Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
184
UXUS97 KGJT 201307
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
707 AM MDT Friday, September 20, 2024
This forecast is for Friday, September 20, 2024:
If the trigger temperature of 77.4 F/25.2 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 955 ft/min (4.9 m/s)
Maximum height of thermals.................. 15495 ft MSL (10649 ft AGL)
Forecast maximum temperature................... 84.0 F/29.3 C
Time of trigger temperature.................... 1145 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................. 9150 ft MSL (4304 ft AGL)
Thermal soaring outlook for Saturday 09/21..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:00:49 / 19:13:48 MDT
Total possible sunshine........... 12 hr 12 min 59 sec (732 min 59 sec)
Altitude of sun at 13:07:18 MDT... 51.52 degrees
Upper air data from rawinsonde observation taken on 09/20/2024 at 0600 MDT
Freezing level.................. 14301 ft MSL (9455 ft AGL)
Convective condensation level... 16766 ft MSL (11920 ft AGL)
Lifted condensation level....... 16741 ft MSL (11895 ft AGL)
Lifted index.................... +2.8
K index......................... +20.1
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 -63.7 -82.7 235 54 28 3.7 2.0 88.8 191.9 34.7 M M
45000 -57.6 -71.7 240 84 43 -1.7 -0.9 73.5 164.2 27.7 M M
40000 -50.3 -58.5 235 101 52 7.3 4.0 62.0 143.6 22.0 M M
38000 -46.1 -51.0 235 106 55 6.4 3.5 59.5 139.1 20.9 M M
36000 -42.7 -44.9 230 100 51 4.7 2.6 56.0 132.8 19.0 M M
34000 -39.1 -38.4 225 90 47 5.6 3.1 52.9 127.2 17.2 M M
32000 -34.7 -30.5 230 86 44 9.3 5.1 49.9 121.9 15.5 M M
30000 -31.1 -24.0 225 76 39 4.6 2.5 46.9 116.4 13.6 M M
29000 -30.4 -22.7 225 73 38 7.5 4.1 44.0 111.3 11.6 M M
28000 -27.8 -18.0 225 72 37 8.8 4.8 43.7 110.6 11.4 M M
27000 -25.5 -13.9 225 66 34 7.9 4.4 42.8 109.0 10.9 M M
26000 -23.4 -10.1 230 57 29 6.9 3.8 41.8 107.3 10.2 M M
25000 -21.0 -5.8 230 53 27 8.3 4.6 41.1 106.0 9.8 M M
24000 -19.0 -2.2 225 46 24 6.3 3.5 40.0 104.0 9.0 M M
23000 -16.6 2.1 225 48 25 5.9 3.2 39.3 102.8 8.6 M M
22000 -15.1 4.8 225 42 22 6.8 3.7 37.6 99.7 7.2 M M
21000 -13.1 8.4 220 36 18 6.9 3.8 36.6 97.9 6.4 M M
20000 -11.0 12.2 215 36 18 7.4 4.0 35.6 96.1 5.7 M M
19500 -10.1 13.8 215 36 18 1.7 0.9 34.9 94.9 5.1 M M
19000 -9.8 14.4 210 35 18 6.9 3.8 33.7 92.6 4.0 M M
18500 -11.3 11.7 210 34 17 -7.7 -4.2 30.4 86.7 1.0 M M
18000 -10.2 13.6 205 31 16 6.9 3.8 30.1 86.2 0.6 M M
