RSS FeedsIssued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 250112
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
612 PM MST Tuesday November 24, 2009
This forecast is for Wednesday November 25, 2009:
If the trigger temperature of 50.0 F/10.0 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 46 ft/min (0.2 m/s)
Maximum height of thermals.................. 8914 ft MSL (3591 ft AGL)
Forecast maximum temperature................... 49.0 F/9.9 C
Time of trigger temperature.................... 1415 MST
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast opaque high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 7300 ft MSL (1977 ft AGL)
Thermal soaring outlook for Thursday 11/26..... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Neither
Potential height of wave....................... 28177 ft MSL (22854 ft AGL)
Wave soaring outlook for Thursday 11/26........ Poor
Remarks...
Sunrise/Sunset.................... 06:55:33 / 16:37:35 MST
Total possible sunshine........... 9 hr 42 min 2 sec (582 min 2 sec)
Altitude of sun at 11:46:43 MST... 29.41 degrees
Upper air data from numerical model forecast valid on 11/25/2009 at 0500 MST
Freezing level.................. 5596 ft MSL (273 ft AGL)
Additional freezing level....... 7849 ft MSL (2526 ft AGL)
Convective condensation level... 16993 ft MSL (11670 ft AGL)
Lifted condensation level....... 13190 ft MSL (7867 ft AGL)
Lifted index.................... +9.9
K index......................... +10.4
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 -59.2 -74.6 316 24 12 0.2 0.1 102.3 216.2 52.9 M M
45000 -58.9 -74.0 322 37 19 0.7 0.4 78.8 173.8 42.2 M M
40000 -64.4 -83.9 336 56 29 -3.9 -2.1 46.3 115.4 24.1 M M
38000 -64.3 -83.7 339 62 32 5.8 3.2 37.8 100.1 19.1 M M
36000 -60.9 -77.6 343 65 33 5.7 3.1 34.1 93.4 17.0 M M
34000 -57.2 -71.0 346 68 35 9.7 5.3 31.3 88.4 15.5 M M
32000 -51.6 -60.9 348 68 35 9.3 5.1 30.8 87.4 15.6 M M
30000 -45.4 -49.7 349 67 35 9.2 5.1 30.5 86.9 15.8 M M
29000 -42.6 -44.7 347 66 34 9.2 5.1 30.2 86.4 15.8 M M
28000 -39.8 -39.6 345 64 33 9.2 5.1 30.1 86.1 15.9 M M
27000 -37.1 -34.8 343 63 32 7.9 4.3 29.9 85.9 15.9 M M
26000 -34.9 -30.8 339 60 31 7.4 4.1 28.9 84.0 15.3 M M
25000 -32.7 -26.9 335 57 30 7.5 4.1 28.1 82.5 14.8 M M
24000 -30.5 -22.9 330 55 28 7.4 4.1 27.3 81.2 14.4 M M
23000 -28.3 -18.9 327 53 27 7.4 4.1 26.3 79.4 13.8 M M
22000 -26.1 -15.0 325 51 26 7.4 4.1 25.5 77.9 13.2 M M
21000 -23.9 -11.0 322 48 25 7.7 4.2 24.7 76.5 12.7 M M
