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Soaring Guidance
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
000
UXUS97 KPUB 201041
SRGPUB
SOARING FORECAST
NATIONAL WEATHER SERVICE PUEBLO CO
441 AM MDT MON MAY 20 2013
EXPERIMENTAL PRODUCT
This forecast is for Monday May 20, 2013:
If the trigger temperature of 47.1 F/8.4 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 754 ft/min (3.8 m/s)
Maximum height of thermals.................. 18262 ft MSL (10600 ft AGL)
Forecast maximum temperature................... 59.0 F/15.5 C
Time of trigger temperature.................... 0800 MDT
Time of overdevelopment........................ 1300 MDT
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 15673 ft MSL (8012 ft AGL)
Thermal soaring outlook for Tuesday 05/21...... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Increasing
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 15555 ft MSL (7893 ft AGL)
Wave soaring outlook for Tuesday 05/21......... Poor
Remarks...
Sunrise/Sunset.................... 05:42:27 / 20:09:03 MDT
Total possible sunshine........... 14 hr 26 min 37 sec (866 min 37 sec)
Altitude of sun at 12:55:56 MDT... 71.13 degrees
Upper air data from numerical model forecast valid on 05/20/2013 at 0600 MDT
Freezing level.................. 10270 ft MSL (2608 ft AGL)
Convective condensation level... 12730 ft MSL (5068 ft AGL)
Lifted condensation level....... 15195 ft MSL (7533 ft AGL)
Lifted index.................... -3.1
K index......................... +19.6
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 -66.6 262 15 8 3.8 2.1 94.4 201.9 47.1 M M
45000 -48.8 -55.8 275 25 13 3.8 2.1 80.5 176.9 41.5 M M
40000 -43.1 -45.6 268 34 18 3.9 2.1 67.1 152.7 35.2 M M
38000 -43.4 -46.1 267 29 15 -3.0 -1.6 58.0 136.4 29.8 M M
36000 -45.1 -49.2 267 19 10 -3.8 -1.6 47.1 116.8 22.8 M M
34000 -46.6 -51.9 269 8 4 1.5 0.8 37.4 99.3 16.3 M M
32000 -45.9 -50.6 087 11 5 1.0 0.6 30.0 86.0 11.2 M M
30000 -44.8 -48.6 087 25 13 8.0 4.4 24.0 75.2 6.9 M M
29000 -42.6 -44.7 086 20 10 7.3 4.0 22.9 73.3 6.2 M M
28000 -39.8 -39.6 083 14 7 7.3 4.0 21.8 71.2 5.4 M M
27000 -37.6 -35.7 077 9 5 7.7 4.3 21.0 69.8 4.8 M M
26000 -35.2 -31.4 070 5 3 8.0 4.4 20.2 68.4 4.2 M M
25000 -32.8 -27.0 037 2 1 8.0 4.4 19.6 67.3 3.7 M M
24000 -30.4 -22.7 300 3 2 8.0 4.4 19.1 66.4 3.3 M M
23000 -28.0 -18.4 305 4 2 8.1 4.4 18.4 65.1 2.8 M M
22000 -25.6 -14.1 309 5 3 8.1 4.4 17.8 64.0 2.3 M M
