Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
086
UXUS97 KBOU 011229
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0627 MDT Wednesday, May 1, 2024
This forecast is for Wednesday, May 1, 2024:
If the trigger temperature of 61.6 F/16.5 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 541 ft/min (2.7 m/s)
Maximum height of thermals.................. 12632 ft MSL (7304 ft AGL)
Forecast maximum temperature................... 70.0 F/21.6 C
Time of trigger temperature.................... 1015 MDT
Time of overdevelopment........................ 1400 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10109 ft MSL (4781 ft AGL)
Thermal soaring outlook for Thursday 05/02..... Fair
Wave Soaring Index............................. Fair
Wave Soaring Index trend (to 1800 MDT)......... Decreasing
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 39554 ft MSL (34226 ft AGL)
Wave soaring outlook for Thursday 05/02........ Poor
Remarks... Frontal passage early this afternoon, followed by scattered showers
and an isolated thunderstorm.
Sunrise/Sunset.................... 05:58:51 / 19:54:08 MDT
Total possible sunshine........... 13 hr 55 min 17 sec (835 min 17 sec)
Altitude of sun at 12:56:29 MDT... 65.62 degrees
Upper air data from numerical model forecast valid on 05/01/2024 at 0600 MDT
Freezing level.................. 12261 ft MSL (6933 ft AGL)
Convective condensation level... 15543 ft MSL (10215 ft AGL)
Lifted condensation level....... 15352 ft MSL (10025 ft AGL)
Lifted index.................... +1.1
K index......................... +18.3
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 -57.7 -71.9 255 48 25 2.3 1.3 M M M M M
45000 -54.6 -66.3 255 60 31 -2.8 -1.5 M M M M M
40000 -58.2 -72.8 255 69 36 -2.5 -1.3 M M M M M
38000 -57.1 -70.8 255 68 35 5.1 2.8 M M M M M
36000 -54.0 -65.2 250 64 33 5.1 2.8 M M M M M
34000 -50.0 -58.0 245 61 31 7.7 4.2 M M M M M
32000 -45.4 -49.7 245 61 32 7.8 4.3 M M M M M
30000 -40.7 -41.3 240 61 32 7.9 4.3 35.2 95.3 10.6 M M
29000 -38.3 -36.9 240 60 31 7.9 4.3 34.4 93.9 10.1 M M
28000 -35.9 -32.6 240 60 31 7.9 4.3 33.7 92.7 9.7 M M
27000 -33.6 -28.5 240 59 30 7.4 4.1 33.1 91.6 9.4 M M
26000 -31.4 -24.5 240 57 30 7.3 4.0 32.0 89.7 8.6 M M
25000 -29.2 -20.6 240 56 29 7.3 4.0 31.1 88.0 8.0 M M
24000 -27.0 -16.6 240 55 28 7.1 3.9 30.3 86.6 7.5 M M
23000 -25.0 -13.0 245 53 27 6.8 3.7 29.2 84.5 6.5 M M
22000 -23.0 -9.4 245 50 26 6.8 3.7 28.1 82.5 5.7 M M
21000 -21.0 -5.8 250 48 25 6.6 3.6 27.1 80.8 4.9 M M
