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Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 100033
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
533 PM MST Tuesday February 9, 2010
This forecast is for Wednesday February 10, 2010:
If the trigger temperature of 42.1 F/5.6 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 252 ft/min (1.3 m/s)
Maximum height of thermals.................. 8949 ft MSL (3626 ft AGL)
Forecast maximum temperature................... 41.0 F/5.5 C
Time of trigger temperature.................... 1415 MST
Time of overdevelopment........................ 1700 MST
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 7173 ft MSL (1849 ft AGL)
Thermal soaring outlook for Thursday 02/11..... 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....................... 34184 ft MSL (28861 ft AGL)
Wave soaring outlook for Thursday 02/11........ Poor
Remarks... None
Sunrise/Sunset.................... 06:57:49 / 17:28:41 MST
Total possible sunshine........... 10 hr 30 min 52 sec (630 min 52 sec)
Altitude of sun at 12:13:35 MST... 36.08 degrees
Upper air data from numerical model forecast valid on 02/10/2010 at 0500 MST
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 16184 ft MSL (10861 ft AGL)
Lifted condensation level....... 13679 ft MSL (8356 ft AGL)
Lifted index.................... +6.5
K index......................... +0.9
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 -54.7 -66.5 269 39 20 1.1 0.6 110.4 230.8 60.0 M M
45000 -53.1 -63.6 263 48 25 1.1 0.6 89.5 193.1 51.3 M M
40000 -51.7 -61.1 262 56 29 0.9 0.5 68.2 154.7 41.0 M M
38000 -51.2 -60.2 262 58 30 -1.8 -1.0 59.6 139.2 36.4 M M
36000 -52.4 -62.3 263 53 27 -2.0 -1.1 48.6 119.5 29.9 M M
34000 -53.6 -64.5 265 47 24 -2.0 -1.1 38.8 101.8 23.8 M M
32000 -54.1 -65.4 269 40 20 -0.3 -0.2 29.7 85.5 17.9 M M
30000 -54.3 -65.7 275 32 16 -0.2 -0.1 21.5 70.8 12.3 M M
29000 -53.1 -63.6 278 29 15 8.0 4.4 19.3 66.8 10.8 M M
28000 -50.6 -59.1 280 28 15 8.2 4.5 18.6 65.5 10.4 M M
27000 -48.2 -54.8 282 27 14 8.2 4.5 18.1 64.5 10.1 M M
26000 -45.7 -50.3 285 27 14 8.6 4.7 17.6 63.7 9.9 M M
25000 -43.1 -45.6 286 26 13 8.6 4.7 17.1 62.7 9.6 M M
24000 -40.5 -40.9 287 26 13 8.6 4.7 16.7 62.0 9.3 M M
23000 -38.0 -36.4 289 25 13 7.6 4.2 16.2 61.2 9.1 M M
22000 -35.7 -32.3 289 25 13 7.6 4.2 15.4 59.7 8.5 M M
21000 -33.4 -28.1 290 24 12 7.7 4.2 14.6 58.3 8.0 M M
20000 -30.3 -22.5 289 23 12 8.7 4.7 13.9 57.1 7.5 M M
19500 -29.0 -20.2 287 22 12 8.7 4.7 13.7 56.7 7.4 M M
