Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 250120
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
720 PM MDT Friday October 24, 2008
This forecast is for Saturday October 25, 2008:
If the trigger temperature of 63.8 F/17.7 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 596 ft/min (3.0 m/s)
Maximum height of thermals.................. 13053 ft MSL (7730 ft AGL)
Forecast maximum temperature................... 72.0 F/22.7 C
Time of trigger temperature.................... 1115 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................. 10640 ft MSL (5317 ft AGL)
Thermal soaring outlook for Sunday 10/26....... 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....................... 18101 ft MSL (12778 ft AGL)
Wave soaring outlook for Sunday 10/26.......... Poor
Remarks... None
Sunrise/Sunset.................... 07:21:02 / 18:06:55 MDT
Total possible sunshine........... 10 hr 45 min 53 sec (645 min 53 sec)
Altitude of sun at 12:43:35 MDT... 37.84 degrees
Upper air data from numerical model forecast valid on 10/25/2008 at 0600 MDT
Freezing level.................. 12412 ft MSL (7089 ft AGL)
Convective condensation level... 25557 ft MSL (20234 ft AGL)
Lifted condensation level....... 20324 ft MSL (15001 ft AGL)
Lifted index.................... +9.7
K index......................... -9.5
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 -65.0 -85.0 321 32 17 1.5 0.8 86.9 188.4 37.4 M M
45000 -62.4 -80.3 327 43 22 2.8 1.5 67.0 152.6 27.8 M M
40000 -58.2 -72.8 357 73 38 3.0 1.7 51.0 123.9 19.1 M M
38000 -54.2 -65.6 355 75 39 7.2 3.9 48.0 118.5 17.6 M M
36000 -49.9 -57.8 351 76 39 7.2 3.9 45.9 114.7 16.6 M M
34000 -45.3 -49.5 350 76 39 7.9 4.3 44.1 111.4 15.7 M M
32000 -40.6 -41.1 350 75 39 7.9 4.3 42.6 108.7 15.0 M M
30000 -35.2 -31.4 350 74 38 8.2 4.5 41.1 105.9 14.2 M M
29000 -32.8 -27.0 349 73 38 8.2 4.5 40.5 104.8 13.9 M M
28000 -30.4 -22.7 349 72 37 8.2 4.5 40.0 103.9 13.7 M M
27000 -28.0 -18.4 350 69 35 7.7 4.2 39.2 102.6 13.3 M M
26000 -25.7 -14.3 351 63 32 7.7 4.2 38.4 101.1 12.7 M M
25000 -23.4 -10.1 352 57 29 7.7 4.2 37.7 99.8 12.3 M M
24000 -21.3 -6.3 352 52 27 6.3 3.4 36.8 98.2 11.7 M M
23000 -19.4 -2.9 345 49 25 6.3 3.5 35.4 95.8 10.7 M M
22000 -17.5 0.5 338 47 24 6.3 3.5 34.2 93.6 9.8 M M
21000 -15.7 3.7 334 47 24 5.6 3.1 32.9 91.3 8.8 M M
20000 -14.1 6.6 333 47 24 5.6 3.1 31.4 88.5 7.6 M M
19500 -13.3 8.1 332 47 24 5.6 3.1 30.7 87.2 7.0 M M
19000 -12.4 9.7 331 48 24 5.6 3.1 30.0 86.0 6.5 M M
