National Weather Service Text Product
AFOS product SRGBOU
Dates interpreted at 00:00 UTCDisplaying AFOS PIL: SRGBOU
Product Timestamp: 2021-05-21 00:30 UTC
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855
UXUS97 KBOU 210030
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1829 MDT Thursday, May 20, 2021
This forecast is for Friday, May 21, 2021:
If the trigger temperature of 76.0 F/24.5 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 916 ft/min (4.7 m/s)
Maximum height of thermals.................. 15458 ft MSL (10118 ft AGL)
Forecast maximum temperature................... 82.0 F/28.2 C
Time of trigger temperature.................... 1045 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ Between 20 mph and 30 mph
Height of the -3 thermal index................. 9776 ft MSL (4436 ft AGL)
Thermal soaring outlook for Saturday 05/22..... Excellent
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....................... 34445 ft MSL (29105 ft AGL)
Wave soaring outlook for Saturday 05/22........ Poor
Remarks... None
Sunrise/Sunset.................... 05:39:23 / 20:12:52 MDT
Total possible sunshine........... 14 hr 33 min 29 sec (873 min 29 sec)
Altitude of sun at 12:56:07 MDT... 70.55 degrees
Upper air data from numerical model forecast valid on 05/21/2021 at 0600 MDT
Freezing level.................. 14357 ft MSL (9017 ft AGL)
Convective condensation level... 19256 ft MSL (13916 ft AGL)
Lifted condensation level....... 18309 ft MSL (12969 ft AGL)
Lifted index.................... +0.9
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 -57.6 -71.7 215 23 12 3.2 1.7 M M M M M
45000 -54.1 -65.4 220 28 14 -2.3 -1.2 M M M M M
40000 -57.4 -71.3 210 25 13 -3.0 -1.7 M M M M M
38000 -54.2 -65.6 220 26 14 5.7 3.1 M M M M M
36000 -50.8 -59.4 230 29 15 5.7 3.1 M M M M M
34000 -46.5 -51.7 230 29 15 8.2 4.5 M M M M M
32000 -41.6 -42.9 225 28 14 8.2 4.5 M M M M M
30000 -36.4 -33.5 220 28 14 8.9 4.9 39.0 102.2 8.4 M M
29000 -33.7 -28.7 215 27 14 9.0 4.9 38.6 101.6 8.3 M M
28000 -31.1 -24.0 215 27 14 9.0 4.9 38.4 101.2 8.2 M M
27000 -28.7 -19.7 210 27 14 6.9 3.8 37.7 99.8 7.7 M M
26000 -26.7 -16.1 205 26 13 6.9 3.8 36.5 97.8 6.8 M M
25000 -24.6 -12.3 200 26 13 6.9 3.8 35.5 95.9 6.1 M M
24000 -22.5 -8.5 195 25 13 7.9 4.3 34.6 94.3 5.4 M M
23000 -20.1 -4.2 195 24 12 7.8 4.3 33.8 92.9 4.8 M M
22000 -17.8 -0.0 190 22 12 7.8 4.3 33.2 91.8 4.4 M M
21000 -14.9 5.2 190 22 11 7.5 4.1 32.2 90.0 3.6 M M
20000 -12.7 9.1 190 22 11 7.5 4.1 31.4 88.6 2.9 M M
