Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 100038
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
638 PM MDT Saturday May 9, 2009
This forecast is for Sunday May 10, 2009:
If the trigger temperature of 53.9 F/12.2 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 11293 ft MSL (5970 ft AGL)
Forecast maximum temperature................... 63.0 F/17.7 C
Time of trigger temperature.................... 1030 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................. 10299 ft MSL (4976 ft AGL)
Thermal soaring outlook for Monday 05/11....... Good
Wave Soaring Index............................. Excellent
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... 11975 ft MSL (6652 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 18134 ft MSL (12811 ft AGL)
Wave soaring outlook for Monday 05/11.......... Fair
Remarks...
Sunrise/Sunset.................... 05:49:36 / 20:01:56 MDT
Total possible sunshine........... 14 hr 12 min 20 sec (852 min 20 sec)
Altitude of sun at 12:55:58 MDT... 68.02 degrees
Upper air data from numerical model forecast valid on 05/10/2009 at 0600 MDT
Freezing level.................. 9421 ft MSL (4098 ft AGL)
Convective condensation level... 8639 ft MSL (3316 ft AGL)
Lifted condensation level....... 11225 ft MSL (5902 ft AGL)
Lifted index.................... -0.2
K index......................... +17.4
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 -59.1 -74.4 282 53 27 0.9 0.5 97.9 208.2 46.5 M M
45000 -57.8 -72.0 282 66 34 -0.0 -0.0 77.3 171.1 36.9 M M
40000 -57.7 -71.9 280 74 38 0.0 0.0 54.2 129.6 24.4 M M
38000 -56.2 -69.2 280 77 39 4.0 2.2 47.7 117.8 20.6 M M
36000 -53.8 -64.8 279 78 40 4.0 2.2 42.5 108.6 17.6 M M
34000 -50.2 -58.4 277 78 40 8.0 4.4 38.5 101.3 15.2 M M
32000 -45.4 -49.7 274 75 39 7.9 4.4 37.0 98.5 14.5 M M
30000 -40.9 -41.6 271 74 38 7.0 3.9 35.3 95.6 13.6 M M
29000 -38.8 -37.8 270 73 38 7.1 3.9 34.2 93.5 12.9 M M
28000 -36.7 -34.1 268 74 38 7.1 3.9 33.2 91.8 12.3 M M
27000 -34.5 -30.1 266 73 38 8.0 4.4 32.3 90.2 11.8 M M
26000 -32.1 -25.8 267 70 36 7.9 4.3 31.5 88.7 11.3 M M
25000 -29.8 -21.6 267 68 35 7.9 4.3 30.9 87.5 10.8 M M
24000 -27.4 -17.3 268 65 34 7.4 4.0 30.2 86.4 10.5 M M
23000 -25.3 -13.5 267 60 31 7.2 4.0 29.2 84.6 9.7 M M
22000 -23.1 -9.6 267 56 29 7.2 4.0 28.3 83.0 9.1 M M
21000 -20.9 -5.6 267 52 27 7.9 4.3 27.5 81.5 8.5 M M
20000 -18.6 -1.5 268 51 26 7.8 4.3 26.8 80.2 7.9 M M
19500 -17.4 0.7 269 50 26 7.8 4.3 26.4 79.6 7.7 M M
