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Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 220120
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
1920 MDT Saturday, April 21, 2018
This forecast is for Sunday, April 22, 2018:
If the trigger temperature of 59.2 F/15.1 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 702 ft/min (3.6 m/s)
Maximum height of thermals.................. 13878 ft MSL (8571 ft AGL)
Forecast maximum temperature................... 67.0 F/19.9 C
Time of trigger temperature.................... 1145 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................. 10839 ft MSL (5533 ft AGL)
Thermal soaring outlook for Monday 04/23....... 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....................... 14402 ft MSL (9095 ft AGL)
Wave soaring outlook for Monday 04/23.......... Poor
Remarks... Ridge of high pressure overhead Sunday Monday.
Sunrise/Sunset.................... 06:11:50 / 19:43:50 MDT
Total possible sunshine........... 13 hr 32 min 1 sec (812 min 1 sec)
Altitude of sun at 12:58:00 MDT... 62.60 degrees
Upper air data from numerical model forecast valid on 04/22/2018 at 0600 MDT
Freezing level.................. 10702 ft MSL (5395 ft AGL)
Convective condensation level... 12292 ft MSL (6985 ft AGL)
Lifted condensation level....... 13215 ft MSL (7909 ft AGL)
Lifted index.................... +2.0
K index......................... -7.2
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 -62.2 -80.0 240 23 12 3.1 1.7 M M M M M
45000 -57.8 -72.0 250 27 14 0.8 0.4 M M M M M
40000 -56.7 -70.1 280 31 16 0.7 0.4 M M M M M
38000 -54.1 -65.4 290 35 18 5.5 3.0 M M M M M
36000 -50.8 -59.4 300 40 21 5.5 3.0 M M M M M
34000 -47.2 -53.0 305 42 22 6.7 3.7 M M M M M
32000 -43.2 -45.8 305 36 19 6.7 3.7 M M M M M
30000 -38.8 -37.8 310 27 14 6.4 3.5 37.4 99.3 13.5 M M
29000 -36.9 -34.4 315 22 11 6.4 3.5 36.0 96.8 12.7 M M
28000 -35.0 -31.0 320 16 8 6.4 3.5 34.8 94.6 11.9 M M
27000 -32.8 -27.0 330 13 7 8.7 4.7 33.9 92.9 11.3 M M
26000 -30.2 -22.4 325 14 7 8.6 4.7 33.3 92.0 11.0 M M
25000 -27.6 -17.7 325 15 8 8.6 4.7 33.0 91.3 10.8 M M
24000 -25.2 -13.4 325 16 8 6.8 3.7 32.4 90.4 10.5 M M
23000 -23.1 -9.6 335 18 9 6.9 3.8 31.3 88.4 9.7 M M
22000 -21.0 -5.8 340 20 10 6.9 3.8 30.3 86.6 9.0 M M
21000 -19.0 -2.2 350 21 11 6.7 3.7 29.3 84.8 8.3 M M
20000 -17.0 1.4 355 22 11 6.7 3.7 28.2 82.8 7.4 M M
19500 -16.0 3.2 355 22 11 6.7 3.7 27.7 81.8 7.0 M M
19000 -15.0 5.0 360 22 12 6.7 3.7 27.2 81.0 6.6 M M