20000 -21.6 -6.9 320 47 24 7.7 4.2 23.9 75.1 12.2 M M
19500 -20.4 -4.7 319 47 24 7.7 4.2 23.6 74.5 11.9 M M
19000 -19.3 -2.7 317 46 24 7.8 4.3 23.3 73.9 11.7 M M
18500 -18.2 -0.8 316 46 24 6.3 3.5 22.9 73.3 11.4 M M
18000 -17.4 0.7 315 44 23 5.6 3.1 22.2 71.9 10.8 M M
17500 -16.6 2.1 314 43 22 5.4 3.0 21.5 70.6 10.2 M M
17000 -15.9 3.4 313 41 21 3.7 2.0 20.5 69.0 9.5 M M
16500 -15.1 4.8 312 39 20 4.0 2.2 19.0 66.3 8.2 M M
16000 -14.5 5.9 313 37 19 4.3 2.4 18.1 64.6 7.4 M M
15500 -13.8 7.2 313 35 18 4.3 2.4 17.2 62.9 6.6 M M
15000 -13.2 8.2 314 33 17 5.0 2.7 16.3 61.4 5.9 M M
14500 -12.4 9.7 315 30 16 4.8 2.6 15.5 60.0 5.2 M M
14000 -11.6 11.1 316 28 14 6.1 3.4 14.8 58.7 4.6 M M
13500 -10.7 12.7 316 25 13 6.1 3.3 14.2 57.6 4.0 M M
13000 -9.8 14.4 317 22 11 6.4 3.5 13.7 56.6 3.5 M M
12500 -8.8 16.2 319 19 10 6.5 3.5 13.1 55.6 3.1 M M
12000 -7.8 18.0 321 16 8 6.9 3.8 12.6 54.7 2.6 M M
11500 -6.8 19.8 326 14 7 6.9 3.8 12.2 53.9 2.2 M M
11000 -5.7 21.7 332 11 6 7.4 4.0 11.7 53.1 1.8 M M
10500 -4.6 23.7 342 10 5 7.5 4.1 11.4 52.4 1.5 M M
10250 -4.0 24.8 348 9 5 7.2 3.9 11.2 52.1 1.3 M M
10000 -3.5 25.7 353 8 4 6.8 3.7 11.0 51.7 1.1 M M
9750 -3.0 26.6 359 8 4 6.8 3.7 10.7 51.3 0.9 M M
9500 -2.5 27.5 005 8 4 6.9 3.8 10.5 50.9 0.7 M M
9250 -2.0 28.4 011 7 4 6.1 3.3 10.2 50.4 0.4 M M
9000 -1.6 29.1 011 7 4 5.3 2.9 9.9 49.8 0.1 M M
8750 -1.2 29.8 011 7 4 5.7 3.1 9.6 49.2 -0.2 234 1.2
8500 -0.8 30.6 011 7 4 5.1 2.8 9.3 48.7 -0.5 214 1.1
8250 -0.4 31.3 012 7 4 3.9 2.1 8.8 47.9 -0.9 197 1.0
8000 -0.2 31.6 014 8 4 3.3 1.8 8.4 47.0 -1.4 182 0.9
7750 0.1 32.2 015 9 4 3.8 2.1 7.9 46.2 -1.9 167 0.8
7500 0.3 32.5 016 9 5 2.1 1.2 7.4 45.3 -2.3 152 0.8
7250 0.4 32.7 020 10 5 0.6 0.3 6.7 44.1 -3.0 143 0.7
7000 0.4 32.7 022 11 6 0.9 0.5 6.0 42.9 -3.7 134 0.7
6750 0.5 32.9 025 12 6 1.1 0.6 5.4 41.7 -4.4 125 0.6
6500 0.6 33.1 027 12 6 1.5 0.8 4.7 40.5 -5.0 115 0.6
6250 0.7 33.3 030 11 6 1.9 1.1 4.1 39.4 -5.7 104 0.5
6000 0.8 33.4 033 10 5 0.7 0.4 3.5 38.3 -6.3 94 0.5
5750 0.6 33.1 037 8 4 -5.4 -3.0 2.6 36.7 -7.2 91 0.5
5500 -0.1 31.8 049 5 2 -11.7 -6.4 1.2 34.1 -8.7 105 0.5
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/25/2009 at 0800 MST | 11/25/2009 at 1100 MST
|
K index... +2.5 | K index... -3.2
|
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 -60.3 -76.5 330 26 13 0.9 0.5 | -60.7 -77.3 328 27 14 0.9 0.5
45000 -58.9 -74.0 342 38 20 1.1 0.6 | -59.3 -74.7 333 33 17 0.9 0.5
40000 -64.6 -84.3 343 60 31 -4.0 -2.2 | -63.7 -82.7 346 51 26 -3.1 -1.7