21000 -23.2 -9.8 313 6 3 7.8 4.3 17.3 63.1 1.9 M M
20000 -20.9 -5.6 319 5 3 7.8 4.3 16.5 61.7 1.2 M M
19500 -19.8 -3.6 323 5 3 7.8 4.3 16.2 61.1 0.9 M M
19000 -18.6 -1.5 327 5 3 7.8 4.3 15.9 60.6 0.6 M M
18500 -17.5 0.5 330 5 3 6.7 3.7 15.6 60.0 0.3 M M
18000 -16.6 2.1 313 6 3 5.9 3.2 14.9 58.8 -0.3 934 4.7
17500 -15.8 3.6 301 7 4 5.9 3.2 14.3 57.7 -0.9 894 4.5
17000 -14.9 5.2 297 8 4 6.4 3.5 13.7 56.6 -1.5 852 4.3
16500 -13.9 7.0 295 10 5 6.4 3.5 13.1 55.6 -2.0 809 4.1
16000 -13.0 8.6 296 11 5 6.4 3.5 12.5 54.6 -2.6 767 3.9
15500 -12.1 10.2 300 11 6 6.5 3.5 12.0 53.6 -3.1 724 3.7
15000 -11.1 12.0 303 12 6 6.7 3.7 11.5 52.6 -3.7 681 3.5
14500 -10.1 13.8 309 11 6 6.9 3.8 11.0 51.8 -4.2 636 3.2
14000 -9.1 15.6 316 10 5 7.0 3.8 10.5 50.9 -4.7 592 3.0
13500 -8.1 17.4 321 10 5 7.2 3.9 10.1 50.2 -5.1 546 2.8
13000 -7.0 19.4 326 10 5 7.3 4.0 9.7 49.4 -5.6 499 2.5
12500 -5.9 21.4 330 9 5 8.4 4.6 9.4 48.9 -5.9 449 2.3
12000 -4.6 23.7 333 9 5 8.4 4.6 9.2 48.5 -6.1 397 2.0
11750 -4.0 24.8 335 9 5 8.7 4.7 9.1 48.4 -6.2 371 1.9
11500 -3.4 25.9 337 9 5 8.8 4.8 9.0 48.2 -6.3 344 1.7
11250 -2.7 27.1 339 9 5 8.8 4.8 8.9 48.1 -6.5 317 1.6
11000 -2.1 28.2 340 9 5 8.7 4.8 8.9 47.9 -6.5 290 1.5
10750 -1.4 29.5 343 10 5 8.2 4.5 8.8 47.8 -6.7 264 1.3
10500 -0.8 30.6 348 10 5 8.0 4.4 8.6 47.5 -6.8 239 1.2
10250 0.3 32.5 356 11 5 8.0 4.4 8.4 47.1 -7.1 189 1.0
10000 0.9 33.6 359 11 6 7.7 4.2 8.2 46.8 -7.3 164 0.8
9750 1.5 34.7 002 11 6 7.6 4.2 8.1 46.5 -7.5 140 0.7
9500 2.1 35.8 004 11 6 7.7 4.2 7.9 46.2 -7.7 115 0.6
9250 2.6 36.7 007 11 6 7.5 4.1 7.7 45.9 -7.9 91 0.5
9000 3.2 37.8 005 11 6 7.4 4.1 7.6 45.6 -8.1 67 0.3
8750 3.7 38.7 002 12 6 6.9 3.8 7.4 45.3 -8.3 43 0.2
8500 4.3 39.7 359 13 7 8.6 4.7 7.2 44.9 -8.5 19 0.1
8250 4.7 40.5 356 13 7 -2.6 -1.4 6.9 44.4 -8.8 M M
8000 3.6 38.5 336 9 4 -25.8 -14.1 5.0 41.0 -10.7 25 0.1
7750 2.5 36.5 295 7 3 16.8 9.2 3.2 37.7 -12.5 51 0.3
7500 M M M M M M M M M M M M
7250 M M M M M M M M M M M M
7000 M M M M M M M M M M M M
6750 M M M M M M M M M M M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/20/2013 at 0900 MDT | 05/20/2013 at 1200 MDT
|
K index... +20.4 | K index... +20.4
|
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 -55.1 -67.2 236 14 7 3.5 1.9 | -55.0 -67.0 253 15 7 3.4 1.9
45000 -49.9 -57.8 245 18 9 3.4 1.9 | -49.7 -57.5 262 22 11 2.8 1.5
40000 -44.5 -48.1 271 25 13 3.4 1.9 | -45.5 -49.9 268 22 11 2.8 1.5
38000 -44.5 -48.1 274 22 11 -1.8 -1.0 | -45.7 -50.3 269 18 9 -1.9 -1.0
