Soaring Forecast
National Weather Service Denver/Boulder, Colorado
533 AM MST Wednesday February 10, 2010
This forecast is for Wednesday February 10, 2010:
If the trigger temperature of 41.7 F/5.4 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 370 ft/min (1.9 m/s)
Maximum height of thermals.................. 10105 ft MSL (4820 ft AGL)
Forecast maximum temperature................... 42.0 F/6.0 C
Time of trigger temperature.................... 1415 MST
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................. 6737 ft MSL (1452 ft AGL)
Thermal soaring outlook for Thursday 02/11..... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1700 MST)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1700 MST)................ Neither
Potential height of wave....................... 20503 ft MSL (15218 ft AGL)
Wave soaring outlook for Thursday 02/11........ Good
Remarks...
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 rawinsonde observation taken on 02/10/2010 at 0500 MST
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 15246 ft MSL (9961 ft AGL)
Lifted condensation level....... 13231 ft MSL (7945 ft AGL)
Lifted index.................... +4.6
K index......................... -4.3
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 -54.8 -66.6 269 38 20 5.3 2.9 112.4 234.3 60.5 M M
45000 -53.5 -64.3 261 46 24 4.0 2.2 89.7 193.4 50.9 M M
40000 -53.5 -64.3 260 57 29 2.2 1.2 65.4 149.6 38.8 M M
38000 -51.8 -61.2 260 56 29 4.9 2.7 59.1 138.4 35.7 M M
36000 -52.6 -62.7 260 50 26 -13.4 -7.4 49.2 120.5 29.8 M M
34000 -53.0 -63.4 260 45 23 0.4 0.2 40.1 104.2 24.3 M M
32000 -53.5 -64.3 261 40 20 -0.7 -0.4 31.3 88.3 18.6 M M
30000 -54.6 -66.3 264 34 18 -6.7 -3.7 21.8 71.2 12.0 M M
29000 -54.0 -65.2 270 33 17 7.9 4.3 18.6 65.5 9.8 M M
28000 -51.7 -61.1 272 31 16 7.8 4.3 17.8 64.0 9.3 M M
27000 -48.8 -55.8 275 29 15 8.1 4.5 16.9 62.5 8.8 M M
26000 -46.3 -51.3 277 28 14 8.3 4.6 16.4 61.4 8.5 M M
25000 -43.8 -46.8 280 26 13 8.3 4.6 15.9 60.6 8.2 M M
24000 -41.3 -42.3 280 22 12 8.3 4.6 15.3 59.5 7.8 M M
23000 -38.9 -38.0 279 19 10 7.6 4.2 14.7 58.5 7.5 M M
22000 -36.5 -33.7 276 20 10 9.0 4.9 14.1 57.4 7.0 M M
21000 -33.8 -28.8 272 22 11 8.9 4.9 13.8 56.8 6.8 M M
20000 -31.1 -24.0 270 23 12 8.9 4.9 13.6 56.4 6.8 M M
19500 -29.8 -21.6 273 23 12 8.9 4.9 13.4 56.1 6.6 M M
19000 -28.5 -19.3 277 22 11 8.9 4.9 13.2 55.7 6.5 M M
18500 -27.2 -17.0 281 22 11 8.9 4.9 13.0 55.5 6.4 M M