19500 -11.6 11.1 190 22 11 7.5 4.1 31.1 87.9 2.6 M M
19000 -10.5 13.1 190 22 11 7.5 4.1 30.7 87.3 2.3 M M
18500 -9.3 15.3 190 22 11 7.5 4.1 30.3 86.6 2.0 M M
18000 -8.2 17.2 195 22 11 7.5 4.1 29.9 85.9 1.6 M M
17500 -7.1 19.2 195 22 11 7.5 4.1 29.5 85.2 1.3 M M
17000 -6.0 21.2 195 21 11 7.5 4.1 29.2 84.5 1.0 M M
16500 -4.8 23.4 195 21 11 7.6 4.2 28.8 83.8 0.6 M M
16000 -3.7 25.3 195 21 11 7.7 4.2 28.4 83.2 0.3 M M
15500 -2.6 27.3 200 21 11 7.8 4.3 28.1 82.6 -0.0 916 4.7
15000 -1.4 29.5 200 21 11 7.9 4.3 27.8 82.0 -0.3 866 4.4
14500 -0.3 31.5 200 20 10 7.8 4.3 27.5 81.5 -0.6 817 4.1
14000 1.0 33.8 200 20 10 8.6 4.7 27.2 81.0 -0.9 766 3.9
13500 2.2 36.0 200 19 10 8.6 4.7 27.0 80.6 -1.1 713 3.6
13000 3.5 38.3 200 19 10 8.1 4.5 26.8 80.2 -1.3 661 3.4
12500 4.7 40.5 205 19 10 8.1 4.4 26.5 79.8 -1.6 610 3.1
12000 5.9 42.6 205 18 9 8.6 4.7 26.3 79.3 -1.8 558 2.8
11500 7.2 45.0 205 16 8 8.8 4.8 26.1 79.0 -2.0 504 2.6
11000 8.5 47.3 205 15 8 7.2 4.0 25.9 78.7 -2.2 452 2.3
10500 9.4 48.9 210 15 8 6.0 3.3 25.4 77.8 -2.7 408 2.1
10250 9.9 49.8 215 15 8 9.1 5.0 25.2 77.4 -3.0 386 2.0
10000 10.7 51.3 215 14 7 10.3 5.6 25.3 77.5 -2.9 354 1.8
9750 11.4 52.5 215 14 7 7.9 4.3 25.2 77.3 -3.0 327 1.7
9500 12.0 53.6 215 13 7 8.5 4.7 25.1 77.1 -3.1 301 1.5
9250 12.6 54.7 215 13 7 8.4 4.6 25.0 77.0 -3.2 274 1.4
9000 13.3 55.9 215 12 6 8.8 4.8 24.9 76.8 -3.3 248 1.3
8750 14.0 57.2 215 12 6 9.1 5.0 24.8 76.7 -3.4 220 1.1
8500 14.6 58.3 215 12 6 9.1 5.0 24.8 76.6 -3.4 192 1.0
8250 15.3 59.5 215 11 6 8.7 4.8 24.7 76.5 -3.5 165 0.8
8000 15.9 60.6 215 11 6 8.2 4.5 24.6 76.3 -3.6 138 0.7
7750 16.5 61.7 210 11 6 7.8 4.3 24.5 76.1 -3.7 113 0.6
7500 17.2 63.0 210 10 5 9.1 5.0 24.4 75.8 -3.9 87 0.4
7250 17.8 64.0 210 10 5 4.5 2.5 24.2 75.6 -4.0 62 0.3
7000 17.8 64.0 210 9 5 -1.0 -0.6 23.5 74.3 -4.7 54 0.3
6750 17.7 63.9 210 8 4 -0.2 -0.1 22.7 72.9 -5.5 49 0.2
6500 17.6 63.7 210 8 4 -1.2 -0.6 22.0 71.5 -6.4 43 0.2
6250 17.3 63.1 210 7 3 -9.8 -5.4 20.9 69.6 -7.5 47 0.2
6000 16.1 61.0 210 5 3 -15.3 -8.4 19.1 66.3 -9.4 74 0.4
5750 14.9 58.8 210 4 2 -14.6 -8.0 17.3 63.1 -11.3 102 0.5
5500 13.4 56.1 210 3 1 -26.5 -14.6 15.1 59.1 -13.6 140 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/21/2021 at 0900 MDT | 05/21/2021 at 1200 MDT
|
CAPE... 0.0 LI... +2.9 | CAPE... +6.2 LI... +1.6
CINH... 0.0 K Index... +16.4 | CINH... -28.2 K Index... +18.8
|
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 -71.5 210 23 12 3.3 1.8 | -57.6 -71.7 205 23 12 2.8 1.5
45000 -53.9 -65.0 220 27 14 -2.0 -1.1 | -54.5 -66.1 205 28 15 -1.7 -0.9
