Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 231321
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
721 AM MDT Thursday October 23, 2008
This forecast is for Thursday October 23, 2008:
If the trigger temperature of 45.4 F/7.4 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 153 ft/min (0.8 m/s)
Maximum height of thermals.................. 12612 ft MSL (7289 ft AGL)
Forecast maximum temperature................... 53.0 F/12.1 C
Time of trigger temperature.................... 1100 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 11267 ft MSL (5944 ft AGL)
Thermal soaring outlook for Friday 10/24....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... 12695 ft MSL (7372 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Weak NVA
Potential height of wave....................... 13432 ft MSL (8109 ft AGL)
Wave soaring outlook for Friday 10/24.......... Poor
Remarks...
Sunrise/Sunset.................... 07:18:50 / 18:09:35 MDT
Total possible sunshine........... 10 hr 50 min 44 sec (650 min 44 sec)
Altitude of sun at 12:43:49 MDT... 38.53 degrees
Upper air data from numerical model forecast valid on 10/23/2008 at 0600 MDT
Freezing level.................. 5493 ft MSL (170 ft AGL)
Additional freezing level....... 7565 ft MSL (2242 ft AGL)
Convective condensation level... 21662 ft MSL (16339 ft AGL)
Lifted condensation level....... 17047 ft MSL (11724 ft AGL)
Lifted index.................... +10.7
K index......................... -12.7
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 -71.9 358 30 15 1.3 0.7 102.2 215.9 52.0 M M
45000 -55.7 -68.3 003 54 28 -0.2 -0.1 81.4 178.6 42.8 M M
40000 -55.8 -68.4 013 92 47 -0.1 -0.0 58.1 136.6 30.5 M M
38000 -54.4 -65.9 013 103 53 4.2 2.3 51.5 124.6 26.8 M M
36000 -51.9 -61.4 012 111 57 4.2 2.3 46.5 115.7 24.1 M M
34000 -49.2 -56.6 011 116 60 5.9 3.3 42.3 108.1 21.7 M M
32000 -45.7 -50.3 011 106 55 5.8 3.2 38.8 101.9 19.8 M M
30000 -41.8 -43.2 010 94 48 5.9 3.2 35.4 95.7 17.8 M M
29000 -40.0 -40.0 011 85 44 5.9 3.2 33.8 92.8 16.8 M M
28000 -38.3 -36.9 011 77 40 5.9 3.2 32.3 90.1 15.8 M M
27000 -36.5 -33.7 012 69 36 6.5 3.6 30.9 87.7 15.0 M M
26000 -34.4 -29.9 014 66 34 7.1 3.9 29.8 85.6 14.3 M M
25000 -32.3 -26.1 016 63 32 7.1 3.9 28.8 83.8 13.6 M M
24000 -30.2 -22.4 017 60 31 7.1 3.9 27.9 82.2 13.1 M M
23000 -28.1 -18.6 018 57 29 6.8 3.7 26.7 80.1 12.3 M M
22000 -26.1 -15.0 019 55 28 6.8 3.7 25.7 78.2 11.5 M M
21000 -24.1 -11.4 020 53 27 5.8 3.2 24.7 76.4 10.8 M M
20000 -22.6 -8.7 018 50 26 5.2 2.8 22.9 73.3 9.5 M M
