Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 171339
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0739 MDT Friday, May 17, 2013
This forecast is for Friday, May 17, 2013:
If the trigger temperature of 76.9 F/25.0 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1491 ft/min (7.6 m/s)
Maximum height of thermals.................. 20849 ft MSL (15562 ft AGL)
Forecast maximum temperature................... 88.0 F/31.6 C
Time of trigger temperature.................... 1000 MDT
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................. 17987 ft MSL (12700 ft AGL)
Thermal soaring outlook for Saturday 05/18..... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 35299 ft MSL (30012 ft AGL)
Wave soaring outlook for Saturday 05/18........ Poor
Remarks... None
Sunrise/Sunset.................... 05:42:59 / 20:08:37 MDT
Total possible sunshine........... 14 hr 25 min 38 sec (865 min 38 sec)
Altitude of sun at 12:55:59 MDT... 69.71 degrees
Upper air data from numerical model forecast valid on 05/17/2013 at 0600 MDT
Freezing level.................. 14118 ft MSL (8831 ft AGL)
Convective condensation level... 17367 ft MSL (12080 ft AGL)
Lifted condensation level....... 18949 ft MSL (13662 ft AGL)
Lifted index.................... -2.1
K index......................... +13.8
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 -61.2 -78.2 250 21 11 -1.5 -0.8 M M M M M
45000 -63.1 -81.6 255 26 13 1.2 0.6 M M M M M
40000 -61.3 -78.3 250 22 11 0.3 0.2 M M M M M
38000 -57.1 -70.8 250 26 13 8.0 4.4 M M M M M
36000 -52.2 -62.0 250 31 16 8.0 4.4 M M M M M
34000 -47.4 -53.3 250 33 17 8.2 4.5 M M M M M
32000 -42.5 -44.5 250 32 16 8.2 4.5 M M M M M
30000 -36.9 -34.4 250 29 15 8.3 4.5 38.1 100.6 5.3 M M
29000 -34.4 -29.9 250 28 14 8.3 4.5 37.5 99.6 4.9 M M
28000 -32.0 -25.6 250 27 14 8.3 4.6 37.1 98.8 4.6 M M
27000 -29.6 -21.3 250 26 13 7.8 4.3 36.4 97.5 4.1 M M
26000 -27.2 -17.0 255 26 13 7.8 4.3 35.6 96.1 3.5 M M
25000 -24.9 -12.8 255 25 13 7.8 4.3 34.9 94.8 3.0 M M
24000 -22.6 -8.7 255 25 13 7.5 4.1 34.2 93.5 2.5 M M
23000 -20.4 -4.7 255 25 13 7.5 4.1 33.3 91.9 1.8 M M
22000 -18.1 -0.6 255 24 13 7.5 4.1 32.5 90.6 1.1 M M
21000 -16.1 3.0 250 23 12 6.2 3.4 31.5 88.6 0.2 M M
20000 -14.3 6.3 245 21 11 6.2 3.4 30.2 86.3 -0.9 1422 7.2