40000 -56.9 -70.4 215 28 15 -0.5 -0.3 | -57.0 -70.6 210 32 17 -0.0 -0.0
38000 -54.0 -65.2 215 29 15 5.2 2.8 | -53.9 -65.0 210 34 17 5.6 3.1
36000 -50.9 -59.6 215 30 16 5.2 2.8 | -50.5 -58.9 210 35 18 5.6 3.1
34000 -46.7 -52.1 215 30 15 8.6 4.7 | -46.1 -51.0 210 35 18 8.7 4.8
32000 -41.6 -42.9 210 28 15 8.6 4.7 | -40.2 -40.4 205 33 17 8.7 4.8
30000 -35.7 -32.3 205 28 14 8.9 4.9 | -35.1 -31.2 200 31 16 8.5 4.6
29000 -33.1 -27.6 205 28 14 8.9 4.9 | -32.6 -26.7 200 31 16 8.5 4.7
28000 -30.4 -22.7 205 28 14 9.0 4.9 | -30.1 -22.2 200 30 16 8.5 4.7
27000 -28.0 -18.4 205 28 14 7.7 4.2 | -27.6 -17.7 200 30 15 8.2 4.5
26000 -25.7 -14.3 205 28 14 7.7 4.2 | -25.2 -13.4 200 30 15 8.2 4.5
25000 -23.4 -10.1 205 28 14 7.7 4.3 | -22.7 -8.9 200 30 15 8.2 4.5
24000 -21.2 -6.2 205 28 14 7.3 4.0 | -20.4 -4.7 200 30 15 7.4 4.1
23000 -19.1 -2.4 205 28 14 7.3 4.0 | -18.2 -0.8 200 30 15 7.4 4.1
22000 -16.9 1.6 200 28 14 7.3 4.0 | -16.0 3.2 205 30 15 7.4 4.1
21000 -14.8 5.4 200 28 14 6.8 3.7 | -14.1 6.6 205 30 15 5.9 3.2
20000 -12.8 9.0 205 28 14 6.8 3.7 | -12.4 9.7 205 30 15 5.8 3.2
19500 -11.8 10.8 205 28 14 6.8 3.7 | -11.5 11.3 205 30 15 5.8 3.2
19000 -10.8 12.6 205 28 14 6.8 3.7 | -10.2 13.6 205 30 15 5.0 2.7
18500 -9.8 14.4 205 28 14 6.6 3.6 | -9.6 14.7 205 30 15 4.6 2.5
18000 -8.8 16.2 205 28 14 6.7 3.7 | -8.9 16.0 205 30 15 4.6 2.5
17500 -7.4 18.7 205 28 14 6.6 3.6 | -8.1 17.4 205 29 15 5.8 3.2
17000 -6.4 20.5 205 28 14 6.6 3.6 | -7.3 18.9 205 28 14 5.7 3.1
16500 -5.4 22.3 205 27 14 7.0 3.8 | -6.4 20.5 205 27 14 7.3 4.0
16000 -4.3 24.3 200 26 13 7.1 3.9 | -5.2 22.6 205 25 13 7.8 4.3
15500 -3.3 26.1 200 25 13 7.4 4.1 | -4.1 24.6 200 24 13 8.1 4.4
15000 -2.1 28.2 200 24 13 7.9 4.3 | -2.8 27.0 200 23 12 8.6 4.7
14500 -1.0 30.2 200 23 12 7.9 4.3 | -1.5 29.3 200 22 12 8.6 4.7
14000 0.3 32.5 200 23 12 8.5 4.6 | -0.2 31.6 200 22 11 9.3 5.1
13500 1.5 34.7 195 22 11 8.4 4.6 | 1.2 34.2 195 21 11 9.3 5.1
13000 2.8 37.0 195 21 11 8.5 4.7 | 2.6 36.7 195 21 11 9.2 5.1
12500 4.0 39.2 195 20 10 8.5 4.7 | 3.9 39.0 195 20 10 9.2 5.1
12000 5.3 41.5 195 20 10 8.2 4.5 | 5.3 41.5 190 20 10 9.0 4.9
11500 6.5 43.7 195 19 10 8.3 4.5 | 6.6 43.9 190 19 10 9.0 4.9
11000 7.7 45.9 195 18 9 7.1 3.9 | 7.9 46.2 190 18 9 8.0 4.4
10500 8.7 47.7 195 18 9 6.3 3.4 | 9.0 48.2 185 17 9 7.6 4.2
10250 9.2 48.6 195 18 9 9.7 5.3 | 9.7 49.5 185 17 9 11.2 6.1
10000 10.1 50.2 195 16 8 10.1 5.5 | 10.6 51.1 185 17 9 11.6 6.3
9750 10.6 51.1 195 15 8 6.9 3.8 | 11.3 52.3 185 16 8 8.9 4.9
9500 11.2 52.2 195 15 8 8.0 4.4 | 12.0 53.6 185 16 8 9.7 5.3
