Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 241153
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
552 AM MDT Friday October 24, 2008
This forecast is for Friday October 24, 2008:
If the trigger temperature of 61.1 F/16.2 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 351 ft/min (1.8 m/s)
Maximum height of thermals.................. 10033 ft MSL (4710 ft AGL)
Forecast maximum temperature................... 62.0 F/17.1 C
Time of trigger temperature.................... 1430 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................. 7149 ft MSL (1826 ft AGL)
Thermal soaring outlook for Saturday 10/25..... 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)................ Weak NVA
Potential height of wave....................... 22767 ft MSL (17444 ft AGL)
Wave soaring outlook for Saturday 10/25........ Fair
Remarks... None
Sunrise/Sunset.................... 07:19:56 / 18:08:14 MDT
Total possible sunshine........... 10 hr 48 min 19 sec (648 min 19 sec)
Altitude of sun at 12:43:41 MDT... 38.19 degrees
Upper air data from numerical model forecast valid on 10/24/2008 at 0600 MDT
Freezing level.................. 10992 ft MSL (5669 ft AGL)
Convective condensation level... 18632 ft MSL (13309 ft AGL)
Lifted condensation level....... 15694 ft MSL (10371 ft AGL)
Lifted index.................... +6.6
K index......................... +6.0
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 -60.5 -76.9 314 39 20 1.2 0.7 96.3 205.3 45.8 M M
45000 -58.5 -73.3 317 45 23 2.5 1.4 75.5 167.8 36.2 M M
40000 -54.9 -66.8 310 57 29 2.4 1.3 58.1 136.6 27.3 M M
38000 -53.7 -64.7 307 55 28 1.7 0.9 51.0 123.8 23.2 M M
36000 -52.7 -62.9 303 50 26 1.7 0.9 44.0 111.2 19.0 M M
34000 -51.1 -60.0 299 46 24 5.6 3.1 38.2 100.8 15.4 M M
32000 -47.7 -53.9 300 43 22 5.7 3.1 34.7 94.4 13.2 M M
30000 -43.2 -45.8 300 41 21 8.9 4.9 32.0 89.7 11.6 M M
29000 -40.5 -40.9 300 41 21 8.9 4.9 31.6 89.0 11.4 M M
28000 -37.9 -36.2 300 42 21 8.9 4.9 31.4 88.5 11.3 M M
27000 -35.2 -31.4 300 42 22 8.9 4.9 31.2 88.1 11.3 M M
26000 -32.6 -26.7 301 42 22 8.9 4.9 30.7 87.3 11.1 M M
25000 -29.9 -21.8 302 42 22 8.9 4.9 30.5 86.8 11.0 M M
24000 -27.2 -17.0 302 42 22 8.2 4.5 30.2 86.4 10.9 M M
23000 -24.9 -12.8 305 41 21 7.9 4.3 29.5 85.0 10.4 M M
22000 -22.5 -8.5 308 40 20 7.9 4.4 28.8 83.9 10.0 M M
21000 -20.2 -4.4 311 38 20 6.2 3.4 28.1 82.6 9.5 M M
20000 -18.3 -0.9 315 34 18 6.3 3.5 26.8 80.3 8.6 M M
