Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 221133
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
533 AM MDT Wednesday October 22, 2008
This forecast is for Wednesday October 22, 2008:
If the trigger temperature of 39.2 F/4.0 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 757 ft/min (3.8 m/s)
Maximum height of thermals.................. 14224 ft MSL (8901 ft AGL)
Forecast maximum temperature................... 46.0 F/8.2 C
Time of trigger temperature.................... None
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ More than 30 mph
Height of the -3 thermal index................. 9845 ft MSL (4522 ft AGL)
Thermal soaring outlook for Thursday 10/23..... Fair
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....................... 15180 ft MSL (9857 ft AGL)
Wave soaring outlook for Thursday 10/23........ Good
Remarks...
Sunrise/Sunset.................... 07:17:45 / 18:10:56 MDT
Total possible sunshine........... 10 hr 53 min 11 sec (653 min 11 sec)
Altitude of sun at 12:43:56 MDT... 38.88 degrees
Upper air data from numerical model forecast valid on 10/22/2008 at 0600 MDT
Freezing level.................. 6279 ft MSL (956 ft AGL)
Convective condensation level... 11313 ft MSL (5990 ft AGL)
Lifted condensation level....... 12064 ft MSL (6741 ft AGL)
Lifted index.................... +2.7
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 -56.1 -69.0 316 22 11 2.4 1.3 105.7 222.3 56.1 M M
45000 -52.4 -62.3 320 30 15 2.3 1.3 88.9 192.0 49.5 M M
40000 -49.3 -56.7 327 32 16 2.1 1.1 70.1 158.1 40.6 M M
38000 -48.1 -54.6 329 31 16 2.0 1.1 63.4 146.0 37.2 M M
36000 -46.7 -52.1 331 26 13 2.0 1.1 55.4 131.8 32.8 M M
34000 -45.5 -49.9 333 22 11 1.2 0.7 49.2 120.6 29.3 M M
32000 -45.1 -49.2 341 18 9 0.6 0.4 41.2 106.2 24.3 M M
30000 -44.7 -48.5 353 16 8 0.8 0.5 34.2 93.5 19.6 M M
29000 -44.4 -47.9 357 14 7 1.0 0.6 30.5 86.8 17.1 M M
28000 -44.1 -47.4 003 13 7 1.0 0.6 27.0 80.5 14.6 M M
27000 -43.8 -46.8 009 12 6 1.1 0.6 23.7 74.6 12.3 M M
26000 -42.8 -45.0 018 13 7 5.1 2.8 21.2 70.2 10.5 M M
25000 -41.2 -42.2 025 16 8 5.3 2.9 19.4 66.9 9.2 M M
24000 -39.7 -39.5 031 19 10 5.3 2.9 17.8 64.0 8.0 M M
23000 -37.7 -35.9 026 20 10 7.5 4.1 16.6 61.8 7.1 M M
22000 -35.5 -31.9 014 20 10 7.6 4.2 15.7 60.3 6.5 M M
21000 -33.2 -27.8 003 21 11 7.6 4.1 15.0 59.0 6.0 M M
20000 -31.3 -24.3 348 23 12 6.2 3.4 13.8 56.8 5.0 M M
19500 -30.4 -22.7 341 25 13 6.2 3.4 13.1 55.7 4.5 M M
19000 -29.4 -20.9 335 28 14 6.2 3.4 12.5 54.6 4.0 M M