18000 -25.8 -14.4 285 22 11 8.4 4.6 12.9 55.2 6.3 M M
17500 -24.6 -12.3 287 21 11 8.0 4.4 12.6 54.6 6.1 M M
17000 -23.4 -10.1 289 21 11 8.0 4.4 12.3 54.1 5.8 M M
16500 -22.3 -8.1 292 20 11 8.0 4.4 12.0 53.6 5.6 M M
16000 -21.1 -6.0 294 20 10 8.0 4.4 11.7 53.1 5.4 M M
15500 -19.9 -3.8 289 19 10 8.0 4.4 11.4 52.5 5.2 M M
15000 -18.7 -1.7 282 18 9 8.1 4.4 11.1 52.0 4.9 M M
14500 -17.5 0.5 275 17 9 7.0 3.9 10.8 51.4 4.6 M M
14000 -16.5 2.3 267 17 9 7.0 3.8 10.3 50.6 4.3 M M
13500 -14.9 5.2 265 16 8 7.0 3.8 9.7 49.4 3.7 M M
13000 -13.9 7.0 266 16 8 7.0 3.8 9.2 48.6 3.3 M M
12500 -12.9 8.8 271 18 9 7.0 3.9 8.8 47.8 2.9 M M
12000 -11.8 10.8 276 20 10 7.5 4.1 8.3 47.0 2.5 M M
11500 -11.1 12.0 284 21 11 0.9 0.5 7.5 45.5 1.7 M M
11000 -10.9 12.4 290 22 11 5.6 3.1 6.2 43.1 0.4 M M
10500 -9.7 14.5 295 20 10 8.0 4.4 5.9 42.6 0.2 M M
10250 -9.1 15.6 298 19 10 8.2 4.5 5.8 42.4 0.0 M M
10000 -8.5 16.7 302 18 9 8.2 4.5 5.7 42.2 -0.1 354 1.8
9750 -7.9 17.8 304 16 8 9.1 5.0 5.6 42.0 -0.2 328 1.7
9500 -7.2 19.0 303 15 7 10.2 5.6 5.6 42.0 -0.2 298 1.5
9250 -6.5 20.3 301 13 7 7.2 3.9 5.5 42.0 -0.2 270 1.4
9000 -6.1 21.0 300 11 6 4.6 2.5 5.2 41.3 -0.5 252 1.3
8750 -5.7 21.7 303 10 5 5.3 2.9 4.8 40.7 -0.9 233 1.2
8500 -5.3 22.5 307 10 5 5.1 2.8 4.5 40.0 -1.3 214 1.1
8250 -5.0 23.0 310 9 5 5.1 2.8 4.1 39.4 -1.6 196 1.0
8000 -4.6 23.7 314 9 5 5.1 2.8 3.8 38.8 -2.0 177 0.9
7750 -4.2 24.4 311 7 4 7.9 4.3 3.5 38.3 -2.3 156 0.8
7500 -3.5 25.7 306 6 3 10.3 5.7 3.5 38.2 -2.3 128 0.7
7250 -2.8 27.0 297 4 2 8.5 4.7 3.5 38.2 -2.3 100 0.5
7000 -2.1 28.2 280 3 2 13.5 7.4 3.5 38.2 -2.4 71 0.4
6750 -1.7 28.9 279 3 1 -16.7 -9.2 3.1 37.7 -2.7 52 0.3
6500 -4.6 23.7 278 3 1 -43.8 -24.0 -0.5 31.1 -6.3 132 0.7
6250 -7.0 19.4 276 2 1 -20.6 -11.3 -3.7 25.3 -9.5 198 1.0
6000 -7.8 18.0 275 2 1 -4.2 -2.3 -5.2 22.6 -11.1 214 1.1
5750 -8.0 17.6 239 2 1 -3.1 -1.7 -6.2 20.9 -12.0 213 1.1
5500 -8.7 16.3 199 2 1 -21.4 -11.8 -7.7 18.2 -13.5 227 1.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
02/10/2010 at 0800 MST | 02/10/2010 at 1100 MST
|
K index... +2.2 | K index... -0.1
|
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 -54.5 -66.1 271 38 19 0.6 0.3 | -55.0 -67.0 272 38 19 1.4 0.8
45000 -53.6 -64.5 266 44 23 0.6 0.3 | -52.8 -63.0 263 47 24 1.4 0.8
40000 -52.2 -62.0 263 55 28 1.0 0.6 | -50.8 -59.4 260 53 27 1.3 0.7
38000 -51.6 -60.9 262 60 31 -1.1 -0.6 | -50.1 -58.2 259 54 28 -1.1 -0.6
36000 -52.3 -62.1 260 56 29 -1.2 -0.6 | -51.2 -60.2 260 53 27 -1.8 -1.0
