Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 051243
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
643 AM MDT Tuesday May 5, 2009
This forecast is for Tuesday May 5, 2009:
If the trigger temperature of 61.9 F/16.6 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 541 ft/min (2.7 m/s)
Maximum height of thermals.................. 16392 ft MSL (11107 ft AGL)
Forecast maximum temperature................... 74.0 F/23.8 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................. 15032 ft MSL (9747 ft AGL)
Thermal soaring outlook for Wednesday 05/06.... Excellent
Wave Soaring Index............................. Excellent
Wave Soaring Index trend (to 1800 MDT)......... Slight improvement
Height of stable layer (12-18K ft MSL)......... 14904 ft MSL (9619 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 22303 ft MSL (17018 ft AGL)
Wave soaring outlook for Wednesday 05/06....... Fair
Remarks... Moderate to strong westerly flow aloft with some embedded moisture.
Sunrise/Sunset.................... 05:55:02 / 19:57:02 MDT
Total possible sunshine........... 14 hr 1 min 59 sec (841 min 59 sec)
Altitude of sun at 12:56:13 MDT... 66.67 degrees
Upper air data from rawinsonde observation taken on 05/05/2009 at 0600 MDT
Freezing level.................. 10987 ft MSL (5702 ft AGL)
Convective condensation level... 12478 ft MSL (7193 ft AGL)
Lifted condensation level....... 14975 ft MSL (9690 ft AGL)
Lifted index.................... +1.9
K index......................... +18.9
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 -63.3 -81.9 298 52 27 6.6 3.6 93.7 200.6 40.2 M M
45000 -63.0 -81.4 275 72 37 5.0 2.8 68.5 155.3 27.8 M M
40000 -62.4 -80.3 283 97 50 7.2 3.9 46.3 115.4 15.2 M M
38000 -57.7 -71.9 285 85 44 8.0 4.4 44.5 112.1 14.4 M M
36000 -53.5 -64.3 285 73 38 9.0 5.0 42.1 107.8 13.1 M M
34000 -47.4 -53.3 279 64 33 8.9 4.9 41.2 106.1 12.8 M M
32000 -42.1 -43.8 276 59 30 8.9 4.9 40.4 104.8 12.6 M M
30000 -36.7 -34.1 279 55 28 9.2 5.0 40.1 104.2 12.6 M M
29000 -34.0 -29.2 278 54 28 9.2 5.0 39.8 103.6 12.5 M M
28000 -31.2 -24.2 277 52 27 8.5 4.7 39.6 103.3 12.6 M M
27000 -29.0 -20.2 276 51 26 7.5 4.1 38.7 101.7 12.0 M M
26000 -26.7 -16.1 275 50 26 7.4 4.1 37.9 100.3 11.5 M M
25000 -24.5 -12.1 275 46 24 7.7 4.2 37.1 98.7 10.9 M M
24000 -22.8 -9.0 280 40 20 4.5 2.5 35.5 96.0 9.8 M M
23000 -21.2 -6.2 289 36 19 5.8 3.2 34.0 93.1 8.6 M M
22000 -20.2 -4.4 275 38 19 -5.9 -3.2 31.7 89.0 6.7 M M
