Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
252
UXUS97 KGJT 171307
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
707 AM MDT Tuesday, September 17, 2024
This forecast is for Tuesday, September 17, 2024:
If the trigger temperature of 73.4 F/23.0 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 762 ft/min (3.9 m/s)
Maximum height of thermals.................. 11826 ft MSL (6987 ft AGL)
Forecast maximum temperature................... 77.0 F/25.5 C
Time of trigger temperature.................... 1245 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................. 6866 ft MSL (2027 ft AGL)
Thermal soaring outlook for Wednesday 09/18.... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:58:05 / 19:18:39 MDT
Total possible sunshine........... 12 hr 20 min 34 sec (740 min 34 sec)
Altitude of sun at 13:08:22 MDT... 52.67 degrees
Upper air data from rawinsonde observation taken on 09/17/2024 at 0600 MDT
Freezing level.................. 13967 ft MSL (9128 ft AGL)
Convective condensation level... 12433 ft MSL (7594 ft AGL)
Lifted condensation level....... 12131 ft MSL (7291 ft AGL)
Lifted index.................... -0.8
K index......................... +29.0
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 -58.7 -73.7 225 49 25 -2.8 -1.6 97.7 207.9 42.1 M M
45000 -59.7 -75.5 235 62 32 3.7 2.1 71.6 160.9 28.9 M M
40000 -54.7 -66.5 235 85 44 4.8 2.6 56.6 133.9 21.0 M M
38000 -49.9 -57.8 230 88 45 8.0 4.4 55.0 131.0 20.4 M M
36000 -44.2 -47.6 230 89 46 6.8 3.7 53.6 128.6 20.1 M M
34000 -40.1 -40.2 225 84 43 3.7 2.0 51.2 124.1 18.8 M M
32000 -37.0 -34.6 220 82 42 5.9 3.3 47.4 117.3 16.5 M M
30000 -33.9 -29.0 220 75 39 4.7 2.6 43.7 110.6 14.1 M M
29000 -32.4 -26.3 215 76 39 5.9 3.2 41.8 107.3 12.8 M M
28000 -30.6 -23.1 215 76 39 7.5 4.1 40.5 104.9 11.9 M M
27000 -28.6 -19.5 210 69 36 6.0 3.3 39.2 102.6 11.1 M M
26000 -26.8 -16.2 205 68 35 6.9 3.8 37.9 100.2 10.1 M M
25000 -24.7 -12.5 205 59 30 10.1 5.5 36.8 98.2 9.3 M M
24000 -20.1 -4.2 210 52 27 14.5 8.0 39.0 102.3 11.2 M M
23000 -17.5 0.5 210 52 27 8.3 4.6 38.7 101.7 11.0 M M
22000 -15.3 4.5 210 49 25 6.2 3.4 37.9 100.2 10.4 M M
21000 -13.4 7.9 210 52 27 5.4 2.9 36.8 98.2 9.5 M M
20000 -11.9 10.6 200 49 25 4.9 2.7 35.0 95.0 8.1 M M
19500 -11.2 11.8 200 48 25 4.9 2.7 34.2 93.5 7.4 M M
19000 -10.2 13.6 200 47 24 4.9 2.7 32.8 91.1 6.3 M M
18500 -9.4 15.1 200 48 25 5.2 2.8 32.0 89.6 5.6 M M
18000 -8.6 16.5 200 49 25 6.8 3.7 31.4 88.5 5.1 M M
17500 -7.6 18.3 200 51 27 6.2 3.4 30.8 87.5 4.6 M M
17000 -6.8 19.8 200 51 26 5.8 3.2 30.2 86.3 4.0 M M
16500 -5.9 21.4 205 49 25 5.5 3.0 29.5 85.1 3.4 M M