19500 -13.4 7.9 245 20 10 6.2 3.4 29.6 85.2 -1.5 1381 7.0
19000 -12.5 9.5 240 19 10 6.4 3.5 29.0 84.2 -2.0 1339 6.8
18500 -11.5 11.3 240 18 9 7.2 3.9 28.5 83.3 -2.5 1294 6.6
18000 -10.5 13.1 235 18 9 7.1 3.9 28.0 82.5 -2.9 1248 6.3
17500 -9.4 15.1 235 17 9 8.4 4.6 27.7 81.8 -3.3 1200 6.1
17000 -8.1 17.4 235 17 9 8.7 4.8 27.5 81.5 -3.5 1147 5.8
16500 -6.8 19.8 240 16 8 8.7 4.8 27.3 81.2 -3.7 1094 5.6
16000 -5.5 22.1 240 16 8 8.8 4.8 27.1 80.9 -3.9 1040 5.3
15500 -4.2 24.4 245 16 8 8.8 4.8 27.0 80.6 -4.1 986 5.0
15000 -2.2 28.0 250 16 8 9.3 5.1 26.8 80.3 -4.3 903 4.6
14500 -0.8 30.6 250 16 8 9.3 5.1 26.8 80.2 -4.3 847 4.3
14000 0.6 33.1 250 16 8 9.3 5.1 26.7 80.0 -4.4 790 4.0
13500 2.0 35.6 250 15 8 9.4 5.1 26.6 79.9 -4.5 734 3.7
13000 3.4 38.1 250 15 8 9.3 5.1 26.6 79.8 -4.6 677 3.4
12500 4.8 40.6 250 14 7 9.3 5.1 26.5 79.7 -4.7 621 3.2
12000 6.2 43.2 245 13 7 9.4 5.2 26.4 79.6 -4.8 565 2.9
11500 7.6 45.7 245 13 7 9.6 5.2 26.4 79.4 -4.9 508 2.6
11000 8.9 48.0 240 12 6 7.7 4.2 26.2 79.2 -5.1 454 2.3
10500 10.0 50.0 235 12 6 7.6 4.1 25.9 78.6 -5.4 405 2.1
10250 10.6 51.1 235 12 6 10.0 5.5 25.8 78.4 -5.6 379 1.9
10000 11.4 52.5 230 11 6 9.7 5.3 25.9 78.5 -5.5 348 1.8
9750 12.0 53.6 230 11 6 7.5 4.1 25.7 78.3 -5.7 323 1.6
9500 12.6 54.7 230 11 6 8.2 4.5 25.6 78.0 -5.8 297 1.5
9250 13.2 55.8 225 11 6 7.6 4.2 25.4 77.8 -5.9 272 1.4
9000 13.7 56.7 225 11 6 7.1 3.9 25.2 77.4 -6.2 249 1.3
8750 14.3 57.7 220 12 6 7.4 4.0 25.1 77.1 -6.4 226 1.1
8500 14.8 58.6 220 12 6 7.1 3.9 24.9 76.8 -6.6 202 1.0
8250 15.3 59.5 215 12 6 8.0 4.4 24.7 76.4 -6.8 179 0.9
8000 15.9 60.6 215 12 6 7.4 4.0 24.6 76.2 -7.0 154 0.8
7750 16.4 61.5 215 11 6 5.5 3.0 24.3 75.7 -7.3 134 0.7
7500 16.8 62.2 210 11 6 5.7 3.1 24.0 75.1 -7.6 114 0.6
7250 17.2 63.0 210 10 5 7.6 4.1 23.7 74.7 -7.9 94 0.5
7000 17.8 64.0 215 10 5 8.0 4.4 23.6 74.5 -8.1 69 0.3
6750 18.4 65.1 220 11 6 9.7 5.3 23.5 74.2 -8.3 44 0.2
6500 19.0 66.2 225 12 6 0.8 0.4 23.3 74.0 -8.4 19 0.1
6250 18.3 64.9 225 12 6 -15.1 -8.3 21.9 71.5 -9.9 32 0.2
6000 16.9 62.4 225 12 6 -17.4 -9.5 19.9 67.8 -12.0 64 0.3
5750 15.4 59.7 220 13 7 -26.0 -14.3 17.7 63.8 -14.3 104 0.5
5500 12.4 54.3 215 12 6 -52.3 -28.7 14.1 57.4 -18.0 185 0.9