19000 -27.7 -17.9 286 22 11 8.7 4.8 13.5 56.4 7.3 M M
18500 -26.4 -15.5 285 22 11 8.7 4.8 13.4 56.1 7.2 M M
18000 -25.1 -13.2 285 21 11 8.3 4.5 13.2 55.7 7.1 M M
17500 -23.9 -11.0 286 21 11 8.3 4.5 12.9 55.3 6.9 M M
17000 -22.7 -8.9 287 21 11 7.8 4.3 12.7 54.8 6.7 M M
16500 -21.6 -6.9 288 21 11 7.5 4.1 12.3 54.1 6.3 M M
16000 -20.4 -4.7 290 21 11 7.4 4.1 11.9 53.4 6.0 M M
15500 -19.4 -2.9 292 21 11 7.1 3.9 11.4 52.6 5.7 M M
15000 -18.3 -0.9 294 21 11 7.1 3.9 11.0 51.8 5.3 M M
14500 -17.3 0.9 294 21 11 6.7 3.6 10.5 50.9 4.9 M M
14000 -16.3 2.7 295 21 11 6.6 3.6 10.0 50.0 4.4 M M
13500 -15.3 4.5 295 20 11 7.4 4.1 9.6 49.2 4.0 M M
13000 -14.2 6.4 295 20 10 7.4 4.1 9.2 48.5 3.7 M M
12500 -13.0 8.6 294 20 10 7.4 4.1 8.8 47.8 3.4 M M
12000 -11.9 10.6 294 20 10 7.4 4.1 8.4 47.1 3.0 M M
11500 -10.8 12.6 293 20 10 7.4 4.0 8.0 46.5 2.7 M M
11000 -9.7 14.5 293 20 10 7.4 4.1 7.7 45.8 2.3 M M
10500 -8.7 16.3 292 19 10 6.6 3.6 7.2 45.0 1.9 M M
10250 -8.2 17.2 292 18 9 6.7 3.7 7.0 44.6 1.7 M M
10000 -7.7 18.1 292 18 9 6.7 3.7 6.7 44.1 1.5 M M
9750 -7.2 19.0 291 17 9 5.6 3.1 6.5 43.6 1.2 M M
9500 -6.8 19.8 291 15 8 4.7 2.6 6.1 43.0 0.8 M M
9250 -6.5 20.3 291 14 7 5.0 2.7 5.7 42.3 0.5 M M
9000 -6.1 21.0 291 12 6 4.7 2.6 5.3 41.6 0.1 M M
8750 -5.8 21.6 290 11 6 4.3 2.4 4.9 40.9 -0.3 240 1.2
8500 -5.5 22.1 290 10 5 4.2 2.3 4.5 40.1 -0.7 223 1.1
8250 -5.2 22.6 290 8 4 4.1 2.3 4.0 39.3 -1.1 207 1.1
8000 -4.9 23.2 290 7 4 4.4 2.4 3.6 38.5 -1.6 190 1.0
7750 -4.5 23.9 292 7 4 4.7 2.6 3.2 37.8 -2.0 172 0.9
7500 -4.2 24.4 293 7 3 4.8 2.6 2.8 37.1 -2.4 155 0.8
7250 -3.8 25.2 295 6 3 4.1 2.2 2.4 36.4 -2.7 137 0.7
7000 -3.6 25.5 294 6 3 2.5 1.3 1.9 35.5 -3.3 122 0.6
6750 -3.4 25.9 290 5 3 2.2 1.2 1.4 34.4 -3.8 110 0.6
6500 -3.3 26.1 285 4 2 1.8 1.0 0.8 33.4 -4.4 98 0.5
6250 -3.4 25.9 272 4 2 -6.7 -3.7 -0.1 31.9 -5.3 94 0.5
6000 -4.2 24.4 247 5 2 -13.7 -7.5 -1.7 29.0 -6.9 112 0.6
5750 -5.1 22.8 233 6 3 -8.6 -4.7 -3.3 26.0 -8.5 131 0.7
5500 -6.0 21.2 224 8 4 -24.7 -13.6 -5.0 23.0 -10.2 152 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
02/10/2010 at 0800 MST | 02/10/2010 at 1100 MST
|
K index... +6.1 | K index... +6.8
|
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 -54.4 -65.9 274 39 20 0.9 0.5 | -54.7 -66.5 272 38 19 1.2 0.6
45000 -53.0 -63.4 266 48 25 0.9 0.5 | -52.9 -63.2 268 48 25 1.2 0.6
40000 -51.9 -61.4 266 52 27 0.7 0.4 | -52.2 -62.0 266 49 25 0.3 0.2
38000 -51.5 -60.7 266 53 27 -1.4 -0.7 | -52.0 -61.6 265 48 25 -0.7 -0.4