18500 -14.0 6.8 360 23 12 6.5 3.6 26.7 80.0 6.2 M M
18000 -13.1 8.4 360 22 12 6.5 3.6 26.1 79.0 5.7 M M
17500 -12.1 10.2 005 22 11 6.2 3.4 25.6 78.1 5.3 M M
17000 -11.2 11.8 360 22 12 5.8 3.2 24.9 76.8 4.7 M M
16500 -10.3 13.5 360 23 12 5.8 3.2 24.2 75.6 4.1 M M
16000 -9.6 14.7 360 23 12 4.5 2.5 23.4 74.2 3.5 M M
15500 -8.5 16.7 355 24 12 4.6 2.5 22.2 71.9 2.4 M M
15000 -7.8 18.0 355 25 13 4.5 2.5 21.3 70.3 1.6 M M
14500 -7.2 19.0 350 26 14 4.5 2.5 20.4 68.7 0.8 M M
14000 -6.5 20.3 350 27 14 5.1 2.8 19.6 67.2 0.0 M M
13500 -5.7 21.7 350 29 15 5.0 2.7 18.8 65.9 -0.7 668 3.4
13000 -4.9 23.2 350 29 15 7.1 3.9 18.2 64.8 -1.3 628 3.2
12500 -3.9 25.0 345 30 15 7.0 3.8 17.8 64.0 -1.8 584 3.0
12000 -2.9 26.8 345 30 16 8.2 4.5 17.4 63.3 -2.2 538 2.7
11500 -1.7 28.9 345 30 16 8.4 4.6 17.1 62.9 -2.6 489 2.5
11000 -0.6 30.9 345 30 15 8.1 4.4 16.9 62.4 -2.9 440 2.2
10500 0.5 32.9 345 29 15 9.2 5.1 16.6 61.9 -3.3 391 2.0
10250 1.1 34.0 350 28 15 3.6 2.0 16.5 61.7 -3.4 367 1.9
10000 1.2 34.2 350 28 14 4.9 2.7 15.9 60.5 -4.1 357 1.8
9750 1.9 35.4 350 26 14 11.3 6.2 15.9 60.6 -4.1 328 1.7
9500 2.6 36.7 350 25 13 10.1 5.6 15.9 60.6 -4.1 299 1.5
9250 3.3 37.9 355 23 12 6.5 3.6 15.9 60.6 -4.2 272 1.4
9000 3.6 38.5 355 22 11 4.1 2.3 15.4 59.8 -4.6 256 1.3
8750 4.0 39.2 350 21 11 7.2 4.0 15.1 59.2 -5.0 235 1.2
8500 4.5 40.1 350 20 10 6.9 3.8 14.9 58.9 -5.2 212 1.1
8250 5.0 41.0 350 18 9 5.1 2.8 14.7 58.4 -5.5 192 1.0
8000 5.3 41.5 345 16 8 4.2 2.3 14.2 57.6 -5.9 174 0.9
7750 5.6 42.1 345 15 8 4.2 2.3 13.8 56.9 -6.3 158 0.8
7500 5.9 42.6 340 13 7 2.7 1.5 13.4 56.0 -6.8 142 0.7
7250 6.0 42.8 335 11 6 1.4 0.8 12.7 54.9 -7.4 131 0.7
7000 6.1 43.0 330 9 5 1.6 0.9 12.1 53.8 -8.0 120 0.6
6750 6.3 43.3 320 7 4 1.3 0.7 11.5 52.7 -8.7 109 0.6
6500 6.3 43.3 310 5 3 0.7 0.4 10.8 51.5 -9.3 99 0.5
6250 6.4 43.5 295 5 2 0.1 0.0 10.1 50.2 -10.1 91 0.5
6000 6.4 43.5 275 4 2 1.6 0.9 9.4 48.9 -10.8 83 0.4
5750 6.2 43.2 255 4 2 -14.9 -8.2 8.4 47.2 -11.8 83 0.4
5500 3.9 39.0 220 3 2 -43.0 -23.6 5.4 41.8 -14.8 143 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/22/2018 at 0900 MDT | 04/22/2018 at 1200 MDT
|
K index... -3.9 LI... +3.2 | K index... +10.7 LI... +2.5
CAPE... 0.0 CIN... 0.0 | CAPE... 0.0 CIN... 0.0
|
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 -61.6 -78.9 245 22 11 2.8 1.5 | -61.3 -78.3 245 23 12 2.3 1.3
45000 -57.7 -71.9 245 25 13 -0.0 -0.0 | -58.0 -72.4 240 24 12 0.1 0.0
40000 -57.6 -71.7 280 35 18 0.1 0.1 | -57.7 -71.9 275 31 16 0.2 0.1
