Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
390
UXUS97 KGJT 181306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
706 AM MDT Wednesday, September 18, 2024
This forecast is for Wednesday, September 18, 2024:
If the trigger temperature of 67.4 F/19.7 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 840 ft/min (4.3 m/s)
Maximum height of thermals.................. 14910 ft MSL (10071 ft AGL)
Forecast maximum temperature................... 77.0 F/25.5 C
Time of trigger temperature.................... 1130 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................. 11972 ft MSL (7133 ft AGL)
Thermal soaring outlook for Thursday 09/19..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:59:00 / 19:17:02 MDT
Total possible sunshine........... 12 hr 18 min 2 sec (738 min 2 sec)
Altitude of sun at 13:08:01 MDT... 52.29 degrees
Upper air data from rawinsonde observation taken on 09/18/2024 at 0600 MDT
Freezing level.................. 12145 ft MSL (7306 ft AGL)
Convective condensation level... 18669 ft MSL (13830 ft AGL)
Lifted condensation level....... 16516 ft MSL (11677 ft AGL)
Lifted index.................... +6.4
K index......................... +6.6
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 -59.6 -75.3 255 53 27 -2.2 -1.2 96.6 205.8 41.3 M M
45000 -55.0 -67.0 255 76 39 3.1 1.7 79.7 175.4 33.8 M M
40000 -51.0 -59.8 255 91 47 4.3 2.3 63.0 145.4 25.1 M M
38000 -47.9 -54.2 260 97 50 -3.1 -1.7 57.9 136.2 22.4 M M
36000 -48.7 -55.7 260 84 43 8.3 4.6 48.1 118.6 16.2 M M
34000 -43.4 -46.1 255 78 40 8.9 4.9 47.3 117.1 16.0 M M
32000 -38.1 -36.6 255 71 37 9.0 4.9 46.5 115.8 15.8 M M
30000 -33.0 -27.4 250 73 38 6.7 3.7 45.5 113.9 15.4 M M
29000 -30.9 -23.6 250 72 37 7.1 3.9 44.5 112.0 14.8 M M
28000 -28.8 -19.8 255 69 36 6.8 3.7 43.4 110.1 14.1 M M
27000 -26.5 -15.7 255 69 35 6.6 3.6 42.7 108.8 13.7 M M
26000 -24.5 -12.1 255 63 32 7.5 4.1 41.5 106.7 12.9 M M
25000 -22.1 -7.8 250 58 30 7.9 4.3 40.8 105.4 12.5 M M
24000 -19.7 -3.5 245 57 29 8.2 4.5 40.1 104.2 12.1 M M
23000 -17.8 -0.0 245 57 30 4.8 2.6 39.0 102.2 11.3 M M
22000 -16.5 2.3 250 51 26 4.1 2.2 36.9 98.5 9.8 M M
21000 -14.7 5.5 245 47 24 5.2 2.9 35.5 95.9 8.7 M M
20000 -12.8 9.0 245 45 23 5.7 3.1 33.4 92.1 7.1 M M
19500 -11.9 10.6 250 43 22 5.5 3.0 32.8 91.0 6.6 M M
19000 -11.2 11.8 245 40 21 5.5 3.0 32.0 89.5 5.9 M M
18500 -10.4 13.3 250 39 20 5.5 3.0 31.2 88.2 5.3 M M
18000 -9.5 14.9 250 38 20 5.9 3.3 30.5 86.9 4.7 M M