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/17/2013 at 0900 MDT | 05/17/2013 at 1200 MDT
|
K index... +8.3 LI... +2.0 | K index... -1.6 LI... +2.1
CAPE... 0.0 CIN... -0.2 | CAPE... 0.0 CIN... -0.2
|
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 -61.3 -78.3 250 19 10 -0.8 -0.4 | -61.0 -77.8 240 17 9 -1.4 -0.8
45000 -62.2 -80.0 240 23 12 0.7 0.4 | -62.7 -80.9 225 26 14 1.0 0.5
40000 -61.1 -78.0 225 29 15 -0.0 -0.0 | -61.2 -78.2 230 33 17 0.2 0.1
38000 -57.1 -70.8 225 28 15 7.6 4.1 | -57.1 -70.8 225 33 17 7.6 4.2
36000 -52.6 -62.7 230 28 14 7.6 4.1 | -52.5 -62.5 225 33 17 7.7 4.2
34000 -47.9 -54.2 235 27 14 8.1 4.4 | -47.8 -54.0 225 32 16 8.0 4.4
32000 -43.0 -45.4 240 26 13 8.1 4.4 | -43.0 -45.4 225 31 16 8.0 4.4
30000 -37.5 -35.5 240 26 13 8.1 4.5 | -37.6 -35.7 230 30 16 8.0 4.4
29000 -35.1 -31.2 240 26 13 8.1 4.5 | -35.2 -31.4 230 30 16 8.0 4.4
28000 -32.6 -26.7 240 26 14 8.2 4.5 | -32.7 -26.9 235 30 16 8.1 4.4
27000 -30.3 -22.5 240 27 14 7.7 4.3 | -30.5 -22.9 235 31 16 7.3 4.0
26000 -27.9 -18.2 240 27 14 7.7 4.2 | -28.3 -18.9 235 32 16 7.3 4.0
25000 -25.6 -14.1 240 27 14 7.8 4.3 | -26.1 -15.0 235 32 17 7.4 4.0
24000 -23.2 -9.8 240 27 14 8.1 4.5 | -23.7 -10.7 235 32 16 8.4 4.6
23000 -20.8 -5.4 245 27 14 8.1 4.5 | -21.2 -6.2 235 30 16 8.4 4.6
22000 -18.4 -1.1 245 27 14 8.1 4.5 | -18.7 -1.7 235 29 15 8.4 4.6
21000 -16.1 3.0 240 26 13 7.1 3.9 | -16.3 2.7 230 27 14 8.1 4.4
20000 -14.0 6.8 235 24 12 7.1 3.9 | -13.8 7.2 230 25 13 8.0 4.4
19500 -12.9 8.8 230 23 12 7.1 3.9 | -12.6 9.3 230 24 12 8.0 4.4
19000 -11.9 10.6 230 22 11 6.8 3.7 | -11.4 11.5 230 23 12 8.0 4.4
18500 -11.0 12.2 225 20 10 5.6 3.1 | -10.2 13.6 230 21 11 7.9 4.4
18000 -10.2 13.6 220 18 10 5.6 3.1 | -9.0 15.8 230 20 10 7.9 4.3
17500 -9.3 15.3 215 17 9 7.7 4.2 | -7.8 18.0 235 19 10 8.5 4.6
17000 -8.1 17.4 215 16 8 8.0 4.4 | -6.6 20.1 235 18 9 8.5 4.7
16500 -6.9 19.6 215 15 8 8.4 4.6 | -5.3 22.5 235 18 9 8.3 4.5
16000 -5.6 21.9 220 15 7 9.0 4.9 | -4.1 24.6 240 19 10 7.8 4.3
15500 -3.6 25.5 225 14 7 8.8 4.8 | -2.4 27.7 240 20 10 6.8 3.8
15000 -2.3 27.9 235 15 8 8.6 4.7 | -1.5 29.3 235 20 10 6.2 3.4
14500 -1.0 30.2 240 15 8 8.8 4.8 | -0.6 30.9 230 20 10 6.5 3.6
14000 0.3 32.5 240 15 8 9.1 5.0 | 0.5 32.9 225 19 10 7.6 4.2
13500 1.6 34.9 245 16 8 9.1 5.0 | 1.5 34.7 220 19 10 7.7 4.2