21000 -19.8 -3.6 283 36 18 5.3 2.9 28.7 83.6 4.3 M M
20000 -17.8 -0.0 294 34 18 6.7 3.7 27.6 81.6 3.4 M M
19500 -16.8 1.8 296 34 17 6.7 3.7 27.0 80.6 2.9 M M
19000 -15.8 3.6 298 33 17 6.7 3.7 26.5 79.6 2.4 M M
18500 -14.8 5.4 300 33 17 7.3 4.0 26.0 78.7 2.0 M M
18000 -13.7 7.3 304 31 16 7.7 4.2 25.6 78.1 1.7 M M
17500 -12.5 9.5 303 31 16 7.0 3.9 25.3 77.5 1.4 M M
17000 -11.2 11.8 299 31 16 6.2 3.4 24.4 75.8 0.5 M M
16500 -10.3 13.5 296 31 16 6.2 3.4 23.8 74.8 -0.0 940 4.8
16000 -9.4 15.1 293 31 16 5.4 3.0 23.2 73.8 -0.6 898 4.6
15500 -9.2 15.4 288 29 15 -1.0 -0.6 21.8 71.2 -1.8 877 4.5
15000 -9.3 15.3 282 28 14 -1.5 -0.8 20.1 68.1 -3.4 865 4.4
14500 -8.8 16.2 275 27 14 7.7 4.2 19.0 66.1 -4.5 838 4.3
14000 -7.8 18.0 270 25 13 7.1 3.9 18.5 65.3 -4.9 792 4.0
13500 -6.8 19.8 271 22 11 6.9 3.8 18.1 64.5 -5.4 746 3.8
13000 -5.6 21.9 273 18 9 9.4 5.2 17.8 64.0 -5.7 696 3.5
12500 -4.2 24.4 276 15 8 9.5 5.2 17.8 64.0 -5.7 639 3.2
12000 -2.7 27.1 279 12 6 9.5 5.2 17.7 63.9 -5.8 581 3.0
11500 -1.3 29.7 275 9 5 9.5 5.2 17.7 63.8 -5.9 524 2.7
11000 0.1 32.2 268 7 3 9.5 5.2 17.6 63.7 -6.0 467 2.4
10500 1.5 34.7 254 4 2 9.8 5.4 17.6 63.6 -6.1 410 2.1
10250 2.2 36.0 240 4 2 8.4 4.6 17.6 63.6 -6.1 381 1.9
10000 2.8 37.0 222 3 2 8.3 4.5 17.4 63.3 -6.3 357 1.8
9750 3.5 38.3 209 3 1 9.6 5.3 17.4 63.3 -6.4 329 1.7
9500 4.1 39.4 195 3 1 9.2 5.1 17.3 63.2 -6.4 301 1.5
9250 4.8 40.6 181 3 1 9.3 5.1 17.3 63.2 -6.5 272 1.4
9000 5.5 41.9 170 3 2 9.3 5.1 17.3 63.1 -6.5 244 1.2
8750 6.2 43.2 170 2 1 9.3 5.1 17.2 63.0 -6.6 216 1.1
8500 6.9 44.4 171 2 1 9.2 5.1 17.2 63.0 -6.6 188 1.0
8250 7.6 45.7 172 1 1 9.6 5.3 17.2 62.9 -6.7 160 0.8
8000 8.3 46.9 175 1 1 8.3 4.6 17.1 62.9 -6.7 132 0.7
7750 8.8 47.8 331 1 1 5.5 3.0 16.9 62.4 -7.0 109 0.6
7500 9.1 48.4 337 3 2 4.7 2.6 16.5 61.8 -7.4 91 0.5
7250 9.5 49.1 339 6 3 4.9 2.7 16.2 61.1 -7.8 74 0.4
7000 9.8 49.6 339 8 4 4.9 2.7 15.8 60.4 -8.2 56 0.3
6750 10.2 50.4 333 6 3 4.8 2.6 15.4 59.8 -8.6 38 0.2
6500 10.5 50.9 319 4 2 5.4 3.0 15.1 59.1 -9.0 20 0.1
6250 10.9 51.6 284 3 1 3.1 1.7 14.7 58.4 -9.4 2 0.0
6000 10.9 51.6 233 3 1 -1.1 -0.6 14.0 57.2 -10.2 M M
5750 10.7 51.3 203 2 1 -1.4 -0.7 13.1 55.7 -11.1 M M
5500 10.5 50.9 136 2 1 -2.8 -1.5 12.3 54.1 -12.1 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/05/2009 at 0900 MDT | 05/05/2009 at 1200 MDT
|
K index... +20.0 | K index... +21.2
|
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 -61.9 -79.4 277 46 24 0.7 0.4 | -60.8 -77.4 281 43 22 0.8 0.5