19500 -21.8 -7.2 017 48 25 5.2 2.8 22.1 71.8 8.8 M M
19000 -21.0 -5.8 016 46 24 5.3 2.9 21.3 70.4 8.2 M M
18500 -20.3 -4.5 015 45 23 6.3 3.5 20.6 69.1 7.6 M M
18000 -19.1 -2.4 014 44 23 7.9 4.3 20.2 68.4 7.3 M M
17500 -18.0 -0.4 014 43 22 8.0 4.4 19.9 67.8 7.0 M M
17000 -16.9 1.6 012 42 22 6.7 3.7 19.5 67.1 6.7 M M
16500 -15.3 4.5 009 41 21 6.7 3.7 18.8 65.8 6.1 M M
16000 -14.5 5.9 006 42 21 4.4 2.4 18.0 64.4 5.5 M M
15500 -13.8 7.2 004 42 22 4.6 2.5 17.2 62.9 4.8 M M
15000 -13.1 8.4 002 44 23 4.7 2.6 16.3 61.3 4.1 M M
14500 -12.4 9.7 001 46 24 4.7 2.6 15.4 59.8 3.3 M M
14000 -11.7 10.9 359 48 25 4.0 2.2 14.6 58.3 2.6 M M
13500 -11.1 12.0 358 49 25 3.9 2.2 13.6 56.5 1.7 M M
13000 -10.6 12.9 356 49 25 2.4 1.3 12.6 54.7 0.8 M M
12500 -10.3 13.5 354 48 25 1.8 1.0 11.3 52.3 -0.4 545 2.8
12000 -10.0 14.0 352 46 24 2.8 1.5 10.1 50.1 -1.6 522 2.7
11500 -9.6 14.7 351 43 22 3.1 1.7 9.0 48.2 -2.6 493 2.5
11000 -9.0 15.8 350 40 21 6.6 3.6 8.1 46.6 -3.5 461 2.3
10500 -7.9 17.8 350 38 20 7.4 4.0 7.8 46.0 -3.8 412 2.1
10250 -7.3 18.9 350 37 19 8.3 4.5 7.6 45.7 -4.0 388 2.0
10000 -6.6 20.1 351 37 19 9.7 5.3 7.6 45.6 -4.1 360 1.8
9750 -5.9 21.4 351 37 19 10.0 5.5 7.6 45.6 -4.1 331 1.7
9500 -5.1 22.8 352 36 19 10.0 5.5 7.6 45.7 -4.1 301 1.5
9250 -4.4 24.1 352 36 19 9.7 5.3 7.6 45.7 -4.1 271 1.4
9000 -3.7 25.3 353 35 18 9.3 5.1 7.6 45.6 -4.1 243 1.2
8750 -3.0 26.6 353 35 18 9.5 5.2 7.6 45.6 -4.1 214 1.1
8500 -2.3 27.9 353 34 18 9.2 5.0 7.5 45.6 -4.2 186 0.9
8250 -1.6 29.1 353 34 17 8.0 4.4 7.5 45.4 -4.3 159 0.8
8000 -1.1 30.0 352 32 16 7.3 4.0 7.3 45.1 -4.4 134 0.7
7750 -0.5 31.1 350 30 16 8.0 4.4 7.1 44.8 -4.6 110 0.6
7500 0.1 32.2 349 29 15 6.0 3.3 6.9 44.5 -4.8 86 0.4
7250 0.4 32.7 347 26 14 3.8 2.1 6.5 43.7 -5.2 69 0.3
7000 0.7 33.3 344 24 12 4.1 2.3 6.1 43.0 -5.7 53 0.3
6750 1.0 33.8 340 21 11 4.1 2.2 5.7 42.2 -6.1 36 0.2
6500 1.3 34.3 335 19 10 4.2 2.3 5.2 41.4 -6.5 20 0.1
6250 1.6 34.9 329 18 9 4.4 2.4 4.8 40.7 -7.0 3 0.0
6000 1.9 35.4 322 16 8 4.0 2.2 4.4 39.9 -7.4 M M
5750 1.9 35.4 314 14 7 -8.4 -4.6 3.6 38.6 -8.2 M M
5500 0.4 32.7 305 10 5 -27.3 -15.0 1.5 34.7 -10.4 16 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/23/2008 at 0900 MDT | 10/23/2008 at 1200 MDT
|
K index... -13.4 | K index... -16.3
|
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 -57.6 -71.7 359 25 13 1.0 0.6 | -59.4 -74.9 355 32 16 0.6 0.3
45000 -56.1 -69.0 007 53 27 -1.3 -0.7 | -58.5 -73.3 003 60 31 1.0 0.5
40000 -57.9 -72.2 011 94 49 -1.2 -0.7 | -57.1 -70.8 006 86 44 0.9 0.5
38000 -56.2 -69.2 012 102 53 5.9 3.2 | -55.0 -67.0 006 90 46 5.0 2.7