20000 -19.1 -2.4 250 44 23 6.5 3.6 25.8 78.5 3.9 M M
19500 -18.1 -0.6 250 43 22 6.5 3.6 25.3 77.5 3.4 M M
19000 -17.2 1.0 250 41 21 6.6 3.6 24.7 76.5 2.9 M M
18500 -15.7 3.7 255 39 20 7.9 4.3 24.0 75.2 2.3 M M
18000 -14.5 5.9 255 40 20 7.8 4.3 23.7 74.6 2.0 M M
17500 -13.4 7.9 255 40 21 7.8 4.3 23.4 74.1 1.7 M M
17000 -12.2 10.0 255 39 20 7.8 4.3 23.0 73.4 1.4 M M
16500 -11.1 12.0 255 37 19 7.8 4.3 22.7 72.9 1.1 M M
16000 -9.8 14.4 250 37 19 9.0 5.0 22.5 72.5 0.9 M M
15500 -8.5 16.7 250 36 19 8.9 4.9 22.4 72.2 0.7 M M
15000 -7.2 19.0 250 35 18 9.0 4.9 22.2 72.0 0.6 M M
14500 -5.8 21.6 250 34 18 9.0 4.9 22.1 71.8 0.5 M M
14000 -4.5 23.9 250 34 17 8.9 4.9 22.0 71.6 0.4 M M
13500 -3.1 26.4 245 33 17 8.9 4.9 21.8 71.3 0.2 M M
13000 -1.8 28.8 245 32 17 8.7 4.8 21.7 71.1 0.1 M M
12500 -0.5 31.1 245 31 16 8.4 4.6 21.5 70.7 -0.1 523 2.7
12000 0.7 33.3 240 30 16 7.8 4.3 21.3 70.4 -0.3 470 2.4
11500 1.7 35.1 240 28 15 6.2 3.4 20.8 69.4 -0.8 427 2.2
11000 2.6 36.7 235 26 13 5.4 3.0 20.2 68.4 -1.3 385 2.0
10500 3.2 37.8 230 25 13 3.2 1.8 19.3 66.7 -2.2 353 1.8
10250 3.4 38.1 225 24 13 3.8 2.1 18.8 65.8 -2.7 339 1.7
10000 3.7 38.7 220 23 12 4.4 2.4 18.4 65.0 -3.2 323 1.6
9750 4.0 39.2 215 23 12 4.0 2.2 17.9 64.3 -3.6 307 1.6
9500 4.2 39.6 210 24 12 3.7 2.0 17.4 63.4 -4.1 292 1.5
9250 4.5 40.1 205 24 12 3.9 2.1 17.0 62.6 -4.6 276 1.4
9000 4.8 40.6 200 25 13 3.4 1.9 16.5 61.7 -5.0 261 1.3
8750 5.0 41.0 200 26 13 2.8 1.5 16.0 60.8 -5.6 246 1.3
8500 5.2 41.4 195 28 14 2.8 1.5 15.4 59.8 -6.1 233 1.2
8250 5.4 41.7 190 29 15 2.8 1.6 14.9 58.8 -6.7 219 1.1
8000 5.6 42.1 185 31 16 3.5 1.9 14.4 57.9 -7.2 205 1.0
7750 5.9 42.6 185 32 16 3.9 2.1 13.9 57.1 -7.6 189 1.0
7500 6.2 43.2 180 32 17 3.7 2.0 13.5 56.3 -8.1 173 0.9
7250 6.5 43.7 180 33 17 3.8 2.1 13.0 55.4 -8.6 157 0.8
7000 6.8 44.2 175 33 17 4.1 2.2 12.6 54.6 -9.0 141 0.7
6750 7.1 44.8 175 34 17 4.0 2.2 12.1 53.9 -9.5 124 0.6
6500 7.4 45.3 175 31 16 4.0 2.2 11.7 53.1 -9.9 107 0.5
6250 7.7 45.9 175 28 14 2.3 1.3 11.2 52.2 -10.4 92 0.5
6000 7.8 46.0 170 25 13 0.4 0.2 10.6 51.0 -11.1 82 0.4
5750 7.8 46.0 170 23 12 2.7 1.5 9.9 49.9 -11.8 73 0.4
5500 8.0 46.4 165 16 8 -0.3 -0.2 9.4 48.9 -12.4 60 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/01/2024 at 0900 MDT | 05/01/2024 at 1200 MDT
|
CAPE... 0.0 LI... +1.4 | CAPE... +115.2 LI... -0.9
CINH... 0.0 K Index... +18.1 | CINH... -32.8 K Index... +22.3
|
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 -57.0 -70.6 250 43 22 1.2 0.7 | -56.5 -69.7 245 41 21 0.2 0.1
45000 -55.4 -67.7 250 60 31 -1.8 -1.0 | -56.2 -69.2 245 62 32 -1.3 -0.7