34000 -53.0 -63.4 258 53 27 -1.1 -0.6 | -52.3 -62.1 260 51 26 -1.8 -1.0
32000 -53.5 -64.3 260 45 23 -0.6 -0.3 | -53.3 -63.9 264 43 22 -1.4 -0.8
30000 -53.8 -64.8 267 34 17 -0.4 -0.2 | -54.2 -65.6 277 29 15 -1.8 -1.0
29000 -52.8 -63.0 271 31 16 7.0 3.8 | -52.9 -63.2 283 26 13 7.5 4.1
28000 -50.6 -59.1 274 29 15 7.3 4.0 | -50.6 -59.1 286 25 13 7.7 4.2
27000 -48.5 -55.3 278 28 14 7.3 4.0 | -48.4 -55.1 290 24 12 7.7 4.2
26000 -46.2 -51.2 282 27 14 8.3 4.6 | -46.0 -50.8 293 23 12 9.0 4.9
25000 -43.7 -46.7 284 26 13 8.3 4.6 | -43.3 -45.9 294 22 11 8.8 4.8
24000 -41.2 -42.2 287 26 13 8.3 4.6 | -40.7 -41.3 295 21 11 8.8 4.8
23000 -38.7 -37.7 289 25 13 8.5 4.7 | -38.1 -36.6 295 21 11 8.0 4.4
22000 -36.1 -33.0 291 23 12 8.5 4.7 | -35.7 -32.3 292 19 10 8.1 4.4
21000 -33.5 -28.3 293 22 11 8.5 4.7 | -33.3 -27.9 289 18 9 8.1 4.4
20000 -31.0 -23.8 296 21 11 8.2 4.5 | -30.8 -23.4 288 17 9 8.3 4.6
19500 -29.2 -20.6 298 20 10 8.2 4.5 | -29.6 -21.3 289 16 8 8.3 4.6
19000 -27.9 -18.2 299 20 10 8.2 4.5 | -28.3 -18.9 289 16 8 8.3 4.6
18500 -26.7 -16.1 301 19 10 8.2 4.5 | -27.1 -16.8 289 15 8 8.3 4.6
18000 -25.5 -13.9 302 19 10 8.2 4.5 | -25.8 -14.4 290 15 8 8.2 4.5
17500 -24.3 -11.7 302 19 10 8.2 4.5 | -24.6 -12.3 290 15 8 8.1 4.4
17000 -23.0 -9.4 302 18 9 7.8 4.3 | -23.4 -10.1 290 15 8 8.1 4.4
16500 -21.9 -7.4 301 17 9 7.5 4.1 | -21.7 -7.1 290 15 8 7.7 4.2
16000 -20.8 -5.4 300 17 9 7.4 4.1 | -20.6 -5.1 289 15 8 7.6 4.2
15500 -19.7 -3.5 299 16 8 7.1 3.9 | -19.4 -2.9 289 15 8 7.6 4.2
15000 -18.7 -1.7 298 16 8 7.1 3.9 | -18.3 -0.9 290 15 8 7.6 4.2
14500 -17.6 0.3 298 15 8 7.8 4.3 | -17.2 1.0 290 16 8 7.3 4.0
14000 -16.4 2.5 299 15 8 7.7 4.2 | -16.1 3.0 291 17 9 7.4 4.1
13500 -15.3 4.5 300 14 7 8.0 4.4 | -15.0 5.0 290 18 9 6.9 3.8
13000 -14.1 6.6 302 14 7 7.9 4.4 | -14.0 6.8 290 19 10 6.9 3.8
12500 -12.9 8.8 303 14 7 8.1 4.5 | -12.9 8.8 289 19 10 7.7 4.2
12000 -11.6 11.1 304 16 8 8.2 4.5 | -11.8 10.8 287 20 10 7.6 4.2
11500 -10.4 13.3 304 17 9 7.9 4.3 | -10.7 12.7 286 20 10 7.5 4.1
11000 -9.3 15.3 303 18 9 8.0 4.4 | -9.5 14.9 285 19 10 7.6 4.2
10500 -8.1 17.4 302 18 9 7.2 4.0 | -8.5 16.7 284 18 9 7.0 3.8
10250 -7.6 18.3 302 17 9 7.3 4.0 | -7.9 17.8 283 17 9 7.1 3.9
10000 -7.0 19.4 302 17 9 7.3 4.0 | -7.4 18.7 282 17 8 7.0 3.8
9750 -6.5 20.3 302 16 8 5.9 3.2 | -6.9 19.6 282 16 8 6.4 3.5
9500 -6.2 20.8 302 14 7 4.8 2.6 | -6.5 20.3 281 14 7 6.0 3.3
9250 -5.8 21.6 303 13 7 5.2 2.8 | -6.0 21.2 281 13 7 6.1 3.4