36000 -52.8 -63.0 266 48 25 -2.1 -1.2 | -52.6 -62.7 264 46 24 -1.0 -0.5
34000 -54.1 -65.4 266 43 22 -2.1 -1.2 | -53.2 -63.8 263 44 23 -1.0 -0.5
32000 -54.6 -66.3 268 36 19 -0.1 -0.1 | -53.8 -64.8 264 37 19 -1.0 -0.6
30000 -54.6 -66.3 273 29 15 0.1 0.0 | -54.5 -66.1 269 27 14 -1.8 -1.0
29000 -53.0 -63.4 276 27 14 8.2 4.5 | -53.0 -63.4 271 26 13 8.2 4.5
28000 -50.5 -58.9 278 27 14 8.3 4.5 | -50.5 -58.9 272 26 13 8.2 4.5
27000 -48.1 -54.6 279 27 14 8.3 4.5 | -48.0 -54.4 274 26 14 8.2 4.5
26000 -45.6 -50.1 281 27 14 8.6 4.7 | -45.5 -49.9 276 26 14 8.7 4.8
25000 -43.0 -45.4 283 27 14 8.5 4.7 | -42.9 -45.2 279 26 13 8.7 4.7
24000 -40.5 -40.9 286 26 14 8.5 4.7 | -40.4 -40.7 283 26 13 8.7 4.7
23000 -38.0 -36.4 288 26 13 8.0 4.4 | -37.8 -36.0 286 25 13 8.1 4.4
22000 -35.5 -31.9 289 24 13 8.1 4.4 | -35.4 -31.7 289 23 12 8.1 4.5
21000 -33.1 -27.6 290 23 12 8.1 4.4 | -33.0 -27.4 292 22 11 8.1 4.5
20000 -30.7 -23.3 290 22 11 8.3 4.6 | -30.5 -22.9 292 20 11 8.5 4.7
19500 -29.4 -20.9 290 21 11 8.3 4.6 | -29.2 -20.6 291 20 10 8.6 4.7
19000 -28.2 -18.8 290 20 11 8.4 4.6 | -27.9 -18.2 290 19 10 8.6 4.7
18500 -26.9 -16.4 289 20 10 8.3 4.6 | -26.6 -15.9 288 18 9 8.6 4.7
18000 -25.7 -14.3 289 19 10 7.9 4.3 | -25.4 -13.7 287 18 9 7.9 4.3
17500 -24.6 -12.3 289 18 10 7.6 4.2 | -24.2 -11.6 285 17 9 7.5 4.1
17000 -23.5 -10.3 289 18 9 7.5 4.1 | -23.1 -9.6 284 17 9 7.4 4.0
16500 -22.4 -8.3 289 18 9 7.2 4.0 | -22.1 -7.8 284 17 9 6.7 3.7
16000 -20.8 -5.4 291 18 9 7.4 4.1 | -20.6 -5.1 285 16 8 6.9 3.8
15500 -19.6 -3.3 292 18 9 7.6 4.1 | -19.6 -3.3 288 16 8 7.1 3.9
15000 -18.5 -1.3 294 18 9 7.5 4.1 | -18.5 -1.3 292 17 9 7.2 3.9
14500 -17.4 0.7 294 19 10 7.2 3.9 | -17.4 0.7 295 17 9 7.5 4.1
14000 -16.3 2.7 295 19 10 7.2 4.0 | -16.3 2.7 297 18 9 7.5 4.1
13500 -15.3 4.5 296 20 11 7.2 4.0 | -15.2 4.6 299 19 10 7.3 4.0
13000 -14.2 6.4 296 22 11 7.2 4.0 | -14.1 6.6 299 21 11 7.3 4.0
12500 -13.1 8.4 296 23 12 7.2 3.9 | -13.0 8.6 298 22 11 7.5 4.1
12000 -12.1 10.2 296 24 12 7.1 3.9 | -11.9 10.6 297 24 12 7.5 4.1
11500 -11.0 12.2 296 24 12 7.9 4.3 | -10.8 12.6 295 24 13 7.3 4.0
11000 -9.8 14.4 296 24 12 7.9 4.3 | -9.8 14.4 294 24 12 7.3 4.0
10500 -8.8 16.2 296 22 11 6.4 3.5 | -8.7 16.3 293 23 12 7.2 4.0
10250 -8.3 17.1 296 21 11 6.6 3.6 | -8.2 17.2 292 22 11 7.2 4.0
10000 -7.8 18.0 297 20 10 6.4 3.5 | -7.6 18.3 292 21 11 7.2 4.0
9750 -7.3 18.9 297 18 9 5.7 3.1 | -7.1 19.2 291 20 10 7.2 4.0
9500 -6.9 19.6 298 16 8 5.3 2.9 | -6.6 20.1 291 19 10 7.2 3.9
9250 -6.5 20.3 299 15 8 5.6 3.0 | -6.0 21.2 291 17 9 7.3 4.0