17500 -8.2 17.2 210 33 17 9.4 5.2 29.9 85.9 0.4 M M
17000 -6.9 19.6 205 32 16 9.4 5.2 29.9 85.8 0.3 M M
16500 -5.5 22.1 210 30 15 9.2 5.0 29.8 85.6 0.3 M M
16000 -4.2 24.4 200 29 15 8.6 4.7 29.7 85.4 0.1 M M
15500 -2.9 26.8 205 30 15 8.6 4.7 29.5 85.1 -0.0 947 4.8
15000 -1.6 29.1 210 26 13 8.6 4.7 29.4 84.8 -0.2 893 4.5
14500 -0.3 31.5 215 27 14 8.6 4.7 29.2 84.5 -0.3 840 4.3
14000 0.9 33.6 205 28 14 8.6 4.7 29.0 84.2 -0.5 787 4.0
13500 2.2 36.0 200 25 13 8.6 4.7 28.8 83.9 -0.7 734 3.7
13000 3.5 38.3 205 21 11 8.6 4.7 28.6 83.5 -0.9 681 3.5
12500 4.8 40.6 210 18 9 8.6 4.7 28.5 83.2 -1.1 627 3.2
12000 6.1 43.0 215 15 8 8.6 4.7 28.3 82.9 -1.3 574 2.9
11500 7.3 45.1 210 15 8 8.6 4.7 28.1 82.5 -1.5 521 2.6
11000 8.6 47.5 215 13 7 8.6 4.7 27.9 82.1 -1.7 468 2.4
10500 9.9 49.8 200 15 8 8.6 4.7 27.6 81.8 -1.9 415 2.1
10250 10.5 50.9 190 13 7 8.9 4.9 27.5 81.6 -2.0 388 2.0
10000 11.2 52.2 170 9 5 9.0 4.9 27.5 81.5 -2.1 361 1.8
9750 11.9 53.4 170 9 5 9.9 5.4 27.4 81.4 -2.2 333 1.7
9500 12.6 54.7 170 9 5 6.2 3.4 27.4 81.3 -2.2 306 1.6
9250 12.8 55.0 165 10 5 1.6 0.9 26.8 80.3 -2.7 292 1.5
9000 13.0 55.4 160 11 6 3.9 2.1 26.3 79.3 -3.3 279 1.4
8750 13.3 55.9 155 10 5 5.8 3.2 25.9 78.7 -3.6 260 1.3
8500 13.8 56.8 150 8 4 5.9 3.2 25.6 78.1 -3.9 240 1.2
8250 14.2 57.6 145 8 4 5.8 3.2 25.3 77.6 -4.2 219 1.1
8000 14.7 58.5 145 11 5 6.0 3.3 25.0 77.0 -4.5 199 1.0
7750 15.1 59.2 145 11 6 5.5 3.0 24.7 76.5 -4.8 178 0.9
7500 15.5 59.9 150 11 6 7.1 3.9 24.4 76.0 -5.1 158 0.8
7250 16.0 60.8 130 9 5 1.2 0.6 24.1 75.4 -5.4 137 0.7
7000 15.8 60.4 110 9 5 0.3 0.2 23.2 73.8 -6.3 133 0.7
6750 16.2 61.2 110 10 5 7.7 4.2 22.9 73.2 -6.7 114 0.6
6500 16.8 62.2 105 9 5 7.7 4.2 22.7 72.9 -6.8 90 0.5
6250 17.4 63.3 105 9 5 7.9 4.3 22.6 72.7 -7.0 65 0.3
6000 18.0 64.4 105 9 5 7.3 4.0 22.4 72.4 -7.2 41 0.2
5750 18.5 65.3 095 9 5 9.3 5.1 22.3 72.1 -7.3 16 0.1
5500 19.0 66.2 090 10 5 -1.2 -0.7 22.1 71.7 -7.6 M M
5250 18.1 64.6 090 10 5 -22.2 -12.2 20.4 68.7 -9.3 16 0.1
5000 16.0 60.8 105 9 5 -27.9 -15.3 17.6 63.7 -12.1 69 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/20/2024 at 0900 MDT | 09/20/2024 at 1200 MDT
|
CAPE... 0.0 LI... +1.8 | CAPE... 0.0 LI... +2.4
CINH... -0.1 K Index... +20.9 | CINH... -0.0 K Index... +11.2
|
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 -62.5 -80.5 240 52 27 2.8 1.5 | -61.8 -79.2 235 50 26 2.6 1.4
45000 -57.4 -71.3 235 68 35 5.3 2.9 | -57.0 -70.6 225 69 36 5.1 2.8
40000 -49.0 -56.2 230 92 47 5.8 3.2 | -48.9 -56.0 225 96 49 5.4 3.0