16000 -4.8 23.4 205 47 24 9.6 5.3 29.1 84.4 3.0 M M
15500 -3.6 25.5 205 45 23 8.5 4.7 29.0 84.2 2.8 M M
15000 -2.4 27.7 205 46 24 8.1 4.4 28.7 83.6 2.6 M M
14500 -1.2 29.8 205 47 24 8.1 4.4 28.4 83.1 2.3 M M
14000 0.0 32.0 205 48 25 8.0 4.4 28.1 82.7 2.1 M M
13500 1.2 34.2 205 48 25 7.4 4.1 27.8 82.1 1.8 M M
13000 2.1 35.8 205 49 25 5.8 3.2 27.3 81.1 1.2 M M
12500 3.1 37.6 205 45 23 7.8 4.3 26.8 80.3 0.7 M M
12000 4.3 39.7 210 40 21 3.9 2.1 26.6 79.9 0.5 M M
11500 4.6 40.3 210 35 18 8.1 4.4 25.6 78.0 -0.6 540 2.7
11000 5.8 42.4 205 29 15 8.3 4.5 25.3 77.5 -1.0 492 2.5
10500 7.0 44.6 210 29 15 9.1 5.0 25.1 77.2 -1.2 439 2.2
10250 7.7 45.9 205 28 15 8.8 4.8 25.1 77.1 -1.2 412 2.1
10000 8.3 46.9 205 28 14 8.2 4.5 25.0 77.0 -1.3 385 2.0
9750 8.9 48.0 205 28 14 8.0 4.4 24.9 76.7 -1.4 360 1.8
9500 9.5 49.1 205 27 14 8.0 4.4 24.7 76.5 -1.6 335 1.7
9250 10.1 50.2 205 26 13 8.0 4.4 24.6 76.3 -1.7 310 1.6
9000 10.7 51.3 205 24 12 8.0 4.4 24.5 76.1 -1.8 284 1.4
8750 11.3 52.3 200 23 12 8.0 4.4 24.4 75.9 -1.9 259 1.3
8500 11.9 53.4 195 20 10 8.0 4.4 24.2 75.6 -2.1 234 1.2
8250 12.5 54.5 185 19 10 8.0 4.4 24.1 75.4 -2.2 209 1.1
8000 13.1 55.6 180 21 11 8.0 4.4 24.0 75.2 -2.3 184 0.9
7750 13.7 56.7 180 21 11 8.0 4.4 23.9 74.9 -2.5 158 0.8
7500 14.3 57.7 170 18 9 8.0 4.4 23.7 74.7 -2.6 133 0.7
7250 14.9 58.8 165 18 9 8.0 4.4 23.6 74.5 -2.7 108 0.5
7000 15.5 59.9 160 21 11 8.0 4.4 23.5 74.2 -2.9 83 0.4
6750 16.1 61.0 155 21 11 8.0 4.4 23.3 74.0 -3.0 57 0.3
6500 16.7 62.1 150 19 10 8.0 4.4 23.2 73.7 -3.2 32 0.2
6250 17.2 63.0 140 17 9 7.9 4.4 23.0 73.5 -3.3 7 0.0
6000 17.8 64.0 135 16 8 8.3 4.6 22.9 73.2 -3.5 M M
5750 18.4 65.1 130 17 9 6.9 3.8 22.8 73.0 -3.6 M M
5500 18.9 66.0 125 17 9 5.9 3.2 22.5 72.5 -3.9 M M
5250 19.2 66.6 125 17 9 2.8 1.5 22.1 71.9 -4.3 M M
5000 19.0 66.2 115 15 8 -6.6 -3.6 21.3 70.3 -5.3 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/17/2024 at 0900 MDT | 09/17/2024 at 1200 MDT
|
CAPE... +510.5 LI... -3.0 | CAPE... +371.6 LI... -1.3
CINH... -30.3 K Index... +27.2 | CINH... -2.1 K Index... +20.7
|
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 -58.6 -73.5 225 44 23 1.7 0.9 | -57.9 -72.2 225 46 24 1.3 0.7
45000 -55.9 -68.6 225 66 34 2.4 1.3 | -55.5 -67.9 225 74 38 2.9 1.6
40000 -52.3 -62.1 230 92 48 2.9 1.6 | -51.3 -60.3 220 90 46 2.8 1.6
38000 -48.7 -55.7 225 94 49 5.4 3.0 | -48.4 -55.1 220 93 48 4.3 2.4
36000 -45.5 -49.9 220 96 49 5.4 3.0 | -45.9 -50.6 215 96 49 4.3 2.4
34000 -41.9 -43.4 220 94 48 6.4 3.5 | -42.5 -44.5 215 95 49 6.4 3.5
32000 -38.1 -36.6 215 89 46 6.4 3.5 | -38.7 -37.7 210 92 47 6.4 3.5