38000 -64.3 -83.7 347 67 35 6.4 3.5 | -63.2 -81.8 352 58 30 5.8 3.2
36000 -60.5 -76.9 356 73 38 6.3 3.5 | -59.7 -75.5 001 65 33 5.7 3.2
34000 -56.5 -69.7 001 78 40 8.9 4.9 | -55.4 -67.7 005 70 36 8.4 4.6
32000 -51.4 -60.5 356 74 38 8.6 4.7 | -50.3 -58.5 357 65 33 8.5 4.6
30000 -45.5 -49.9 351 69 36 9.1 5.0 | -45.2 -49.4 350 63 33 8.8 4.8
29000 -42.7 -44.9 348 68 35 9.1 5.0 | -42.5 -44.5 349 65 33 8.8 4.8
28000 -40.0 -40.0 346 66 34 9.1 5.0 | -39.9 -39.8 349 66 34 8.8 4.8
27000 -37.3 -35.1 343 65 33 9.4 5.2 | -37.2 -35.0 348 66 34 9.3 5.1
26000 -34.4 -29.9 343 65 33 9.5 5.2 | -34.4 -29.9 347 63 33 9.3 5.1
25000 -31.6 -24.9 343 65 33 9.5 5.2 | -31.6 -24.9 345 60 31 9.3 5.1
24000 -28.7 -19.7 343 65 33 8.4 4.6 | -28.8 -19.8 343 58 30 8.5 4.7
23000 -26.6 -15.9 344 65 34 7.3 4.0 | -26.5 -15.7 343 56 29 7.8 4.3
22000 -24.4 -11.9 345 66 34 7.3 4.0 | -24.1 -11.4 343 55 28 7.8 4.3
21000 -22.2 -8.0 345 66 34 6.6 3.6 | -21.8 -7.2 343 55 28 8.1 4.5
20000 -20.3 -4.5 345 65 33 6.6 3.6 | -19.4 -2.9 345 56 29 8.1 4.5
19500 -19.3 -2.7 345 64 33 6.6 3.6 | -18.1 -0.6 345 57 29 8.2 4.5
19000 -18.3 -0.9 344 63 32 6.6 3.6 | -16.9 1.6 346 58 30 8.2 4.5
18500 -17.4 0.7 344 62 32 5.3 2.9 | -15.8 3.6 347 59 30 6.8 3.7
18000 -16.7 1.9 342 59 30 4.6 2.5 | -14.4 6.1 348 59 30 6.1 3.3
17500 -16.0 3.2 340 56 29 4.7 2.6 | -13.5 7.7 348 58 30 5.4 2.9
17000 -15.2 4.6 337 53 27 6.5 3.6 | -12.7 9.1 349 58 30 5.1 2.8
16500 -13.8 7.2 332 48 25 6.7 3.7 | -12.0 10.4 349 57 29 4.4 2.4
16000 -12.7 9.1 330 46 24 7.7 4.2 | -11.5 11.3 348 54 28 2.4 1.3
15500 -11.6 11.1 328 44 23 7.8 4.3 | -11.2 11.8 347 52 27 2.5 1.3
15000 -10.7 12.7 326 42 22 4.2 2.3 | -10.8 12.6 345 49 25 2.9 1.6
14500 -10.0 14.0 324 41 21 4.7 2.6 | -10.4 13.3 342 46 23 2.8 1.6
14000 -9.5 14.9 322 38 20 2.6 1.4 | -9.9 14.2 339 42 22 3.7 2.0
13500 -9.1 15.6 321 35 18 2.5 1.4 | -9.4 15.1 336 38 20 3.7 2.0
13000 -8.7 16.3 320 32 16 3.5 1.9 | -8.8 16.2 334 35 18 5.2 2.8
12500 -8.2 17.2 318 28 14 3.6 2.0 | -8.0 17.6 335 32 16 5.4 3.0
12000 -7.6 18.3 316 24 13 5.1 2.8 | -7.2 19.0 336 29 15 5.8 3.2
11500 -6.8 19.8 312 22 12 5.4 3.0 | -6.3 20.7 336 26 13 5.8 3.2
11000 -6.0 21.2 308 21 11 5.8 3.2 | -5.4 22.3 337 23 12 6.8 3.7
10500 -5.1 22.8 304 19 10 5.9 3.2 | -4.4 24.1 335 21 11 7.0 3.8
10250 -4.7 23.5 301 18 9 5.7 3.1 | -3.9 25.0 334 20 10 6.9 3.8
10000 -4.2 24.4 298 18 9 5.6 3.0 | -3.3 26.1 333 19 10 6.8 3.7
9750 -3.8 25.2 296 17 9 5.4 3.0 | -2.8 27.0 331 19 10 6.8 3.7
9500 -3.4 25.9 292 16 8 5.9 3.3 | -2.3 27.9 329 18 9 6.9 3.8