18500 -11.6 11.1 331 48 25 5.7 3.1 29.3 84.8 5.9 M M
18000 -10.8 12.6 331 49 25 5.7 3.1 28.6 83.5 5.3 M M
17500 -9.9 14.2 331 50 26 6.1 3.4 27.9 82.3 4.7 M M
17000 -9.0 15.8 330 49 25 6.5 3.5 27.4 81.2 4.2 M M
16500 -7.5 18.5 330 47 24 6.7 3.7 26.5 79.8 3.5 M M
16000 -6.5 20.3 330 45 23 6.7 3.7 26.0 78.9 3.1 M M
15500 -5.5 22.1 329 42 22 6.6 3.6 25.5 78.0 2.7 M M
15000 -4.5 23.9 328 39 20 6.1 3.4 24.9 76.9 2.2 M M
14500 -3.6 25.5 327 35 18 6.2 3.4 24.4 75.8 1.7 M M
14000 -2.7 27.1 326 31 16 5.2 2.8 23.7 74.6 1.1 M M
13500 -1.9 28.6 325 26 13 5.2 2.8 22.9 73.3 0.5 M M
13000 -1.0 30.2 324 22 11 6.3 3.4 22.3 72.1 -0.1 586 3.0
12500 -0.1 31.8 322 18 9 6.3 3.5 21.7 71.1 -0.6 543 2.8
12000 0.8 33.4 319 14 7 5.4 3.0 21.1 70.0 -1.2 501 2.5
11500 1.6 34.9 317 11 6 5.4 2.9 20.4 68.7 -1.8 462 2.3
11000 2.4 36.3 317 10 5 5.2 2.9 19.7 67.5 -2.5 423 2.1
10500 3.2 37.8 322 10 5 5.1 2.8 19.0 66.2 -3.2 385 2.0
10250 3.6 38.5 325 10 5 5.8 3.2 18.6 65.5 -3.6 366 1.9
10000 4.1 39.4 327 10 5 7.2 3.9 18.4 65.1 -3.8 344 1.7
9750 4.6 40.3 329 11 6 7.4 4.1 18.2 64.7 -4.0 320 1.6
9500 5.2 41.4 330 12 6 7.3 4.0 18.0 64.4 -4.2 297 1.5
9250 5.7 42.3 331 12 6 7.6 4.1 17.8 64.1 -4.4 273 1.4
9000 6.3 43.3 330 13 7 7.8 4.3 17.7 63.8 -4.6 249 1.3
8750 6.9 44.4 328 14 7 7.8 4.3 17.5 63.5 -4.7 224 1.1
8500 7.5 45.5 327 15 8 7.8 4.3 17.4 63.2 -4.9 199 1.0
8250 8.0 46.4 326 16 8 7.5 4.1 17.2 63.0 -5.1 174 0.9
8000 8.6 47.5 322 17 9 7.2 3.9 17.0 62.6 -5.3 151 0.8
7750 9.1 48.4 318 18 10 7.6 4.2 16.8 62.3 -5.5 127 0.6
7500 9.6 49.3 315 20 10 6.3 3.5 16.6 62.0 -5.7 104 0.5
7250 10.0 50.0 312 20 11 3.3 1.8 16.3 61.3 -6.1 86 0.4
7000 10.2 50.4 307 21 11 1.6 0.9 15.7 60.2 -6.7 73 0.4
6750 10.3 50.5 303 21 11 4.3 2.4 15.1 59.2 -7.2 61 0.3
6500 10.5 50.9 299 21 11 -5.0 -2.8 14.6 58.2 -7.8 49 0.2
6250 9.5 49.1 293 18 9 -15.5 -8.5 12.9 55.1 -9.5 70 0.4
6000 8.5 47.3 286 16 8 -9.9 -5.4 11.1 52.1 -11.3 92 0.5
5750 7.6 45.7 275 13 7 -22.1 -12.1 9.5 49.0 -13.0 114 0.6
5500 4.7 40.5 257 9 5 -55.2 -30.3 5.8 42.4 -16.7 194 1.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/25/2008 at 0900 MDT | 10/25/2008 at 1200 MDT
|
K index... -1.2 | K index... +2.9
|
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 -66.8 -88.2 320 32 17 1.2 0.7 | -67.7 -89.9 307 28 15 0.9 0.5
45000 -64.6 -84.3 326 40 21 3.6 2.0 | -65.3 -85.5 321 41 21 4.6 2.5
40000 -58.9 -74.0 344 65 33 5.0 2.8 | -58.4 -73.1 337 57 29 6.0 3.3
38000 -54.4 -65.9 343 64 33 7.6 4.2 | -53.8 -64.8 337 58 30 7.6 4.2