13000 3.0 37.4 250 16 8 9.4 5.1 | 2.8 37.0 220 19 10 9.1 5.0
12500 4.4 39.9 250 16 8 9.4 5.1 | 4.1 39.4 220 19 10 9.0 4.9
12000 5.7 42.3 255 16 8 9.3 5.1 | 5.4 41.7 220 18 9 9.3 5.1
11500 7.1 44.8 255 16 8 9.5 5.2 | 6.8 44.2 220 17 9 9.5 5.2
11000 8.5 47.3 255 16 8 8.3 4.6 | 8.0 46.4 220 15 8 7.5 4.1
10500 9.7 49.5 255 15 8 9.3 5.1 | 9.1 48.4 220 12 6 8.7 4.7
10250 10.5 50.9 255 15 8 11.9 6.5 | 9.8 49.6 225 10 5 11.3 6.2
10000 11.4 52.5 255 15 8 10.4 5.7 | 10.6 51.1 225 9 5 10.5 5.8
9750 12.1 53.8 255 15 8 8.6 4.7 | 11.3 52.3 230 9 5 9.2 5.1
9500 12.7 54.9 255 15 8 9.2 5.1 | 12.1 53.8 230 8 4 9.8 5.4
9250 13.4 56.1 255 15 8 8.6 4.7 | 12.8 55.0 235 8 4 8.6 4.7
9000 14.0 57.2 255 15 7 8.4 4.6 | 13.4 56.1 235 7 4 9.1 5.0
8750 14.7 58.5 250 14 7 8.9 4.9 | 14.1 57.4 240 7 4 10.6 5.8
8500 15.3 59.5 250 14 7 8.8 4.8 | 14.9 58.8 240 7 4 10.2 5.6
8250 16.0 60.8 250 14 7 8.7 4.8 | 15.7 60.3 240 7 4 10.7 5.9
8000 16.6 61.9 245 14 7 8.2 4.5 | 16.5 61.7 240 7 4 10.3 5.7
7750 17.2 63.0 245 14 7 7.9 4.4 | 17.2 63.0 240 7 4 9.5 5.2
7500 17.8 64.0 245 14 7 8.1 4.4 | 17.9 64.2 245 7 4 9.8 5.4
7250 18.5 65.3 245 14 7 9.1 5.0 | 18.7 65.7 245 7 4 10.4 5.7
7000 19.1 66.4 245 14 7 8.7 4.8 | 19.4 66.9 245 7 4 10.3 5.7
6750 19.7 67.5 245 15 8 7.9 4.4 | 20.2 68.4 245 7 4 9.2 5.0
6500 20.2 68.4 245 16 8 3.7 2.0 | 20.9 69.6 245 7 3 10.0 5.5
6250 20.2 68.4 245 14 7 -0.9 -0.5 | 21.7 71.1 250 7 3 11.7 6.4
6000 20.0 68.0 245 12 6 -1.3 -0.7 | 22.6 72.7 250 7 3 11.1 6.1
5750 19.8 67.6 240 9 5 -2.5 -1.4 | 23.4 74.1 250 6 3 11.7 6.4
5500 19.5 67.1 225 6 3 3.1 1.7 | 24.5 76.1 250 6 3 19.0 10.4
05/17/2013 at 1500 MDT | 05/17/2013 at 1800 MDT
|
K index... +9.2 LI... +1.1 | K index... +16.0 LI... +0.2
CAPE... 0.0 CIN... -0.6 | CAPE... +21.3 CIN... -29.9
|
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 -60.8 -77.4 250 20 10 -1.7 -0.9 | -60.0 -76.0 260 18 9 -0.6 -0.3
45000 -62.9 -81.2 240 30 15 0.9 0.5 | -60.9 -77.6 250 24 12 -0.4 -0.2
40000 -61.5 -78.7 235 43 22 0.3 0.2 | -61.5 -78.7 240 40 21 -1.0 -0.6
38000 -57.5 -71.5 240 43 22 7.6 4.2 | -57.6 -71.7 235 41 21 7.8 4.3
36000 -53.0 -63.4 240 41 21 7.6 4.2 | -53.0 -63.4 235 42 21 7.8 4.3
34000 -48.2 -54.8 240 40 20 8.2 4.5 | -47.6 -53.7 235 41 21 8.0 4.4