45000 -60.7 -77.3 282 65 34 1.1 0.6 | -59.5 -75.1 281 57 29 1.2 0.6
40000 -59.1 -74.4 279 78 40 1.2 0.7 | -57.8 -72.0 278 60 31 1.1 0.6
38000 -56.2 -69.2 279 75 39 6.4 3.5 | -55.8 -68.4 277 55 29 4.6 2.5
36000 -52.4 -62.3 279 69 36 6.4 3.5 | -53.0 -63.4 277 48 25 4.6 2.5
34000 -48.2 -54.8 278 63 33 8.0 4.4 | -49.8 -57.6 275 42 22 7.6 4.1
32000 -43.4 -46.1 276 56 29 8.0 4.4 | -44.6 -48.3 273 40 21 7.6 4.2
30000 -37.9 -36.2 274 52 27 8.7 4.8 | -40.0 -40.0 275 40 21 8.1 4.5
29000 -35.3 -31.5 274 52 27 8.7 4.8 | -37.5 -35.5 280 42 21 8.1 4.5
28000 -32.7 -26.9 274 52 27 8.7 4.8 | -35.1 -31.2 285 43 22 8.1 4.5
27000 -30.3 -22.5 275 52 27 6.3 3.5 | -32.6 -26.7 288 45 23 9.3 5.1
26000 -28.3 -18.9 278 50 26 6.6 3.6 | -29.9 -21.8 290 43 22 9.2 5.0
25000 -26.4 -15.5 281 48 25 6.6 3.6 | -27.1 -16.8 291 42 22 9.2 5.0
24000 -24.4 -11.9 284 47 24 5.7 3.1 | -24.5 -12.1 293 41 21 7.0 3.8
23000 -22.9 -9.2 285 43 22 5.1 2.8 | -22.7 -8.9 291 37 19 5.9 3.2
22000 -21.4 -6.5 285 39 20 5.1 2.8 | -21.0 -5.8 290 33 17 5.9 3.2
21000 -19.9 -3.8 284 35 18 5.7 3.1 | -19.3 -2.7 289 29 15 5.2 2.9
20000 -18.1 -0.6 283 33 17 5.8 3.2 | -17.8 -0.0 290 28 14 5.2 2.9
19500 -17.3 0.9 282 32 17 5.8 3.2 | -17.0 1.4 291 27 14 5.2 2.9
19000 -16.4 2.5 281 32 16 5.8 3.2 | -16.3 2.7 292 27 14 5.2 2.9
18500 -15.6 3.9 280 31 16 6.1 3.4 | -15.5 4.1 292 26 13 5.9 3.2
18000 -14.6 5.7 280 31 16 6.3 3.5 | -14.6 5.7 292 26 13 6.3 3.4
17500 -13.7 7.3 279 30 16 6.4 3.5 | -13.2 8.2 291 25 13 6.1 3.3
17000 -12.8 9.0 277 30 15 5.6 3.1 | -12.3 9.9 290 23 12 6.0 3.3
16500 -11.6 11.1 275 28 15 5.7 3.1 | -11.4 11.5 289 22 11 6.1 3.4
16000 -10.8 12.6 274 27 14 5.8 3.2 | -10.5 13.1 290 21 11 6.7 3.7
15500 -9.9 14.2 274 26 13 5.6 3.1 | -9.5 14.9 292 20 11 6.5 3.6
15000 -9.0 15.8 275 25 13 7.4 4.0 | -8.4 16.9 293 21 11 8.6 4.7
14500 -7.9 17.8 278 25 13 7.3 4.0 | -7.1 19.2 294 22 11 8.4 4.6
14000 -6.8 19.8 280 25 13 7.9 4.3 | -5.9 21.4 295 23 12 8.7 4.8
13500 -5.6 21.9 282 26 13 8.1 4.4 | -4.6 23.7 295 25 13 8.8 4.8
13000 -4.4 24.1 284 27 14 8.3 4.6 | -3.3 26.1 294 26 13 8.5 4.7
12500 -3.1 26.4 283 28 14 8.4 4.6 | -2.1 28.2 294 25 13 8.4 4.6
12000 -1.9 28.6 283 29 15 8.0 4.4 | -0.8 30.6 293 24 12 8.4 4.6
11500 -0.8 30.6 282 28 14 7.6 4.2 | 0.4 32.7 293 22 11 8.4 4.6
11000 0.3 32.5 280 27 14 7.9 4.4 | 1.6 34.9 292 20 10 8.8 4.9
10500 1.6 34.9 277 24 12 8.3 4.6 | 3.0 37.4 292 18 9 9.2 5.1
10250 2.2 36.0 275 23 12 8.3 4.6 | 3.7 38.7 292 17 9 9.3 5.1
10000 2.8 37.0 274 22 11 8.4 4.6 | 4.4 39.9 292 16 8 9.0 4.9
