Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
323
UXUS97 KGJT 181307
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
707 AM MDT Saturday, May 18, 2024
This forecast is for Saturday, May 18, 2024:
If the trigger temperature of 75.8 F/24.4 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1632 ft/min (8.3 m/s)
Maximum height of thermals.................. 21593 ft MSL (16754 ft AGL)
Forecast maximum temperature................... 86.0 F/30.5 C
Time of trigger temperature.................... 1045 MDT
Time of overdevelopment........................ 1700 MDT
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 15715 ft MSL (10875 ft AGL)
Thermal soaring outlook for Sunday 05/19....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:57:48 / 20:23:26 MDT
Total possible sunshine........... 14 hr 25 min 39 sec (865 min 39 sec)
Altitude of sun at 13:10:37 MDT... 70.53 degrees
Upper air data from rawinsonde observation taken on 05/18/2024 at 0600 MDT
Freezing level.................. 13483 ft MSL (8644 ft AGL)
Convective condensation level... 16881 ft MSL (12042 ft AGL)
Lifted condensation level....... 18094 ft MSL (13255 ft AGL)
Lifted index.................... -2.5
K index......................... +21.1
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 -58.3 -72.9 260 46 24 5.1 2.8 101.3 214.3 40.9 M M
45000 -58.5 -73.3 245 38 20 -3.6 -2.0 75.3 167.5 27.9 M M
40000 -57.6 -71.7 240 43 22 6.3 3.5 53.6 128.5 15.6 M M
38000 -54.0 -65.2 250 49 25 5.9 3.3 50.3 122.6 13.8 M M
36000 -51.5 -60.7 255 49 25 4.1 2.2 45.5 113.8 10.8 M M
34000 -48.2 -54.8 260 47 24 6.3 3.5 41.8 107.2 8.4 M M
32000 -42.9 -45.2 250 45 23 9.1 5.0 41.1 106.0 8.1 M M
30000 -37.4 -35.3 265 48 25 8.2 4.5 39.6 103.2 7.2 M M
29000 -34.7 -30.5 265 47 24 9.0 4.9 39.2 102.6 7.0 M M
28000 -32.4 -26.3 260 43 22 7.3 4.0 38.5 101.2 6.5 M M
27000 -30.1 -22.2 265 41 21 8.2 4.5 37.7 99.9 6.0 M M
26000 -27.6 -17.7 260 46 24 8.2 4.5 37.2 98.9 5.6 M M
25000 -25.1 -13.2 260 45 23 8.4 4.6 36.6 97.8 5.2 M M
24000 -24.3 -11.7 265 42 22 -1.8 -1.0 34.1 93.3 3.2 M M
23000 -22.7 -8.9 270 38 20 5.5 3.0 32.4 90.3 1.9 M M
22000 -21.1 -6.0 260 34 18 5.6 3.0 30.9 87.6 0.6 M M
21000 -19.4 -2.9 270 30 16 7.7 4.2 29.5 85.1 -0.6 1587 8.1
20000 -17.0 1.4 280 30 15 8.4 4.6 29.0 84.3 -1.1 1483 7.5
19500 -15.7 3.7 275 30 16 8.4 4.6 28.8 83.8 -1.3 1431 7.3
19000 -14.5 5.9 270 31 16 8.4 4.6 28.5 83.4 -1.5 1379 7.0
18500 -13.3 8.1 280 32 17 8.3 4.6 28.3 82.9 -1.8 1328 6.7
18000 -12.0 10.4 280 32 16 8.3 4.6 28.1 82.5 -2.0 1276 6.5
17500 -10.8 12.6 280 31 16 8.5 4.7 27.8 82.0 -2.3 1225 6.2
17000 -9.5 14.9 275 29 15 8.9 4.9 27.7 81.8 -2.4 1171 5.9
16500 -7.5 18.5 285 28 14 9.0 4.9 27.4 81.4 -2.7 1090 5.5
16000 -6.3 20.7 275 23 12 8.2 4.5 27.2 81.0 -2.9 1037 5.3
15500 -5.1 22.8 270 19 10 8.6 4.7 27.0 80.6 -3.2 987 5.0
15000 -3.8 25.2 270 19 10 8.7 4.8 26.9 80.4 -3.3 933 4.7
