -28.5 265 67 34 7.8 4.3 | -33.4 -28.1 260 66 34 7.1 3.9
26000 -31.2 -24.2 265 65 33 7.8 4.3 | -31.3 -24.3 260 64 33 6.9 3.8
25000 -28.9 -20.0 265 63 32 7.8 4.3 | -29.3 -20.7 260 62 32 6.9 3.8
24000 -26.6 -15.9 265 61 31 6.9 3.8 | -27.2 -17.0 260 60 31 6.6 3.6
23000 -24.8 -12.6 265 58 30 6.0 3.3 | -25.3 -13.5 260 56 29 6.3 3.4
22000 -23.0 -9.4 270 56 29 6.0 3.3 | -23.4 -10.1 260 53 27 6.3 3.4
21000 -21.1 -6.0 270 53 27 7.2 3.9 | -21.5 -6.7 255 49 25 7.1 3.9
20000 -18.9 -2.0 270 48 25 7.4 4.0 | -19.3 -2.7 255 43 22 7.2 4.0
19500 -17.7 0.1 270 46 24 7.4 4.0 | -18.2 -0.8 250 40 21 7.2 4.0
19000 -16.6 2.1 270 44 23 7.4 4.0 | -16.6 2.1 250 36 19 7.2 4.0
18500 -15.0 5.0 270 40 20 7.6 4.1 | -15.5 4.1 245 34 17 7.6 4.2
18000 -13.8 7.2 270 36 19 7.5 4.1 | -14.4 6.1 240 31 16 7.6 4.2
17500 -12.7 9.1 270 33 17 7.2 3.9 | -13.3 8.1 235 29 15 7.9 4.3
17000 -11.7 10.9 270 34 17 7.0 3.8 | -12.1 10.2 235 28 15 8.1 4.4
16500 -10.6 12.9 275 34 18 7.0 3.8 | -10.9 12.4 235 27 14 8.2 4.5
16000 -9.6 14.7 275 33 17 6.9 3.8 | -9.6 14.7 235 26 14 8.5 4.6
15500 -8.6 16.5 275 32 16 6.9 3.8 | -8.4 16.9 235 26 13 8.4 4.6
15000 -7.5 18.5 275 31 16 7.4 4.1 | -7.1 19.2 235 25 13 9.0 4.9
14500 -6.4 20.5 270 30 16 7.4 4.1 | -5.8 21.6 235 23 12 8.9 4.9
14000 -5.3 22.5 270 30 15 7.6 4.2 | -4.4 24.1 235 22 11 9.2 5.0
13500 -4.2 24.4 270 28 14 7.7 4.2 | -3.1 26.4 230 20 10 9.2 5.1
13000 -3.1 26.4 265 26 14 8.1 4.4 | -1.7 28.9 230 19 10 9.2 5.1
12500 -1.9 28.6 265 24 12 8.3 4.5 | -0.3 31.5 230 18 9 9.2 5.0
12000 -0.7 30.7 265 21 11 8.6 4.7 | 1.1 34.0 235 16 8 9.0 4.9
11500 0.6 33.1 265 19 10 8.8 4.8 | 2.4 36.3 230 15 8 8.8 4.8
11000 2.0 35.6 265 16 8 8.2 4.5 | 3.7 38.7 230 13 7 8.3 4.6
10500 3.1 37.6 265 15 8 6.8 3.7 | 4.9 40.8 230 12 6 7.3 4.0
10250 3.6 38.5 265 14 7 11.0 6.0 | 5.5 41.9 230 11 6 10.5 5.7
10000 4.6 40.3 265 13 7 12.2 6.7 | 6.4 43.5 225 10 5 11.0 6.0
9750 5.3 41.5 265 13 6 8.6 4.7 | 7.0 44.6 225 9 5 8.0 4.4
9500 6.0 42.8 265 12 6 10.1 5.5 | 7.7 45.9 225 8 4 9.2 5.0
9250 6.7 44.1 265 12 6 7.8 4.3 | 8.3 46.9 225 8 4 7.6 4.2
9000 7.3 45.1 270 12 6 8.6 4.7 | 8.8 47.8 230 7 3 8.0 4.4
8750 8.0 46.4 270 12 6 10.9 6.0 | 9.5 49.1 230 6 3 9.6 5.2
8500 8.8 47.8 270 11 6 10.6 5.8 | 10.2 50.4 235 5 3 9.3 5.1
8250 9.6 49.3 270 11 6 9.7 5.3 | 10.9 51.6 240 5 2 9.0 4.9
8000 10.3 50.5 270 11 6 8.9 4.9 | 11.5 52.7 250 4 2 8.9 4.9
7750 11.0 51.8 275 11 6 10.2 5.6 | 12.2 54.0 250 4 2 9.7 5.3
7500 11.8 53.2 275 11 5 11.0 6.0 | 12.9 55.2 255 4 2 10.1 5.5
7250 12.6 54.7 275 10 5 9.7 5.3 | 13.7 56.7 265 3 2 9.5 5.2
7000 13.2 55.8 275 10 5 8.7 4.7 | 14.4 57.9 265 3 2 8.9 4.9
6750 13.9 57.0 275 10 5 10.4 5.7 | 15.1 59.2 270 3 2 9.9 5.4
6500 14.8 58.6 280 10 5 11.1 6.1 | 15.8 60.4 275 3 1 10.4 5.7
6250 15.6 60.1 280 10 5 10.2 5.6 | 16.6 61.9 285 3 1 9.8 5.4
6000 16.3 61.3 280 9 5 9.9 5.4 | 17.3 63.1 290 3 1 9.5 5.2
5750 17.0 62.6 285 9 5 10.3 5.7 | 18.0 64.4 295 3 1 10.0 5.5
5500 18.0 64.4 285 8 4 16.5 9.1 | 18.8 65.8 300 2 1 12.0 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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