9750 3.4 38.1 272 20 10 8.4 4.6 | 5.1 41.2 292 15 8 8.8 4.8
9500 4.0 39.2 270 19 10 8.4 4.6 | 5.7 42.3 292 14 7 8.9 4.9
9250 4.6 40.3 268 18 9 8.4 4.6 | 6.4 43.5 292 12 6 8.8 4.8
9000 5.2 41.4 266 16 8 8.2 4.5 | 7.0 44.6 292 11 6 8.3 4.5
8750 5.9 42.6 265 15 8 8.1 4.5 | 7.6 45.7 291 10 5 8.0 4.4
8500 6.5 43.7 264 14 7 8.2 4.5 | 8.2 46.8 290 8 4 8.0 4.4
8250 7.1 44.8 263 13 7 8.0 4.4 | 8.8 47.8 288 7 4 8.2 4.5
8000 7.6 45.7 261 12 6 7.7 4.2 | 9.4 48.9 285 6 3 8.6 4.7
7750 8.2 46.8 259 10 5 7.6 4.1 | 10.0 50.0 281 5 3 8.7 4.8
7500 8.8 47.8 256 9 5 7.9 4.3 | 10.6 51.1 275 4 2 8.6 4.7
7250 9.4 48.9 251 8 4 6.8 3.7 | 11.3 52.3 266 3 2 9.1 5.0
7000 9.8 49.6 243 7 3 5.7 3.1 | 12.0 53.6 265 3 2 9.7 5.3
6750 10.2 50.4 232 6 3 6.1 3.4 | 12.7 54.9 264 3 1 9.6 5.2
6500 10.7 51.3 219 6 3 5.3 2.9 | 13.4 56.1 262 2 1 9.8 5.4
6250 11.0 51.8 206 5 3 3.2 1.7 | 14.2 57.6 261 2 1 10.5 5.8
6000 11.1 52.0 195 6 3 2.3 1.3 | 15.0 59.0 259 2 1 11.2 6.2
5750 11.2 52.2 185 6 3 2.4 1.3 | 15.8 60.4 258 2 1 9.9 5.4
5500 11.4 52.5 177 7 3 3.9 2.1 | 16.6 61.9 256 2 1 14.5 7.9
05/05/2009 at 1500 MDT | 05/05/2009 at 1800 MDT
|
K index... +25.5 | K index... +24.9
|
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 -59.6 -75.3 289 46 24 1.1 0.6 | -58.7 -73.7 290 45 23 1.0 0.5
45000 -57.9 -72.2 285 61 32 0.8 0.4 | -57.3 -71.1 298 70 36 -0.1 -0.0
40000 -56.7 -70.1 288 60 31 0.8 0.4 | -57.2 -71.0 303 81 42 0.0 0.0
38000 -55.4 -67.7 284 55 28 3.0 1.6 | -55.5 -67.9 305 82 42 4.6 2.5
36000 -53.6 -64.5 275 47 24 3.0 1.6 | -52.8 -63.0 306 80 41 4.6 2.5
34000 -50.6 -59.1 265 42 21 7.8 4.3 | -49.3 -56.7 306 75 38 6.3 3.5
32000 -45.9 -50.6 261 39 20 7.8 4.3 | -45.5 -49.9 301 63 33 6.3 3.5
30000 -41.1 -42.0 262 39 20 8.4 4.6 | -41.6 -42.9 296 55 28 7.1 3.9
29000 -38.6 -37.5 267 41 21 8.4 4.6 | -39.4 -38.9 294 53 27 7.1 3.9
28000 -36.1 -33.0 271 43 22 8.4 4.6 | -37.3 -35.1 292 50 26 7.1 3.9
27000 -33.6 -28.5 274 45 23 7.9 4.3 | -35.1 -31.2 290 48 25 8.2 4.5
26000 -31.3 -24.3 272 41 21 7.9 4.3 | -32.6 -26.7 289 47 24 8.3 4.5
25000 -28.9 -20.0 270 37 19 7.9 4.3 | -30.2 -22.4 289 45 23 8.3 4.6
24000 -26.6 -15.9 267 33 17 7.1 3.9 | -27.7 -17.9 289 43 22 7.9 4.3
23000 -24.6 -12.3 271 32 17 6.5 3.6 | -25.5 -13.9 288 39 20 7.6 4.2
22000 -22.7 -8.9 276 32 16 6.5 3.6 | -23.2 -9.8 288 34 18 7.6 4.2
21000 -20.8 -5.4 280 31 16 6.8 3.7 | -21.0 -5.8 287 30 16 6.7 3.7
20000 -18.7 -1.7 283 32 16 6.8 3.7 | -19.1 -2.4 289 30 15 6.6 3.6
19500 -17.7 0.1 285 32 16 6.8 3.7 | -18.1 -0.6 290 30 15 6.6 3.6