38000 -45.5 -49.9 230 94 49 5.8 3.2 | -45.7 -50.3 225 99 51 5.4 3.0
36000 -42.0 -43.6 225 97 50 5.8 3.2 | -42.5 -44.5 225 101 52 5.4 3.0
34000 -38.7 -37.7 225 93 48 5.5 3.0 | -39.2 -38.6 225 97 50 5.5 3.0
32000 -35.4 -31.7 225 87 45 5.5 3.0 | -35.9 -32.6 220 91 47 5.5 3.0
30000 -31.9 -25.4 225 81 42 6.0 3.3 | -32.4 -26.3 220 83 43 6.0 3.3
29000 -30.1 -22.2 225 77 40 6.0 3.3 | -30.6 -23.1 220 79 41 6.0 3.3
28000 -28.3 -18.9 225 74 38 6.0 3.3 | -28.8 -19.8 220 75 38 6.0 3.3
27000 -26.3 -15.3 225 70 36 7.1 3.9 | -26.8 -16.2 220 70 36 6.8 3.7
26000 -23.6 -10.5 225 63 33 7.1 3.9 | -24.2 -11.6 220 63 32 6.8 3.8
25000 -21.5 -6.7 225 58 30 7.2 3.9 | -22.2 -8.0 220 57 29 6.8 3.8
24000 -19.4 -2.9 225 53 28 6.7 3.7 | -20.1 -4.2 220 53 27 6.7 3.7
23000 -17.4 0.7 225 49 25 6.7 3.7 | -18.1 -0.6 220 48 25 6.7 3.7
22000 -15.4 4.3 220 45 23 6.8 3.7 | -16.1 3.0 220 44 23 6.7 3.7
21000 -13.6 7.5 220 41 21 5.9 3.3 | -14.0 6.8 220 41 21 7.0 3.9
20000 -11.8 10.8 220 38 20 6.0 3.3 | -11.9 10.6 220 38 20 7.0 3.9
19500 -10.9 12.4 220 36 19 6.0 3.3 | -10.9 12.4 220 37 19 7.0 3.9
19000 -10.1 13.8 215 35 18 5.4 3.0 | -9.8 14.4 220 35 18 6.8 3.7
18500 -9.3 15.3 215 33 17 5.1 2.8 | -8.8 16.2 220 34 17 6.7 3.7
18000 -8.6 16.5 215 31 16 5.1 2.8 | -7.8 18.0 220 32 16 6.7 3.7
17500 -7.9 17.8 210 29 15 5.4 3.0 | -6.9 19.6 220 30 16 6.2 3.4
17000 -7.1 19.2 210 27 14 5.5 3.0 | -5.9 21.4 220 28 15 6.3 3.5
16500 -6.3 20.7 205 25 13 7.0 3.9 | -5.0 23.0 220 27 14 5.9 3.3
16000 -5.2 22.6 205 24 12 7.6 4.2 | -4.2 24.4 215 25 13 5.9 3.2
15500 -4.2 24.4 200 22 12 8.0 4.4 | -3.4 25.9 210 23 12 6.2 3.4
15000 -3.0 26.6 200 21 11 8.6 4.7 | -2.4 27.7 210 21 11 6.8 3.7
14500 -1.7 28.9 200 20 10 8.6 4.7 | -1.5 29.3 205 20 10 6.8 3.8
14000 -0.4 31.3 200 19 10 8.8 4.8 | -0.4 31.3 205 19 10 8.4 4.6
13500 0.8 33.4 205 17 9 8.8 4.8 | 0.8 33.4 205 18 9 8.3 4.5
13000 2.1 35.8 205 16 8 8.6 4.7 | 2.0 35.6 200 17 9 8.8 4.8
12500 3.4 38.1 205 15 8 8.6 4.7 | 3.3 37.9 200 16 8 8.8 4.8
12000 4.7 40.5 205 14 7 8.7 4.8 | 4.6 40.3 200 16 8 9.1 5.0
11500 6.0 42.8 205 13 7 8.7 4.8 | 6.0 42.8 200 15 8 9.2 5.1
11000 7.2 45.0 205 13 7 7.7 4.2 | 7.3 45.1 200 14 7 7.8 4.3
10500 8.4 47.1 205 12 6 7.0 3.9 | 8.4 47.1 200 14 7 6.6 3.6
10250 8.9 48.0 205 12 6 9.5 5.2 | 9.0 48.2 200 13 7 11.5 6.3
10000 9.7 49.5 205 12 6 9.8 5.4 | 10.0 50.0 200 14 7 12.3 6.8
9750 10.3 50.5 200 12 6 7.6 4.2 | 10.7 51.3 200 13 7 8.0 4.4
9500 10.9 51.6 200 12 6 8.0 4.4 | 11.3 52.3 200 13 7 9.4 5.2