19500 -17.4 0.7 318 32 17 6.3 3.5 26.2 79.2 8.1 M M
19000 -16.4 2.5 320 31 16 6.3 3.5 25.7 78.2 7.7 M M
18500 -15.5 4.1 323 29 15 5.8 3.2 25.1 77.1 7.2 M M
18000 -14.7 5.5 325 27 14 5.7 3.1 24.4 75.8 6.6 M M
17500 -13.8 7.2 327 26 13 5.5 3.0 23.7 74.6 6.0 M M
17000 -13.1 8.4 331 25 13 4.4 2.4 22.8 73.1 5.3 M M
16500 -12.1 10.2 336 23 12 5.2 2.8 21.5 70.7 4.2 M M
16000 -11.2 11.8 338 23 12 6.4 3.5 20.9 69.6 3.6 M M
15500 -10.3 13.5 340 23 12 6.4 3.5 20.3 68.6 3.1 M M
15000 -9.2 15.4 339 23 12 7.9 4.4 19.9 67.8 2.7 M M
14500 -8.1 17.4 337 22 11 7.9 4.3 19.6 67.2 2.4 M M
14000 -7.0 19.4 336 21 11 7.5 4.1 19.2 66.6 2.1 M M
13500 -5.9 21.4 337 20 10 7.5 4.1 18.9 66.0 1.7 M M
13000 -4.8 23.4 339 19 10 7.8 4.3 18.5 65.4 1.4 M M
12500 -3.6 25.5 345 20 10 7.8 4.3 18.2 64.8 1.1 M M
12000 -2.4 27.7 349 20 11 8.2 4.5 17.9 64.3 0.8 M M
11500 -1.2 29.8 351 21 11 8.3 4.5 17.7 63.9 0.6 M M
11000 0.0 32.0 353 21 11 8.5 4.6 17.5 63.5 0.4 M M
10500 1.3 34.3 353 20 10 8.6 4.7 17.3 63.1 0.2 M M
10250 1.9 35.4 353 20 10 8.4 4.6 17.2 62.9 0.1 M M
10000 2.6 36.7 354 19 10 7.8 4.3 17.1 62.7 -0.0 346 1.8
9750 3.1 37.6 354 18 9 7.5 4.1 16.9 62.4 -0.2 322 1.6
9500 3.7 38.7 355 18 9 7.7 4.2 16.7 62.1 -0.3 297 1.5
9250 4.3 39.7 355 17 9 7.4 4.0 16.6 61.8 -0.5 273 1.4
9000 4.8 40.6 356 16 8 6.9 3.8 16.3 61.4 -0.7 250 1.3
8750 5.3 41.5 355 15 8 6.8 3.7 16.1 61.0 -0.9 227 1.2
8500 5.8 42.4 355 14 7 7.0 3.9 15.9 60.6 -1.1 204 1.0
8250 6.3 43.3 355 13 7 6.2 3.4 15.7 60.2 -1.4 181 0.9
8000 6.8 44.2 353 12 6 5.4 3.0 15.4 59.6 -1.7 161 0.8
7750 7.2 45.0 350 11 6 5.7 3.1 15.0 59.1 -2.0 141 0.7
7500 7.6 45.7 347 10 5 5.2 2.9 14.7 58.5 -2.3 121 0.6
7250 7.9 46.2 344 10 5 3.7 2.0 14.3 57.8 -2.7 104 0.5
7000 8.1 46.6 343 10 5 2.3 1.3 13.8 56.8 -3.2 90 0.5
6750 8.3 46.9 341 10 5 4.3 2.4 13.3 55.9 -3.8 77 0.4
6500 8.6 47.5 340 10 5 -2.2 -1.2 12.8 55.0 -4.3 63 0.3
6250 8.0 46.4 328 8 4 -10.4 -5.7 11.4 52.5 -5.6 74 0.4
6000 7.3 45.1 309 7 4 -7.0 -3.8 10.0 50.0 -7.1 87 0.4
5750 6.6 43.9 287 7 4 -16.3 -9.0 8.6 47.4 -8.5 100 0.5
5500 4.3 39.7 260 6 3 -45.4 -24.9 5.6 42.0 -11.6 161 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/24/2008 at 0900 MDT | 10/24/2008 at 1200 MDT
|
K index... +8.1 | K index... +11.9
|
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 -60.9 -77.6 320 44 23 2.3 1.3 | -60.5 -76.9 331 41 21 2.1 1.1
45000 -57.2 -71.0 318 50 26 3.1 1.7 | -57.0 -70.6 330 50 26 4.0 2.2
40000 -52.7 -62.9 322 48 25 3.0 1.7 | -51.2 -60.2 335 56 29 3.9 2.1