18500 -28.0 -18.4 329 31 16 6.9 3.8 11.7 53.0 3.3 M M
18000 -26.9 -16.4 332 32 16 7.2 4.0 11.2 52.2 2.9 M M
17500 -25.9 -14.6 335 33 17 7.1 3.9 10.8 51.5 2.5 M M
17000 -24.9 -12.8 340 34 18 6.6 3.6 10.3 50.5 2.1 M M
16500 -23.9 -11.0 345 36 19 6.6 3.6 9.8 49.6 1.6 M M
16000 -22.9 -9.2 349 38 19 6.6 3.6 9.2 48.6 1.2 M M
15500 -21.9 -7.4 354 38 20 6.5 3.6 8.7 47.7 0.7 M M
15000 -20.8 -5.4 358 39 20 8.3 4.6 8.3 46.9 0.3 M M
14500 -19.6 -3.3 360 39 20 8.4 4.6 8.0 46.5 0.1 M M
14000 -18.3 -0.9 001 40 20 8.3 4.6 7.8 46.1 -0.1 728 3.7
13500 -17.1 1.2 001 40 21 8.3 4.6 7.6 45.6 -0.3 676 3.4
13000 -15.8 3.6 001 41 21 8.2 4.5 7.4 45.2 -0.6 624 3.2
12500 -14.6 5.7 360 41 21 8.2 4.5 7.1 44.8 -0.8 573 2.9
12000 -13.4 7.9 359 41 21 7.6 4.2 6.8 44.3 -1.1 522 2.7
11500 -12.3 9.9 358 41 21 7.6 4.1 6.4 43.6 -1.5 474 2.4
11000 -11.2 11.8 357 41 21 7.2 4.0 6.1 42.9 -1.8 426 2.2
10500 -10.2 13.6 355 40 21 7.4 4.0 5.7 42.2 -2.3 380 1.9
10250 -9.6 14.7 355 40 21 6.5 3.6 5.5 41.8 -2.5 357 1.8
10000 -9.2 15.4 354 40 20 5.6 3.1 5.1 41.2 -2.8 337 1.7
9750 -8.8 16.2 354 39 20 5.8 3.2 4.8 40.7 -3.1 317 1.6
9500 -8.4 16.9 353 39 20 6.0 3.3 4.5 40.1 -3.4 296 1.5
9250 -7.9 17.8 352 38 20 7.3 4.0 4.3 39.7 -3.7 275 1.4
9000 -7.3 18.9 351 38 19 8.1 4.4 4.1 39.4 -3.8 250 1.3
8750 -6.7 19.9 351 37 19 7.8 4.3 4.0 39.2 -4.0 225 1.1
8500 -6.1 21.0 350 37 19 8.3 4.5 3.8 38.9 -4.2 200 1.0
8250 -5.5 22.1 350 36 19 8.8 4.8 3.7 38.7 -4.3 173 0.9
8000 -4.8 23.4 350 35 18 8.8 4.8 3.7 38.6 -4.4 146 0.7
7750 -4.2 24.4 350 34 18 8.8 4.9 3.6 38.5 -4.4 119 0.6
7500 -3.5 25.7 351 33 17 9.0 4.9 3.5 38.4 -4.5 92 0.5
7250 -2.9 26.8 351 31 16 9.0 5.0 3.5 38.3 -4.6 65 0.3
7000 -2.2 28.0 351 30 15 8.9 4.9 3.4 38.2 -4.7 38 0.2
6750 -1.5 29.3 352 28 14 9.4 5.2 3.4 38.1 -4.8 10 0.1
6500 -0.8 30.6 352 27 14 9.9 5.4 3.4 38.1 -4.8 M M
6250 -0.1 31.8 352 25 13 9.6 5.3 3.4 38.1 -4.8 M M
6000 0.6 33.1 352 24 12 10.2 5.6 3.4 38.1 -4.8 M M
5750 1.4 34.5 352 21 11 11.0 6.0 3.4 38.2 -4.8 M M
5500 2.2 36.0 351 18 9 10.8 5.9 3.5 38.3 -4.8 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/22/2008 at 0900 MDT | 10/22/2008 at 1200 MDT
|
K index... +1.6 | K index... +3.1
|
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 -55.5 -67.9 330 26 14 1.9 1.0 | -55.3 -67.5 343 22 11 1.7 0.9
45000 -52.7 -62.9 334 35 18 2.0 1.1 | -52.7 -62.9 345 32 17 2.3 1.2
40000 -49.1 -56.4 344 39 20 2.3 1.3 | -49.1 -56.4 003 40 21 2.4 1.3
38000 -47.8 -54.0 347 40 20 1.9 1.0 | -47.7 -53.9 005 45 23 2.1 1.2
36000 -46.7 -52.1 349 41 21 1.9 1.0 | -46.4 -51.5 004 49 25 2.1 1.2