19000 -16.3 2.7 269 50 26 7.9 4.3 26.1 79.0 7.5 M M
18500 -14.6 5.7 272 50 26 7.1 3.9 25.6 78.0 7.0 M M
18000 -13.5 7.7 274 51 26 7.1 3.9 25.1 77.2 6.7 M M
17500 -12.5 9.5 276 51 26 7.7 4.2 24.7 76.5 6.3 M M
17000 -11.3 11.7 277 50 25 7.8 4.3 24.4 75.9 6.0 M M
16500 -10.2 13.6 278 48 25 7.5 4.1 24.0 75.3 5.8 M M
16000 -9.1 15.6 279 45 23 7.2 3.9 23.6 74.5 5.4 M M
15500 -8.0 17.6 279 43 22 7.2 3.9 23.2 73.7 5.0 M M
15000 -6.9 19.6 280 40 21 8.5 4.6 22.9 73.2 4.8 M M
14500 -5.6 21.9 280 37 19 8.3 4.6 22.6 72.7 4.6 M M
14000 -4.4 24.1 280 34 18 8.6 4.7 22.4 72.4 4.4 M M
13500 -3.1 26.4 280 31 16 8.8 4.8 22.2 72.0 4.2 M M
13000 -1.9 28.6 279 28 15 5.9 3.2 21.9 71.4 3.9 M M
12500 -1.2 29.8 278 25 13 5.6 3.1 21.2 70.1 3.2 M M
12000 -0.6 30.9 277 22 11 0.7 0.4 20.3 68.5 2.3 M M
11500 -0.9 30.4 276 18 10 -0.7 -0.4 18.6 65.4 0.6 M M
11000 -1.0 30.2 275 15 8 0.3 0.2 16.9 62.5 -1.0 365 1.9
10500 -1.0 30.2 273 11 6 0.5 0.3 15.5 59.9 -2.4 349 1.8
10250 -1.0 30.2 272 10 5 1.4 0.8 14.8 58.6 -3.1 341 1.7
10000 -0.8 30.6 271 8 4 4.0 2.2 14.2 57.6 -3.7 328 1.7
9750 -0.5 31.1 272 7 4 4.9 2.7 13.8 56.9 -4.1 311 1.6
9500 -0.1 31.8 272 6 3 4.7 2.6 13.4 56.2 -4.5 293 1.5
9250 0.2 32.4 273 5 2 4.5 2.5 13.0 55.5 -4.9 276 1.4
9000 0.5 32.9 279 4 2 4.1 2.2 12.6 54.7 -5.4 259 1.3
8750 0.8 33.4 288 4 2 4.1 2.2 12.1 53.9 -5.8 243 1.2
8500 1.1 34.0 298 4 2 4.1 2.2 11.7 53.1 -6.3 227 1.2
8250 1.4 34.5 308 4 2 4.0 2.2 11.3 52.3 -6.7 211 1.1
8000 1.7 35.1 324 4 2 3.9 2.2 10.8 51.5 -7.2 195 1.0
7750 2.0 35.6 338 4 2 3.9 2.2 10.4 50.7 -7.6 179 0.9
7500 2.3 36.1 349 5 3 4.0 2.2 9.9 49.9 -8.1 163 0.8
7250 2.5 36.5 359 6 3 4.1 2.3 9.5 49.1 -8.6 146 0.7
7000 2.9 37.2 006 8 4 4.2 2.3 9.1 48.3 -9.0 130 0.7
6750 3.2 37.8 011 10 5 4.1 2.2 8.6 47.5 -9.4 113 0.6
6500 3.5 38.3 013 11 6 6.5 3.6 8.3 46.9 -9.8 95 0.5
6250 4.1 39.4 010 11 6 8.6 4.7 8.1 46.6 -10.0 71 0.4
6000 4.6 40.3 008 11 6 7.6 4.2 8.0 46.4 -10.2 46 0.2
5750 5.2 41.4 006 11 5 9.7 5.3 7.9 46.2 -10.4 22 0.1
5500 6.1 43.0 004 9 5 14.3 7.8 8.0 46.5 -10.3 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/10/2009 at 0900 MDT | 05/10/2009 at 1200 MDT
|
K index... +18.1 | K index... +19.3
|
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 -59.4 -74.9 282 52 27 0.5 0.3 | -60.0 -76.0 284 54 28 0.5 0.3
45000 -58.6 -73.5 283 61 31 0.9 0.5 | -59.1 -74.4 284 61 31 2.2 1.2
40000 -57.4 -71.3 284 77 40 0.8 0.5 | -56.0 -68.8 285 82 42 2.1 1.1