9000 -6.1 21.0 300 13 7 5.0 2.7 | -5.5 22.1 291 16 8 6.8 3.7
8750 -5.8 21.6 300 12 6 4.2 2.3 | -5.0 23.0 290 14 7 6.1 3.3
8500 -5.5 22.1 301 10 5 4.2 2.3 | -4.6 23.7 290 13 7 6.1 3.3
8250 -5.2 22.6 301 9 4 4.2 2.3 | -4.1 24.6 289 12 6 6.0 3.3
8000 -4.9 23.2 301 7 4 4.1 2.2 | -3.7 25.3 289 10 5 5.4 3.0
7750 -4.6 23.7 302 7 4 3.9 2.1 | -3.3 26.1 288 9 5 4.8 2.6
7500 -4.3 24.3 303 7 3 4.3 2.4 | -2.9 26.8 287 8 4 5.3 2.9
7250 -4.0 24.8 304 6 3 2.9 1.6 | -2.6 27.3 286 7 3 4.0 2.2
7000 -3.9 25.0 304 5 3 0.7 0.4 | -2.3 27.9 283 5 3 2.1 1.1
6750 -3.8 25.2 304 5 3 1.0 0.5 | -2.2 28.0 277 4 2 2.2 1.2
6500 -3.8 25.2 304 4 2 -0.6 -0.3 | -2.0 28.4 268 3 2 1.4 0.8
6250 -4.0 24.8 292 4 2 -7.6 -4.2 | -2.1 28.2 248 3 1 -2.4 -1.3
6000 -4.8 23.4 260 4 2 -11.0 -6.0 | -2.4 27.7 218 3 1 -4.5 -2.4
5750 -5.6 21.9 238 5 3 -10.5 -5.8 | -2.7 27.1 195 4 2 -3.8 -2.1
5500 -6.7 19.9 225 6 3 -24.4 -13.4 | -2.9 26.8 183 4 2 0.0 0.0
02/10/2010 at 1400 MST | 02/10/2010 at 1700 MST
|
K index... +10.3 | K index... +13.0
|
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 -54.3 -65.7 274 37 19 0.6 0.3 | -55.0 -67.0 277 38 19 0.8 0.4
45000 -53.4 -64.1 271 47 24 0.6 0.3 | -53.8 -64.8 269 43 22 0.8 0.4
40000 -52.2 -62.0 264 53 27 0.8 0.4 | -52.2 -62.0 268 52 27 1.0 0.6
38000 -51.8 -61.2 261 55 28 -0.7 -0.4 | -51.7 -61.1 268 55 29 -0.6 -0.3
36000 -52.5 -62.5 263 53 27 -1.1 -0.6 | -52.2 -62.0 268 52 27 -0.9 -0.5
34000 -53.1 -63.6 265 51 26 -1.1 -0.6 | -52.7 -62.9 268 49 25 -0.9 -0.5
32000 -53.8 -64.8 268 42 21 -1.1 -0.6 | -53.2 -63.8 269 40 21 -0.8 -0.4
30000 -54.5 -66.1 273 27 14 -1.7 -0.9 | -53.7 -64.7 274 29 15 -0.6 -0.3
29000 -53.0 -63.4 275 25 13 8.1 4.4 | -52.4 -62.3 278 25 13 7.4 4.1
28000 -50.6 -59.1 277 25 13 8.2 4.5 | -50.1 -58.2 281 24 12 7.5 4.1
27000 -48.1 -54.6 279 24 13 8.2 4.5 | -47.9 -54.2 285 22 11 7.5 4.1
26000 -45.6 -50.1 281 24 12 8.8 4.8 | -45.5 -49.9 287 22 11 8.8 4.8
25000 -43.0 -45.4 281 24 13 8.8 4.8 | -42.9 -45.2 286 22 11 8.7 4.8
24000 -40.4 -40.7 281 24 13 8.8 4.8 | -40.4 -40.7 285 22 11 8.7 4.8
23000 -37.8 -36.0 282 24 12 8.1 4.5 | -37.8 -36.0 285 22 11 8.1 4.4
22000 -35.4 -31.7 284 24 12 8.2 4.5 | -35.4 -31.7 285 22 11 8.1 4.5
21000 -32.9 -27.2 286 23 12 8.2 4.5 | -32.9 -27.2 284 22 11 8.1 4.5
20000 -30.4 -22.7 284 21 11 8.7 4.8 | -30.3 -22.5 282 21 11 9.1 5.0
19500 -29.1 -20.4 282 20 11 8.7 4.8 | -29.0 -20.2 279 21 11 9.1 5.0
19000 -27.8 -18.0 279 20 10 8.7 4.8 | -27.6 -17.7 276 20 10 9.1 5.0
18500 -26.5 -15.7 276 19 10 8.7 4.8 | -26.3 -15.3 273 20 10 9.1 5.0