36000 -49.9 -57.8 341 64 33 7.6 4.2 | -49.2 -56.6 337 58 30 7.6 4.2
34000 -45.1 -49.2 340 62 32 8.4 4.6 | -44.4 -47.9 335 57 30 8.2 4.5
32000 -40.1 -40.2 340 60 31 8.4 4.6 | -39.5 -39.1 332 56 29 8.2 4.5
30000 -34.6 -30.3 340 59 30 8.1 4.4 | -34.1 -29.4 331 53 28 8.0 4.4
29000 -32.2 -26.0 340 58 30 8.1 4.4 | -31.7 -25.1 330 52 27 8.0 4.4
28000 -29.8 -21.6 339 58 30 8.2 4.5 | -29.3 -20.7 330 51 26 8.1 4.5
27000 -27.6 -17.7 338 56 29 7.2 4.0 | -27.1 -16.8 330 50 26 7.3 4.0
26000 -25.4 -13.7 337 53 27 7.2 4.0 | -24.9 -12.8 329 50 26 7.4 4.0
25000 -23.3 -9.9 335 50 26 7.2 4.0 | -22.7 -8.9 329 49 25 7.3 4.0
24000 -21.2 -6.2 333 48 25 6.9 3.8 | -20.6 -5.1 329 49 25 6.6 3.6
23000 -19.1 -2.4 331 47 24 6.9 3.8 | -18.7 -1.7 329 50 25 6.6 3.6
22000 -17.1 1.2 329 45 23 6.9 3.8 | -16.7 1.9 329 50 26 6.6 3.6
21000 -15.2 4.6 329 46 24 5.8 3.2 | -14.8 5.4 330 50 26 6.3 3.4
20000 -13.5 7.7 330 50 26 5.7 3.2 | -13.0 8.6 330 50 26 6.3 3.4
19500 -12.7 9.1 331 52 27 5.8 3.2 | -12.1 10.2 330 50 26 6.3 3.4
19000 -11.8 10.8 331 53 27 5.8 3.2 | -11.1 12.0 331 50 25 6.1 3.4
18500 -11.0 12.2 332 53 27 5.9 3.2 | -10.3 13.5 330 49 25 5.3 2.9
18000 -10.1 13.8 333 53 27 5.8 3.2 | -9.5 14.9 330 48 25 5.3 2.9
17500 -9.2 15.4 333 52 27 6.6 3.6 | -8.7 16.3 329 47 24 5.7 3.1
17000 -8.2 17.2 334 51 26 6.8 3.7 | -7.5 18.5 328 44 23 5.7 3.1
16500 -6.7 19.9 336 49 25 7.2 4.0 | -6.6 20.1 328 42 22 6.5 3.6
16000 -5.6 21.9 336 47 24 7.3 4.0 | -5.6 21.9 327 40 20 6.6 3.6
15500 -4.5 23.9 337 45 23 7.5 4.1 | -4.6 23.7 327 37 19 6.9 3.8
15000 -3.4 25.9 338 43 22 7.7 4.2 | -3.5 25.7 327 35 18 7.2 4.0
14500 -2.2 28.0 339 41 21 7.5 4.1 | -2.4 27.7 327 33 17 7.3 4.0
14000 -1.2 29.8 339 39 20 6.6 3.6 | -1.3 29.7 327 31 16 7.3 4.0
13500 -0.2 31.6 339 36 19 6.7 3.7 | -0.2 31.6 327 29 15 7.3 4.0
13000 0.8 33.4 339 33 17 5.3 2.9 | 0.9 33.6 326 26 13 6.5 3.6
12500 1.6 34.9 338 28 15 5.5 3.0 | 1.9 35.4 325 23 12 6.7 3.7
12000 2.3 36.1 336 24 12 4.2 2.3 | 2.8 37.0 323 20 10 5.5 3.0
11500 3.0 37.4 332 19 10 4.3 2.4 | 3.6 38.5 319 16 8 5.7 3.1
11000 3.7 38.7 328 14 7 4.3 2.4 | 4.4 39.9 313 14 7 4.5 2.5
10500 4.3 39.7 325 11 5 4.2 2.3 | 5.1 41.2 305 12 6 4.3 2.4
10250 4.7 40.5 322 9 4 4.8 2.6 | 5.5 41.9 300 11 5 5.7 3.1
10000 5.0 41.0 321 8 4 5.4 3.0 | 6.0 42.8 300 11 5 7.2 3.9
9750 5.4 41.7 321 8 4 5.4 2.9 | 6.5 43.7 300 11 6 6.9 3.8
9500 5.8 42.4 320 8 4 5.2 2.8 | 7.1 44.8 300 11 6 7.0 3.8
9250 6.3 43.3 320 8 4 6.4 3.5 | 7.6 45.7 300 11 6 7.0 3.8