30000 -34.3 -29.7 210 83 43 6.2 3.4 | -34.7 -30.5 205 88 45 6.8 3.7
29000 -32.5 -26.5 210 80 41 6.2 3.4 | -32.7 -26.9 205 85 44 6.8 3.7
28000 -30.7 -23.3 205 76 39 6.2 3.4 | -30.7 -23.3 200 83 43 6.8 3.7
27000 -28.7 -19.7 205 73 38 7.1 3.9 | -28.7 -19.7 200 81 42 6.2 3.4
26000 -26.6 -15.9 205 72 37 7.2 3.9 | -26.9 -16.4 195 79 40 6.2 3.4
25000 -24.5 -12.1 200 70 36 7.2 3.9 | -25.0 -13.0 195 76 39 6.3 3.4
24000 -22.4 -8.3 200 68 35 6.5 3.6 | -23.2 -9.8 195 74 38 6.8 3.7
23000 -20.0 -4.0 200 65 33 6.6 3.6 | -20.6 -5.1 195 72 37 6.9 3.8
22000 -18.0 -0.4 200 63 32 6.6 3.6 | -18.6 -1.5 195 70 36 6.9 3.8
21000 -16.0 3.2 200 60 31 7.2 3.9 | -16.5 2.3 195 68 35 7.1 3.9
20000 -13.9 7.0 200 57 29 7.2 4.0 | -14.4 6.1 200 66 34 7.1 3.9
19500 -12.8 9.0 200 55 28 7.2 4.0 | -13.4 7.9 200 65 33 7.1 3.9
19000 -11.7 10.9 200 54 28 7.3 4.0 | -12.3 9.9 200 64 33 7.0 3.8
18500 -10.7 12.7 200 53 27 7.3 4.0 | -11.3 11.7 200 63 32 6.5 3.6
18000 -9.6 14.7 200 52 27 7.4 4.0 | -10.3 13.5 200 62 32 6.6 3.6
17500 -8.6 16.5 200 52 27 6.5 3.6 | -9.4 15.1 200 61 31 6.5 3.5
17000 -7.7 18.1 205 52 27 6.4 3.5 | -8.4 16.9 200 60 31 6.4 3.5
16500 -6.7 19.9 205 52 27 6.5 3.6 | -7.5 18.5 205 59 30 6.4 3.5
16000 -5.8 21.6 205 52 27 6.6 3.6 | -6.6 20.1 205 57 30 6.2 3.4
15500 -4.8 23.4 205 51 26 6.6 3.6 | -5.7 21.7 205 56 29 6.3 3.4
15000 -3.8 25.2 205 51 26 6.9 3.8 | -4.8 23.4 205 55 28 6.4 3.5
14500 -2.8 27.0 205 50 26 6.9 3.8 | -3.8 25.2 210 53 27 6.3 3.5
14000 -1.8 28.8 205 50 25 7.1 3.9 | -2.9 26.8 210 51 26 7.2 3.9
13500 -0.8 30.6 205 49 25 7.1 3.9 | -1.9 28.6 210 49 25 7.4 4.0
13000 0.2 32.4 205 48 25 7.4 4.1 | -0.8 30.6 210 47 24 7.8 4.3
12500 1.3 34.3 205 47 24 7.6 4.2 | 0.4 32.7 210 46 23 8.1 4.4
12000 2.4 36.3 205 47 24 7.7 4.2 | 1.5 34.7 210 44 23 8.2 4.5
11500 3.5 38.3 205 45 23 7.7 4.2 | 2.7 36.9 210 42 22 8.4 4.6
11000 4.6 40.3 205 43 22 7.4 4.0 | 3.9 39.0 210 40 21 8.1 4.4
10500 5.6 42.1 205 42 21 6.9 3.8 | 5.0 41.0 210 39 20 7.1 3.9
10250 6.1 43.0 200 41 21 7.7 4.2 | 5.6 42.1 210 38 20 10.2 5.6
10000 6.6 43.9 200 39 20 8.1 4.4 | 6.5 43.7 210 37 19 11.4 6.2
9750 7.2 45.0 200 38 20 7.6 4.2 | 7.2 45.0 210 37 19 8.9 4.9
9500 7.7 45.9 200 37 19 7.5 4.1 | 7.8 46.0 210 37 19 9.2 5.1
9250 8.3 46.9 200 36 19 8.5 4.7 | 8.5 47.3 210 36 19 9.9 5.4
9000 8.9 48.0 195 36 18 8.7 4.8 | 9.3 48.7 205 36 18 10.2 5.6
8750 9.5 49.1 195 35 18 7.8 4.3 | 10.0 50.0 205 35 18 9.6 5.2
8500 10.6 51.1 195 32 17 8.0 4.4 | 11.4 52.5 205 34 17 9.4 5.2
8250 11.2 52.2 195 32 16 8.0 4.4 | 12.1 53.8 205 34 17 9.4 5.1
8000 11.8 53.2 190 31 16 8.0 4.4 | 12.8 55.0 205 33 17 10.0 5.5