9250 11.8 53.2 195 14 7 6.7 3.6 | 12.7 54.9 180 15 8 9.1 5.0
9000 12.2 54.0 200 15 7 7.3 4.0 | 13.4 56.1 180 15 8 9.0 5.0
8750 12.9 55.2 200 14 7 8.8 4.8 | 14.1 57.4 180 15 7 9.4 5.2
8500 13.5 56.3 200 13 7 8.8 4.8 | 14.8 58.6 180 14 7 9.3 5.1
8250 14.1 57.4 200 12 6 7.3 4.0 | 15.4 59.7 180 14 7 9.4 5.2
8000 14.6 58.3 200 12 6 6.5 3.6 | 16.1 61.0 180 13 7 9.6 5.2
7750 15.1 59.2 200 12 6 8.0 4.4 | 16.8 62.2 180 13 7 9.5 5.2
7500 15.8 60.4 200 11 6 8.8 4.8 | 17.6 63.7 180 13 7 9.7 5.3
7250 16.3 61.3 200 10 5 4.9 2.7 | 18.3 64.9 180 12 6 8.8 4.8
7000 16.5 61.7 195 10 5 1.7 0.9 | 18.9 66.0 180 12 6 8.5 4.7
6750 16.8 62.2 195 9 5 5.3 2.9 | 19.6 67.3 180 12 6 10.4 5.7
6500 17.2 63.0 190 8 4 5.0 2.7 | 20.4 68.7 180 11 6 11.1 6.1
6250 17.3 63.1 190 7 4 0.5 0.3 | 21.2 70.2 175 11 6 10.6 5.8
6000 17.2 63.0 190 6 3 -1.2 -0.6 | 22.0 71.6 175 10 5 10.9 6.0
5750 17.1 62.8 190 6 3 0.4 0.2 | 22.8 73.0 175 10 5 9.6 5.3
5500 17.1 62.8 190 4 2 3.7 2.0 | 23.5 74.3 175 9 5 13.7 7.5
05/21/2021 at 1500 MDT | 05/21/2021 at 1800 MDT
|
CAPE... +45.7 LI... +0.4 | CAPE... +66.5 LI... -0.9
CINH... -1.3 K Index... +19.6 | CINH... -14.1 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 -58.0 -72.4 200 24 12 2.4 1.3 | -58.1 -72.6 195 25 13 2.8 1.5
45000 -55.6 -68.1 205 31 16 -1.4 -0.8 | -55.2 -67.4 200 32 16 -1.5 -0.8
40000 -57.6 -71.7 205 34 18 1.2 0.7 | -57.4 -71.3 200 37 19 1.5 0.8
38000 -53.9 -65.0 205 35 18 6.6 3.6 | -53.6 -64.5 200 37 19 6.6 3.6
36000 -49.9 -57.8 205 35 18 6.6 3.6 | -49.1 -56.4 195 38 19 6.7 3.7
34000 -44.4 -47.9 205 34 18 9.0 4.9 | -44.1 -47.4 195 35 18 9.0 4.9
32000 -39.0 -38.2 200 33 17 9.0 4.9 | -38.7 -37.7 190 32 16 9.1 5.0
30000 -33.9 -29.0 200 32 16 8.4 4.6 | -33.5 -28.3 190 31 16 8.5 4.7
29000 -31.4 -24.5 200 32 16 8.4 4.6 | -30.9 -23.6 195 32 16 8.5 4.7
28000 -28.9 -20.0 200 31 16 8.5 4.7 | -28.4 -19.1 195 32 16 8.6 4.7
27000 -26.5 -15.7 200 31 16 7.8 4.3 | -26.1 -15.0 195 32 16 7.6 4.2
26000 -24.2 -11.6 205 31 16 7.8 4.3 | -23.8 -10.8 195 31 16 7.6 4.2
25000 -21.9 -7.4 205 31 16 7.8 4.3 | -21.6 -6.9 200 30 15 7.6 4.1
24000 -19.7 -3.5 205 30 16 6.8 3.7 | -19.5 -3.1 200 29 15 6.2 3.4
23000 -17.7 0.1 205 29 15 6.8 3.7 | -17.7 0.1 205 27 14 6.2 3.4
22000 -15.7 3.7 210 29 15 6.8 3.7 | -15.9 3.4 205 26 13 6.2 3.4
21000 -13.8 7.2 210 27 14 6.0 3.3 | -14.1 6.6 210 25 13 5.7 3.2
20000 -12.1 10.2 205 26 13 6.0 3.3 | -12.0 10.4 210 25 13 5.8 3.2
19500 -10.7 12.7 205 25 13 6.0 3.3 | -11.2 11.8 210 25 13 5.7 3.1
19000 -9.9 14.2 205 25 13 6.2 3.4 | -10.3 13.5 210 26 13 6.7 3.7