38000 -55.5 -67.9 283 79 41 4.2 2.3 | -54.1 -65.4 286 84 43 3.8 2.1
36000 -52.7 -62.9 281 79 41 4.2 2.3 | -51.6 -60.9 287 83 43 3.8 2.1
34000 -49.4 -56.9 278 79 40 7.4 4.1 | -48.6 -55.5 286 84 43 6.7 3.7
32000 -45.0 -49.0 276 77 40 7.4 4.0 | -44.6 -48.3 282 85 44 6.7 3.7
30000 -40.5 -40.9 274 75 39 7.5 4.1 | -40.5 -40.9 281 84 43 7.2 4.0
29000 -38.3 -36.9 273 74 38 7.5 4.1 | -38.3 -36.9 282 81 42 7.2 4.0
28000 -36.0 -32.8 273 72 37 7.5 4.1 | -36.1 -33.0 283 78 40 7.2 4.0
27000 -33.8 -28.8 273 71 36 6.9 3.8 | -34.0 -29.2 284 75 38 6.7 3.7
26000 -31.7 -25.1 275 68 35 7.0 3.8 | -32.0 -25.6 284 71 36 6.7 3.7
25000 -29.6 -21.3 277 66 34 7.0 3.8 | -30.0 -22.0 283 67 35 6.7 3.7
24000 -27.5 -17.5 279 65 33 6.5 3.6 | -27.9 -18.2 283 64 33 6.6 3.6
23000 -25.7 -14.3 279 64 33 6.3 3.4 | -26.0 -14.8 282 63 32 6.6 3.6
22000 -23.8 -10.8 280 64 33 6.3 3.4 | -24.0 -11.2 281 62 32 6.6 3.6
21000 -21.9 -7.4 280 64 33 7.4 4.1 | -22.0 -7.6 280 61 31 7.0 3.8
20000 -19.7 -3.5 281 63 32 7.4 4.0 | -19.9 -3.8 278 57 29 7.0 3.8
19500 -18.6 -1.5 282 62 32 7.4 4.0 | -18.9 -2.0 277 55 28 7.0 3.8
19000 -17.0 1.4 283 61 31 7.5 4.1 | -17.4 0.7 276 52 27 7.1 3.9
18500 -15.8 3.6 282 58 30 8.0 4.4 | -16.3 2.7 275 49 25 7.3 4.0
18000 -14.6 5.7 281 55 28 8.0 4.4 | -15.3 4.5 272 46 24 7.2 4.0
17500 -13.5 7.7 280 52 27 7.7 4.2 | -14.1 6.6 270 43 22 9.0 4.9
17000 -12.3 9.9 278 48 25 7.7 4.2 | -12.8 9.0 269 41 21 9.2 5.0
16500 -11.2 11.8 275 45 23 8.1 4.5 | -11.4 11.5 268 39 20 9.2 5.0
16000 -9.9 14.2 274 42 22 8.6 4.7 | -10.1 13.8 267 37 19 9.1 5.0
15500 -8.7 16.3 271 39 20 8.7 4.8 | -8.7 16.3 267 35 18 9.0 5.0
15000 -7.3 18.9 270 36 19 9.4 5.2 | -7.5 18.5 268 32 17 7.7 4.2
14500 -5.9 21.4 270 34 18 9.5 5.2 | -6.4 20.5 268 30 15 8.0 4.4
14000 -4.6 23.7 269 32 16 7.9 4.3 | -5.4 22.3 269 27 14 6.0 3.3
13500 -3.4 25.9 269 29 15 8.3 4.5 | -4.5 23.9 271 24 13 6.3 3.4
13000 -2.5 27.5 269 25 13 4.0 2.2 | -3.7 25.3 272 22 11 4.2 2.3
12500 -2.0 28.4 270 22 11 3.6 2.0 | -3.1 26.4 275 19 10 4.2 2.3
12000 -1.6 29.1 272 19 10 1.7 0.9 | -2.7 27.1 278 16 8 1.5 0.8
11500 -1.5 29.3 274 16 8 1.3 0.7 | -2.6 27.3 282 13 7 1.0 0.5
11000 -1.4 29.5 276 13 7 0.3 0.2 | -2.4 27.7 289 10 5 1.7 0.9
10500 -1.4 29.5 276 10 5 -0.1 -0.0 | -2.2 28.0 297 8 4 1.6 0.9
10250 -1.5 29.3 277 9 4 1.0 0.5 | -2.1 28.2 303 6 3 2.6 1.4
10000 -1.3 29.7 278 8 4 3.2 1.7 | -1.8 28.8 309 5 3 4.3 2.3
9750 -1.1 30.0 281 7 3 3.7 2.0 | -1.5 29.3 316 5 2 4.5 2.5
9500 -0.8 30.6 284 6 3 3.5 1.9 | -1.2 29.8 325 4 2 4.3 2.4
