Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
526
UXUS97 KBOU 180104
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1903 MDT Friday, May 17, 2024
This forecast is for Saturday, May 18, 2024:
If the trigger temperature of 72.1 F/22.3 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1099 ft/min (5.6 m/s)
Maximum height of thermals.................. 16939 ft MSL (11650 ft AGL)
Forecast maximum temperature................... 78.0 F/26.0 C
Time of trigger temperature.................... 1200 MDT
Time of overdevelopment........................ 1500 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 9828 ft MSL (4539 ft AGL)
Thermal soaring outlook for Sunday 05/19....... Good
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)................ Neither
Potential height of wave....................... 39685 ft MSL (34396 ft AGL)
Wave soaring outlook for Sunday 05/19.......... Poor
Remarks...
Sunrise/Sunset.................... 05:41:26 / 20:10:29 MDT
Total possible sunshine........... 14 hr 29 min 3 sec (869 min 3 sec)
Altitude of sun at 12:55:58 MDT... 70.00 degrees
Upper air data from numerical model forecast valid on 05/18/2024 at 0600 MDT
Freezing level.................. 13220 ft MSL (7931 ft AGL)
Convective condensation level... 15535 ft MSL (10246 ft AGL)
Lifted condensation level....... 16047 ft MSL (10759 ft AGL)
Lifted index.................... -0.8
K index......................... +18.5
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 -58.8 -73.8 255 32 17 1.7 0.9 M M M M M
45000 -56.8 -70.2 250 35 18 -0.9 -0.5 M M M M M
40000 -58.2 -72.8 260 57 29 -1.8 -1.0 M M M M M
38000 -55.2 -67.4 260 56 29 5.9 3.2 M M M M M
36000 -51.7 -61.1 255 54 28 5.9 3.2 M M M M M
34000 -47.5 -53.5 260 52 27 8.2 4.5 M M M M M
32000 -42.6 -44.7 260 50 26 8.2 4.5 M M M M M
30000 -37.8 -36.0 260 47 24 7.8 4.3 38.5 101.3 9.8 M M
29000 -35.4 -31.7 260 45 23 7.8 4.3 37.7 99.8 9.3 M M
28000 -32.5 -26.5 260 43 22 7.8 4.3 36.9 98.4 8.8 M M
27000 -30.3 -22.5 260 41 21 7.1 3.9 35.9 96.7 8.2 M M
26000 -28.2 -18.8 265 39 20 7.1 3.9 34.9 94.7 7.4 M M
25000 -26.1 -15.0 265 37 19 7.0 3.9 33.9 93.0 6.7 M M
24000 -24.0 -11.2 265 36 18 6.8 3.7 32.9 91.2 6.0 M M
23000 -22.0 -7.6 270 35 18 6.8 3.7 31.8 89.2 5.1 M M
22000 -19.9 -3.8 275 35 18 6.8 3.7 30.7 87.3 4.3 M M
21000 -17.9 -0.2 275 35 18 6.8 3.7 29.7 85.5 3.5 M M
20000 -15.9 3.4 280 36 18 6.8 3.7 28.6 83.5 2.6 M M
19500 -14.9 5.2 280 36 18 6.8 3.7 28.1 82.6 2.2 M M
19000 -13.8 7.2 280 36 19 6.9 3.8 27.7 81.8 1.8 M M