34000 -45.6 -50.1 351 42 22 1.6 0.9 | -45.1 -49.2 003 54 28 1.7 0.9
32000 -45.0 -49.0 350 39 20 0.8 0.4 | -44.7 -48.5 004 45 23 0.7 0.4
30000 -44.6 -48.3 349 35 18 1.0 0.5 | -44.1 -47.4 006 35 18 2.5 1.4
29000 -43.8 -46.8 352 25 13 2.3 1.3 | -43.2 -45.8 011 24 12 3.1 1.7
28000 -43.1 -45.6 359 15 8 2.4 1.3 | -42.3 -44.1 022 14 7 3.1 1.7
27000 -42.4 -44.3 024 7 4 2.2 1.2 | -41.3 -42.3 073 6 3 3.0 1.6
26000 -41.1 -42.0 069 4 2 5.2 2.8 | -40.0 -40.0 099 5 2 5.5 3.0
25000 -39.6 -39.3 106 4 2 5.2 2.9 | -38.3 -36.9 053 2 1 5.5 3.0
24000 -38.0 -36.4 137 5 2 5.2 2.9 | -36.7 -34.1 341 3 2 5.5 3.0
23000 -36.5 -33.7 143 1 1 5.0 2.8 | -35.2 -31.4 327 7 4 4.7 2.6
22000 -35.0 -31.0 327 5 3 5.0 2.8 | -33.8 -28.8 325 12 6 4.7 2.6
21000 -33.5 -28.3 326 12 6 5.0 2.8 | -32.4 -26.3 324 16 8 4.5 2.5
20000 -32.0 -25.6 337 21 11 5.0 2.7 | -31.6 -24.9 341 20 10 2.0 1.1
19500 -31.2 -24.2 341 26 13 5.0 2.7 | -31.3 -24.3 349 23 12 2.0 1.1
19000 -30.5 -22.9 343 31 16 5.0 2.7 | -31.1 -24.0 355 26 13 2.0 1.1
18500 -29.8 -21.6 344 36 18 5.4 3.0 | -30.8 -23.4 360 29 15 2.6 1.4
18000 -28.7 -19.7 346 38 20 8.3 4.5 | -29.8 -21.6 001 30 15 8.8 4.8
17500 -27.5 -17.5 348 40 20 8.1 4.5 | -28.6 -19.5 360 30 15 8.3 4.6
17000 -26.3 -15.3 349 41 21 8.1 4.5 | -27.3 -17.1 359 30 15 8.8 4.8
16500 -25.0 -13.0 349 41 21 8.1 4.5 | -25.3 -13.5 354 29 15 8.8 4.8
16000 -23.3 -9.9 350 40 21 7.9 4.3 | -24.1 -11.4 353 30 15 8.4 4.6
15500 -22.1 -7.8 350 39 20 7.9 4.4 | -22.8 -9.0 353 30 16 8.4 4.6
15000 -20.9 -5.6 349 38 19 7.7 4.2 | -21.6 -6.9 353 32 16 8.2 4.5
14500 -19.8 -3.6 349 36 18 7.8 4.3 | -20.3 -4.5 352 33 17 8.2 4.5
14000 -18.7 -1.7 350 34 18 7.4 4.0 | -19.1 -2.4 352 34 17 7.8 4.3
13500 -17.6 0.3 352 34 17 7.4 4.0 | -18.0 -0.4 350 34 18 7.7 4.2
13000 -16.5 2.3 354 33 17 7.1 3.9 | -16.8 1.8 350 34 18 8.1 4.5
12500 -15.4 4.3 357 33 17 7.0 3.9 | -15.6 3.9 349 34 18 8.2 4.5
12000 -14.4 6.1 360 33 17 7.4 4.1 | -14.4 6.1 349 34 17 8.0 4.4
11500 -13.3 8.1 002 34 18 7.6 4.1 | -13.2 8.2 350 34 17 8.0 4.4
11000 -12.2 10.0 005 35 18 6.4 3.5 | -12.1 10.2 351 34 17 7.7 4.2
10500 -11.3 11.7 006 36 19 6.6 3.6 | -10.9 12.4 353 34 17 7.7 4.2
10250 -10.8 12.6 007 37 19 5.3 2.9 | -10.4 13.3 353 34 17 7.4 4.1
10000 -10.5 13.1 008 39 20 4.3 2.4 | -9.9 14.2 354 33 17 7.2 4.0
9750 -10.2 13.6 008 40 21 4.4 2.4 | -9.3 15.3 354 31 16 7.2 3.9
9500 -9.9 14.2 008 42 21 4.9 2.7 | -8.8 16.2 354 30 15 7.6 4.2
9250 -9.5 14.9 008 42 22 6.4 3.5 | -8.2 17.2 355 29 15 8.6 4.7
9000 -9.0 15.8 006 41 21 7.1 3.9 | -7.5 18.5 355 28 14 9.0 4.9