9000 -5.4 22.3 304 11 6 4.7 2.6 | -5.6 21.9 280 12 6 5.8 3.2
8750 -5.1 22.8 305 10 5 3.9 2.1 | -5.2 22.6 280 11 6 5.4 2.9
8500 -4.8 23.4 305 9 5 3.5 1.9 | -4.8 23.4 281 10 5 5.3 2.9
8250 -4.6 23.7 306 8 4 3.9 2.2 | -4.4 24.1 281 9 5 5.4 2.9
8000 -4.3 24.3 307 6 3 2.6 1.4 | -4.0 24.8 281 8 4 4.8 2.7
7750 -4.2 24.4 310 6 3 1.2 0.7 | -3.7 25.3 283 8 4 4.3 2.4
7500 -4.1 24.6 314 6 3 1.8 1.0 | -3.3 26.1 285 7 3 4.7 2.6
7250 -3.9 25.0 318 5 3 0.7 0.4 | -3.0 26.6 288 6 3 3.8 2.1
7000 -4.0 24.8 318 5 3 -1.5 -0.8 | -2.8 27.0 291 5 2 2.2 1.2
6750 -4.1 24.6 316 4 2 -2.0 -1.1 | -2.6 27.3 296 4 2 2.1 1.1
6500 -4.3 24.3 313 4 2 -2.1 -1.2 | -2.5 27.5 303 3 2 1.7 0.9
6250 -4.6 23.7 303 3 2 -6.2 -3.4 | -2.5 27.5 305 2 1 -3.5 -1.9
6000 -5.2 22.6 272 3 2 -9.5 -5.2 | -3.0 26.6 252 1 1 -6.7 -3.7
5750 -5.8 21.6 248 4 2 -7.1 -3.9 | -3.5 25.7 201 2 1 -6.4 -3.5
5500 -6.6 20.1 234 6 3 -18.9 -10.4 | -3.9 25.0 185 3 2 -3.2 -1.8
02/10/2010 at 1400 MST | 02/10/2010 at 1700 MST
|
K index... +4.2 | K index... +6.9
|
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 -54.4 -65.9 272 39 20 0.9 0.5 | -53.9 -65.0 279 37 19 0.9 0.5
45000 -53.1 -63.6 265 52 27 0.9 0.5 | -52.6 -62.7 274 46 24 0.9 0.5
40000 -51.9 -61.4 263 57 29 0.7 0.4 | -52.2 -62.0 271 48 25 0.1 0.1
38000 -51.5 -60.7 262 57 30 -1.0 -0.6 | -52.2 -62.0 271 49 25 -0.8 -0.4
36000 -52.5 -62.5 263 53 27 -1.7 -0.9 | -52.9 -63.2 271 44 23 -1.2 -0.7
34000 -53.5 -64.3 264 49 25 -1.7 -0.9 | -53.6 -64.5 272 40 20 -1.2 -0.7
32000 -54.2 -65.6 268 38 20 -0.9 -0.5 | -54.0 -65.2 273 33 17 -0.3 -0.2
30000 -54.8 -66.6 279 24 13 -0.7 -0.4 | -54.2 -65.6 274 24 13 -0.2 -0.1
29000 -53.4 -64.1 287 20 10 8.0 4.4 | -52.8 -63.0 276 20 10 7.3 4.0
28000 -50.9 -59.6 293 18 9 8.1 4.4 | -50.6 -59.1 278 18 9 7.4 4.0
27000 -48.5 -55.3 299 17 9 8.1 4.4 | -48.4 -55.1 281 16 8 7.4 4.0
26000 -46.0 -50.8 303 17 9 9.4 5.2 | -46.0 -50.8 283 14 7 9.7 5.3
25000 -43.2 -45.8 301 16 8 9.3 5.1 | -43.2 -45.8 281 14 7 9.4 5.2
24000 -40.4 -40.7 299 16 8 9.3 5.1 | -40.4 -40.7 279 14 7 9.4 5.2
23000 -37.8 -36.0 296 16 8 7.6 4.2 | -37.7 -35.9 278 14 7 7.5 4.1
22000 -35.5 -31.9 291 16 8 7.8 4.3 | -35.4 -31.7 280 15 8 7.7 4.2
21000 -33.1 -27.6 287 17 9 7.8 4.3 | -33.1 -27.6 283 16 8 7.7 4.2
20000 -30.6 -23.1 283 16 8 8.9 4.9 | -30.6 -23.1 281 17 9 9.1 5.0
19500 -29.3 -20.7 281 16 8 8.9 4.9 | -29.2 -20.6 279 17 9 9.1 5.0
19000 -28.0 -18.4 279 16 8 8.9 4.9 | -27.9 -18.2 277 17 9 9.1 5.0
18500 -26.7 -16.1 277 15 8 8.9 4.9 | -26.5 -15.7 275 17 9 9.1 5.0