36000 -45.5 -49.9 276 15 8 -1.7 -1.0 | -46.8 -52.2 270 13 7 -1.9 -1.0
34000 -46.3 -51.3 286 8 4 0.9 0.5 | -47.5 -53.5 273 7 4 2.0 1.1
32000 -45.9 -50.6 070 10 5 0.7 0.4 | -46.4 -51.5 081 5 3 1.9 1.0
30000 -44.7 -48.5 077 24 12 9.0 4.9 | -44.5 -48.1 079 15 8 8.8 4.8
29000 -42.2 -44.0 069 23 12 8.4 4.6 | -41.9 -43.4 063 16 8 8.5 4.7
28000 -39.7 -39.5 061 22 11 8.4 4.6 | -38.7 -37.7 047 19 10 8.5 4.7
27000 -36.5 -33.7 051 21 11 7.9 4.3 | -36.2 -33.2 037 21 11 8.3 4.6
26000 -34.2 -29.6 046 18 9 7.7 4.2 | -33.7 -28.7 031 22 11 8.3 4.6
25000 -31.9 -25.4 039 16 8 7.7 4.2 | -31.2 -24.2 025 22 11 8.3 4.6
24000 -29.6 -21.3 029 14 7 7.6 4.2 | -28.8 -19.8 019 23 12 7.7 4.2
23000 -27.4 -17.3 021 12 6 7.5 4.1 | -26.6 -15.9 013 19 10 7.3 4.0
22000 -25.1 -13.2 010 10 5 7.5 4.1 | -24.4 -11.9 004 15 8 7.3 4.0
21000 -22.9 -9.2 359 9 5 7.4 4.1 | -22.3 -8.1 351 13 6 7.0 3.9
20000 -20.7 -5.3 359 9 5 7.4 4.1 | -20.2 -4.4 340 11 6 7.0 3.9
19500 -19.6 -3.3 358 8 4 7.5 4.1 | -19.2 -2.6 333 11 5 7.0 3.9
19000 -18.5 -1.3 358 8 4 7.5 4.1 | -18.1 -0.6 325 10 5 7.1 3.9
18500 -17.5 0.5 357 8 4 6.7 3.7 | -17.1 1.2 318 10 5 7.0 3.9
18000 -16.5 2.3 342 8 4 6.3 3.4 | -16.0 3.2 315 11 6 7.0 3.8
17500 -15.6 3.9 327 8 4 6.2 3.4 | -15.0 5.0 312 11 6 7.0 3.8
17000 -14.7 5.5 315 9 5 6.6 3.6 | -14.0 6.8 313 12 6 6.8 3.7
16500 -13.7 7.3 306 10 5 6.6 3.6 | -13.0 8.6 317 13 7 6.9 3.8
16000 -12.7 9.1 301 12 6 6.9 3.8 | -12.0 10.4 320 14 7 6.3 3.5
15500 -11.7 10.9 303 13 7 7.0 3.8 | -11.1 12.0 324 14 7 6.3 3.5
15000 -10.7 12.7 304 14 7 6.8 3.7 | -10.2 13.6 327 15 8 6.5 3.6
14500 -9.7 14.5 309 15 8 6.7 3.6 | -9.2 15.4 328 14 7 6.6 3.6
14000 -8.8 16.2 314 16 8 6.6 3.6 | -8.3 17.1 329 13 7 6.4 3.5
13500 -7.8 18.0 316 17 9 6.6 3.6 | -7.3 18.9 333 12 6 6.2 3.4
13000 -6.8 19.8 316 18 9 6.6 3.6 | -6.4 20.5 337 11 6 6.5 3.6
12500 -5.8 21.6 314 18 9 6.9 3.8 | -5.4 22.3 340 11 6 7.4 4.1
12000 -4.8 23.4 311 17 9 6.9 3.8 | -4.3 24.3 342 11 6 7.5 4.1
11750 -4.3 24.3 309 17 9 6.9 3.8 | -3.7 25.3 342 11 6 8.0 4.4
11500 -3.8 25.2 307 16 8 7.0 3.8 | -3.1 26.4 339 11 6 8.2 4.5
11250 -3.3 26.1 305 16 8 6.9 3.8 | -2.5 27.5 336 11 5 8.1 4.5
11000 -2.8 27.0 303 16 8 7.1 3.9 | -2.0 28.4 333 11 5 8.5 4.6
10750 -2.3 27.9 303 15 8 7.8 4.3 | -1.3 29.7 330 11 5 9.3 5.1
10500 -1.7 28.9 306 14 7 8.2 4.5 | -0.6 30.9 327 10 5 9.7 5.3
10250 -0.5 31.1 313 12 6 8.5 4.7 | 0.8 33.4 322 10 5 9.7 5.3
10000 0.1 32.2 316 11 6 9.7 5.3 | 1.6 34.9 321 10 5 9.9 5.5