36000 -52.6 -62.7 013 103 53 5.9 3.2 | -52.0 -61.6 007 90 47 5.0 2.7
34000 -48.9 -56.0 013 103 53 7.4 4.1 | -48.6 -55.5 007 91 47 7.3 4.0
32000 -44.0 -47.2 012 100 52 7.4 4.0 | -43.6 -46.5 005 91 47 7.4 4.1
30000 -39.9 -39.8 010 94 49 5.6 3.0 | -39.2 -38.6 004 90 47 7.2 3.9
29000 -38.2 -36.8 010 87 45 5.5 3.0 | -37.1 -34.8 005 90 46 7.2 3.9
28000 -36.6 -33.9 009 80 41 5.5 3.0 | -34.9 -30.8 007 89 46 7.2 3.9
27000 -34.9 -30.8 008 72 37 6.4 3.5 | -32.8 -27.0 008 87 45 7.1 3.9
26000 -32.9 -27.2 009 67 34 6.8 3.7 | -30.7 -23.3 008 82 42 7.1 3.9
25000 -30.8 -23.4 011 61 31 6.8 3.8 | -28.6 -19.5 009 77 39 7.1 3.9
24000 -28.8 -19.8 013 56 29 6.9 3.8 | -26.4 -15.5 010 71 37 6.5 3.6
23000 -26.7 -16.1 015 54 28 7.0 3.8 | -24.7 -12.5 010 66 34 5.9 3.2
22000 -24.6 -12.3 016 52 27 7.0 3.8 | -22.9 -9.2 010 60 31 5.9 3.2
21000 -22.5 -8.5 017 51 26 7.4 4.1 | -21.2 -6.2 010 54 28 6.2 3.4
20000 -20.3 -4.5 018 50 26 7.6 4.2 | -19.3 -2.7 007 50 26 6.3 3.5
19500 -19.1 -2.4 019 49 25 7.7 4.2 | -18.4 -1.1 006 47 24 6.3 3.5
19000 -18.0 -0.4 019 49 25 7.6 4.2 | -17.4 0.7 004 45 23 6.4 3.5
18500 -16.9 1.6 019 48 25 7.3 4.0 | -16.5 2.3 002 43 22 7.0 3.9
18000 -15.9 3.4 017 47 24 6.8 3.7 | -15.4 4.3 360 42 22 7.6 4.2
17500 -14.4 6.1 012 44 23 5.6 3.1 | -13.7 7.3 358 41 21 5.9 3.2
17000 -13.7 7.3 008 43 22 4.6 2.5 | -13.0 8.6 357 41 21 4.7 2.6
16500 -13.0 8.6 004 41 21 4.5 2.5 | -12.4 9.7 356 41 21 4.6 2.5
16000 -12.3 9.9 360 40 21 5.2 2.8 | -11.7 10.9 356 40 21 4.5 2.5
15500 -11.5 11.3 356 40 21 5.3 2.9 | -11.0 12.2 355 39 20 4.6 2.5
15000 -10.9 12.4 354 39 20 2.7 1.5 | -10.4 13.3 355 38 20 3.8 2.1
14500 -10.5 13.1 354 38 20 2.7 1.5 | -9.8 14.4 354 36 19 3.8 2.1
14000 -10.1 13.8 355 37 19 1.5 0.8 | -9.2 15.4 353 35 18 3.7 2.1
13500 -9.9 14.2 356 37 19 1.2 0.6 | -8.6 16.5 352 34 18 3.7 2.0
13000 -9.8 14.4 358 37 19 0.9 0.5 | -8.1 17.4 352 34 18 2.9 1.6
12500 -9.6 14.7 357 38 20 0.8 0.4 | -7.7 18.1 350 34 17 2.6 1.4
12000 -9.5 14.9 357 39 20 1.9 1.0 | -7.3 18.9 349 34 17 3.2 1.8
11500 -9.1 15.6 355 38 20 2.5 1.4 | -6.7 19.9 348 34 17 3.6 2.0
11000 -8.6 16.5 354 37 19 6.7 3.7 | -6.2 20.8 347 34 18 4.9 2.7
10500 -7.3 18.9 354 37 19 8.6 4.7 | -5.3 22.5 346 34 17 5.5 3.0
10250 -6.7 19.9 355 36 19 8.9 4.9 | -4.9 23.2 345 33 17 5.8 3.2
10000 -6.0 21.2 355 36 18 9.2 5.0 | -4.4 24.1 345 33 17 6.8 3.7
9750 -5.3 22.5 356 35 18 9.3 5.1 | -3.9 25.0 345 32 17 7.2 4.0
9500 -4.6 23.7 357 35 18 9.4 5.1 | -3.4 25.9 346 31 16 7.1 3.9
9250 -3.9 25.0 358 34 18 8.8 4.8 | -2.9 26.8 346 31 16 7.1 3.9