8750 -8.5 16.7 004 41 21 6.6 3.6 | -6.9 19.6 356 27 14 8.8 4.8
8500 -8.0 17.6 003 40 21 8.0 4.4 | -6.2 20.8 356 26 14 9.4 5.2
8250 -7.3 18.9 002 39 20 9.2 5.1 | -5.5 22.1 356 26 13 10.1 5.5
8000 -6.6 20.1 001 38 19 8.9 4.9 | -4.7 23.5 356 26 13 9.9 5.4
7750 -6.0 21.2 360 36 19 9.0 4.9 | -4.0 24.8 356 26 13 10.0 5.5
7500 -5.3 22.5 359 35 18 8.8 4.8 | -3.2 26.2 357 25 13 10.2 5.6
7250 -4.7 23.5 359 33 17 8.8 4.8 | -2.5 27.5 357 25 13 10.3 5.6
7000 -4.0 24.8 359 31 16 8.8 4.8 | -1.7 28.9 357 25 13 10.3 5.6
6750 -3.4 25.9 359 29 15 9.5 5.2 | -0.9 30.4 357 24 13 10.0 5.5
6500 -2.6 27.3 359 28 14 10.2 5.6 | -0.2 31.6 357 24 12 10.3 5.7
6250 -1.9 28.6 359 26 14 9.3 5.1 | 0.6 33.1 357 23 12 8.8 4.8
6000 -1.1 30.0 359 25 13 12.4 6.8 | 1.3 34.3 357 23 12 14.5 7.9
5750 -0.0 32.0 358 22 11 16.2 8.9 | 2.8 37.0 357 21 11 21.9 12.0
5500 1.1 34.0 358 20 10 13.3 7.3 | 4.3 39.7 357 20 10 17.3 9.5
10/22/2008 at 1500 MDT | 10/22/2008 at 1800 MDT
|
K index... +4.6 | K index... -11.0
|
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 -55.8 -68.4 341 19 10 1.5 0.8 | -56.6 -69.9 351 20 10 1.2 0.7
45000 -53.5 -64.3 355 32 17 1.6 0.9 | -54.8 -66.6 355 38 20 1.4 0.7
40000 -50.4 -58.7 005 49 25 2.0 1.1 | -52.3 -62.1 006 54 28 1.7 0.9
38000 -49.2 -56.6 007 55 28 2.0 1.1 | -50.9 -59.6 008 63 32 2.5 1.4
36000 -48.0 -54.4 008 60 31 2.0 1.1 | -49.4 -56.9 008 72 37 2.5 1.4
34000 -46.7 -52.1 008 66 34 1.5 0.8 | -47.9 -54.2 008 79 41 3.8 2.1
32000 -46.3 -51.3 008 52 27 0.7 0.4 | -45.6 -50.1 007 76 39 3.8 2.1
30000 -45.9 -50.6 006 38 20 2.6 1.4 | -43.1 -45.6 006 73 38 6.1 3.3
29000 -43.7 -46.7 008 33 17 6.3 3.4 | -41.2 -42.2 005 68 35 6.3 3.4
28000 -41.8 -43.2 009 28 15 6.3 3.4 | -39.4 -38.9 005 63 32 6.3 3.4
27000 -39.9 -39.8 011 24 12 6.1 3.4 | -37.5 -35.5 005 57 30 6.3 3.4
26000 -37.8 -36.0 009 23 12 7.6 4.2 | -35.6 -32.1 005 54 28 6.3 3.5
25000 -35.5 -31.9 004 23 12 7.6 4.2 | -33.7 -28.7 005 51 26 6.3 3.5
24000 -33.2 -27.8 360 23 12 7.8 4.3 | -31.8 -25.2 005 48 25 6.3 3.5
23000 -31.7 -25.1 356 25 13 3.7 2.1 | -30.4 -22.7 005 46 24 3.5 1.9
22000 -30.6 -23.1 354 28 14 3.7 2.0 | -29.3 -20.7 005 45 23 3.4 1.9
21000 -29.4 -20.9 352 31 16 3.4 1.9 | -28.3 -18.9 005 43 22 3.7 2.0
20000 -29.3 -20.7 346 32 16 -0.2 -0.1 | -27.9 -18.2 002 42 22 0.8 0.4
19500 -29.4 -20.9 343 32 17 -0.2 -0.1 | -27.7 -17.9 359 41 21 0.8 0.4
19000 -29.4 -20.9 340 33 17 -0.2 -0.1 | -27.6 -17.7 357 41 21 0.8 0.5
18500 -29.4 -20.9 337 33 17 0.1 0.1 | -27.5 -17.5 354 40 21 1.5 0.8