7750 12.3 54.1 190 29 15 8.1 4.5 | 13.6 56.5 205 32 16 10.4 5.7
7500 12.9 55.2 190 27 14 7.6 4.2 | 14.3 57.7 205 31 16 9.7 5.3
7250 13.4 56.1 190 27 14 6.8 3.8 | 15.0 59.0 205 31 16 8.9 4.9
7000 13.9 57.0 185 26 13 7.3 4.0 | 15.7 60.3 205 31 16 9.9 5.5
6750 14.5 58.1 185 23 12 7.7 4.2 | 16.5 61.7 205 29 15 10.5 5.8
6500 15.0 59.0 180 20 10 7.2 4.0 | 17.2 63.0 205 27 14 11.0 6.1
6250 15.5 59.9 175 19 10 7.0 3.8 | 18.1 64.6 205 27 14 12.5 6.9
6000 16.1 61.0 175 17 9 6.8 3.8 | 19.0 66.2 205 26 13 9.0 4.9
5750 16.5 61.7 175 14 7 7.1 3.9 | 19.5 67.1 205 23 12 10.2 5.6
5500 17.2 63.0 165 11 5 13.1 7.2 | 21.6 70.9 200 19 10 61.7 33.9
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
09/17/2024 at 1500 MDT | 09/17/2024 at 1800 MDT
|
CAPE... +139.3 LI... -1.1 | CAPE... +0.2 LI... +2.5
CINH... -2.3 K Index... +25.4 | CINH... -2.3 K Index... +14.3
|
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 -57.1 -70.8 230 43 22 1.4 0.8 | -56.4 -69.5 230 37 19 2.0 1.1
45000 -54.2 -65.6 230 73 37 4.1 2.3 | -52.9 -63.2 240 61 32 3.4 1.9
40000 -48.0 -54.4 225 83 43 4.2 2.3 | -47.8 -54.0 240 77 40 3.5 1.9
38000 -45.7 -50.3 220 88 45 3.4 1.8 | -46.5 -51.7 245 77 40 1.6 0.9
36000 -43.7 -46.7 220 93 48 3.4 1.8 | -45.5 -49.9 245 77 40 1.6 0.9
34000 -41.4 -42.5 215 94 49 4.2 2.3 | -43.9 -47.0 250 77 40 3.9 2.1
32000 -38.9 -38.0 210 92 48 4.2 2.3 | -41.6 -42.9 255 77 40 3.9 2.1
30000 -36.2 -33.2 210 88 46 4.6 2.5 | -38.3 -36.9 255 76 39 7.5 4.1
29000 -34.9 -30.8 205 85 44 4.6 2.5 | -36.1 -33.0 255 75 38 7.4 4.1
28000 -33.5 -28.3 205 82 42 4.6 2.5 | -33.9 -29.0 255 73 38 7.5 4.1
27000 -31.9 -25.4 200 79 41 7.2 4.0 | -31.6 -24.9 255 71 37 7.4 4.0
26000 -29.9 -21.8 205 78 40 6.9 3.8 | -29.4 -20.9 250 68 35 7.4 4.0
25000 -27.8 -18.0 205 77 40 6.9 3.8 | -27.2 -17.0 245 64 33 7.4 4.0
24000 -25.7 -14.3 205 76 39 7.0 3.8 | -25.0 -13.0 245 61 32 7.5 4.1
23000 -23.1 -9.6 205 72 37 7.0 3.8 | -22.3 -8.1 240 59 31 7.5 4.1
22000 -21.1 -6.0 210 69 36 7.0 3.8 | -20.0 -4.0 240 58 30 7.4 4.1
21000 -19.0 -2.2 210 66 34 6.6 3.6 | -18.0 -0.4 240 55 28 6.2 3.4
20000 -17.1 1.2 210 61 31 6.6 3.6 | -16.1 3.0 235 51 26 6.2 3.4
19500 -16.1 3.0 215 59 30 6.6 3.6 | -15.2 4.6 235 49 25 6.2 3.4
19000 -15.2 4.6 215 56 29 6.6 3.6 | -14.3 6.3 235 47 24 6.2 3.4
18500 -14.2 6.4 215 54 28 7.2 3.9 | -13.3 8.1 230 45 23 6.3 3.4
18000 -13.1 8.4 215 52 27 7.2 3.9 | -12.4 9.7 230 44 23 6.3 3.4
17500 -12.1 10.2 215 50 26 7.7 4.2 | -11.5 11.3 230 42 22 6.2 3.4
17000 -11.0 12.2 215 48 24 7.9 4.3 | -10.6 12.9 225 40 21 6.3 3.4
16500 -9.8 14.4 215 45 23 8.0 4.4 | -9.7 14.5 225 38 20 6.4 3.5
16000 -8.6 16.5 215 43 22 8.2 4.5 | -8.7 16.3 220 36 19 7.1 3.9