18500 -8.9 16.0 205 26 14 6.2 3.4 | -9.3 15.3 205 26 13 7.0 3.8
18000 -8.0 17.6 205 28 14 6.2 3.4 | -8.3 17.1 205 26 14 7.1 3.9
17500 -7.2 19.0 205 28 14 5.3 2.9 | -7.2 19.0 200 26 13 7.5 4.1
17000 -6.4 20.5 205 28 14 5.3 2.9 | -6.1 21.0 200 26 13 7.4 4.1
16500 -5.5 22.1 205 27 14 6.7 3.7 | -5.0 23.0 200 25 13 7.2 4.0
16000 -4.5 23.9 200 27 14 7.1 3.9 | -4.0 24.8 195 24 12 7.2 3.9
15500 -3.4 25.9 200 27 14 7.8 4.3 | -2.9 26.8 195 22 11 7.3 4.0
15000 -2.1 28.2 200 26 14 9.2 5.0 | -1.8 28.8 195 21 11 7.6 4.2
14500 -0.7 30.7 195 26 13 9.2 5.1 | -0.7 30.7 195 20 11 7.6 4.2
14000 0.6 33.1 195 25 13 9.5 5.2 | 0.5 32.9 195 20 10 8.5 4.7
13500 2.1 35.8 195 25 13 9.5 5.2 | 1.8 35.2 195 19 10 8.4 4.6
13000 3.5 38.3 190 24 13 9.6 5.3 | 3.1 37.6 195 19 10 8.7 4.8
12500 4.9 40.8 190 24 12 9.6 5.3 | 4.3 39.7 195 18 9 8.7 4.8
12000 6.3 43.3 190 24 12 9.5 5.2 | 5.7 42.3 195 18 9 9.2 5.0
11500 7.8 46.0 190 23 12 9.6 5.3 | 7.0 44.6 195 17 9 9.2 5.1
11000 9.1 48.4 185 23 12 8.6 4.7 | 8.4 47.1 195 17 9 8.5 4.7
10500 10.4 50.7 185 23 12 8.6 4.7 | 9.6 49.3 195 17 9 8.4 4.6
10250 11.1 52.0 185 22 12 11.0 6.0 | 10.3 50.5 195 17 9 11.3 6.2
10000 12.0 53.6 185 22 11 10.7 5.9 | 11.2 52.2 195 16 8 11.4 6.2
9750 12.7 54.9 185 22 11 8.8 4.9 | 11.9 53.4 195 16 8 9.2 5.1
9500 13.3 55.9 185 22 11 9.5 5.2 | 12.7 54.9 195 16 8 9.9 5.4
9250 14.0 57.2 180 22 11 8.8 4.8 | 13.4 56.1 190 16 8 9.3 5.1
9000 14.7 58.5 180 21 11 9.0 4.9 | 14.1 57.4 190 16 8 9.3 5.1
8750 15.4 59.7 180 21 11 9.6 5.3 | 14.8 58.6 190 16 8 9.8 5.4
8500 16.1 61.0 180 20 11 9.7 5.3 | 15.5 59.9 190 16 8 9.7 5.3
8250 16.8 62.2 180 20 10 8.8 4.8 | 16.2 61.2 190 15 8 9.5 5.2
8000 17.4 63.3 175 19 10 8.9 4.9 | 16.9 62.4 190 15 8 9.7 5.3
7750 18.1 64.6 175 19 10 10.1 5.5 | 17.7 63.9 190 15 8 10.1 5.5
7500 18.8 65.8 175 18 9 10.1 5.5 | 18.4 65.1 190 15 8 10.1 5.6
7250 19.6 67.3 175 18 9 9.7 5.3 | 19.2 66.6 190 14 7 9.6 5.3
7000 20.3 68.5 175 17 9 9.5 5.2 | 19.8 67.6 185 14 7 9.2 5.1
6750 21.0 69.8 175 17 9 10.3 5.7 | 20.5 68.9 185 14 7 9.9 5.4
6500 21.8 71.2 170 17 9 10.6 5.8 | 21.3 70.3 185 13 7 10.0 5.5
6250 22.6 72.7 170 16 8 10.6 5.8 | 22.0 71.6 185 13 7 9.9 5.4
6000 23.3 73.9 170 15 8 10.8 5.9 | 22.8 73.0 185 12 6 9.9 5.4
5750 24.1 75.4 170 14 7 10.6 5.8 | 23.5 74.3 185 11 6 9.5 5.2
5500 25.0 77.0 170 13 7 14.1 7.8 | 24.1 75.4 185 10 5 9.2 5.0
________________________________________________________________________________
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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