32000 -42.7 -44.9 240 38 20 8.2 4.5 | -42.9 -45.2 235 39 20 8.0 4.4
30000 -37.6 -35.7 235 37 19 8.6 4.7 | -37.9 -36.2 230 37 19 8.5 4.7
29000 -35.1 -31.2 235 36 18 8.6 4.7 | -35.3 -31.5 230 36 19 8.5 4.7
28000 -32.5 -26.5 230 35 18 8.6 4.7 | -32.8 -27.0 230 35 18 8.5 4.7
27000 -30.1 -22.2 230 35 18 7.8 4.3 | -30.4 -22.7 230 34 17 7.7 4.2
26000 -27.7 -17.9 225 36 19 7.8 4.3 | -28.0 -18.4 230 33 17 7.7 4.2
25000 -25.4 -13.7 225 37 19 7.8 4.3 | -25.7 -14.3 235 32 17 7.7 4.2
24000 -23.1 -9.6 220 37 19 7.4 4.1 | -23.5 -10.3 235 31 16 7.2 3.9
23000 -20.9 -5.6 220 35 18 7.4 4.1 | -21.4 -6.5 235 30 15 7.2 4.0
22000 -18.7 -1.7 220 34 17 7.4 4.1 | -19.2 -2.6 235 29 15 7.3 4.0
21000 -16.4 2.5 220 32 17 7.8 4.3 | -16.9 1.6 230 27 14 8.1 4.4
20000 -14.0 6.8 225 31 16 7.8 4.3 | -14.5 5.9 225 25 13 8.1 4.5
19500 -12.9 8.8 225 31 16 7.8 4.3 | -13.3 8.1 220 24 12 8.2 4.5
19000 -11.7 10.9 225 30 16 7.9 4.3 | -12.1 10.2 220 23 12 8.4 4.6
18500 -10.5 13.1 225 30 15 8.3 4.6 | -10.8 12.6 215 22 11 9.2 5.1
18000 -9.2 15.4 225 29 15 8.3 4.6 | -9.5 14.9 210 21 11 9.2 5.1
17500 -8.0 17.6 225 29 15 8.3 4.6 | -8.1 17.4 205 21 11 8.6 4.7
17000 -6.8 19.8 220 28 14 8.3 4.6 | -6.9 19.6 205 20 10 8.5 4.7
16500 -5.6 21.9 220 27 14 8.5 4.6 | -5.0 23.0 200 20 10 9.3 5.1
16000 -3.7 25.3 220 25 13 8.7 4.8 | -3.6 25.5 200 19 10 9.4 5.1
15500 -2.4 27.7 215 24 12 8.8 4.8 | -2.2 28.0 200 19 10 9.5 5.2
15000 -1.1 30.0 215 23 12 8.8 4.9 | -0.8 30.6 200 19 10 9.5 5.2
14500 0.2 32.4 210 22 11 8.8 4.8 | 0.7 33.3 200 19 10 9.6 5.2
14000 1.5 34.7 210 20 10 8.6 4.7 | 2.1 35.8 195 18 9 9.6 5.2
13500 2.8 37.0 205 19 10 8.6 4.7 | 3.5 38.3 195 18 9 9.6 5.3
13000 4.0 39.2 205 18 9 8.8 4.8 | 4.9 40.8 195 17 9 9.2 5.1
12500 5.3 41.5 200 16 8 8.9 4.9 | 6.3 43.3 195 17 9 9.2 5.1
12000 6.6 43.9 195 15 8 8.6 4.7 | 7.7 45.9 195 16 8 9.5 5.2
11500 7.9 46.2 195 13 7 8.7 4.8 | 9.1 48.4 195 15 8 9.6 5.3
11000 9.1 48.4 195 12 6 8.4 4.6 | 10.5 50.9 195 14 7 8.4 4.6
10500 10.4 50.7 190 11 6 9.2 5.0 | 11.7 53.1 200 13 7 9.4 5.2
10250 11.1 52.0 190 10 5 11.2 6.1 | 12.5 54.5 200 12 6 11.4 6.2
10000 12.0 53.6 190 10 5 10.6 5.8 | 13.3 55.9 200 11 6 10.0 5.5
9750 12.7 54.9 195 10 5 9.6 5.3 | 14.0 57.2 200 11 5 8.9 4.9
9500 13.4 56.1 195 9 5 10.0 5.5 | 14.7 58.5 200 10 5 9.2 5.1