9250 11.5 52.7 195 12 6 8.4 4.6 | 12.0 53.6 200 13 7 8.1 4.4
9000 12.2 54.0 195 12 6 7.7 4.2 | 13.3 55.9 200 12 6 9.8 5.4
8750 13.2 55.8 185 12 6 6.9 3.8 | 14.0 57.2 200 12 6 9.8 5.4
8500 13.7 56.7 180 11 6 6.4 3.5 | 14.7 58.5 195 12 6 8.8 4.8
8250 14.1 57.4 175 12 6 5.8 3.2 | 15.3 59.5 195 11 6 8.8 4.8
8000 14.6 58.3 175 12 6 5.8 3.2 | 16.1 61.0 195 10 5 10.1 5.5
7750 15.0 59.0 170 11 6 5.8 3.2 | 16.8 62.2 195 10 5 10.3 5.6
7500 15.4 59.7 165 10 5 4.7 2.6 | 17.6 63.7 195 10 5 9.2 5.0
7250 15.7 60.3 160 10 5 3.7 2.1 | 18.2 64.8 190 10 5 8.6 4.7
7000 16.0 60.8 160 10 5 4.3 2.3 | 18.9 66.0 190 9 5 10.4 5.7
6750 16.3 61.3 150 8 4 3.8 2.1 | 19.7 67.5 190 9 5 11.1 6.1
6500 16.5 61.7 145 7 4 2.8 1.5 | 20.5 68.9 190 9 5 10.8 5.9
6250 16.7 62.1 140 7 3 2.2 1.2 | 21.4 70.5 190 9 4 11.5 6.3
6000 16.9 62.4 130 6 3 3.7 2.0 | 22.2 72.0 190 8 4 8.0 4.4
5750 17.3 63.1 120 4 2 8.3 4.5 | 22.7 72.9 190 8 4 11.6 6.4
5500 18.1 64.6 105 4 2 11.6 6.4 | 25.5 77.9 185 7 3 81.9 44.9
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
09/20/2024 at 1500 MDT | 09/20/2024 at 1800 MDT
|
CAPE... +0.1 LI... +2.2 | CAPE... 0.0 LI... +2.3
CINH... -0.2 K Index... +14.3 | CINH... 0.0 K Index... +12.4
|
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 -61.7 -79.1 230 48 25 2.5 1.4 | -61.3 -78.3 230 46 24 1.7 1.0
45000 -57.0 -70.6 225 70 36 5.1 2.8 | -57.6 -71.7 225 66 34 4.8 2.7
40000 -48.9 -56.0 225 95 49 5.3 2.9 | -49.8 -57.6 230 83 43 6.0 3.3
38000 -45.8 -50.4 225 97 50 5.3 2.9 | -46.3 -51.3 225 85 44 5.9 3.2
36000 -42.6 -44.7 225 100 51 5.3 2.9 | -42.8 -45.0 225 88 45 5.9 3.2
34000 -39.5 -39.1 220 96 49 5.3 2.9 | -39.7 -39.5 225 85 44 4.9 2.7
32000 -36.3 -33.3 220 90 46 5.3 2.9 | -36.8 -34.2 225 79 40 4.8 2.7
30000 -32.8 -27.0 220 82 42 6.1 3.3 | -33.2 -27.8 225 71 36 6.5 3.6
29000 -31.0 -23.8 220 78 40 6.1 3.4 | -31.3 -24.3 225 66 34 6.5 3.6
28000 -29.1 -20.4 220 75 38 6.1 3.3 | -29.3 -20.7 225 62 32 6.5 3.6
27000 -27.2 -17.0 220 70 36 6.9 3.8 | -27.2 -17.0 225 59 30 7.2 3.9
26000 -24.6 -12.3 220 63 33 6.9 3.8 | -24.5 -12.1 225 55 28 7.2 3.9
25000 -22.5 -8.5 220 58 30 6.9 3.8 | -22.4 -8.3 225 53 27 7.2 3.9
24000 -20.4 -4.7 220 53 27 7.2 3.9 | -20.3 -4.5 225 49 25 6.9 3.8
23000 -18.2 -0.8 220 48 25 7.2 3.9 | -18.2 -0.8 225 44 23 6.9 3.8
22000 -16.1 3.0 220 44 23 7.2 3.9 | -16.1 3.0 225 39 20 6.9 3.8
21000 -14.0 6.8 220 40 21 7.1 3.9 | -14.0 6.8 220 35 18 7.1 3.9
20000 -11.8 10.8 220 36 19 7.1 3.9 | -11.9 10.6 220 30 16 7.1 3.9
19500 -10.8 12.6 220 34 18 7.1 3.9 | -10.9 12.4 220 28 14 7.1 3.9