17500 -8.6 16.5 245 38 20 6.2 3.4 29.9 85.8 4.1 M M
17000 -7.8 18.0 245 35 18 3.7 2.0 29.1 84.4 3.5 M M
16500 -7.4 18.7 245 32 16 3.0 1.6 28.0 82.3 2.4 M M
16000 -6.8 19.8 245 35 18 6.6 3.6 27.0 80.6 1.6 M M
15500 -5.9 21.4 240 33 17 4.2 2.3 26.4 79.5 1.0 M M
15000 -5.4 22.3 240 32 16 4.4 2.4 25.4 77.7 0.1 M M
14500 -4.6 23.7 225 33 17 6.0 3.3 24.7 76.5 -0.6 803 4.1
14000 -3.7 25.3 235 31 16 6.0 3.3 24.1 75.3 -1.1 761 3.9
13500 -2.8 27.0 235 29 15 6.0 3.3 23.4 74.2 -1.7 719 3.7
13000 -1.9 28.6 230 25 13 5.9 3.2 22.8 73.1 -2.3 677 3.4
12500 -0.8 30.6 225 21 11 8.5 4.7 22.4 72.3 -2.7 631 3.2
12000 0.4 32.7 220 17 9 8.5 4.6 22.2 71.9 -3.0 580 2.9
11500 1.7 35.1 215 18 9 8.6 4.7 22.0 71.6 -3.2 526 2.7
11000 3.0 37.4 220 17 9 8.9 4.9 21.8 71.2 -3.4 473 2.4
10500 4.1 39.4 225 15 8 6.4 3.5 21.5 70.6 -3.7 424 2.2
10250 4.6 40.3 225 14 7 7.0 3.8 21.2 70.2 -4.0 403 2.0
10000 5.1 41.2 225 14 7 7.5 4.1 21.0 69.9 -4.2 380 1.9
9750 5.6 42.1 210 13 7 7.8 4.3 20.9 69.6 -4.4 356 1.8
9500 6.2 43.2 215 12 6 7.7 4.2 20.7 69.3 -4.6 332 1.7
9250 6.7 44.1 220 11 6 7.5 4.1 20.5 69.0 -4.8 308 1.6
9000 7.3 45.1 225 11 6 7.5 4.1 20.4 68.7 -5.0 284 1.4
8750 7.8 46.0 225 11 6 7.5 4.1 20.2 68.4 -5.2 260 1.3
8500 8.4 47.1 240 11 6 7.5 4.1 20.0 68.1 -5.3 236 1.2
8250 9.0 48.2 240 11 6 7.5 4.1 19.9 67.8 -5.5 211 1.1
8000 9.5 49.1 240 12 6 7.5 4.1 19.7 67.5 -5.7 187 1.0
7750 10.1 50.2 240 12 6 7.5 4.1 19.5 67.1 -5.9 163 0.8
7500 10.6 51.1 245 11 6 7.5 4.1 19.3 66.8 -6.1 139 0.7
7250 11.2 52.2 245 9 5 7.5 4.1 19.2 66.5 -6.3 115 0.6
7000 11.8 53.2 245 6 3 7.5 4.1 19.0 66.2 -6.5 91 0.5
6750 12.3 54.1 240 4 2 7.5 4.1 18.8 65.9 -6.6 67 0.3
6500 12.9 55.2 255 2 1 7.6 4.2 18.6 65.6 -6.8 42 0.2
6250 13.4 56.1 160 1 0 7.2 3.9 18.5 65.2 -7.0 18 0.1
6000 14.0 57.2 125 3 2 8.8 4.8 18.3 64.9 -7.2 M M
5750 14.5 58.1 130 5 2 0.4 0.2 18.1 64.5 -7.5 M M
5500 13.9 57.0 135 7 4 -11.1 -6.1 16.8 62.2 -8.8 M M
5250 13.0 55.4 140 10 5 -11.6 -6.4 15.2 59.3 -10.5 1 0.0
5000 12.1 53.8 135 12 6 -11.8 -6.5 13.6 56.4 -12.1 21 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/18/2024 at 0900 MDT | 09/18/2024 at 1200 MDT
|
CAPE... 0.0 LI... +7.1 | CAPE... 0.0 LI... +7.4
CINH... -0.1 K Index... +2.1 | CINH... -0.1 K Index... -1.2
|
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 -59.2 -74.6 245 57 30 1.7 0.9 | -60.2 -76.4 240 60 31 1.6 0.9
45000 -56.2 -69.2 250 84 43 3.2 1.7 | -57.1 -70.8 250 85 44 4.0 2.2
40000 -51.5 -60.7 255 98 50 3.5 1.9 | -50.7 -59.3 250 96 50 4.9 2.7