9250 14.2 57.6 195 9 5 9.5 5.2 | 15.4 59.7 205 9 5 9.2 5.0
9000 14.9 58.8 195 9 5 9.6 5.2 | 16.1 61.0 205 8 4 9.3 5.1
8750 15.6 60.1 195 9 5 10.1 5.5 | 16.8 62.2 210 8 4 9.5 5.2
8500 16.4 61.5 195 9 4 9.6 5.2 | 17.5 63.5 210 7 4 8.8 4.8
8250 17.1 62.8 195 9 4 11.4 6.3 | 18.2 64.8 215 7 3 11.3 6.2
8000 18.0 64.4 195 8 4 10.9 6.0 | 19.1 66.4 220 6 3 11.0 6.0
7750 18.7 65.7 200 8 4 8.6 4.7 | 19.8 67.6 225 6 3 8.4 4.6
7500 19.4 66.9 200 8 4 9.3 5.1 | 20.4 68.7 225 6 3 9.0 5.0
7250 20.1 68.2 200 8 4 10.5 5.8 | 21.1 70.0 230 6 3 10.2 5.6
7000 20.9 69.6 200 8 4 11.0 6.0 | 21.9 71.4 235 6 3 10.8 5.9
6750 21.7 71.1 200 7 4 9.6 5.3 | 22.7 72.9 235 5 3 9.5 5.2
6500 22.4 72.3 205 7 4 10.0 5.5 | 23.4 74.1 240 5 3 9.6 5.3
6250 23.2 73.8 205 7 4 11.1 6.1 | 24.1 75.4 240 5 3 10.3 5.7
6000 24.0 75.2 205 7 4 11.3 6.2 | 24.9 76.8 245 5 3 10.6 5.8
5750 24.8 76.6 210 7 3 9.9 5.4 | 25.7 78.3 250 5 3 9.2 5.0
5500 25.7 78.3 210 6 3 14.8 8.1 | 26.3 79.3 250 5 3 9.9 5.4
________________________________________________________________________________
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:
CAPE (Convective Available Potential Energy) - An integrated measure of the
energy available for convective development, also known as the positive
area on a thermodynamic diagram. Units are Joules per kilogram. Larger
values are indicative of greater instability and the possibility of
stronger convective activity, including thunderstorms. Values around or
greater than 1000 suggest the possibility of severe weather should
convective activity develop.
CIN (Convective Inhibition) - An integrated measure of the amount of energy
needed to initiate convective activity, also known as the negative area on
a thermodynamic diagram. Units are Joules per kilogram. The more negative
this number, the more energy is required to initiate convection. This
inhibitive energy can be overcome through surface heating, cooling aloft,
lifting mechanisms (orographic, frontal, gravity waves, etc.)
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 (LI) - 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, cirrostratus, 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.
042613
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- Page last modified: May 1st, 2013 15:32 UTC