18000 -28.9 -20.0 335 32 16 6.3 3.5 | -27.1 -16.8 349 37 19 2.1 1.2
17500 -28.0 -18.4 335 30 15 5.8 3.2 | -26.8 -16.2 342 34 18 2.4 1.3
17000 -27.1 -16.8 336 28 15 7.4 4.1 | -26.2 -15.2 338 32 17 5.8 3.2
16500 -26.0 -14.8 336 28 14 7.5 4.1 | -25.3 -13.5 336 30 16 5.5 3.0
16000 -24.3 -11.7 339 27 14 7.7 4.2 | -24.4 -11.9 336 29 15 6.1 3.4
15500 -23.1 -9.6 343 27 14 7.6 4.2 | -23.5 -10.3 339 28 14 6.0 3.3
15000 -22.0 -7.6 346 28 14 8.3 4.6 | -22.5 -8.5 341 27 14 8.0 4.4
14500 -20.7 -5.3 349 29 15 8.3 4.6 | -21.3 -6.3 344 26 13 8.3 4.5
14000 -19.5 -3.1 352 29 15 8.5 4.7 | -20.0 -4.0 346 25 13 8.7 4.8
13500 -18.2 -0.8 353 30 16 8.6 4.7 | -18.7 -1.7 346 25 13 8.8 4.8
13000 -16.9 1.6 354 31 16 8.4 4.6 | -17.4 0.7 347 25 13 9.1 5.0
12500 -15.7 3.7 354 31 16 8.4 4.6 | -16.0 3.2 346 25 13 9.2 5.0
12000 -14.4 6.1 353 31 16 8.5 4.6 | -14.7 5.5 346 25 13 9.3 5.1
11500 -13.2 8.2 351 29 15 8.4 4.6 | -13.3 8.1 346 26 13 9.4 5.1
11000 -11.9 10.6 349 27 14 9.7 5.3 | -11.9 10.6 345 26 13 9.1 5.0
10500 -10.4 13.3 349 27 14 9.7 5.3 | -10.6 12.9 344 27 14 9.0 5.0
10250 -9.7 14.5 349 26 13 9.8 5.4 | -9.9 14.2 344 27 14 9.1 5.0
10000 -9.0 15.8 349 26 13 9.9 5.4 | -9.2 15.4 344 27 14 9.2 5.1
9750 -8.2 17.2 349 26 13 9.9 5.4 | -8.5 16.7 344 26 14 9.2 5.1
9500 -7.5 18.5 349 26 13 9.9 5.4 | -7.8 18.0 344 26 14 9.3 5.1
9250 -6.8 19.8 350 26 13 9.8 5.4 | -7.1 19.2 344 26 13 9.4 5.2
9000 -6.0 21.2 350 26 13 9.8 5.4 | -6.4 20.5 344 26 13 9.6 5.2
8750 -5.3 22.5 350 26 13 9.7 5.3 | -5.7 21.7 345 26 13 9.5 5.2
8500 -4.6 23.7 350 26 13 9.9 5.4 | -5.0 23.0 345 26 13 9.6 5.3
8250 -3.8 25.2 350 25 13 10.2 5.6 | -4.3 24.3 346 25 13 9.8 5.4
8000 -3.1 26.4 350 25 13 10.2 5.6 | -3.5 25.7 346 25 13 9.9 5.4
7750 -2.3 27.9 350 25 13 10.1 5.6 | -2.8 27.0 347 25 13 9.8 5.4
7500 -1.5 29.3 350 25 13 10.0 5.5 | -2.1 28.2 347 25 13 9.7 5.3
7250 -0.8 30.6 350 25 13 10.0 5.5 | -1.3 29.7 348 25 13 9.7 5.3
7000 -0.0 32.0 350 24 13 10.0 5.5 | -0.6 30.9 348 24 13 9.7 5.3
6750 0.7 33.3 350 24 13 9.9 5.5 | 0.1 32.2 349 24 12 9.8 5.4
6500 1.4 34.5 351 24 12 10.2 5.6 | 0.9 33.6 349 24 12 9.8 5.4
6250 2.2 36.0 351 23 12 9.3 5.1 | 1.6 34.9 349 23 12 9.9 5.4
6000 2.9 37.2 351 23 12 12.7 7.0 | 2.3 36.1 350 22 11 9.7 5.3
5750 4.2 39.6 351 22 11 18.9 10.4 | 3.0 37.4 349 20 10 9.4 5.1
5500 5.6 42.1 352 20 10 18.7 10.2 | 3.7 38.7 348 18 9 9.3 5.1
________________________________________________________________________________
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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