38000 -51.4 -60.5 319 47 24 1.6 0.9 | -49.9 -57.8 334 55 29 1.1 0.6
36000 -50.5 -58.9 313 46 24 1.6 0.9 | -49.2 -56.6 331 53 27 1.1 0.6
34000 -49.3 -56.7 307 44 23 3.6 2.0 | -48.3 -54.9 327 51 26 4.0 2.2
32000 -47.2 -53.0 304 39 20 3.5 1.9 | -45.7 -50.3 319 48 25 3.8 2.1
30000 -44.1 -47.4 301 35 18 7.6 4.2 | -43.2 -45.8 313 45 23 5.5 3.0
29000 -41.8 -43.2 302 34 18 7.7 4.2 | -41.5 -42.7 311 41 21 5.6 3.1
28000 -39.5 -39.1 303 34 17 7.7 4.2 | -39.8 -39.6 308 38 20 5.6 3.1
27000 -37.2 -35.0 304 33 17 8.3 4.5 | -38.1 -36.6 306 35 18 7.1 3.9
26000 -34.7 -30.5 308 34 17 8.4 4.6 | -35.8 -32.4 310 34 17 7.8 4.3
25000 -32.2 -26.0 311 34 18 8.4 4.6 | -33.5 -28.3 316 33 17 7.8 4.3
24000 -29.7 -21.5 314 35 18 7.6 4.2 | -31.1 -24.0 321 32 16 7.4 4.1
23000 -27.6 -17.7 318 32 16 7.0 3.9 | -29.1 -20.4 320 29 15 6.9 3.8
22000 -25.5 -13.9 322 28 14 7.0 3.9 | -27.0 -16.6 317 25 13 6.9 3.8
21000 -23.3 -9.9 327 25 13 7.5 4.1 | -24.9 -12.8 315 22 12 8.1 4.4
20000 -21.1 -6.0 332 23 12 7.5 4.1 | -22.5 -8.5 320 21 11 8.3 4.5
19500 -19.9 -3.8 334 22 12 7.5 4.1 | -21.2 -6.2 322 21 11 8.3 4.5
19000 -18.8 -1.8 337 22 11 7.5 4.1 | -20.0 -4.0 324 20 10 8.2 4.5
18500 -17.7 0.1 339 21 11 7.8 4.3 | -18.8 -1.8 327 20 10 8.7 4.8
18000 -16.5 2.3 340 21 11 7.8 4.3 | -17.4 0.7 327 20 10 9.0 4.9
17500 -15.3 4.5 340 20 10 7.8 4.3 | -15.4 4.3 328 20 10 8.3 4.5
17000 -13.7 7.3 339 20 10 7.4 4.0 | -14.2 6.4 329 20 10 8.0 4.4
16500 -12.6 9.3 338 20 10 7.5 4.1 | -13.0 8.6 331 20 10 8.0 4.4
16000 -11.5 11.3 334 20 10 7.8 4.3 | -11.9 10.6 330 20 10 7.9 4.4
15500 -10.3 13.5 330 20 10 7.8 4.3 | -10.7 12.7 329 20 10 8.0 4.4
15000 -9.3 15.3 325 20 10 6.3 3.5 | -9.7 14.5 328 20 10 6.3 3.4
14500 -8.4 16.9 321 19 10 6.5 3.6 | -8.7 16.3 327 20 10 6.4 3.5
14000 -7.4 18.7 318 19 10 6.1 3.4 | -7.8 18.0 326 19 10 6.6 3.6
13500 -6.5 20.3 317 19 10 6.1 3.3 | -6.8 19.8 325 19 10 6.6 3.6
13000 -5.6 21.9 318 19 10 6.8 3.7 | -5.8 21.6 324 18 9 6.5 3.6
12500 -4.6 23.7 322 19 10 6.9 3.8 | -4.9 23.2 322 17 9 6.4 3.5
12000 -3.6 25.5 326 19 10 6.9 3.8 | -3.9 25.0 321 16 8 7.0 3.8
11500 -2.6 27.3 331 20 10 6.9 3.8 | -2.9 26.8 323 16 8 7.1 3.9
11000 -1.5 29.3 337 20 10 7.3 4.0 | -1.8 28.8 325 15 8 7.6 4.1
10500 -0.4 31.3 341 21 11 7.3 4.0 | -0.6 30.9 326 14 7 7.7 4.2
10250 0.1 32.2 343 21 11 7.4 4.1 | -0.1 31.8 327 14 7 7.7 4.2
10000 0.7 33.3 345 21 11 7.6 4.2 | 0.5 32.9 329 14 7 7.6 4.2
9750 1.3 34.3 348 21 11 7.7 4.2 | 1.1 34.0 332 13 7 7.6 4.1
9500 1.8 35.2 350 21 11 7.7 4.2 | 1.6 34.9 335 13 7 7.5 4.1