9000 -3.3 26.1 359 34 17 8.0 4.4 | -2.3 27.9 347 30 15 7.1 3.9
8750 -2.7 27.1 360 33 17 8.0 4.4 | -1.8 28.8 348 29 15 7.1 3.9
8500 -2.1 28.2 002 32 17 8.0 4.4 | -1.3 29.7 348 28 14 7.1 3.9
8250 -1.5 29.3 003 31 16 6.3 3.4 | -0.7 30.7 349 27 14 6.9 3.8
8000 -1.2 29.8 003 30 15 5.0 2.7 | -0.3 31.5 350 26 13 6.6 3.6
7750 -0.8 30.6 004 28 14 5.6 3.1 | 0.2 32.4 351 24 13 7.0 3.8
7500 -0.4 31.3 005 27 14 4.5 2.5 | 0.7 33.3 353 23 12 5.9 3.2
7250 -0.1 31.8 005 24 13 2.9 1.6 | 1.1 34.0 353 20 10 4.3 2.3
7000 0.1 32.2 005 22 11 2.8 1.6 | 1.4 34.5 354 17 9 4.0 2.2
6750 0.3 32.5 005 20 10 2.9 1.6 | 1.7 35.1 355 13 7 4.5 2.5
6500 0.5 32.9 005 17 9 3.3 1.8 | 2.1 35.8 355 10 5 8.2 4.5
6250 0.8 33.4 004 15 8 3.6 1.9 | 2.8 37.0 355 10 5 11.0 6.1
6000 1.0 33.8 002 12 6 3.3 1.8 | 3.6 38.5 354 9 5 8.9 4.9
5750 1.3 34.3 360 9 5 4.8 2.7 | 4.4 39.9 353 9 5 14.6 8.0
5500 1.7 35.1 360 7 3 8.1 4.5 | 6.0 42.8 355 9 5 27.6 15.2
10/23/2008 at 1500 MDT | 10/23/2008 at 1800 MDT
|
K index... -13.1 | K index... -13.1
|
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 -60.4 -76.7 343 33 17 -0.2 -0.1 | -61.7 -79.1 333 36 18 -0.1 -0.1
45000 -60.7 -77.3 356 56 29 1.0 0.5 | -61.7 -79.1 347 56 29 2.4 1.3
40000 -58.6 -73.5 354 82 42 1.4 0.8 | -58.3 -72.9 349 70 36 2.3 1.3
38000 -55.9 -68.6 354 85 44 5.8 3.2 | -55.6 -68.1 349 73 38 5.4 2.9
36000 -52.5 -62.5 355 85 44 5.8 3.2 | -52.4 -62.3 348 76 39 5.4 2.9
34000 -48.6 -55.5 356 85 44 7.9 4.3 | -48.8 -55.8 348 77 40 7.4 4.1
32000 -43.8 -46.8 355 86 44 7.9 4.4 | -44.3 -47.7 349 78 40 7.4 4.1
30000 -38.6 -37.5 356 86 44 7.5 4.1 | -39.0 -38.2 350 77 40 8.5 4.7
29000 -36.4 -33.5 358 84 43 7.5 4.1 | -36.5 -33.7 351 77 40 8.5 4.7
28000 -34.1 -29.4 360 83 42 7.5 4.1 | -34.0 -29.2 352 77 39 8.5 4.7
27000 -31.9 -25.4 002 81 42 7.6 4.2 | -31.5 -24.7 353 76 39 7.9 4.3
26000 -29.6 -21.3 004 78 40 7.6 4.2 | -29.1 -20.4 355 74 38 7.9 4.3
25000 -27.4 -17.3 005 75 39 7.6 4.2 | -26.7 -16.1 356 72 37 7.9 4.3
24000 -25.1 -13.2 006 72 37 6.6 3.6 | -24.4 -11.9 358 70 36 7.4 4.0
23000 -23.3 -9.9 007 64 33 6.1 3.3 | -22.2 -8.0 358 69 35 7.2 3.9
22000 -21.5 -6.7 008 57 29 6.1 3.3 | -20.1 -4.2 358 67 34 7.2 4.0
21000 -19.7 -3.5 010 50 26 5.7 3.1 | -18.1 -0.6 358 64 33 5.2 2.8
20000 -18.0 -0.4 011 48 25 5.7 3.1 | -16.5 2.3 357 58 30 5.2 2.9
19500 -17.2 1.0 012 47 24 5.7 3.1 | -15.7 3.7 356 55 28 5.2 2.9
19000 -16.4 2.5 013 46 24 5.7 3.1 | -14.9 5.2 355 52 27 5.3 2.9
18500 -15.5 4.1 013 45 23 6.1 3.4 | -14.2 6.4 355 49 25 5.4 3.0
18000 -14.6 5.7 011 45 23 6.4 3.5 | -13.3 8.1 354 48 25 5.5 3.0