38000 -54.8 -66.6 285 36 18 5.9 3.2 | -55.0 -67.0 285 32 17 5.8 3.2
36000 -51.3 -60.3 295 36 19 5.9 3.2 | -51.6 -60.9 290 32 17 5.8 3.2
34000 -47.6 -53.7 300 34 18 6.6 3.6 | -47.9 -54.2 295 31 16 6.6 3.6
32000 -43.7 -46.7 300 29 15 6.6 3.6 | -43.9 -47.0 295 26 13 6.6 3.6
30000 -39.9 -39.8 300 23 12 6.1 3.3 | -39.6 -39.3 295 20 11 6.0 3.3
29000 -37.6 -35.7 295 18 9 6.1 3.3 | -37.8 -36.0 295 17 9 6.0 3.3
28000 -35.8 -32.4 295 14 7 6.1 3.4 | -36.0 -32.8 295 15 7 6.1 3.3
27000 -33.7 -28.7 295 12 6 8.4 4.6 | -34.0 -29.2 300 13 6 8.0 4.4
26000 -31.2 -24.2 305 13 7 8.4 4.6 | -31.6 -24.9 305 12 6 8.0 4.4
25000 -28.7 -19.7 310 14 7 8.4 4.6 | -29.2 -20.6 315 11 6 8.0 4.4
24000 -26.3 -15.3 320 14 7 7.3 4.0 | -26.8 -16.2 320 11 6 7.9 4.3
23000 -24.1 -11.4 335 14 7 7.4 4.1 | -24.4 -11.9 330 10 5 7.9 4.3
22000 -21.8 -7.2 350 14 7 7.4 4.1 | -22.1 -7.8 335 10 5 7.9 4.3
21000 -19.6 -3.3 360 16 8 7.2 4.0 | -19.8 -3.6 345 10 5 7.0 3.8
20000 -17.5 0.5 360 17 9 7.3 4.0 | -17.7 0.1 350 11 6 7.0 3.9
19500 -16.4 2.5 360 17 9 7.3 4.0 | -16.7 1.9 355 12 6 7.0 3.9
19000 -15.3 4.5 005 18 9 7.3 4.0 | -15.6 3.9 355 13 7 7.0 3.8
18500 -14.3 6.3 005 18 9 6.6 3.6 | -14.5 5.9 355 13 7 7.7 4.2
18000 -13.2 8.2 360 19 10 6.7 3.7 | -13.4 7.9 360 14 7 7.7 4.2
17500 -12.2 10.0 360 19 10 6.6 3.6 | -12.3 9.9 360 15 8 6.8 3.7
17000 -11.3 11.7 360 20 10 6.4 3.5 | -11.4 11.5 360 16 8 6.4 3.5
16500 -10.3 13.5 360 20 10 6.4 3.5 | -10.4 13.3 360 18 9 6.4 3.5
16000 -9.4 15.1 360 21 11 5.6 3.1 | -9.5 14.9 360 19 10 6.6 3.6
15500 -8.2 17.2 360 22 11 5.5 3.0 | -8.0 17.6 360 20 10 6.2 3.4
15000 -7.4 18.7 355 23 12 5.3 2.9 | -7.2 19.0 360 20 10 5.8 3.2
14500 -6.6 20.1 355 23 12 5.3 2.9 | -6.4 20.5 360 21 11 5.9 3.2
14000 -5.9 21.4 355 24 12 4.7 2.6 | -5.6 21.9 360 21 11 5.9 3.3
13500 -5.3 22.5 355 24 13 4.8 2.6 | -4.7 23.5 360 20 10 6.0 3.3
13000 -4.5 23.9 350 25 13 6.6 3.6 | -3.9 25.0 355 20 10 5.9 3.2
12500 -3.6 25.5 350 25 13 6.5 3.6 | -3.0 26.6 355 19 10 5.7 3.1
12000 -2.6 27.3 350 25 13 7.8 4.3 | -2.0 28.4 355 19 10 7.7 4.2
11500 -1.5 29.3 350 25 13 7.8 4.3 | -0.9 30.4 350 19 10 7.7 4.2
11000 -0.4 31.3 350 24 12 6.8 3.7 | 0.1 32.2 350 18 9 6.2 3.4
10500 0.5 32.9 350 23 12 7.8 4.3 | 0.9 33.6 350 17 9 6.7 3.7
10250 1.0 33.8 350 23 12 3.1 1.7 | 1.3 34.3 350 17 9 3.1 1.7
10000 1.1 34.0 355 22 12 4.8 2.6 | 1.5 34.7 355 16 8 4.6 2.5
9750 1.8 35.2 355 22 11 10.5 5.8 | 2.0 35.6 355 16 8 8.9 4.9
9500 2.4 36.3 355 21 11 8.9 4.9 | 2.6 36.7 360 15 8 7.6 4.1