9250 2.4 36.3 352 21 11 7.6 4.2 | 2.2 36.0 339 13 7 7.6 4.2
9000 3.0 37.4 353 21 11 7.5 4.1 | 2.8 37.0 342 13 7 7.8 4.3
8750 3.5 38.3 354 20 10 7.5 4.1 | 3.4 38.1 346 13 7 7.8 4.3
8500 4.1 39.4 356 19 10 7.5 4.1 | 3.9 39.0 350 13 7 7.8 4.3
8250 4.6 40.3 357 19 10 6.6 3.6 | 4.5 40.1 353 13 7 7.5 4.1
8000 5.1 41.2 356 17 9 5.8 3.2 | 5.1 41.2 355 12 6 7.3 4.0
7750 5.5 41.9 356 16 8 6.1 3.3 | 5.6 42.1 357 11 6 7.3 4.0
7500 6.0 42.8 355 14 7 5.6 3.1 | 6.2 43.2 359 10 5 7.4 4.0
7250 6.4 43.5 353 13 6 4.8 2.6 | 6.7 44.1 002 9 5 7.6 4.2
7000 6.7 44.1 350 11 6 4.4 2.4 | 7.3 45.1 006 8 4 7.7 4.2
6750 7.0 44.6 346 10 5 5.0 2.7 | 7.8 46.0 012 6 3 7.4 4.1
6500 7.4 45.3 340 8 4 1.9 1.0 | 8.4 47.1 019 5 3 9.1 5.0
6250 7.3 45.1 327 7 4 -1.0 -0.5 | 9.2 48.6 020 5 2 10.8 5.9
6000 7.3 45.1 310 6 3 0.1 0.1 | 10.0 50.0 021 5 2 9.5 5.2
5750 7.3 45.1 290 6 3 -1.3 -0.7 | 10.7 51.3 023 4 2 13.1 7.2
5500 7.0 44.6 270 5 3 -4.2 -2.3 | 12.1 53.8 021 5 2 23.0 12.6
10/24/2008 at 1500 MDT | 10/24/2008 at 1800 MDT
|
K index... +20.6 | K index... +20.9
|
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 -76.7 331 42 22 2.2 1.2 | -61.4 -78.5 329 43 22 2.9 1.6
45000 -57.1 -70.8 332 55 28 3.6 2.0 | -57.0 -70.6 338 55 28 2.3 1.3
40000 -51.8 -61.2 341 65 33 3.5 1.9 | -53.5 -64.3 346 71 37 2.3 1.3
38000 -50.2 -58.4 345 72 37 2.0 1.1 | -51.8 -61.2 349 79 41 3.1 1.7
36000 -49.0 -56.2 349 81 42 2.0 1.1 | -49.9 -57.8 352 87 45 3.1 1.7
34000 -47.3 -53.1 351 86 44 4.1 2.2 | -47.8 -54.0 354 91 47 4.9 2.7
32000 -44.8 -48.6 348 78 40 4.1 2.3 | -44.5 -48.1 351 84 43 4.9 2.7
30000 -42.1 -43.8 345 70 36 5.5 3.0 | -41.1 -42.0 347 79 41 7.2 3.9
29000 -40.4 -40.7 344 66 34 5.6 3.1 | -38.9 -38.0 344 78 40 7.2 3.9
28000 -38.7 -37.7 342 61 32 5.6 3.1 | -36.8 -34.2 341 76 39 7.2 3.9
27000 -37.0 -34.6 340 57 29 6.3 3.5 | -34.7 -30.5 338 75 38 6.6 3.6
26000 -35.1 -31.2 337 55 28 6.6 3.6 | -32.7 -26.9 337 70 36 6.5 3.6
25000 -33.1 -27.6 335 53 27 6.6 3.6 | -30.7 -23.3 337 65 33 6.5 3.6
24000 -31.1 -24.0 332 51 26 6.6 3.6 | -28.8 -19.8 336 59 31 6.4 3.5
23000 -29.1 -20.4 327 45 23 6.7 3.7 | -26.9 -16.4 337 57 30 6.2 3.4
22000 -27.1 -16.8 320 40 21 6.7 3.7 | -25.0 -13.0 338 55 28 6.2 3.4
21000 -25.1 -13.2 313 37 19 7.9 4.3 | -23.2 -9.8 338 53 27 6.0 3.3
20000 -22.7 -8.9 313 36 19 8.1 4.4 | -21.4 -6.5 337 49 25 6.0 3.3
19500 -21.5 -6.7 313 36 18 8.1 4.4 | -20.5 -4.9 336 47 24 6.0 3.3
19000 -20.3 -4.5 313 35 18 8.1 4.5 | -19.6 -3.3 336 45 23 6.0 3.3