9000 6.8 44.2 322 8 4 7.6 4.2 | 8.1 46.6 301 12 6 7.0 3.9
8750 7.4 45.3 323 9 5 7.3 4.0 | 8.6 47.5 301 13 7 7.0 3.9
8500 7.9 46.2 324 9 5 7.3 4.0 | 9.2 48.6 301 15 8 7.0 3.8
8250 8.4 47.1 324 10 5 7.2 4.0 | 9.7 49.5 301 16 8 6.8 3.7
8000 9.0 48.2 322 11 6 7.1 3.9 | 10.2 50.4 299 16 8 6.7 3.7
7750 9.5 49.1 320 12 6 7.5 4.1 | 10.7 51.3 297 17 9 6.7 3.7
7500 10.0 50.0 318 14 7 5.8 3.2 | 11.2 52.2 296 18 9 6.7 3.7
7250 10.4 50.7 314 15 8 3.1 1.7 | 11.7 53.1 295 16 8 6.7 3.7
7000 10.6 51.1 309 16 8 2.9 1.6 | 12.2 54.0 294 14 7 6.7 3.7
6750 10.8 51.4 305 17 9 3.0 1.7 | 12.7 54.9 293 12 6 6.7 3.7
6500 10.8 51.4 301 17 9 -3.8 -2.1 | 13.2 55.8 292 10 5 7.4 4.0
6250 10.2 50.4 294 14 7 -9.2 -5.0 | 13.8 56.8 293 9 5 8.2 4.5
6000 9.6 49.3 284 11 6 -6.7 -3.7 | 14.3 57.7 294 8 4 7.0 3.9
5750 9.1 48.4 268 9 5 -11.1 -6.1 | 14.9 58.8 296 6 3 10.9 6.0
5500 7.8 46.0 249 7 4 -20.7 -11.4 | 16.1 61.0 294 6 3 21.2 11.7
10/25/2008 at 1500 MDT | 10/25/2008 at 1800 MDT
|
K index... +6.3 | K index... +8.7
|
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 -68.3 -90.9 294 28 14 1.0 0.5 | -69.4 -92.9 291 33 17 0.3 0.2
45000 -65.6 -86.1 313 41 21 4.9 2.7 | -67.6 -89.7 305 44 22 6.3 3.4
40000 -58.3 -72.9 325 52 27 6.5 3.6 | -57.8 -72.0 313 47 24 7.4 4.1
38000 -53.6 -64.5 327 50 26 7.8 4.3 | -53.2 -63.8 314 47 24 7.8 4.3
36000 -49.0 -56.2 329 48 25 7.8 4.3 | -48.5 -55.3 316 47 24 7.8 4.3
34000 -44.1 -47.4 328 48 25 8.3 4.6 | -43.7 -46.7 316 48 25 8.2 4.5
32000 -39.1 -38.4 325 49 25 8.4 4.6 | -38.8 -37.8 317 49 25 8.3 4.5
30000 -33.6 -28.5 324 49 25 8.0 4.4 | -34.1 -29.4 317 49 25 7.5 4.1
29000 -31.3 -24.3 324 49 25 8.0 4.4 | -31.3 -24.3 316 49 25 7.6 4.1
28000 -28.9 -20.0 324 49 25 8.0 4.4 | -29.1 -20.4 316 48 25 7.6 4.2
27000 -26.6 -15.9 325 48 25 7.6 4.2 | -26.9 -16.4 317 48 24 7.4 4.1
26000 -24.3 -11.7 326 48 25 7.6 4.2 | -24.7 -12.5 318 47 24 7.4 4.1
25000 -22.1 -7.8 327 48 25 7.6 4.2 | -22.5 -8.5 318 47 24 7.4 4.1
24000 -19.9 -3.8 328 48 24 7.2 3.9 | -20.3 -4.5 319 46 24 7.5 4.1
23000 -17.7 0.1 329 48 25 7.2 3.9 | -18.0 -0.4 318 45 23 7.6 4.1
22000 -15.6 3.9 330 48 25 7.2 3.9 | -15.8 3.6 318 44 23 7.6 4.2
21000 -13.7 7.3 330 48 24 6.1 3.3 | -13.6 7.5 319 45 23 7.1 3.9
20000 -11.9 10.6 329 47 24 6.1 3.3 | -11.5 11.3 321 47 24 7.1 3.9
19500 -11.0 12.2 328 46 24 6.1 3.3 | -10.5 13.1 322 48 25 7.1 3.9
19000 -10.1 13.8 327 46 24 5.8 3.2 | -9.4 15.1 323 49 25 6.9 3.8
18500 -9.4 15.1 327 45 23 4.3 2.4 | -8.5 16.7 324 49 25 6.4 3.5