9750 0.9 33.6 318 11 6 10.1 5.5 | 2.3 36.1 321 10 5 10.0 5.5
9500 1.6 34.9 320 11 6 10.0 5.5 | 3.1 37.6 321 10 5 10.0 5.5
9250 2.4 36.3 323 11 6 10.0 5.5 | 3.8 38.8 321 10 5 10.1 5.5
9000 3.1 37.6 324 11 5 9.9 5.4 | 4.6 40.3 322 10 5 10.2 5.6
8750 3.9 39.0 325 10 5 10.0 5.5 | 5.3 41.5 323 10 5 10.2 5.6
8500 4.6 40.3 327 10 5 9.7 5.3 | 6.1 43.0 323 9 5 10.2 5.6
8250 5.4 41.7 328 10 5 13.7 7.5 | 7.0 44.6 325 9 5 15.0 8.2
8000 6.7 44.1 332 9 5 21.4 11.8 | 8.4 47.1 328 8 4 23.0 12.6
7750 8.0 46.4 337 8 4 7.5 4.1 | 9.8 49.6 333 8 4 8.7 4.8
7500 M M M M M M M | M M M M M M M
7250 M M M M M M M | M M M M M M M
7000 M M M M M M M | M M M M M M M
6750 M M M M M M M | M M M M M M M
05/20/2013 at 1500 MDT | 05/20/2013 at 1800 MDT
|
K index... +21.9 | K index... +22.2
|
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 -54.5 -66.1 262 15 8 3.6 2.0 | -54.8 -66.6 265 12 6 3.8 2.1
45000 -49.3 -56.7 270 23 12 2.7 1.5 | -49.2 -56.6 273 18 9 2.0 1.1
40000 -45.3 -49.5 262 23 12 2.7 1.5 | -46.2 -51.2 272 19 10 2.0 1.1
38000 -45.7 -50.3 264 19 10 -2.7 -1.5 | -47.4 -53.3 278 14 7 -4.1 -2.2
36000 -47.5 -53.5 272 12 6 -2.7 -1.5 | -49.8 -57.6 304 7 4 -4.1 -2.2
34000 -48.2 -54.8 296 6 3 3.0 1.6 | -50.9 -59.6 006 6 3 6.1 3.3
32000 -46.3 -51.3 033 4 2 3.1 1.7 | -47.2 -53.0 023 9 5 6.1 3.3
30000 -43.6 -46.5 052 10 5 8.2 4.5 | -43.2 -45.8 022 12 6 8.3 4.6
29000 -41.2 -42.2 038 10 5 8.3 4.6 | -40.7 -41.3 010 13 7 8.4 4.6
28000 -38.7 -37.7 026 12 6 8.3 4.6 | -37.6 -35.7 358 15 8 8.4 4.6
27000 -36.2 -33.2 018 14 7 8.6 4.7 | -35.1 -31.2 352 17 9 8.4 4.6
26000 -33.6 -28.5 012 16 8 8.7 4.8 | -32.6 -26.7 351 20 10 8.4 4.6
25000 -31.0 -23.8 007 19 10 8.7 4.8 | -30.1 -22.2 350 22 11 8.4 4.6
24000 -28.4 -19.1 004 22 11 8.4 4.6 | -27.6 -17.7 348 24 12 7.3 4.0
23000 -25.8 -14.4 348 18 9 6.9 3.8 | -25.5 -13.9 336 21 11 7.0 3.8
22000 -23.7 -10.7 329 17 9 6.9 3.8 | -23.5 -10.3 321 20 10 7.0 3.8
21000 -21.7 -7.1 315 17 9 7.3 4.0 | -21.4 -6.5 309 20 10 7.0 3.9
20000 -19.5 -3.1 317 17 9 7.3 4.0 | -19.3 -2.7 310 21 11 7.1 3.9
19500 -18.5 -1.3 318 17 9 7.3 4.0 | -18.3 -0.9 310 22 11 7.1 3.9
19000 -17.4 0.7 319 18 9 7.4 4.0 | -17.2 1.0 310 23 12 7.2 3.9
18500 -16.4 2.5 321 18 10 6.3 3.5 | -16.3 2.7 311 23 12 5.3 2.9
18000 -15.5 4.1 325 21 11 6.2 3.4 | -15.5 4.1 316 25 13 5.0 2.8
17500 -14.6 5.7 328 24 12 6.2 3.4 | -14.8 5.4 320 26 14 5.4 2.9
17000 -13.7 7.3 330 26 14 6.0 3.3 | -13.9 7.0 326 28 14 6.3 3.5
16500 -12.8 9.0 332 29 15 5.9 3.2 | -13.0 8.6 331 30 15 6.2 3.4