9250 -3.0 26.6 289 15 8 3.7 2.0 | -1.8 28.8 327 17 9 6.3 3.5
9000 -2.9 26.8 284 14 7 1.5 0.8 | -1.4 29.5 324 17 9 5.7 3.1
8750 -2.7 27.1 278 13 7 2.2 1.2 | -0.9 30.4 321 16 8 5.9 3.2
8500 -2.6 27.3 271 12 6 1.5 0.8 | -0.5 31.1 317 16 8 5.7 3.1
8250 -2.5 27.5 265 10 5 -0.4 -0.2 | -0.1 31.8 314 16 8 5.1 2.8
8000 -2.6 27.3 259 9 5 -1.2 -0.7 | 0.3 32.5 312 16 8 4.5 2.5
7750 -2.7 27.1 251 8 4 -1.3 -0.7 | 0.6 33.1 310 15 8 5.7 3.2
7500 -2.8 27.0 241 7 4 -0.2 -0.1 | 1.0 33.8 307 15 8 1.4 0.8
7250 -2.7 27.1 229 6 3 1.2 0.6 | 0.8 33.4 304 11 6 -3.2 -1.8
7000 -2.7 27.1 212 5 2 0.4 0.2 | 0.6 33.1 297 7 4 -2.9 -1.6
6750 -2.7 27.1 187 4 2 2.4 1.3 | 0.4 32.7 272 3 2 -1.2 -0.7
6500 -2.3 27.9 175 5 3 6.2 3.4 | 0.4 32.7 215 2 1 3.6 2.0
6250 -1.8 28.8 172 6 3 7.3 4.0 | 0.7 33.3 185 3 1 5.0 2.8
6000 -1.3 29.7 170 8 4 6.5 3.6 | 1.1 34.0 168 4 2 5.1 2.8
5750 -0.9 30.4 170 8 4 4.4 2.4 | 1.6 34.9 160 5 2 10.3 5.7
5500 -0.7 30.7 170 7 3 2.2 1.2 | 2.6 36.7 156 4 2 17.3 9.5
11/25/2009 at 1400 MST | 11/25/2009 at 1700 MST
|
K index... +5.0 | K index... +9.0
|
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 -61.1 -78.0 339 24 12 0.4 0.2 | -61.8 -79.2 340 24 12 0.6 0.3
45000 -60.5 -76.9 341 32 16 0.0 0.0 | -60.9 -77.6 347 32 17 0.0 0.0
40000 -65.0 -85.0 345 53 27 -3.1 -1.7 | -64.2 -83.6 341 54 28 -2.2 -1.2
38000 -64.1 -83.4 350 58 30 6.8 3.7 | -63.2 -81.8 346 57 30 5.6 3.1
36000 -60.1 -76.2 359 61 31 6.8 3.7 | -59.8 -75.6 358 57 29 5.6 3.1
34000 -55.9 -68.6 005 63 33 8.7 4.8 | -56.0 -68.8 006 58 30 9.4 5.2
32000 -50.1 -58.2 356 59 30 8.6 4.7 | -49.8 -57.6 357 54 28 9.3 5.1
30000 -44.8 -48.6 350 57 29 9.0 5.0 | -44.3 -47.7 350 53 27 8.9 4.9
29000 -42.1 -43.8 348 58 30 9.0 5.0 | -41.6 -42.9 348 54 28 8.9 4.9
28000 -39.4 -38.9 347 58 30 9.0 5.0 | -39.0 -38.2 347 56 29 8.9 4.9
27000 -36.7 -34.1 346 59 30 9.1 5.0 | -36.3 -33.3 346 56 29 9.2 5.1
26000 -34.0 -29.2 345 58 30 9.1 5.0 | -33.5 -28.3 344 53 27 9.2 5.1
25000 -31.2 -24.2 345 56 29 9.1 5.0 | -30.8 -23.4 343 49 25 9.2 5.1
24000 -28.5 -19.3 345 55 28 8.0 4.4 | -28.0 -18.4 341 46 24 8.2 4.5
23000 -26.4 -15.5 344 55 28 7.2 4.0 | -25.7 -14.3 342 47 24 7.8 4.3
22000 -24.2 -11.6 343 55 28 7.2 4.0 | -23.4 -10.1 344 48 25 7.8 4.3
21000 -22.1 -7.8 342 54 28 7.0 3.9 | -21.1 -6.0 345 49 25 6.6 3.6
20000 -20.0 -4.0 342 54 28 7.0 3.9 | -19.2 -2.6 343 50 26 6.7 3.7
19500 -18.9 -2.0 342 54 28 7.1 3.9 | -18.2 -0.8 342 50 26 6.7 3.7
19000 -17.9 -0.2 342 54 28 7.1 3.9 | -17.2 1.0 342 51 26 6.8 3.7