19000 -9.7 14.5 220 32 17 6.7 3.7 | -9.8 14.4 215 26 13 6.8 3.8
18500 -8.8 16.2 220 30 16 6.4 3.5 | -8.8 16.2 215 24 12 6.7 3.7
18000 -7.8 18.0 220 28 15 6.5 3.5 | -7.8 18.0 215 22 12 6.7 3.7
17500 -6.9 19.6 215 26 14 6.4 3.5 | -6.8 19.8 210 21 11 6.8 3.7
17000 -6.0 21.2 215 24 13 6.4 3.5 | -5.9 21.4 210 20 10 6.8 3.7
16500 -5.0 23.0 215 23 12 7.0 3.8 | -4.8 23.4 205 19 10 7.4 4.1
16000 -4.0 24.8 210 21 11 7.2 4.0 | -3.7 25.3 205 18 9 7.7 4.2
15500 -3.0 26.6 210 20 10 7.6 4.2 | -2.6 27.3 205 17 9 8.0 4.4
15000 -1.8 28.8 210 19 10 8.4 4.6 | -1.4 29.5 205 17 9 8.6 4.7
14500 -0.6 30.9 205 18 10 8.4 4.6 | -0.1 31.8 205 16 8 8.6 4.7
14000 0.7 33.3 205 18 9 8.9 4.9 | 1.2 34.2 205 16 8 9.3 5.1
13500 2.0 35.6 205 17 9 8.9 4.9 | 2.5 36.5 205 15 8 9.2 5.1
13000 3.3 37.9 205 17 9 9.0 5.0 | 3.9 39.0 205 15 7 9.3 5.1
12500 4.7 40.5 205 16 8 9.0 5.0 | 5.3 41.5 210 14 7 9.3 5.1
12000 6.0 42.8 205 15 8 9.2 5.0 | 6.6 43.9 210 13 7 9.1 5.0
11500 7.4 45.3 205 15 8 9.2 5.1 | 8.0 46.4 210 13 7 9.1 5.0
11000 8.7 47.7 205 14 7 8.2 4.5 | 9.3 48.7 210 12 6 8.2 4.5
10500 9.9 49.8 205 13 7 7.8 4.3 | 10.4 50.7 215 11 6 7.8 4.3
10250 10.5 50.9 205 13 7 11.2 6.1 | 11.1 52.0 215 11 6 11.3 6.2
10000 11.5 52.7 205 13 7 11.4 6.2 | 12.0 53.6 215 11 6 10.9 6.0
9750 12.2 54.0 210 13 7 9.0 4.9 | 12.7 54.9 215 11 5 8.0 4.4
9500 12.9 55.2 210 12 6 9.7 5.3 | 13.3 55.9 220 10 5 8.5 4.7
9250 13.6 56.5 210 12 6 9.1 5.0 | 14.0 57.2 220 9 5 9.5 5.2
9000 15.0 59.0 215 11 6 10.0 5.5 | 15.4 59.7 225 10 5 8.3 4.6
8750 15.7 60.3 215 11 6 9.8 5.4 | 16.0 60.8 225 9 5 8.8 4.8
8500 16.5 61.7 215 12 6 10.1 5.6 | 16.6 61.9 230 9 5 8.2 4.5
8250 17.3 63.1 215 11 6 10.2 5.6 | 17.2 63.0 240 8 4 8.8 4.8
8000 18.0 64.4 215 11 6 9.9 5.4 | 17.9 64.2 240 8 4 9.7 5.3
7750 18.7 65.7 215 11 6 10.1 5.5 | 18.7 65.7 240 8 4 9.8 5.4
7500 19.5 67.1 215 11 6 9.5 5.2 | 19.4 66.9 240 9 4 8.9 4.9
7250 20.2 68.4 215 11 5 9.3 5.1 | 20.0 68.0 245 8 4 8.3 4.6
7000 20.9 69.6 220 10 5 10.2 5.6 | 20.7 69.3 245 8 4 9.6 5.3
6750 21.7 71.1 220 10 5 10.7 5.9 | 21.4 70.5 245 8 4 10.2 5.6
6500 22.5 72.5 220 10 5 11.0 6.0 | 22.2 72.0 245 8 4 10.5 5.8
6250 23.3 73.9 220 10 5 12.1 6.6 | 23.0 73.4 245 8 4 11.3 6.2
6000 24.2 75.6 220 9 5 8.0 4.4 | 23.8 74.8 250 8 4 8.2 4.5
5750 24.7 76.5 220 9 5 11.2 6.1 | 24.3 75.7 245 8 4 6.7 3.7
5500 27.5 81.5 225 8 4 84.0 46.1 | 25.6 78.1 255 7 3 39.7 21.8
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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