18500 -12.8 9.0 280 36 19 7.2 3.9 27.2 81.0 1.4 M M
18000 -11.8 10.8 280 36 19 7.2 4.0 26.8 80.2 1.0 M M
17500 -10.7 12.7 280 36 19 7.1 3.9 26.3 79.4 0.6 M M
17000 -9.7 14.5 280 35 18 7.2 3.9 25.9 78.5 0.1 M M
16500 -8.6 16.5 280 34 17 7.4 4.1 25.4 77.8 -0.3 1067 5.4
16000 -7.5 18.5 275 32 16 8.1 4.4 25.1 77.2 -0.6 1018 5.2
15500 -6.4 20.5 275 30 15 8.0 4.4 24.8 76.7 -1.0 969 4.9
15000 -5.1 22.8 275 28 14 9.2 5.1 24.6 76.4 -1.2 917 4.7
14500 -3.2 26.2 275 25 13 9.2 5.0 24.5 76.1 -1.4 836 4.2
14000 -1.8 28.8 270 24 12 9.2 5.0 24.4 75.9 -1.6 781 4.0
13500 -0.5 31.1 270 22 11 9.2 5.1 24.3 75.8 -1.7 726 3.7
13000 0.9 33.6 265 20 11 9.2 5.1 24.2 75.6 -1.8 671 3.4
12500 2.2 36.0 265 19 10 9.2 5.1 24.1 75.4 -1.9 615 3.1
12000 3.6 38.5 260 17 9 9.4 5.2 24.1 75.3 -2.0 559 2.8
11500 5.0 41.0 255 16 8 9.5 5.2 24.0 75.2 -2.1 503 2.6
11000 6.3 43.3 250 14 7 8.7 4.8 23.9 75.0 -2.2 448 2.3
10500 7.6 45.7 245 13 7 9.6 5.3 23.7 74.7 -2.4 394 2.0
10250 8.3 46.9 240 12 6 5.1 2.8 23.7 74.6 -2.5 368 1.9
10000 8.5 47.3 240 12 6 5.4 3.0 23.1 73.7 -3.0 353 1.8
9750 9.2 48.6 240 11 5 9.8 5.4 23.1 73.5 -3.0 326 1.7
9500 9.8 49.6 235 10 5 9.6 5.3 23.0 73.5 -3.1 298 1.5
9250 10.5 50.9 230 9 5 6.0 3.3 23.0 73.4 -3.2 271 1.4
9000 10.8 51.4 235 8 4 5.3 2.9 22.5 72.5 -3.6 255 1.3
8750 11.4 52.5 240 7 4 8.8 4.8 22.4 72.3 -3.8 230 1.2
8500 12.0 53.6 245 7 3 8.0 4.4 22.3 72.1 -3.9 205 1.0
8250 12.5 54.5 255 6 3 5.8 3.2 22.1 71.8 -4.1 181 0.9
8000 12.9 55.2 265 6 3 4.4 2.4 21.7 71.0 -4.5 164 0.8
7750 13.3 55.9 275 6 3 6.3 3.4 21.4 70.4 -4.8 144 0.7
7500 13.7 56.7 285 6 3 5.8 3.2 21.1 70.0 -5.1 123 0.6
7250 14.1 57.4 290 5 3 3.9 2.1 20.7 69.3 -5.5 105 0.5
7000 14.3 57.7 295 4 2 3.1 1.7 20.2 68.4 -6.0 91 0.5
6750 14.5 58.1 305 4 2 3.6 2.0 19.7 67.5 -6.5 76 0.4
6500 14.7 58.5 310 4 2 1.4 0.8 19.2 66.6 -7.1 63 0.3
6250 14.7 58.5 315 3 1 -1.1 -0.6 18.5 65.2 -7.9 57 0.3
6000 14.6 58.3 325 2 1 0.3 0.1 17.7 63.8 -8.7 52 0.3
5750 14.6 58.3 355 1 0 -3.2 -1.8 16.9 62.4 -9.5 46 0.2
5500 13.8 56.8 000 0 0 -18.3 -10.1 15.4 59.8 -11.0 63 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/18/2024 at 0900 MDT | 05/18/2024 at 1200 MDT
|
CAPE... +0.4 LI... +0.9 | CAPE... +75.0 LI... -1.3
CINH... -0.2 K Index... +16.4 | CINH... -6.2 K Index... +24.4
|
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 -58.9 -74.0 255 37 19 1.7 0.9 | -58.7 -73.7 250 40 20 0.9 0.5
45000 -56.8 -70.2 250 38 19 -0.7 -0.4 | -57.5 -71.5 240 41 21 -0.5 -0.3
40000 -58.1 -72.6 255 53 28 -1.6 -0.9 | -58.3 -72.9 245 46 24 -1.2 -0.7