18000 -25.2 -13.4 272 18 9 7.9 4.4 | -24.9 -12.8 270 19 10 8.5 4.7
17500 -24.1 -11.4 268 18 9 7.4 4.1 | -23.7 -10.7 266 19 10 8.2 4.5
17000 -23.0 -9.4 264 17 9 7.3 4.0 | -22.5 -8.5 261 19 10 7.9 4.4
16500 -22.0 -7.6 263 17 9 6.5 3.5 | -21.5 -6.7 260 19 10 6.0 3.3
16000 -20.5 -4.9 264 16 8 6.6 3.6 | -20.1 -4.2 258 18 9 6.1 3.3
15500 -19.6 -3.3 268 16 8 6.6 3.6 | -19.3 -2.7 261 18 9 5.9 3.2
15000 -18.6 -1.5 272 15 8 6.7 3.7 | -18.4 -1.1 264 17 9 6.0 3.3
14500 -17.5 0.5 277 16 8 7.6 4.2 | -17.4 0.7 270 16 8 6.5 3.6
14000 -16.4 2.5 282 16 8 7.6 4.1 | -16.5 2.3 278 16 8 6.4 3.5
13500 -15.2 4.6 285 17 9 7.7 4.2 | -15.4 4.3 285 16 8 7.7 4.3
13000 -14.1 6.6 288 19 10 7.7 4.2 | -14.3 6.3 291 17 9 7.6 4.2
12500 -13.0 8.6 290 21 11 7.8 4.3 | -13.1 8.4 295 18 9 8.1 4.5
12000 -11.8 10.8 291 22 12 7.8 4.3 | -11.9 10.6 298 20 10 8.1 4.4
11500 -10.7 12.7 292 24 12 7.7 4.2 | -10.7 12.7 299 21 11 8.2 4.5
11000 -9.5 14.9 293 24 13 7.7 4.2 | -9.5 14.9 300 22 12 8.2 4.5
10500 -8.3 17.1 294 24 13 8.3 4.5 | -8.3 17.1 300 23 12 8.6 4.7
10250 -7.7 18.1 295 24 12 8.2 4.5 | -7.7 18.1 301 22 11 8.5 4.7
10000 -7.1 19.2 295 24 12 8.2 4.5 | -7.1 19.2 301 22 11 8.5 4.7
9750 -6.5 20.3 296 23 12 8.1 4.5 | -6.4 20.5 302 21 11 8.4 4.6
9500 -6.0 21.2 297 22 11 8.0 4.4 | -5.8 21.6 302 20 10 8.3 4.6
9250 -5.4 22.3 298 20 10 8.2 4.5 | -5.2 22.6 303 19 10 8.5 4.6
9000 -4.8 23.4 299 19 10 7.6 4.2 | -4.6 23.7 304 18 9 8.0 4.4
8750 -4.3 24.3 301 17 9 6.7 3.7 | -4.1 24.6 305 17 9 7.4 4.0
8500 -3.8 25.2 302 15 8 6.6 3.6 | -3.6 25.5 306 15 8 7.3 4.0
8250 -3.3 26.1 305 13 7 6.8 3.7 | -3.0 26.6 307 13 7 7.4 4.1
8000 -2.9 26.8 307 12 6 5.9 3.2 | -2.5 27.5 308 11 6 6.3 3.4
7750 -2.5 27.5 308 9 5 5.1 2.8 | -2.1 28.2 306 9 5 5.3 2.9
7500 -2.1 28.2 310 7 4 5.5 3.0 | -1.7 28.9 304 7 3 5.5 3.0
7250 -1.6 29.1 313 5 3 4.8 2.7 | -1.3 29.7 299 4 2 5.6 3.1
7000 -1.3 29.7 310 3 2 3.8 2.1 | -0.8 30.6 283 3 2 5.9 3.2
6750 -1.0 30.2 283 1 1 3.7 2.0 | -0.4 31.3 252 2 1 6.0 3.3
6500 -0.7 30.7 181 1 1 3.7 2.0 | 0.1 32.2 218 3 1 5.9 3.3
6250 -0.4 31.3 164 3 1 2.4 1.3 | 0.5 32.9 199 4 2 4.1 2.3
6000 -0.3 31.5 169 3 2 1.7 1.0 | 0.7 33.3 194 4 2 2.4 1.3
5750 -0.2 31.6 172 3 2 1.3 0.7 | 1.0 33.8 191 5 3 4.3 2.4
5500 -0.1 31.8 176 3 2 3.8 2.1 | 1.2 34.2 188 6 3 -1.6 -0.9
________________________________________________________________________________
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.
071806
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- Page last modified: Nov 10th, 2009 17:45 UTC