40000 -57.9 -72.2 250 74 38 -1.7 -1.0 | -58.2 -72.8 240 77 39 -1.4 -0.8
38000 -56.5 -69.7 250 74 38 5.4 3.0 | -56.5 -69.7 240 79 41 6.1 3.3
36000 -53.2 -63.8 245 69 35 5.4 3.0 | -52.9 -63.2 240 78 40 6.1 3.3
34000 -49.2 -56.6 240 65 33 7.3 4.0 | -48.6 -55.5 235 77 40 6.8 3.7
32000 -44.8 -48.6 235 63 33 7.3 4.0 | -44.5 -48.1 235 75 38 6.8 3.7
30000 -40.3 -40.5 235 62 32 7.7 4.2 | -40.3 -40.5 235 72 37 7.5 4.1
29000 -38.0 -36.4 235 60 31 7.7 4.2 | -38.0 -36.4 235 69 36 7.5 4.1
28000 -35.6 -32.1 235 59 30 7.7 4.2 | -35.8 -32.4 235 67 35 7.5 4.1
27000 -33.3 -27.9 235 58 30 6.9 3.8 | -33.5 -28.3 235 65 33 7.0 3.8
26000 -31.4 -24.5 235 56 29 6.6 3.6 | -31.5 -24.7 235 63 32 6.7 3.7
25000 -29.4 -20.9 235 55 28 6.6 3.6 | -29.5 -21.1 235 60 31 6.7 3.7
24000 -27.4 -17.3 240 54 28 6.8 3.7 | -27.5 -17.5 240 58 30 6.7 3.7
23000 -25.2 -13.4 240 53 27 7.4 4.1 | -25.5 -13.9 240 57 29 6.8 3.7
22000 -23.0 -9.4 240 51 26 7.4 4.1 | -23.4 -10.1 240 55 28 6.8 3.7
21000 -20.8 -5.4 245 50 26 7.0 3.8 | -21.4 -6.5 240 53 27 7.1 3.9
20000 -18.8 -1.8 245 49 25 6.8 3.7 | -19.3 -2.7 240 50 26 7.3 4.0
19500 -17.8 -0.0 245 48 25 6.8 3.7 | -18.2 -0.8 240 48 25 7.3 4.0
19000 -16.8 1.8 245 47 24 6.8 3.7 | -17.1 1.2 240 46 24 7.3 4.0
18500 -15.8 3.6 250 47 24 6.9 3.8 | -16.1 3.0 240 44 23 7.4 4.1
18000 -14.3 6.3 250 45 23 7.0 3.8 | -15.0 5.0 240 42 22 7.5 4.1
17500 -13.3 8.1 250 43 22 7.0 3.9 | -13.9 7.0 240 40 21 7.6 4.2
17000 -12.2 10.0 250 41 21 7.1 3.9 | -12.2 10.0 245 38 20 7.4 4.0
16500 -11.2 11.8 250 39 20 7.1 3.9 | -11.2 11.8 245 37 19 7.4 4.0
16000 -10.1 13.8 250 37 19 8.3 4.5 | -10.0 14.0 245 36 19 8.4 4.6
15500 -8.9 16.0 250 35 18 8.1 4.5 | -8.8 16.2 245 35 18 8.3 4.6
15000 -7.7 18.1 250 33 17 8.6 4.7 | -7.5 18.5 250 33 17 9.1 5.0
14500 -6.4 20.5 255 31 16 8.7 4.8 | -6.2 20.8 245 32 16 9.2 5.0
14000 -5.1 22.8 255 30 15 8.8 4.8 | -4.8 23.4 245 30 16 9.2 5.0
13500 -3.8 25.2 255 28 14 8.8 4.8 | -3.4 25.9 245 29 15 9.1 5.0
13000 -2.5 27.5 255 26 13 8.8 4.8 | -2.1 28.2 245 27 14 9.0 4.9
12500 -1.2 29.8 255 24 12 8.8 4.8 | -0.8 30.6 245 25 13 8.9 4.9
12000 0.2 32.4 260 22 12 8.7 4.8 | 0.6 33.1 240 23 12 8.8 4.9
11500 1.4 34.5 260 21 11 8.4 4.6 | 1.9 35.4 240 21 11 8.7 4.8
11000 2.7 36.9 260 20 10 7.9 4.3 | 3.2 37.8 240 20 10 8.3 4.5
10500 3.7 38.7 260 19 10 6.1 3.3 | 4.3 39.7 235 18 9 6.3 3.5
10250 4.2 39.6 260 18 9 8.1 4.5 | 4.8 40.6 235 17 9 9.3 5.1
10000 4.9 40.8 255 18 9 9.1 5.0 | 5.6 42.1 235 16 8 10.9 6.0
9750 5.4 41.7 255 18 9 5.9 3.2 | 6.3 43.3 235 15 8 7.9 4.3