38000 -48.7 -55.7 250 89 46 4.1 2.2 | -47.9 -54.2 250 94 48 4.8 2.6
36000 -46.3 -51.3 250 81 42 4.1 2.2 | -45.0 -49.0 245 92 47 4.8 2.6
34000 -42.5 -44.5 250 75 39 7.5 4.1 | -41.6 -42.9 245 87 45 6.1 3.3
32000 -38.0 -36.4 250 70 36 7.5 4.1 | -37.9 -36.2 245 80 41 6.1 3.3
30000 -33.2 -27.8 250 67 34 8.3 4.5 | -33.4 -28.1 245 76 39 8.5 4.6
29000 -30.7 -23.3 250 66 34 8.3 4.5 | -30.9 -23.6 245 75 38 8.5 4.6
28000 -28.2 -18.8 250 64 33 8.3 4.5 | -28.4 -19.1 245 73 38 8.5 4.6
27000 -25.9 -14.6 250 63 32 7.2 3.9 | -26.0 -14.8 245 71 36 7.8 4.3
26000 -23.8 -10.8 250 61 31 7.2 3.9 | -23.6 -10.5 245 68 35 7.7 4.2
25000 -21.7 -7.1 250 59 30 7.2 4.0 | -20.7 -5.3 240 64 33 7.8 4.3
24000 -19.2 -2.6 245 55 28 5.9 3.3 | -18.7 -1.7 240 60 31 5.9 3.3
23000 -17.5 0.5 245 51 27 5.9 3.2 | -17.0 1.4 240 56 29 5.9 3.3
22000 -15.7 3.7 245 48 25 5.9 3.2 | -15.2 4.6 240 52 27 6.0 3.3
21000 -14.0 6.8 245 45 23 5.8 3.2 | -13.5 7.7 240 47 24 5.9 3.2
20000 -12.2 10.0 245 42 21 5.8 3.2 | -11.7 10.9 240 43 22 5.9 3.2
19500 -11.3 11.7 250 40 21 5.8 3.2 | -10.8 12.6 240 41 21 5.9 3.2
19000 -10.5 13.1 250 39 20 5.8 3.2 | -10.0 14.0 240 39 20 5.8 3.2
18500 -9.6 14.7 250 38 19 5.8 3.2 | -9.1 15.6 240 37 19 5.7 3.1
18000 -8.7 16.3 250 36 19 5.8 3.2 | -8.2 17.2 240 35 18 5.7 3.1
17500 -7.9 17.8 250 35 18 5.3 2.9 | -7.4 18.7 240 33 17 5.7 3.1
17000 -7.1 19.2 250 34 17 5.3 2.9 | -6.5 20.3 240 31 16 5.7 3.1
16500 -6.4 20.5 245 33 17 5.0 2.8 | -5.7 21.7 240 30 15 5.5 3.0
16000 -5.7 21.7 245 32 16 4.6 2.5 | -4.9 23.2 240 29 15 5.1 2.8
15500 -5.0 23.0 245 31 16 4.6 2.5 | -4.2 24.4 240 28 15 5.1 2.8
15000 -4.3 24.3 240 30 16 4.7 2.6 | -3.5 25.7 240 28 14 4.4 2.4
14500 -3.7 25.3 240 29 15 4.7 2.6 | -2.9 26.8 240 27 14 4.5 2.4
14000 -3.0 26.6 240 28 14 4.9 2.7 | -2.2 28.0 240 26 13 4.7 2.6
13500 -2.3 27.9 235 27 14 4.9 2.7 | -1.5 29.3 235 24 13 4.7 2.6
13000 -1.5 29.3 235 25 13 5.6 3.1 | -0.8 30.6 235 23 12 5.6 3.1
12500 -0.7 30.7 230 23 12 5.8 3.2 | 0.0 32.0 230 22 11 5.8 3.2
12000 0.2 32.4 230 21 11 6.5 3.6 | 0.9 33.6 230 20 10 6.7 3.7
11500 1.2 34.2 225 19 10 6.9 3.8 | 2.0 35.6 230 18 10 7.1 3.9
11000 2.2 36.0 225 17 9 6.7 3.7 | 3.0 37.4 225 17 9 7.0 3.9
10500 3.2 37.8 220 14 7 6.1 3.3 | 4.0 39.2 225 15 8 6.2 3.4
10250 3.6 38.5 220 13 7 8.5 4.7 | 4.6 40.3 225 14 7 10.3 5.6
10000 4.4 39.9 215 12 6 9.3 5.1 | 5.5 41.9 220 14 7 10.9 6.0
9750 5.0 41.0 215 12 6 7.3 4.0 | 6.1 43.0 220 13 7 7.3 4.0
9500 5.5 41.9 215 11 6 7.9 4.3 | 6.7 44.1 220 12 6 8.6 4.7