18000 -8.8 16.2 327 43 22 4.4 2.4 | -7.5 18.5 324 49 25 6.5 3.5
17500 -8.1 17.4 326 41 21 4.9 2.7 | -6.6 20.1 324 48 25 6.1 3.3
17000 -7.4 18.7 325 38 20 5.1 2.8 | -5.7 21.7 324 47 24 6.1 3.3
16500 -6.2 20.8 324 35 18 5.7 3.2 | -4.8 23.4 324 45 23 5.9 3.2
16000 -5.3 22.5 322 33 17 5.8 3.2 | -3.6 25.5 323 39 20 5.5 3.0
15500 -4.5 23.9 321 31 16 5.9 3.3 | -2.8 27.0 322 35 18 4.9 2.7
15000 -3.6 25.5 319 29 15 6.0 3.3 | -2.1 28.2 321 30 16 4.6 2.5
14500 -2.7 27.1 317 27 14 6.1 3.4 | -1.4 29.5 318 25 13 4.6 2.5
14000 -1.7 28.9 314 24 12 6.4 3.5 | -0.8 30.6 318 21 11 4.8 2.6
13500 -0.7 30.7 311 21 11 6.4 3.5 | -0.0 32.0 319 17 9 4.8 2.6
13000 0.2 32.4 309 19 10 6.2 3.4 | 0.8 33.4 321 14 7 6.2 3.4
12500 1.2 34.2 306 16 8 6.2 3.4 | 1.7 35.1 326 12 6 6.1 3.4
12000 2.2 36.0 306 14 7 6.6 3.6 | 2.6 36.7 331 11 6 6.0 3.3
11500 3.1 37.6 310 13 6 6.4 3.5 | 3.5 38.3 335 11 6 5.9 3.3
11000 4.2 39.6 314 12 6 7.8 4.3 | 4.5 40.1 339 12 6 6.8 3.7
10500 5.4 41.7 317 13 7 7.7 4.2 | 5.5 41.9 341 13 7 6.4 3.5
10250 5.9 42.6 318 13 7 7.8 4.3 | 6.0 42.8 341 14 7 7.9 4.3
10000 6.5 43.7 315 15 8 7.9 4.3 | 6.7 44.1 339 15 8 9.5 5.2
9750 7.1 44.8 313 16 8 7.9 4.3 | 7.3 45.1 336 16 8 9.1 5.0
9500 7.7 45.9 311 18 9 7.9 4.3 | 8.0 46.4 334 17 9 9.2 5.1
9250 8.3 46.9 309 19 10 7.9 4.3 | 8.7 47.7 332 18 9 8.4 4.6
9000 8.9 48.0 307 20 10 8.0 4.4 | 9.3 48.7 326 20 10 7.7 4.2
8750 9.5 49.1 305 21 11 7.9 4.4 | 9.9 49.8 321 22 11 8.0 4.4
8500 10.0 50.0 303 22 11 8.0 4.4 | 10.5 50.9 316 24 12 7.7 4.2
8250 10.7 51.3 302 23 12 8.6 4.7 | 11.0 51.8 313 25 13 6.6 3.6
8000 11.3 52.3 301 22 11 9.0 5.0 | 11.5 52.7 311 25 13 6.2 3.4
7750 12.0 53.6 300 22 11 8.8 4.9 | 11.9 53.4 308 25 13 6.0 3.3
7500 12.6 54.7 300 21 11 9.2 5.0 | 12.4 54.3 305 25 13 7.0 3.9
7250 13.3 55.9 299 21 11 9.8 5.4 | 13.0 55.4 305 25 13 8.6 4.7
7000 14.1 57.4 300 21 11 9.8 5.4 | 13.6 56.5 305 24 12 8.8 4.8
6750 14.8 58.6 300 20 11 9.8 5.4 | 14.3 57.7 305 23 12 8.7 4.8
6500 15.6 60.1 300 20 10 10.1 5.6 | 14.9 58.8 305 21 11 9.1 5.0
6250 16.3 61.3 300 19 10 10.7 5.9 | 15.6 60.1 306 20 10 8.9 4.9
6000 17.1 62.8 300 19 10 9.9 5.4 | 16.3 61.3 306 18 9 10.2 5.6
5750 17.9 64.2 301 18 9 12.6 6.9 | 17.0 62.6 307 17 9 5.1 2.8
5500 19.1 66.4 301 16 8 20.5 11.2 | 16.8 62.2 306 13 7 -9.4 -5.2
________________________________________________________________________________
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:
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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