17500 -13.6 7.5 008 45 23 6.5 3.5 | -12.5 9.5 354 46 24 5.5 3.0
17000 -12.6 9.3 005 45 23 6.6 3.6 | -11.7 10.9 355 45 23 6.1 3.3
16500 -11.7 10.9 002 44 23 6.7 3.7 | -10.3 13.5 356 45 23 6.2 3.4
16000 -10.4 13.3 359 43 22 4.6 2.6 | -9.3 15.3 356 44 23 6.9 3.8
15500 -9.7 14.5 357 42 21 5.0 2.8 | -8.3 17.1 355 44 22 7.5 4.1
15000 -9.1 15.6 356 40 21 2.1 1.1 | -7.7 18.1 354 43 22 0.7 0.4
14500 -8.8 16.2 354 39 20 2.2 1.2 | -7.5 18.5 352 41 21 1.3 0.7
14000 -8.4 16.9 351 37 19 2.7 1.5 | -7.4 18.7 349 40 21 0.2 0.1
13500 -8.0 17.6 348 37 19 2.8 1.5 | -7.4 18.7 345 39 20 -0.0 -0.0
13000 -7.6 18.3 344 37 19 4.5 2.5 | -7.2 19.0 342 38 20 5.5 3.0
12500 -6.7 19.9 342 37 19 5.4 3.0 | -6.0 21.2 342 37 19 7.8 4.3
12000 -5.9 21.4 340 36 19 6.8 3.7 | -4.8 23.4 341 35 18 7.9 4.4
11500 -4.8 23.4 339 35 18 7.6 4.2 | -3.7 25.3 341 33 17 8.0 4.4
11000 -3.6 25.5 338 33 17 7.6 4.2 | -2.5 27.5 340 30 16 7.0 3.8
10500 -2.5 27.5 337 31 16 7.6 4.2 | -1.6 29.1 340 27 14 6.4 3.5
10250 -2.0 28.4 337 29 15 7.4 4.1 | -1.1 30.0 341 25 13 6.4 3.5
10000 -1.4 29.5 337 28 14 6.5 3.6 | -0.6 30.9 341 24 12 6.7 3.7
9750 -1.0 30.2 337 27 14 6.0 3.3 | -0.1 31.8 343 22 11 6.8 3.8
9500 -0.5 31.1 338 26 13 6.2 3.4 | 0.4 32.7 344 21 11 6.7 3.7
9250 -0.1 31.8 338 25 13 5.7 3.1 | 0.9 33.6 346 19 10 7.1 3.9
9000 0.3 32.5 340 23 12 4.8 2.6 | 1.5 34.7 347 18 9 8.0 4.4
8750 0.6 33.1 342 21 11 4.7 2.6 | 2.1 35.8 349 17 9 8.2 4.5
8500 1.0 33.8 344 19 10 4.3 2.4 | 2.7 36.9 350 16 8 8.2 4.5
8250 1.3 34.3 348 17 9 6.1 3.4 | 3.3 37.9 352 15 8 8.1 4.5
8000 1.9 35.4 350 15 8 8.0 4.4 | 3.9 39.0 353 14 7 8.1 4.5
7750 2.5 36.5 353 14 7 7.4 4.1 | 4.5 40.1 355 13 7 8.1 4.5
7500 3.0 37.4 356 12 6 8.0 4.4 | 5.1 41.2 356 12 6 8.2 4.5
7250 3.7 38.7 358 11 6 9.2 5.1 | 5.8 42.4 358 11 6 8.4 4.6
7000 4.4 39.9 358 11 6 9.8 5.4 | 6.4 43.5 360 10 5 8.6 4.7
6750 5.1 41.2 358 11 6 9.6 5.2 | 7.0 44.6 002 9 5 8.4 4.6
6500 5.8 42.4 357 11 6 10.0 5.5 | 7.7 45.9 004 8 4 8.8 4.8
6250 6.6 43.9 357 10 5 10.6 5.8 | 8.3 46.9 005 7 4 9.0 5.0
6000 7.4 45.3 357 10 5 9.6 5.3 | 9.0 48.2 007 6 3 9.6 5.3
5750 8.2 46.8 356 10 5 13.0 7.1 | 9.7 49.5 009 5 3 7.3 4.0
5500 9.5 49.1 357 10 5 22.6 12.4 | 10.0 50.0 010 4 2 -0.1 -0.1
________________________________________________________________________________
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:
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 - 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, cirrostatus, 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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