9250 6.1 43.0 210 10 5 7.7 4.2 | 7.3 45.1 220 12 6 7.3 4.0
9000 6.7 44.1 210 9 5 7.3 4.0 | 7.8 46.0 220 10 5 7.9 4.3
8750 7.2 45.0 205 9 5 7.0 3.9 | 9.1 48.4 220 9 5 9.2 5.1
8500 7.7 45.9 205 9 4 7.2 3.9 | 9.8 49.6 220 9 5 7.6 4.2
8250 8.8 47.8 195 8 4 6.3 3.4 | 10.3 50.5 220 7 4 7.3 4.0
8000 9.2 48.6 190 8 4 6.1 3.4 | 11.0 51.8 225 7 3 10.2 5.6
7750 9.7 49.5 185 7 4 6.4 3.5 | 11.8 53.2 220 7 4 11.5 6.3
7500 10.2 50.4 180 7 4 5.2 2.9 | 12.6 54.7 220 7 4 8.8 4.8
7250 10.5 50.9 175 7 4 4.1 2.3 | 13.1 55.6 225 6 3 6.9 3.8
7000 10.8 51.4 175 7 4 6.2 3.4 | 13.7 56.7 225 5 3 11.2 6.1
6750 11.4 52.5 165 6 3 6.8 3.7 | 14.7 58.5 225 6 3 12.7 6.9
6500 11.8 53.2 160 6 3 5.2 2.9 | 15.5 59.9 225 6 3 10.1 5.5
6250 12.1 53.8 155 5 3 4.6 2.5 | 16.3 61.3 230 5 3 9.9 5.4
6000 12.5 54.5 145 5 3 5.9 3.2 | 17.0 62.6 230 4 2 8.7 4.8
5750 13.1 55.6 145 4 2 10.5 5.8 | 17.7 63.9 225 5 3 14.3 7.8
5500 14.0 57.2 125 3 2 16.5 9.0 | 20.3 68.5 240 4 2 67.2 36.9
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
09/18/2024 at 1500 MDT | 09/18/2024 at 1800 MDT
|
CAPE... 0.0 LI... +5.7 | CAPE... 0.0 LI... +5.3
CINH... -0.1 K Index... +4.0 | CINH... -0.0 K Index... +6.5
|
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 -61.0 -77.8 240 58 30 1.3 0.7 | -61.4 -78.5 245 59 30 1.0 0.6
45000 -57.9 -72.2 245 83 43 4.9 2.7 | -58.4 -73.1 245 84 43 5.3 2.9
40000 -50.2 -58.4 250 97 50 5.0 2.7 | -50.1 -58.2 250 97 50 5.1 2.8
38000 -47.2 -53.0 250 96 50 5.0 2.7 | -47.0 -52.6 250 94 48 5.1 2.8
36000 -44.2 -47.6 245 96 49 5.0 2.7 | -43.9 -47.0 245 90 47 5.1 2.8
34000 -41.1 -42.0 245 92 47 5.3 2.9 | -40.7 -41.3 245 87 45 5.5 3.0
32000 -37.9 -36.2 240 86 44 5.3 2.9 | -37.3 -35.1 245 84 43 5.5 3.0
30000 -33.8 -28.8 240 82 42 8.1 4.4 | -33.3 -27.9 245 79 41 7.5 4.1
29000 -31.3 -24.3 240 80 41 8.1 4.4 | -31.1 -24.0 240 76 39 7.5 4.1
28000 -28.9 -20.0 240 79 41 8.1 4.4 | -28.8 -19.8 240 73 38 7.5 4.1
27000 -26.5 -15.7 240 76 39 7.8 4.3 | -26.6 -15.9 240 70 36 7.5 4.1
26000 -24.2 -11.6 240 73 37 7.8 4.3 | -24.3 -11.7 240 67 34 7.5 4.1
25000 -21.8 -7.2 240 69 36 7.8 4.3 | -21.5 -6.7 240 62 32 7.5 4.1
24000 -19.1 -2.4 240 64 33 6.8 3.7 | -19.4 -2.9 240 59 30 6.9 3.8
23000 -17.1 1.2 235 60 31 6.8 3.7 | -17.3 0.9 240 55 28 6.9 3.8
22000 -15.0 5.0 235 55 28 6.8 3.7 | -15.2 4.6 240 51 26 7.0 3.9
21000 -13.2 8.2 235 51 26 5.6 3.1 | -13.4 7.9 240 47 24 5.7 3.1
20000 -11.6 11.1 235 46 24 5.6 3.1 | -11.7 10.9 240 43 22 5.7 3.1
19500 -10.7 12.7 235 44 23 5.6 3.1 | -10.9 12.4 240 41 21 5.6 3.1