9250 -0.6 30.9 289 5 3 3.8 2.1 | -0.8 30.6 338 3 2 4.8 2.6
9000 -0.3 31.5 297 5 2 4.2 2.3 | -0.5 31.1 351 4 2 5.2 2.9
8750 0.0 32.0 306 5 2 4.2 2.3 | -0.1 31.8 003 4 2 5.1 2.8
8500 0.3 32.5 315 5 2 4.1 2.3 | 0.3 32.5 013 4 2 5.1 2.8
8250 0.6 33.1 324 5 2 3.6 2.0 | 0.6 33.1 020 5 2 4.9 2.7
8000 0.9 33.6 333 5 3 3.3 1.8 | 1.0 33.8 022 6 3 4.9 2.7
7750 1.1 34.0 341 6 3 3.2 1.7 | 1.4 34.5 024 6 3 4.5 2.5
7500 1.3 34.3 346 7 3 3.9 2.1 | 1.7 35.1 025 7 4 6.2 3.4
7250 1.7 35.1 355 8 4 5.1 2.8 | 2.3 36.1 021 7 4 8.4 4.6
7000 2.1 35.8 002 9 5 5.1 2.8 | 2.8 37.0 015 7 4 8.2 4.5
6750 2.5 36.5 008 10 5 5.3 2.9 | 3.4 38.1 010 7 4 8.6 4.7
6500 2.9 37.2 010 11 6 6.6 3.6 | 4.1 39.4 006 7 4 9.6 5.3
6250 3.4 38.1 005 11 5 7.8 4.3 | 4.9 40.8 004 7 4 10.3 5.6
6000 3.9 39.0 360 10 5 6.4 3.5 | 5.6 42.1 002 7 4 9.4 5.2
5750 4.4 39.9 355 10 5 11.0 6.0 | 6.4 43.5 360 7 4 14.1 7.7
5500 5.6 42.1 353 9 5 21.7 11.9 | 7.8 46.0 001 7 3 23.8 13.0
05/10/2009 at 1500 MDT | 05/10/2009 at 1800 MDT
|
K index... +17.8 | K index... +18.1
|
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 -59.5 -75.1 280 57 29 -0.1 -0.1 | -59.7 -75.5 284 58 30 -0.4 -0.2
45000 -59.5 -75.1 286 70 36 1.6 0.9 | -60.2 -76.4 288 76 39 0.8 0.5
40000 -57.3 -71.1 289 91 47 1.5 0.8 | -59.1 -74.4 297 98 51 0.8 0.4
38000 -55.1 -67.2 289 94 48 5.0 2.7 | -56.0 -68.8 298 102 52 7.2 4.0
36000 -51.7 -61.1 290 94 48 5.0 2.7 | -51.1 -60.0 298 102 53 7.2 4.0
34000 -48.4 -55.1 290 93 48 6.5 3.6 | -47.0 -52.6 297 100 52 6.5 3.6
32000 -44.4 -47.9 287 90 46 6.5 3.6 | -43.0 -45.4 292 94 49 6.5 3.6
30000 -40.4 -40.7 285 86 44 7.1 3.9 | -39.1 -38.4 289 90 46 6.5 3.6
29000 -38.3 -36.9 284 83 43 7.1 3.9 | -37.1 -34.8 289 87 45 6.5 3.6
28000 -36.2 -33.2 284 80 41 7.1 3.9 | -35.2 -31.4 289 85 44 6.5 3.6
27000 -34.1 -29.4 284 77 39 7.1 3.9 | -33.2 -27.8 288 82 42 6.5 3.6
26000 -31.9 -25.4 283 73 38 7.1 3.9 | -31.3 -24.3 288 77 39 6.5 3.6
25000 -29.8 -21.6 283 70 36 7.1 3.9 | -29.3 -20.7 287 71 37 6.5 3.6
24000 -27.7 -17.9 282 66 34 6.7 3.7 | -27.4 -17.3 286 66 34 6.6 3.6
23000 -25.7 -14.3 280 63 32 6.6 3.6 | -25.4 -13.7 285 63 32 6.6 3.6
22000 -23.7 -10.7 279 59 31 6.5 3.6 | -23.4 -10.1 283 60 31 6.6 3.6
21000 -21.8 -7.2 277 56 29 6.8 3.7 | -21.4 -6.5 281 57 29 7.3 4.0
20000 -19.7 -3.5 275 52 27 6.8 3.7 | -19.3 -2.7 279 51 26 7.2 4.0
19500 -18.7 -1.7 273 50 26 6.8 3.8 | -18.2 -0.8 277 49 25 7.2 4.0
19000 -17.2 1.0 271 47 24 7.3 4.0 | -16.6 2.1 275 45 23 7.5 4.1