16000 -11.8 10.8 332 30 16 7.1 3.9 | -12.0 10.4 333 30 16 7.1 3.9
15500 -10.8 12.6 332 30 15 7.0 3.9 | -11.0 12.2 332 29 15 7.0 3.9
15000 -9.8 14.4 332 30 15 6.9 3.8 | -9.9 14.2 331 28 15 7.1 3.9
14500 -8.8 16.2 332 29 15 6.9 3.8 | -8.9 16.0 329 27 14 7.2 3.9
14000 -7.8 18.0 332 28 15 6.9 3.8 | -7.8 18.0 328 25 13 7.5 4.1
13500 -6.8 19.8 331 25 13 7.0 3.8 | -6.7 19.9 329 21 11 7.8 4.3
13000 -5.8 21.6 328 22 11 7.2 3.9 | -5.6 21.9 331 18 9 8.1 4.4
12500 -4.7 23.5 322 18 9 7.6 4.1 | -4.3 24.3 335 15 8 8.5 4.7
12000 -3.6 25.5 312 14 7 7.8 4.3 | -3.1 26.4 342 12 6 8.8 4.8
11750 -3.0 26.6 306 13 7 8.4 4.6 | -2.4 27.7 345 11 6 9.6 5.3
11500 -2.4 27.7 300 12 6 8.6 4.7 | -1.7 28.9 349 11 6 9.7 5.3
11250 -1.8 28.8 293 11 6 8.5 4.6 | -1.0 30.2 352 10 5 9.7 5.3
11000 -1.2 29.8 285 10 5 8.9 4.9 | -0.3 31.5 356 10 5 9.7 5.3
10750 -0.5 31.1 282 10 5 9.8 5.4 | 0.4 32.7 357 10 5 9.7 5.3
10500 0.2 32.4 281 10 5 10.0 5.5 | 1.1 34.0 358 10 5 9.8 5.4
10250 1.0 33.8 281 10 5 10.0 5.5 | 2.6 36.7 360 10 5 9.9 5.4
10000 1.7 35.1 281 10 5 9.9 5.4 | 3.4 38.1 360 10 5 10.1 5.6
9750 2.4 36.3 280 10 5 9.8 5.4 | 4.1 39.4 001 10 5 10.1 5.6
9500 3.9 39.0 279 10 5 9.8 5.4 | 4.9 40.8 002 10 5 10.2 5.6
9250 4.6 40.3 278 10 5 9.9 5.4 | 5.6 42.1 003 10 5 9.9 5.4
9000 5.4 41.7 277 10 5 9.9 5.5 | 6.4 43.5 003 10 5 9.7 5.3
8750 6.1 43.0 277 9 5 9.9 5.4 | 7.1 44.8 004 10 5 9.6 5.3
8500 6.9 44.4 276 9 5 10.0 5.5 | 7.8 46.0 004 10 5 10.0 5.5
8250 7.7 45.9 276 9 5 14.4 7.9 | 8.6 47.5 006 10 5 13.3 7.3
8000 9.0 48.2 274 8 4 21.3 11.7 | 9.8 49.6 010 9 5 17.5 9.6
7750 10.3 50.5 273 7 4 9.2 5.1 | 10.9 51.6 015 8 4 10.5 5.8
7500 M M M M M M M | M M M M M M M
7250 M M M M M M M | M M M M M M M
7000 M M M M M M M | M M M M M M M
6750 M M M M M M M | M M M M M M M
________________________________________________________________________________
This product is issued one per day by approximately 0630 MST/0730 MDT
(1330 UTC). It is not continuously monitored nor updated after its initial
issuance.
The information contained herein is based on numerical weather prediction
model data taken near the Air Force Academy in Colorado Springs, Colorado
at
North Latitude: 38 deg 58 min 48.000 sec
West Longitude: 104 deg 49 min 12.000 sec
Elevation: 6572 feet (2003 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.
At this time, the output from this considered experimental.
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: May 1st, 2013 15:32 UTC