15500 -7.4 18.7 215 41 21 8.2 4.5 | -7.7 18.1 220 35 18 6.9 3.8
15000 -6.2 20.8 215 40 21 8.4 4.6 | -6.6 20.1 220 33 17 8.4 4.6
14500 -5.0 23.0 215 39 20 8.4 4.6 | -5.3 22.5 220 32 17 8.3 4.6
14000 -3.8 25.2 215 38 20 8.4 4.6 | -4.1 24.6 220 32 16 9.0 5.0
13500 -2.5 27.5 215 37 19 8.4 4.6 | -2.7 27.1 220 31 16 9.2 5.0
13000 -1.3 29.7 215 37 19 8.9 4.9 | -1.3 29.7 220 31 16 9.3 5.1
12500 0.1 32.2 215 36 19 9.2 5.1 | 0.1 32.2 220 30 15 9.4 5.2
12000 1.4 34.5 215 36 18 9.5 5.2 | 1.5 34.7 225 29 15 9.3 5.1
11500 2.9 37.2 215 36 18 9.6 5.3 | 2.8 37.0 225 29 15 9.2 5.0
11000 4.3 39.7 215 35 18 9.1 5.0 | 4.2 39.6 230 28 15 8.5 4.7
10500 5.6 42.1 215 34 18 7.8 4.3 | 5.4 41.7 230 27 14 6.8 3.8
10250 6.2 43.2 215 33 17 11.1 6.1 | 6.0 42.8 230 27 14 11.4 6.2
10000 7.2 45.0 215 34 18 12.1 6.6 | 7.0 44.6 230 27 14 12.2 6.7
9750 8.0 46.4 215 34 17 9.4 5.1 | 7.7 45.9 235 27 14 8.2 4.5
9500 8.7 47.7 215 33 17 9.9 5.4 | 8.3 46.9 235 26 14 8.7 4.8
9250 9.4 48.9 215 33 17 10.0 5.5 | 9.0 48.2 235 26 13 9.8 5.4
9000 10.2 50.4 215 34 17 10.1 5.5 | 9.8 49.6 235 26 13 10.3 5.6
8750 10.9 51.6 215 33 17 9.9 5.4 | 10.5 50.9 240 25 13 9.1 5.0
8500 12.4 54.3 215 32 17 10.2 5.6 | 11.2 52.2 240 25 13 9.5 5.2
8250 13.2 55.8 215 31 16 10.4 5.7 | 12.6 54.7 240 24 12 9.4 5.2
8000 13.9 57.0 215 30 16 9.9 5.4 | 13.3 55.9 245 24 12 9.7 5.3
7750 14.7 58.5 215 30 15 9.8 5.3 | 14.0 57.2 245 23 12 9.9 5.4
7500 15.4 59.7 215 30 15 9.5 5.2 | 14.7 58.5 245 22 11 9.3 5.1
7250 16.1 61.0 215 29 15 9.0 5.0 | 15.4 59.7 245 22 12 8.5 4.7
7000 16.8 62.2 215 29 15 9.9 5.4 | 16.1 61.0 245 22 11 9.8 5.4
6750 17.5 63.5 215 27 14 10.2 5.6 | 16.9 62.4 245 21 11 10.8 5.9
6500 18.3 64.9 215 26 14 10.9 6.0 | 17.6 63.7 250 19 10 10.3 5.7
6250 19.2 66.6 215 26 13 12.6 6.9 | 18.4 65.1 250 20 10 10.7 5.9
6000 20.0 68.0 215 25 13 8.6 4.7 | 19.2 66.6 250 19 10 8.5 4.6
5750 20.6 69.1 220 23 12 10.0 5.5 | 19.7 67.5 250 17 9 7.8 4.3
5500 22.9 73.2 220 19 10 66.9 36.7 | 21.0 69.8 250 15 8 36.4 20.0
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
________________________________________________________________________________
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 at Walker Field in Grand
Junction, Colorado at
North Latitude: 39 deg 07 min 00.001 sec
West Longitude: 108 deg 31 min 59.998 sec
Elevation: 4839 feet (1475 meters)
and may not be representative of other areas along the Western Slope of
Colorado. 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.
CINH (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.
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