18500 -19.1 -2.4 313 35 18 7.9 4.4 | -18.7 -1.7 335 43 22 5.0 2.8
18000 -17.4 0.7 315 34 17 7.9 4.3 | -18.0 -0.4 333 40 20 4.6 2.5
17500 -16.2 2.8 316 33 17 7.3 4.0 | -17.0 1.4 330 35 18 6.0 3.3
17000 -15.2 4.6 317 32 17 7.2 4.0 | -16.1 3.0 328 32 17 6.6 3.6
16500 -14.1 6.6 318 31 16 7.2 4.0 | -15.1 4.8 325 29 15 7.3 4.0
16000 -13.1 8.4 318 30 15 7.3 4.0 | -14.0 6.8 324 28 14 8.5 4.7
15500 -12.0 10.4 318 29 15 7.3 4.0 | -12.7 9.1 323 26 13 8.6 4.7
15000 -10.9 12.4 318 27 14 7.7 4.2 | -11.5 11.3 322 25 13 8.7 4.8
14500 -9.7 14.5 318 25 13 7.6 4.2 | -10.2 13.6 321 23 12 8.7 4.8
14000 -8.6 16.5 317 23 12 8.5 4.6 | -8.9 16.0 320 22 11 9.1 5.0
13500 -7.3 18.9 315 21 11 8.4 4.6 | -7.6 18.3 319 20 10 9.2 5.0
13000 -6.1 21.0 314 19 10 8.4 4.6 | -6.2 20.8 319 18 9 8.6 4.7
12500 -4.8 23.4 313 18 9 8.4 4.6 | -5.0 23.0 319 17 9 8.6 4.7
12000 -3.6 25.5 312 17 9 8.5 4.6 | -3.7 25.3 319 15 8 8.6 4.7
11500 -2.3 27.9 311 16 8 8.5 4.7 | -2.4 27.7 320 13 7 8.5 4.7
11000 -1.1 30.0 310 14 7 7.8 4.3 | -1.1 30.0 319 12 6 8.9 4.9
10500 0.1 32.2 311 12 6 7.6 4.2 | 0.2 32.4 319 11 6 8.9 4.9
10250 0.7 33.3 312 11 6 7.7 4.2 | 0.9 33.6 318 10 5 9.1 5.0
10000 1.2 34.2 315 9 5 7.7 4.2 | 1.6 34.9 318 10 5 9.4 5.2
9750 1.8 35.2 320 8 4 7.8 4.3 | 2.3 36.1 318 10 5 9.5 5.2
9500 2.4 36.3 327 7 3 7.6 4.1 | 3.0 37.4 318 10 5 9.4 5.2
9250 2.9 37.2 337 6 3 8.3 4.6 | 3.7 38.7 318 9 5 9.5 5.2
9000 3.6 38.5 342 5 3 9.2 5.0 | 4.4 39.9 318 9 5 9.5 5.2
8750 4.3 39.7 347 5 3 9.1 5.0 | 5.1 41.2 317 9 5 9.5 5.2
8500 5.0 41.0 352 5 2 9.1 5.0 | 5.8 42.4 317 9 5 9.5 5.2
8250 5.7 42.3 356 5 2 9.6 5.3 | 6.6 43.9 317 9 5 9.6 5.3
8000 6.4 43.5 357 5 2 10.0 5.5 | 7.3 45.1 316 9 5 9.7 5.3
7750 7.1 44.8 358 5 2 9.9 5.4 | 8.0 46.4 316 9 4 9.7 5.3
7500 7.9 46.2 360 5 2 10.0 5.5 | 8.7 47.7 315 9 4 9.6 5.3
7250 8.6 47.5 001 5 2 10.1 5.5 | 9.4 48.9 315 9 4 9.4 5.2
7000 9.4 48.9 002 5 2 10.1 5.5 | 10.1 50.2 315 8 4 9.4 5.1
6750 10.1 50.2 003 4 2 10.1 5.5 | 10.8 51.4 315 8 4 9.3 5.1
6500 10.9 51.6 004 4 2 10.0 5.5 | 11.5 52.7 316 8 4 9.7 5.3
6250 11.6 52.9 004 4 2 10.3 5.6 | 12.3 54.1 316 7 4 10.0 5.5
6000 12.4 54.3 004 4 2 9.3 5.1 | 13.0 55.4 317 7 4 10.4 5.7
5750 13.2 55.8 005 4 2 12.9 7.1 | 13.8 56.8 317 6 3 8.6 4.7
5500 14.5 58.1 006 5 2 22.9 12.5 | 14.2 57.6 316 6 3 3.4 1.9
________________________________________________________________________________
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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