9500 5.8 42.4 250 17 9 4.7 2.6 | 6.8 44.2 235 14 7 7.2 4.0
9250 6.2 43.2 250 17 9 5.4 3.0 | 7.4 45.3 230 13 7 7.8 4.3
9000 6.5 43.7 245 16 8 3.9 2.1 | 8.0 46.4 230 12 6 8.6 4.7
8750 6.7 44.1 235 16 8 2.6 1.4 | 8.6 47.5 230 11 6 8.0 4.4
8500 6.9 44.4 230 16 8 3.1 1.7 | 9.2 48.6 225 10 5 7.3 4.0
8250 7.1 44.8 225 16 8 3.0 1.6 | 9.7 49.5 225 9 4 7.4 4.0
8000 7.4 45.3 220 16 8 4.1 2.3 | 10.2 50.4 220 8 4 7.8 4.3
7750 7.7 45.9 215 17 9 3.3 1.8 | 10.8 51.4 220 7 4 9.0 4.9
7500 7.8 46.0 210 18 9 1.9 1.0 | 11.5 52.7 220 6 3 9.5 5.2
7250 8.0 46.4 200 18 9 2.1 1.1 | 12.2 54.0 220 6 3 8.9 4.9
7000 8.1 46.6 200 19 10 1.2 0.7 | 12.8 55.0 220 5 3 7.7 4.2
6750 8.2 46.8 195 19 10 2.1 1.2 | 13.4 56.1 220 5 3 9.7 5.3
6500 8.4 47.1 190 18 9 2.1 1.1 | 14.3 57.7 220 5 2 11.7 6.4
6250 8.6 47.5 185 17 9 5.8 3.2 | 15.1 59.2 225 4 2 10.7 5.9
6000 9.2 48.6 185 16 8 9.3 5.1 | 15.9 60.6 225 4 2 10.6 5.8
5750 9.8 49.6 185 16 8 8.9 4.9 | 16.7 62.1 225 4 2 9.7 5.3
5500 10.6 51.1 180 13 7 14.6 8.0 | 17.5 63.5 230 3 2 15.1 8.3
05/01/2024 at 1500 MDT | 05/01/2024 at 1800 MDT
|
CAPE... +233.6 LI... -1.3 | CAPE... +89.6 LI... -1.0
CINH... -76.8 K Index... +24.8 | CINH... -38.0 K Index... +26.5
|
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 -55.4 -67.7 245 36 19 1.2 0.7 | -55.1 -67.2 245 38 19 2.1 1.1
45000 -53.8 -64.8 245 61 32 -2.0 -1.1 | -52.2 -62.0 245 57 29 -2.1 -1.2
40000 -57.6 -71.7 240 83 43 -2.5 -1.4 | -56.7 -70.1 240 78 40 -3.0 -1.6
38000 -56.6 -69.9 235 88 45 5.3 2.9 | -56.2 -69.2 240 84 43 4.7 2.6
36000 -53.4 -64.1 235 89 46 5.3 2.9 | -53.0 -63.4 240 86 44 4.7 2.6
34000 -49.6 -57.3 235 89 46 6.5 3.6 | -50.0 -58.0 235 87 45 6.2 3.4
32000 -45.7 -50.3 235 84 43 6.5 3.6 | -46.2 -51.2 235 82 42 6.3 3.4
30000 -41.7 -43.1 235 78 40 7.4 4.0 | -42.2 -44.0 235 76 39 7.4 4.1
29000 -39.5 -39.1 235 74 38 7.4 4.1 | -40.0 -40.0 235 73 37 7.5 4.1
28000 -37.3 -35.1 235 71 37 7.4 4.1 | -37.8 -36.0 235 69 36 7.5 4.1
27000 -35.0 -31.0 235 68 35 7.0 3.9 | -35.5 -31.9 235 65 34 7.4 4.1
26000 -33.0 -27.4 235 64 33 6.7 3.7 | -33.3 -27.9 235 62 32 7.2 4.0
25000 -31.0 -23.8 235 61 31 6.7 3.7 | -31.2 -24.2 235 59 30 7.3 4.0
24000 -29.0 -20.2 235 58 30 6.9 3.8 | -29.0 -20.2 235 55 29 7.3 4.0
23000 -26.8 -16.2 235 55 28 7.6 4.2 | -26.7 -16.1 235 53 27 7.9 4.3
22000 -24.5 -12.1 235 51 26 7.6 4.2 | -24.4 -11.9 230 50 26 7.9 4.3
21000 -22.3 -8.1 230 48 25 8.1 4.4 | -22.0 -7.6 230 48 25 7.9 4.4
20000 -19.8 -3.6 230 46 24 8.4 4.6 | -19.1 -2.4 230 46 23 8.0 4.4
19500 -18.6 -1.5 230 45 23 8.4 4.6 | -17.9 -0.2 230 45 23 8.0 4.4