38000 -55.1 -67.2 255 53 27 5.9 3.3 | -55.2 -67.4 245 47 24 6.1 3.4
36000 -51.6 -60.9 260 51 26 5.9 3.3 | -51.5 -60.7 250 49 25 6.1 3.4
34000 -47.6 -53.7 260 50 26 7.4 4.0 | -47.6 -53.7 250 49 25 7.2 4.0
32000 -43.2 -45.8 260 48 25 7.4 4.0 | -43.2 -45.8 250 47 24 7.2 4.0
30000 -38.0 -36.4 260 48 25 8.2 4.5 | -38.1 -36.6 255 45 23 8.1 4.4
29000 -35.5 -31.9 260 48 25 8.2 4.5 | -35.6 -32.1 255 45 23 8.1 4.4
28000 -33.0 -27.4 265 48 25 8.2 4.5 | -33.2 -27.8 260 45 23 8.1 4.5
27000 -30.8 -23.4 265 47 24 7.1 3.9 | -31.0 -23.8 260 44 23 6.9 3.8
26000 -28.7 -19.7 265 45 23 7.1 3.9 | -29.0 -20.2 260 43 22 6.9 3.8
25000 -26.6 -15.9 265 44 23 7.1 3.9 | -26.9 -16.4 265 42 21 6.9 3.8
24000 -24.5 -12.1 265 43 22 6.8 3.8 | -24.8 -12.6 265 41 21 7.3 4.0
23000 -22.4 -8.3 265 41 21 6.9 3.8 | -22.7 -8.9 265 39 20 7.3 4.0
22000 -20.4 -4.7 270 40 21 6.9 3.8 | -20.5 -4.9 265 38 20 7.3 4.0
21000 -18.3 -0.9 270 40 20 7.2 3.9 | -18.4 -1.1 260 37 19 6.9 3.8
20000 -16.2 2.8 275 39 20 7.2 4.0 | -16.4 2.5 260 36 19 7.0 3.8
19500 -15.1 4.8 275 39 20 7.2 4.0 | -15.3 4.5 260 36 18 7.0 3.8
19000 -14.0 6.8 280 38 20 7.2 3.9 | -14.3 6.3 260 35 18 7.1 3.9
18500 -13.0 8.6 280 38 20 7.0 3.8 | -13.2 8.2 260 35 18 7.9 4.3
18000 -11.9 10.6 280 38 19 7.0 3.9 | -12.1 10.2 260 34 18 7.8 4.3
17500 -10.9 12.4 280 37 19 7.2 4.0 | -10.9 12.4 260 33 17 8.5 4.6
17000 -9.8 14.4 280 36 19 7.3 4.0 | -9.6 14.7 260 32 17 8.6 4.7
16500 -8.8 16.2 280 35 18 7.6 4.2 | -8.4 16.9 260 31 16 8.7 4.8
16000 -7.6 18.3 275 34 17 8.3 4.6 | -6.4 20.5 255 29 15 8.9 4.9
15500 -5.8 21.6 270 31 16 8.5 4.7 | -5.1 22.8 255 28 14 8.8 4.8
15000 -4.5 23.9 270 29 15 8.7 4.8 | -3.8 25.2 255 27 14 8.8 4.8
14500 -3.2 26.2 265 27 14 8.8 4.9 | -2.6 27.3 255 26 13 8.8 4.8
14000 -1.9 28.6 260 26 13 9.1 5.0 | -1.2 29.8 255 24 13 9.0 4.9
13500 -0.6 30.9 260 24 12 9.1 5.0 | 0.1 32.2 250 23 12 9.0 4.9
13000 0.8 33.4 255 23 12 9.0 4.9 | 1.4 34.5 250 22 11 9.0 4.9
12500 2.1 35.8 255 22 11 9.0 5.0 | 2.8 37.0 250 21 11 9.0 4.9
12000 3.4 38.1 250 21 11 8.8 4.9 | 4.1 39.4 245 19 10 9.0 4.9
11500 4.7 40.5 245 19 10 9.0 4.9 | 5.4 41.7 245 18 9 9.0 4.9
11000 6.0 42.8 240 18 9 8.0 4.4 | 6.7 44.1 245 17 9 8.6 4.7
10500 7.2 45.0 235 17 9 9.2 5.0 | 8.0 46.4 240 16 8 9.7 5.3
10250 7.8 46.0 235 16 8 3.4 1.9 | 8.7 47.7 235 15 8 4.6 2.5
10000 7.8 46.0 230 15 8 2.9 1.6 | 8.8 47.8 235 15 8 4.6 2.5
9750 8.3 46.9 230 14 7 8.0 4.4 | 9.5 49.1 235 14 7 9.4 5.2
9500 8.8 47.8 225 13 7 7.3 4.0 | 10.1 50.2 230 12 6 9.0 4.9