19000 -9.9 14.2 235 41 21 5.6 3.1 | -10.0 14.0 240 38 20 5.5 3.0
18500 -9.1 15.6 235 39 20 5.5 3.0 | -9.2 15.4 240 36 18 5.4 2.9
18000 -8.2 17.2 235 37 19 5.5 3.0 | -8.4 16.9 240 33 17 5.4 3.0
17500 -7.4 18.7 235 34 18 5.1 2.8 | -7.7 18.1 240 31 16 4.6 2.5
17000 -6.7 19.9 235 32 16 5.1 2.8 | -7.0 19.4 235 28 14 4.7 2.6
16500 -6.0 21.2 235 30 15 5.1 2.8 | -6.3 20.7 235 25 13 5.0 2.7
16000 -5.2 22.6 235 28 14 5.0 2.8 | -5.6 21.9 230 23 12 5.2 2.9
15500 -4.5 23.9 235 26 13 5.1 2.8 | -4.8 23.4 230 21 11 5.5 3.0
15000 -3.7 25.3 230 24 13 5.8 3.2 | -3.9 25.0 225 20 10 7.2 4.0
14500 -2.9 26.8 230 23 12 5.7 3.1 | -2.9 26.8 225 18 9 7.1 3.9
14000 -2.0 28.4 230 22 11 6.7 3.7 | -1.8 28.8 220 17 9 8.6 4.7
13500 -1.1 30.0 225 21 11 6.6 3.6 | -0.5 31.1 220 16 8 8.5 4.6
13000 -0.1 31.8 225 19 10 7.8 4.3 | 0.8 33.4 220 15 8 8.8 4.8
12500 1.1 34.0 225 18 9 8.1 4.4 | 2.1 35.8 220 14 7 8.8 4.8
12000 2.3 36.1 220 16 8 8.6 4.7 | 3.4 38.1 225 14 7 8.9 4.9
11500 3.6 38.5 225 15 8 8.8 4.8 | 4.7 40.5 225 13 7 8.9 4.9
11000 4.9 40.8 225 14 7 7.7 4.2 | 6.0 42.8 230 12 6 7.7 4.2
10500 6.0 42.8 225 13 7 6.2 3.4 | 7.1 44.8 230 11 6 6.2 3.4
10250 6.5 43.7 225 12 6 10.8 5.9 | 7.6 45.7 235 11 6 10.9 6.0
10000 7.5 45.5 225 12 6 11.7 6.4 | 8.6 47.5 235 11 6 11.7 6.4
9750 8.1 46.6 230 12 6 7.6 4.2 | 9.3 48.7 240 10 5 7.4 4.1
9500 8.8 47.8 230 11 6 9.3 5.1 | 9.9 49.8 240 10 5 8.9 4.9
9250 9.4 48.9 235 11 5 6.7 3.7 | 10.5 50.9 245 10 5 7.2 3.9
9000 9.9 49.8 240 9 5 7.7 4.2 | 11.0 51.8 250 10 5 7.6 4.2
8750 10.6 51.1 245 9 5 10.6 5.8 | 12.3 54.1 255 9 5 9.2 5.0
8500 12.1 53.8 245 9 5 9.2 5.1 | 13.0 55.4 260 9 4 7.7 4.2
8250 12.7 54.9 255 9 4 8.9 4.9 | 13.5 56.3 270 9 5 7.2 4.0
8000 13.5 56.3 255 8 4 10.2 5.6 | 14.2 57.6 275 9 5 9.2 5.0
7750 14.3 57.7 255 9 4 10.8 5.9 | 14.9 58.8 275 9 4 9.7 5.3
7500 15.0 59.0 255 9 4 9.3 5.1 | 15.6 60.1 275 8 4 8.6 4.7
7250 15.7 60.3 260 8 4 8.3 4.5 | 16.2 61.2 280 9 5 8.1 4.4
7000 16.4 61.5 265 8 4 10.7 5.8 | 16.8 62.2 280 9 5 10.2 5.6
6750 17.2 63.0 260 8 4 11.6 6.4 | 17.7 63.9 280 9 4 11.1 6.1
6500 18.1 64.6 260 8 4 10.6 5.8 | 18.4 65.1 280 8 4 10.0 5.5
6250 18.8 65.8 270 8 4 11.0 6.0 | 19.2 66.6 285 9 5 10.1 5.5
6000 19.6 67.3 275 8 4 8.1 4.4 | 19.9 67.8 285 9 5 8.2 4.5
5750 20.2 68.4 265 8 4 12.1 6.6 | 20.5 68.9 280 8 4 8.2 4.5
5500 23.0 73.4 280 7 4 79.4 43.6 | 21.9 71.4 290 8 4 38.2 21.0
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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