9250 3.0 37.4 360 20 10 7.6 4.2 | 3.1 37.6 360 14 7 5.7 3.1
9000 3.5 38.3 360 19 10 6.5 3.5 | 3.5 38.3 005 14 7 5.3 2.9
8750 4.0 39.2 360 18 9 7.3 4.0 | 3.9 39.0 005 13 7 6.9 3.8
8500 4.5 40.1 005 16 8 6.7 3.7 | 4.5 40.1 010 12 6 6.9 3.8
8250 5.0 41.0 005 15 8 5.4 2.9 | 5.0 41.0 010 11 6 6.9 3.8
8000 5.3 41.5 005 14 7 4.9 2.7 | 5.5 41.9 015 9 5 7.1 3.9
7750 5.7 42.3 005 13 7 5.4 2.9 | 6.0 42.8 015 7 4 7.2 4.0
7500 6.1 43.0 360 12 6 4.0 2.2 | 6.5 43.7 020 6 3 8.6 4.7
7250 6.3 43.3 360 10 5 2.6 1.4 | 7.2 45.0 020 6 3 9.5 5.2
7000 6.5 43.7 355 9 4 3.0 1.7 | 7.9 46.2 020 5 3 9.2 5.1
6750 6.8 44.2 345 7 4 2.9 1.6 | 8.6 47.5 020 5 3 9.7 5.3
6500 6.9 44.4 335 6 3 1.3 0.7 | 9.3 48.7 015 5 2 10.3 5.7
6250 7.0 44.6 330 5 2 0.4 0.2 | 10.1 50.2 015 5 2 10.1 5.6
6000 7.0 44.6 315 4 2 0.5 0.3 | 10.9 51.6 015 4 2 10.8 5.9
5750 7.1 44.8 300 3 1 4.7 2.6 | 11.8 53.2 015 4 2 16.6 9.1
5500 7.8 46.0 275 2 1 12.2 6.7 | 13.4 56.1 015 4 2 24.0 13.2
04/22/2018 at 1500 MDT | 04/22/2018 at 1800 MDT
|
K index... +8.3 LI... +1.2 | K index... +7.0 LI... +1.1
CAPE... 0.0 CIN... 0.0 | CAPE... 0.0 CIN... 0.0
|
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 -61.3 -78.3 250 26 13 2.2 1.2 | -61.2 -78.2 250 24 12 1.7 1.0
45000 -58.3 -72.9 245 32 16 -0.3 -0.1 | -58.8 -73.8 245 34 18 -0.7 -0.4
40000 -58.5 -73.3 270 31 16 -0.1 -0.0 | -59.5 -75.1 275 27 14 -0.4 -0.2
38000 -55.7 -68.3 280 30 16 6.0 3.3 | -56.7 -70.1 285 27 14 6.2 3.4
36000 -52.1 -61.8 285 30 15 6.0 3.3 | -53.0 -63.4 290 29 15 6.2 3.4
34000 -48.3 -54.9 290 28 15 7.1 3.9 | -49.0 -56.2 290 28 15 7.3 4.0
32000 -44.0 -47.2 290 25 13 7.1 3.9 | -44.6 -48.3 295 26 13 7.3 4.0
30000 -39.9 -39.8 295 20 10 6.4 3.5 | -40.3 -40.5 300 22 11 7.1 3.9
29000 -37.5 -35.5 300 16 8 6.4 3.5 | -38.2 -36.8 305 19 10 7.1 3.9
28000 -35.6 -32.1 305 14 7 6.4 3.5 | -35.5 -31.9 320 16 8 7.1 3.9
27000 -33.5 -28.3 310 12 6 7.3 4.0 | -33.4 -28.1 325 14 7 7.3 4.0
26000 -31.4 -24.5 310 10 5 7.3 4.0 | -31.2 -24.2 320 12 6 7.3 4.0
25000 -29.2 -20.6 315 9 5 7.3 4.0 | -29.0 -20.2 320 10 5 7.3 4.0
24000 -26.9 -16.4 320 8 4 8.2 4.5 | -26.7 -16.1 315 9 4 7.9 4.3
23000 -24.5 -12.1 320 8 4 8.1 4.5 | -24.4 -11.9 315 9 5 7.8 4.3
22000 -22.1 -7.8 315 8 4 8.1 4.4 | -22.1 -7.8 320 9 5 7.8 4.3
21000 -19.8 -3.6 320 9 5 6.9 3.8 | -19.9 -3.8 320 9 5 6.9 3.8
20000 -17.7 0.1 325 10 5 7.0 3.8 | -17.8 -0.0 320 10 5 7.0 3.8
19500 -16.7 1.9 330 10 5 7.0 3.8 | -16.8 1.8 320 10 5 7.0 3.8
19000 -15.7 3.7 335 11 6 7.0 3.9 | -15.7 3.7 325 10 5 7.0 3.8