18500 -16.9 1.6 342 54 28 6.4 3.5 | -16.2 2.8 341 51 26 6.1 3.3
18000 -16.0 3.2 343 54 28 6.2 3.4 | -15.3 4.5 339 52 27 5.9 3.3
17500 -15.1 4.8 344 54 28 6.1 3.3 | -14.1 6.6 338 53 27 5.8 3.2
17000 -13.8 7.2 345 54 28 5.7 3.2 | -13.2 8.2 338 53 27 5.8 3.2
16500 -12.9 8.8 346 53 27 5.4 3.0 | -12.4 9.7 337 53 27 5.8 3.2
16000 -12.2 10.0 346 52 27 4.6 2.5 | -11.5 11.3 338 52 27 5.8 3.2
15500 -11.5 11.3 346 51 26 4.6 2.5 | -10.6 12.9 338 51 26 5.8 3.2
15000 -10.9 12.4 345 49 25 3.0 1.7 | -9.9 14.2 339 50 26 4.9 2.7
14500 -10.5 13.1 343 47 24 3.1 1.7 | -9.1 15.6 340 48 24 5.1 2.8
14000 -10.0 14.0 341 45 23 3.6 2.0 | -8.5 16.7 341 45 23 4.1 2.2
13500 -9.4 15.1 338 42 21 3.4 1.9 | -7.8 18.0 342 42 22 4.0 2.2
13000 -8.8 16.2 335 39 20 5.9 3.2 | -7.2 19.0 343 40 20 5.2 2.9
12500 -7.9 17.8 333 35 18 6.1 3.3 | -6.4 20.5 342 38 20 5.2 2.8
12000 -7.0 19.4 331 32 16 7.0 3.9 | -5.5 22.1 341 37 19 7.1 3.9
11500 -5.9 21.4 331 29 15 7.1 3.9 | -4.4 24.1 339 34 18 7.4 4.0
11000 -4.8 23.4 330 27 14 7.5 4.1 | -3.3 26.1 338 32 17 6.8 3.7
10500 -3.7 25.3 327 25 13 7.6 4.1 | -2.3 27.9 336 29 15 6.8 3.7
10250 -3.2 26.2 325 24 13 7.3 4.0 | -1.8 28.8 335 28 14 6.6 3.6
10000 -2.6 27.3 324 24 12 6.9 3.8 | -1.3 29.7 334 27 14 6.4 3.5
9750 -2.1 28.2 322 23 12 6.9 3.8 | -0.9 30.4 332 25 13 6.4 3.5
9500 -1.6 29.1 320 22 12 6.9 3.8 | -0.4 31.3 331 24 12 6.4 3.5
9250 -1.1 30.0 318 22 11 7.1 3.9 | 0.1 32.2 329 23 12 6.7 3.7
9000 -0.5 31.1 318 21 11 7.2 4.0 | 0.6 33.1 326 22 11 7.0 3.9
8750 -0.0 32.0 317 21 11 7.3 4.0 | 1.1 34.0 324 21 11 7.0 3.9
8500 0.5 32.9 316 20 10 6.8 3.7 | 1.6 34.9 321 21 11 6.7 3.7
8250 1.0 33.8 317 19 10 5.2 2.9 | 2.0 35.6 319 20 10 5.5 3.0
8000 1.3 34.3 319 17 9 4.5 2.5 | 2.4 36.3 317 19 10 4.9 2.7
7750 1.6 34.9 322 15 8 5.2 2.8 | 2.7 36.9 315 17 9 5.5 3.0
7500 1.9 35.4 326 13 7 3.3 1.8 | 3.1 37.6 312 15 8 3.9 2.1
7250 2.1 35.8 328 11 5 1.5 0.8 | 3.3 37.9 310 13 7 2.1 1.2
7000 2.2 36.0 331 8 4 1.8 1.0 | 3.5 38.3 306 10 5 2.5 1.4
6750 2.4 36.3 339 5 3 2.0 1.1 | 3.6 38.5 300 8 4 2.2 1.2
6500 2.6 36.7 346 3 2 2.6 1.5 | 3.8 38.8 287 6 3 1.7 0.9
6250 2.7 36.9 350 2 1 2.8 1.5 | 3.9 39.0 263 4 2 1.4 0.8
6000 2.9 37.2 359 1 1 3.1 1.7 | 4.0 39.2 231 4 2 1.7 1.0
5750 3.2 37.8 026 1 0 7.9 4.3 | 4.0 39.2 208 5 3 -4.6 -2.5
5500 4.0 39.2 024 1 1 14.8 8.1 | 3.2 37.8 208 4 2 -15.5 -8.5
________________________________________________________________________________
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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