18500 -16.0 3.2 269 45 23 8.7 4.8 | -15.4 4.3 273 43 22 8.2 4.5
18000 -14.8 5.4 268 42 22 8.7 4.8 | -14.2 6.4 271 41 21 8.2 4.5
17500 -13.5 7.7 267 41 21 9.0 5.0 | -13.0 8.6 270 39 20 9.1 5.0
17000 -12.1 10.2 267 39 20 9.1 5.0 | -11.6 11.1 270 38 19 9.2 5.0
16500 -10.8 12.6 267 38 19 9.1 5.0 | -10.3 13.5 271 36 19 9.3 5.1
16000 -9.5 14.9 267 36 19 9.1 5.0 | -8.9 16.0 272 35 18 9.3 5.1
15500 -8.1 17.4 268 35 18 9.0 4.9 | -7.5 18.5 272 34 18 9.1 5.0
15000 -6.9 19.6 269 33 17 7.5 4.1 | -6.4 20.5 273 32 16 7.1 3.9
14500 -5.8 21.6 269 30 16 8.1 4.4 | -5.4 22.3 274 29 15 7.9 4.3
14000 -5.0 23.0 270 27 14 3.5 1.9 | -4.7 23.5 275 26 14 1.2 0.6
13500 -4.4 24.1 271 24 12 4.1 2.2 | -4.5 23.9 276 23 12 1.7 0.9
13000 -4.1 24.6 273 20 10 0.2 0.1 | -4.3 24.3 277 19 10 2.2 1.2
12500 -4.2 24.4 276 16 8 -0.3 -0.2 | -4.0 24.8 278 15 8 2.1 1.2
12000 -4.1 24.6 280 12 6 3.2 1.8 | -3.6 25.5 278 12 6 4.7 2.6
11500 -3.5 25.7 285 8 4 3.8 2.1 | -2.8 27.0 275 9 4 5.0 2.8
11000 -2.9 26.8 293 5 3 5.1 2.8 | -2.1 28.2 268 6 3 5.4 2.9
10500 -2.1 28.2 307 3 2 5.3 2.9 | -1.3 29.7 253 4 2 5.4 3.0
10250 -1.8 28.8 324 2 1 5.3 2.9 | -0.9 30.4 241 4 2 5.4 2.9
10000 -1.4 29.5 349 1 1 5.2 2.9 | -0.5 31.1 226 3 2 5.2 2.9
9750 -1.0 30.2 043 1 1 5.3 2.9 | -0.1 31.8 204 3 1 5.4 3.0
9500 -0.6 30.9 083 2 1 5.1 2.8 | 0.3 32.5 177 3 1 4.8 2.6
9250 -0.2 31.6 098 3 1 5.7 3.1 | 0.6 33.1 155 3 2 7.0 3.8
9000 0.2 32.4 084 3 1 6.3 3.5 | 1.3 34.3 146 3 2 9.2 5.0
8750 0.6 33.1 074 3 2 6.1 3.3 | 1.9 35.4 138 3 2 8.6 4.7
8500 1.1 34.0 066 4 2 6.5 3.6 | 2.5 36.5 131 3 2 8.9 4.9
8250 1.6 34.9 061 4 2 8.5 4.7 | 3.2 37.8 127 4 2 9.5 5.2
8000 2.3 36.1 059 4 2 9.7 5.3 | 3.9 39.0 127 4 2 9.9 5.4
7750 3.0 37.4 057 4 2 9.3 5.1 | 4.7 40.5 127 4 2 9.8 5.4
7500 3.7 38.7 054 4 2 9.7 5.3 | 5.4 41.7 127 4 2 9.9 5.4
7250 4.4 39.9 052 4 2 10.0 5.5 | 6.2 43.2 127 4 2 10.0 5.5
7000 5.2 41.4 050 4 2 10.0 5.5 | 6.9 44.4 128 4 2 10.0 5.5
6750 5.9 42.6 048 3 2 10.1 5.5 | 7.7 45.9 129 4 2 10.0 5.5
6500 6.7 44.1 046 3 2 10.4 5.7 | 8.4 47.1 129 4 2 10.1 5.5
6250 7.5 45.5 044 3 2 11.0 6.0 | 9.2 48.6 129 4 2 10.4 5.7
6000 8.3 46.9 043 3 2 9.7 5.3 | 9.9 49.8 129 4 2 9.5 5.2
5750 9.1 48.4 041 3 1 14.2 7.8 | 10.7 51.3 129 4 2 12.7 7.0
5500 10.5 50.9 038 3 2 24.8 13.6 | 11.9 53.4 127 4 2 20.5 11.3
________________________________________________________________________________
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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