9250 9.3 48.7 220 12 6 4.1 2.3 | 10.7 51.3 220 11 6 4.2 2.3
9000 9.5 49.1 215 11 6 1.7 1.0 | 10.8 51.4 215 10 5 2.6 1.4
8750 9.7 49.5 210 9 5 3.4 1.9 | 11.2 52.2 205 8 4 6.2 3.4
8500 9.9 49.8 205 7 4 3.0 1.6 | 11.6 52.9 190 7 4 5.3 2.9
8250 10.1 50.2 195 5 3 2.0 1.1 | 12.0 53.6 170 6 3 4.8 2.6
8000 10.2 50.4 180 4 2 1.8 1.0 | 12.4 54.3 150 6 3 6.3 3.5
7750 10.4 50.7 160 4 2 3.4 1.9 | 13.0 55.4 140 6 3 10.0 5.5
7500 10.6 51.1 135 4 2 3.4 1.9 | 13.8 56.8 135 7 3 9.6 5.3
7250 10.8 51.4 125 5 3 2.7 1.5 | 14.4 57.9 130 7 3 7.4 4.1
7000 11.0 51.8 120 6 3 2.6 1.4 | 14.9 58.8 130 7 4 7.5 4.1
6750 11.3 52.3 115 7 4 7.8 4.3 | 15.6 60.1 125 7 4 12.9 7.1
6500 12.1 53.8 115 8 4 10.2 5.6 | 16.7 62.1 120 7 4 12.5 6.9
6250 12.7 54.9 110 8 4 8.5 4.6 | 17.4 63.3 120 7 4 9.2 5.0
6000 13.3 55.9 110 8 4 8.1 4.4 | 18.1 64.6 115 7 4 9.1 5.0
5750 14.0 57.2 110 8 4 12.5 6.9 | 18.9 66.0 115 7 4 14.0 7.7
5500 15.3 59.5 105 7 4 22.9 12.6 | 20.4 68.7 110 7 4 28.2 15.5
05/18/2024 at 1500 MDT | 05/18/2024 at 1800 MDT
|
CAPE... +96.7 LI... -0.4 | CAPE... +22.8 LI... -0.3
CINH... -43.9 K Index... +26.7 | CINH... -203.2 K Index... +25.6
|
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 -58.0 -72.4 250 41 21 0.9 0.5 | -57.2 -71.0 255 40 21 1.8 1.0
45000 -57.0 -70.6 245 43 22 -1.2 -0.7 | -55.5 -67.9 250 44 22 -3.6 -2.0
40000 -58.8 -73.8 235 47 24 -2.0 -1.1 | -60.9 -77.6 225 47 24 -4.4 -2.4
38000 -55.9 -68.6 240 49 25 5.9 3.2 | -57.7 -71.9 225 47 24 7.1 3.9
36000 -52.3 -62.1 240 51 26 5.9 3.2 | -53.5 -64.3 220 46 24 7.1 3.9
34000 -48.3 -54.9 245 50 26 7.4 4.1 | -48.7 -55.7 220 45 23 8.8 4.8
32000 -43.8 -46.8 250 46 24 7.5 4.1 | -43.4 -46.1 225 45 23 8.8 4.8
30000 -39.1 -38.4 250 44 22 8.4 4.6 | -37.7 -35.9 230 44 23 8.0 4.4
29000 -35.9 -32.6 250 42 22 8.4 4.6 | -35.3 -31.5 235 44 23 8.0 4.4
28000 -33.4 -28.1 245 41 21 8.5 4.7 | -32.9 -27.2 235 44 22 8.0 4.4
27000 -31.0 -23.8 245 40 20 8.0 4.4 | -30.5 -22.9 240 42 22 8.2 4.5
26000 -28.6 -19.5 245 38 20 8.1 4.4 | -28.1 -18.6 245 40 21 8.2 4.5
25000 -26.2 -15.2 245 36 19 8.1 4.4 | -25.6 -14.1 250 39 20 8.2 4.5
24000 -23.8 -10.8 245 35 18 7.8 4.3 | -23.3 -9.9 250 37 19 7.8 4.3
23000 -21.5 -6.7 245 34 17 7.8 4.3 | -20.9 -5.6 250 34 17 7.8 4.3
22000 -19.2 -2.6 245 32 17 7.8 4.3 | -18.6 -1.5 250 31 16 7.8 4.3
21000 -16.9 1.6 250 31 16 7.7 4.2 | -16.4 2.5 255 29 15 7.3 4.0
20000 -14.7 5.5 250 29 15 7.7 4.2 | -14.3 6.3 255 28 14 7.3 4.0
19500 -13.6 7.5 250 29 15 7.7 4.2 | -13.2 8.2 255 28 14 7.3 4.0
19000 -12.4 9.7 250 28 14 7.6 4.2 | -12.1 10.2 255 27 14 7.4 4.1