19000 -17.3 0.9 230 44 22 8.4 4.6 | -16.7 1.9 230 44 23 8.0 4.4
18500 -16.1 3.0 230 42 22 8.5 4.7 | -15.5 4.1 230 43 22 8.2 4.5
18000 -14.2 6.4 230 41 21 8.6 4.7 | -14.3 6.3 230 42 22 8.2 4.5
17500 -12.9 8.8 230 40 20 8.7 4.8 | -13.1 8.4 230 41 21 8.2 4.5
17000 -11.6 11.1 230 38 20 8.7 4.8 | -11.9 10.6 230 39 20 8.2 4.5
16500 -10.3 13.5 235 37 19 8.7 4.8 | -10.7 12.7 230 37 19 8.3 4.5
16000 -9.1 15.6 235 35 18 8.7 4.8 | -9.5 14.9 230 35 18 8.0 4.4
15500 -7.8 18.0 235 34 17 8.7 4.8 | -8.3 17.1 230 33 17 8.0 4.4
15000 -6.5 20.3 235 32 17 8.7 4.8 | -7.2 19.0 230 31 16 7.5 4.1
14500 -5.2 22.6 235 30 16 8.7 4.8 | -6.1 21.0 230 27 14 7.3 4.0
14000 -3.9 25.0 235 28 15 8.6 4.7 | -5.1 22.8 230 24 13 7.2 4.0
13500 -2.6 27.3 235 26 13 8.5 4.7 | -4.0 24.8 230 21 11 7.1 3.9
13000 -1.4 29.5 235 24 12 8.4 4.6 | -3.0 26.6 230 18 9 7.1 3.9
12500 -0.1 31.8 235 21 11 8.3 4.6 | -2.0 28.4 225 14 7 6.7 3.7
12000 1.1 34.0 235 19 10 8.2 4.5 | -1.0 30.2 225 11 6 6.6 3.6
11500 2.3 36.1 240 16 8 7.9 4.3 | -0.1 31.8 225 7 4 6.1 3.4
11000 3.4 38.1 245 12 6 7.6 4.2 | 0.8 33.4 225 4 2 6.1 3.3
10500 4.4 39.9 250 9 5 5.6 3.1 | 1.6 34.9 000 0 0 5.1 2.8
10250 4.9 40.8 260 8 4 8.2 4.5 | 2.0 35.6 035 2 1 6.4 3.5
10000 5.6 42.1 270 7 3 10.1 5.5 | 2.6 36.7 030 3 1 8.5 4.7
9750 6.2 43.2 290 6 3 7.5 4.1 | 3.2 37.8 025 4 2 7.2 4.0
9500 6.7 44.1 305 6 3 6.6 3.6 | 3.7 38.7 025 5 3 6.1 3.4
9250 7.2 45.0 325 7 4 7.0 3.8 | 4.1 39.4 025 7 4 5.9 3.2
9000 7.8 46.0 335 8 4 8.8 4.8 | 4.6 40.3 025 8 4 7.9 4.4
8750 8.5 47.3 335 8 4 9.2 5.0 | 5.3 41.5 015 8 4 8.3 4.6
8500 9.1 48.4 340 9 5 8.0 4.4 | 5.7 42.3 015 9 5 6.3 3.5
8250 9.7 49.5 345 10 5 8.8 4.8 | 6.2 43.2 010 10 5 7.4 4.1
8000 10.3 50.5 350 11 5 6.9 3.8 | 6.7 44.1 010 11 6 5.1 2.8
7750 10.8 51.4 355 12 6 7.8 4.3 | 7.0 44.6 015 13 7 4.8 2.6
7500 11.5 52.7 355 12 6 10.5 5.8 | 7.5 45.5 015 13 7 6.8 3.7
7250 12.3 54.1 355 13 7 9.2 5.0 | 8.0 46.4 015 14 7 5.7 3.1
7000 12.9 55.2 355 14 7 6.1 3.3 | 8.3 46.9 015 15 8 3.2 1.8
6750 13.3 55.9 360 14 7 8.7 4.8 | 8.5 47.3 020 16 8 5.4 3.0
6500 14.2 57.6 360 14 7 13.1 7.2 | 9.1 48.4 020 16 8 8.3 4.6
6250 15.1 59.2 360 14 7 10.3 5.6 | 9.6 49.3 015 16 8 7.8 4.3
6000 15.7 60.3 360 15 8 7.7 4.2 | 10.2 50.4 020 16 8 8.2 4.5
5750 16.3 61.3 360 15 8 9.5 5.2 | 10.9 51.6 020 17 8 8.9 4.9
5500 17.3 63.1 355 13 7 17.9 9.8 | 11.6 52.9 015 14 7 13.8 7.6
________________________________________________________________________________
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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