19000 -16.7 1.9 286 32 17 6.8 3.7 | -17.1 1.2 291 30 15 6.6 3.6
18500 -15.7 3.7 287 33 17 6.7 3.7 | -16.1 3.0 292 29 15 6.7 3.7
18000 -14.3 6.3 288 32 16 6.6 3.6 | -14.6 5.7 291 29 15 6.7 3.7
17500 -13.3 8.1 288 32 16 6.2 3.4 | -13.7 7.3 290 28 14 6.7 3.7
17000 -12.4 9.7 289 31 16 6.1 3.3 | -12.7 9.1 290 28 14 6.6 3.6
16500 -11.6 11.1 290 31 16 6.2 3.4 | -11.7 10.9 290 27 14 6.9 3.8
16000 -10.6 12.9 290 30 16 6.5 3.6 | -10.6 12.9 290 27 14 7.7 4.2
15500 -9.7 14.5 290 30 15 6.4 3.5 | -9.5 14.9 290 27 14 7.6 4.2
15000 -8.6 16.5 290 28 15 7.8 4.3 | -8.3 17.1 291 28 14 8.6 4.7
14500 -7.5 18.5 289 27 14 7.6 4.2 | -7.0 19.4 291 28 14 8.5 4.6
14000 -6.3 20.7 289 26 13 8.8 4.8 | -5.7 21.7 291 29 15 8.6 4.7
13500 -5.0 23.0 289 24 12 8.9 4.9 | -4.5 23.9 290 29 15 8.6 4.7
13000 -3.7 25.3 289 23 12 9.5 5.2 | -3.2 26.2 289 30 15 8.7 4.8
12500 -2.3 27.9 290 22 11 9.8 5.4 | -1.9 28.6 289 30 15 8.7 4.8
12000 -0.8 30.6 290 21 11 9.9 5.4 | -0.6 30.9 288 29 15 8.6 4.7
11500 0.7 33.3 290 20 10 9.9 5.4 | 0.6 33.1 286 28 15 8.5 4.7
11000 2.2 36.0 290 19 10 9.8 5.4 | 1.9 35.4 285 27 14 8.7 4.8
10500 3.6 38.5 291 18 9 9.7 5.3 | 3.1 37.6 284 26 13 8.7 4.8
10250 4.3 39.7 291 18 9 9.6 5.3 | 3.8 38.8 284 25 13 8.8 4.8
10000 5.0 41.0 291 17 9 9.7 5.3 | 4.4 39.9 283 24 12 9.0 5.0
9750 5.8 42.4 292 17 9 9.8 5.4 | 5.1 41.2 283 23 12 9.2 5.1
9500 6.5 43.7 292 16 8 9.8 5.4 | 5.8 42.4 283 23 12 9.2 5.0
9250 7.2 45.0 293 16 8 9.8 5.4 | 6.5 43.7 283 22 11 9.2 5.1
9000 8.0 46.4 293 15 8 9.9 5.4 | 7.1 44.8 283 21 11 9.3 5.1
8750 8.7 47.7 294 15 7 10.0 5.5 | 7.8 46.0 284 20 10 9.3 5.1
8500 9.4 48.9 295 14 7 10.0 5.5 | 8.5 47.3 285 20 10 9.3 5.1
8250 10.2 50.4 296 14 7 9.9 5.4 | 9.2 48.6 285 19 10 9.5 5.2
8000 10.9 51.6 296 13 7 9.8 5.4 | 9.9 49.8 286 18 9 9.9 5.4
7750 11.6 52.9 297 13 7 9.7 5.3 | 10.7 51.3 287 18 9 10.0 5.5
7500 12.3 54.1 298 12 6 9.8 5.4 | 11.4 52.5 288 17 9 10.0 5.5
7250 13.1 55.6 299 12 6 9.7 5.3 | 12.1 53.8 289 17 9 9.8 5.4
7000 13.8 56.8 300 12 6 9.6 5.3 | 12.9 55.2 290 16 8 9.6 5.3
6750 14.5 58.1 301 11 6 9.6 5.3 | 13.6 56.5 291 16 8 9.7 5.3
6500 15.2 59.4 303 11 5 9.6 5.3 | 14.3 57.7 292 15 8 9.6 5.3
6250 15.9 60.6 304 10 5 9.6 5.3 | 15.0 59.0 293 14 7 9.6 5.3
6000 16.6 61.9 305 9 5 9.6 5.3 | 15.7 60.3 295 13 7 9.5 5.2
5750 17.3 63.1 306 8 4 9.5 5.2 | 16.4 61.5 297 12 6 9.6 5.3
5500 18.0 64.4 307 7 4 10.0 5.5 | 17.2 63.0 299 11 6 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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