18000 -25.3 -13.5 275 15 8 8.5 4.7 | -25.1 -13.2 272 17 9 8.9 4.9
17500 -24.1 -11.4 274 15 8 8.3 4.6 | -23.8 -10.8 272 17 9 8.7 4.8
17000 -22.9 -9.2 274 14 7 8.2 4.5 | -22.5 -8.5 271 17 9 8.6 4.7
16500 -21.7 -7.1 275 14 7 7.7 4.2 | -21.4 -6.5 271 16 8 7.4 4.0
16000 -19.9 -3.8 280 14 7 7.6 4.1 | -19.7 -3.5 271 15 8 7.2 3.9
15500 -18.9 -2.0 281 14 7 7.2 4.0 | -18.7 -1.7 272 15 8 6.5 3.6
15000 -17.8 -0.0 282 14 7 7.2 4.0 | -17.7 0.1 273 15 7 6.6 3.6
14500 -16.7 1.9 282 14 7 7.4 4.1 | -16.7 1.9 274 14 7 6.9 3.8
14000 -15.6 3.9 282 14 7 7.4 4.1 | -15.7 3.7 275 14 7 6.8 3.7
13500 -14.5 5.9 283 15 7 7.3 4.0 | -14.6 5.7 278 14 7 8.3 4.6
13000 -13.4 7.9 284 15 8 7.2 4.0 | -13.4 7.9 282 15 8 8.2 4.5
12500 -12.3 9.9 286 17 9 8.1 4.4 | -12.2 10.0 286 16 8 8.2 4.5
12000 -11.1 12.0 287 19 10 8.0 4.4 | -11.0 12.2 290 18 9 8.3 4.5
11500 -9.9 14.2 288 20 10 8.3 4.5 | -9.8 14.4 293 19 10 8.1 4.4
11000 -8.7 16.3 289 22 11 8.3 4.6 | -8.6 16.5 295 21 11 8.1 4.5
10500 -7.5 18.5 290 22 11 7.7 4.2 | -7.4 18.7 296 22 11 7.8 4.3
10250 -7.0 19.4 291 22 11 7.8 4.3 | -6.9 19.6 297 22 11 7.9 4.3
10000 -6.4 20.5 292 22 11 7.8 4.3 | -6.3 20.7 297 22 11 7.9 4.3
9750 -5.9 21.4 292 22 11 7.3 4.0 | -5.7 21.7 298 22 11 7.4 4.1
9500 -5.3 22.5 293 21 11 7.0 3.9 | -5.2 22.6 300 21 11 7.0 3.9
9250 -4.8 23.4 295 20 10 7.3 4.0 | -4.7 23.5 301 20 10 7.3 4.0
9000 -4.3 24.3 296 19 10 6.8 3.7 | -4.2 24.4 302 20 10 6.8 3.7
8750 -3.9 25.0 297 18 9 5.9 3.2 | -3.8 25.2 304 18 9 5.3 2.9
8500 -3.5 25.7 300 16 8 5.6 3.1 | -3.5 25.7 306 17 9 4.6 2.5
8250 -3.1 26.4 302 15 8 6.0 3.3 | -3.2 26.2 308 15 8 5.1 2.8
8000 -2.7 27.1 305 14 7 4.6 2.5 | -2.8 27.0 311 13 7 3.8 2.1
7750 -2.4 27.7 308 12 6 3.1 1.7 | -2.6 27.3 314 11 6 2.2 1.2
7500 -2.1 28.2 312 10 5 3.7 2.0 | -2.4 27.7 318 9 5 2.5 1.3
7250 -1.9 28.6 317 8 4 3.0 1.6 | -2.2 28.0 324 7 3 2.4 1.3
7000 -1.7 28.9 323 7 3 1.7 0.9 | -2.0 28.4 332 5 2 2.7 1.5
6750 -1.5 29.3 331 5 3 1.3 0.7 | -1.7 28.9 340 3 2 2.8 1.5
6500 -1.4 29.5 345 4 2 1.5 0.8 | -1.5 29.3 007 1 1 3.0 1.7
6250 -1.3 29.7 009 3 1 0.5 0.3 | -1.2 29.8 086 1 1 2.1 1.2
6000 -1.3 29.7 025 2 1 0.0 0.0 | -1.1 30.0 115 2 1 1.1 0.6
5750 -1.4 29.5 059 1 1 -0.4 -0.2 | -1.1 30.0 132 2 1 1.9 1.1
5500 -1.4 29.5 101 2 1 2.5 1.4 | -1.0 30.2 142 3 1 0.0 0.0
________________________________________________________________________________
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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