18500 -14.6 5.7 335 11 6 7.4 4.1 | -14.7 5.5 325 10 5 7.4 4.1
18000 -13.5 7.7 340 12 6 7.4 4.0 | -13.6 7.5 330 10 5 7.4 4.0
17500 -12.4 9.7 345 12 6 7.2 3.9 | -12.5 9.5 330 10 5 7.4 4.0
17000 -11.4 11.5 350 13 6 7.1 3.9 | -11.4 11.5 335 10 5 7.3 4.0
16500 -10.3 13.5 355 13 7 7.0 3.8 | -10.3 13.5 335 9 5 7.4 4.0
16000 -9.3 15.3 355 14 7 6.4 3.5 | -9.2 15.4 335 10 5 7.5 4.1
15500 -8.4 16.9 355 14 7 6.4 3.5 | -8.1 17.4 330 10 5 7.5 4.1
15000 -6.9 19.6 355 15 8 7.0 3.8 | -6.5 20.3 335 11 5 7.2 3.9
14500 -5.8 21.6 355 16 8 7.0 3.8 | -5.4 22.3 335 11 6 7.3 4.0
14000 -4.8 23.4 355 16 8 7.1 3.9 | -4.4 24.1 340 11 6 7.5 4.1
13500 -3.8 25.2 355 17 9 7.1 3.9 | -3.3 26.1 345 11 6 7.5 4.1
13000 -2.7 27.1 355 16 8 7.3 4.0 | -2.3 27.9 345 11 5 6.9 3.8
12500 -1.7 28.9 355 16 8 7.4 4.1 | -1.3 29.7 350 10 5 6.9 3.8
12000 -0.7 30.7 355 15 8 6.7 3.7 | -0.2 31.6 355 9 5 7.4 4.1
11500 0.3 32.5 355 14 7 6.7 3.7 | 0.9 33.6 005 8 4 7.6 4.1
11000 1.3 34.3 355 13 7 7.1 3.9 | 1.8 35.2 010 6 3 5.7 3.1
10500 2.3 36.1 360 12 6 7.6 4.2 | 2.6 36.7 025 3 2 6.1 3.3
10250 2.8 37.0 360 11 6 3.5 1.9 | 3.0 37.4 045 2 1 3.9 2.2
10000 3.0 37.4 360 10 5 4.1 2.3 | 3.3 37.9 050 2 1 6.6 3.6
9750 3.5 38.3 010 8 4 8.2 4.5 | 4.0 39.2 070 2 1 10.3 5.6
9500 3.9 39.0 020 6 3 7.3 4.0 | 4.6 40.3 095 2 1 9.4 5.2
9250 4.4 39.9 035 4 2 6.7 3.7 | 5.3 41.5 105 2 1 8.4 4.6
9000 4.9 40.8 040 4 2 7.6 4.2 | 5.9 42.6 105 2 1 9.2 5.1
8750 5.5 41.9 040 4 2 9.3 5.1 | 6.7 44.1 105 2 1 11.1 6.1
8500 6.2 43.2 045 4 2 9.2 5.1 | 7.5 45.5 105 2 1 10.5 5.8
8250 6.9 44.4 045 4 2 9.6 5.3 | 8.2 46.8 105 2 1 10.1 5.6
8000 7.6 45.7 045 4 2 9.8 5.4 | 9.0 48.2 100 2 1 9.8 5.4
7750 8.3 46.9 045 4 2 10.7 5.9 | 9.7 49.5 100 2 1 9.4 5.2
7500 9.1 48.4 045 4 2 10.3 5.7 | 10.4 50.7 100 2 1 9.6 5.3
7250 9.9 49.8 045 4 2 9.6 5.3 | 11.1 52.0 100 2 1 10.1 5.5
7000 10.6 51.1 045 3 2 9.8 5.4 | 11.9 53.4 100 2 1 9.9 5.5
6750 11.3 52.3 045 3 2 10.1 5.6 | 12.6 54.7 100 2 1 9.6 5.3
6500 12.1 53.8 045 3 2 10.6 5.8 | 13.3 55.9 095 2 1 10.1 5.5
6250 12.9 55.2 045 3 2 11.2 6.1 | 14.1 57.4 095 2 1 10.9 6.0
6000 13.7 56.7 045 3 2 9.3 5.1 | 14.9 58.8 095 2 1 9.8 5.4
5750 14.5 58.1 040 3 2 14.4 7.9 | 15.6 60.1 095 2 1 11.2 6.1
5500 16.1 61.0 045 3 2 28.3 15.5 | 16.7 62.1 095 2 1 16.8 9.2
________________________________________________________________________________
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.
CIN (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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