18500 -11.3 11.7 250 27 14 7.4 4.0 | -11.0 12.2 260 27 14 7.9 4.3
18000 -10.3 13.5 250 26 13 7.5 4.1 | -9.9 14.2 260 26 14 8.0 4.4
17500 -9.2 15.4 255 25 13 6.6 3.6 | -8.8 16.2 260 26 13 7.1 3.9
17000 -8.3 17.1 255 24 12 6.6 3.6 | -7.8 18.0 265 26 13 7.0 3.8
16500 -7.3 18.9 255 23 12 6.7 3.7 | -6.8 19.8 270 26 13 7.1 3.9
16000 -6.3 20.7 255 21 11 6.9 3.8 | -5.7 21.7 270 26 13 7.3 4.0
15500 -5.3 22.5 255 19 10 7.0 3.8 | -4.6 23.7 275 25 13 7.2 4.0
15000 -4.2 24.4 250 17 9 8.2 4.5 | -3.0 26.6 275 24 12 7.8 4.3
14500 -3.0 26.6 250 16 8 8.1 4.4 | -1.8 28.8 275 23 12 7.9 4.3
14000 -1.8 28.8 245 15 8 8.6 4.7 | -0.6 30.9 275 22 11 8.2 4.5
13500 -0.5 31.1 240 14 7 8.5 4.7 | 0.6 33.1 275 20 10 8.2 4.5
13000 0.8 33.4 235 13 7 9.0 4.9 | 1.8 35.2 275 18 9 8.2 4.5
12500 2.1 35.8 225 12 6 9.1 5.0 | 3.0 37.4 270 16 8 8.2 4.5
12000 4.1 39.4 220 11 6 9.2 5.0 | 4.1 39.4 265 13 7 7.6 4.2
11500 5.5 41.9 215 10 5 9.2 5.0 | 5.2 41.4 255 11 6 7.7 4.2
11000 6.9 44.4 210 9 5 8.9 4.9 | 6.4 43.5 245 9 5 7.8 4.3
10500 8.2 46.8 210 8 4 6.5 3.6 | 7.5 45.5 225 8 4 8.7 4.8
10250 8.5 47.3 210 8 4 3.7 2.0 | 8.1 46.6 215 8 4 3.9 2.1
10000 9.0 48.2 205 8 4 8.9 4.9 | 8.2 46.8 210 8 4 4.2 2.3
9750 9.8 49.6 200 7 4 11.8 6.5 | 8.8 47.8 200 8 4 9.0 4.9
9500 10.7 51.3 195 6 3 10.5 5.8 | 9.4 48.9 190 9 5 8.5 4.7
9250 11.3 52.3 190 6 3 5.9 3.2 | 9.9 49.8 185 10 5 5.3 2.9
9000 11.7 53.1 190 6 3 7.5 4.1 | 10.2 50.4 180 11 5 4.2 2.3
8750 12.5 54.5 180 6 3 12.0 6.6 | 10.6 51.1 175 12 6 7.1 3.9
8500 13.3 55.9 175 6 3 9.7 5.3 | 11.1 52.0 175 14 7 6.2 3.4
8250 13.9 57.0 175 6 3 6.3 3.5 | 11.5 52.7 170 15 8 4.1 2.2
8000 14.4 57.9 170 5 3 7.2 4.0 | 11.7 53.1 170 16 8 3.2 1.8
7750 15.1 59.2 170 6 3 12.1 6.6 | 12.0 53.6 170 17 9 5.7 3.1
7500 16.0 60.8 160 6 3 9.7 5.3 | 12.4 54.3 170 19 10 5.1 2.8
7250 16.5 61.7 160 6 3 5.9 3.2 | 12.7 54.9 165 20 10 2.6 1.4
7000 17.0 62.6 160 6 3 6.6 3.6 | 12.8 55.0 165 21 11 2.1 1.2
6750 17.6 63.7 155 6 3 9.6 5.3 | 12.9 55.2 165 22 11 1.0 0.6
6500 18.3 64.9 150 7 4 9.0 5.0 | 12.9 55.2 170 23 12 1.6 0.9
6250 18.8 65.8 145 7 3 6.7 3.7 | 13.1 55.6 170 23 12 3.4 1.9
6000 19.4 66.9 145 7 3 7.4 4.1 | 13.3 55.9 170 23 12 1.9 1.0
5750 20.0 68.0 140 7 3 10.1 5.5 | 13.5 56.3 165 22 11 6.7 3.7
5500 20.8 69.4 135 6 3 13.6 7.5 | 14.4 57.9 165 19 10 18.5 10.2
________________________________________________________________________________
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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