14500 -2.5 27.5 275 17 9 8.7 4.8 26.7 80.1 -3.5 879 4.5
14000 -1.2 29.8 270 16 8 8.7 4.8 26.6 79.8 -3.6 825 4.2
13500 0.1 32.2 270 14 7 8.7 4.8 26.4 79.5 -3.8 771 3.9
13000 1.4 34.5 295 13 7 8.7 4.8 26.2 79.2 -4.0 718 3.6
12500 2.7 36.9 295 13 7 8.7 4.8 26.0 78.9 -4.2 664 3.4
12000 4.0 39.2 290 12 6 8.7 4.8 25.9 78.5 -4.4 610 3.1
11500 5.3 41.5 290 10 5 9.0 5.0 25.7 78.2 -4.6 556 2.8
11000 6.8 44.2 295 11 6 10.1 5.5 25.7 78.2 -4.6 498 2.5
10500 8.3 46.9 295 9 5 9.7 5.3 25.7 78.3 -4.6 439 2.2
10250 8.9 48.0 300 9 5 8.2 4.5 25.7 78.2 -4.7 412 2.1
10000 9.5 49.1 295 8 4 7.9 4.3 25.5 77.9 -4.9 387 2.0
9750 10.1 50.2 295 8 4 8.4 4.6 25.4 77.7 -5.0 361 1.8
9500 10.7 51.3 295 8 4 8.3 4.5 25.3 77.5 -5.1 336 1.7
9250 11.3 52.3 295 9 4 8.3 4.6 25.2 77.3 -5.2 310 1.6
9000 12.0 53.6 295 9 5 8.3 4.5 25.1 77.1 -5.3 284 1.4
8750 12.6 54.7 295 8 4 8.3 4.6 25.0 76.9 -5.5 258 1.3
8500 13.2 55.8 295 7 4 8.3 4.6 24.9 76.7 -5.6 232 1.2
8250 13.8 56.8 300 6 3 8.3 4.6 24.7 76.5 -5.7 206 1.0
8000 14.4 57.9 325 6 3 8.3 4.5 24.6 76.3 -5.8 180 0.9
7750 15.0 59.0 330 7 4 8.3 4.6 24.5 76.1 -6.0 154 0.8
7500 15.7 60.3 325 6 3 8.2 4.5 24.4 75.9 -6.1 128 0.7
7250 16.3 61.3 330 7 4 8.6 4.7 24.3 75.7 -6.2 102 0.5
7000 16.9 62.4 340 7 3 7.3 4.0 24.2 75.5 -6.4 77 0.4
6750 17.3 63.1 355 6 3 4.2 2.3 23.8 74.9 -6.7 57 0.3
6500 17.5 63.5 350 5 2 3.2 1.7 23.4 74.0 -7.2 42 0.2
6250 17.8 64.0 305 5 2 3.5 1.9 22.9 73.2 -7.7 28 0.1
6000 18.0 64.4 285 6 3 3.5 1.9 22.4 72.3 -8.2 13 0.1
5750 18.2 64.8 285 5 3 2.9 1.6 21.9 71.5 -8.7 M M
5500 18.5 65.3 280 4 2 5.3 2.9 21.4 70.6 -9.3 M M
5250 18.7 65.7 265 2 1 -3.6 -2.0 21.0 69.7 -9.8 M M
5000 17.5 63.5 000 0 0 -29.6 -16.2 19.0 66.2 -11.7 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/18/2024 at 0900 MDT | 05/18/2024 at 1200 MDT
|
CAPE... 0.0 LI... +1.2 | CAPE... +29.3 LI... +0.3
CINH... -0.0 K Index... +22.1 | CINH... -28.0 K Index... +23.6
|
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 -57.7 -71.9 250 33 17 1.0 0.6 | -57.2 -71.0 245 36 19 1.3 0.7
45000 -56.6 -69.9 245 34 17 -1.3 -0.7 | -55.9 -68.6 240 39 20 -2.0 -1.1
40000 -58.7 -73.7 235 45 23 -2.3 -1.3 | -58.8 -73.8 240 43 22 -2.6 -1.4
38000 -55.4 -67.7 240 45 23 6.6 3.6 | -56.1 -69.0 240 43 22 5.7 3.1
36000 -51.5 -60.7 245 45 23 6.6 3.6 | -52.7 -62.9 235 42 22 5.7 3.1
34000 -47.5 -53.5 245 44 23 6.9 3.8 | -48.7 -55.7 240 41 21 7.6 4.2
32000 -43.3 -45.9 250 42 21 6.9 3.8 | -44.1 -47.4 245 40 21 7.6 4.2
30000 -38.8 -37.8 255 41 21 8.0 4.4 | -39.4 -38.9 245 39 20 8.0 4.4
29000 -36.4 -33.5 255 41 21 8.0 4.4 | -37.0 -34.6 245 39 20 8.0 4.4
28000 -34.0 -29.2 255 42 22 8.0 4.4 | -34.6 -30.3 250 39 20 8.0 4.4
27000 -31.7 -25.1 255 42 21 7.1 3.9 | -31.7 -25.1 250 39 20 7.6 4.2
26000 -29.0 -20.2 255 40 21 7.2 3.9 | -29.4 -20.9 250 38 20 7.6 4.2
25000 -26.9 -16.4 255 39 20 7.2 3.9 | -27.2 -17.0 255 38 19 7.6 4.2
24000 -24.8 -12.6 255 37 19 6.6 3.6 | -25.0 -13.0 255 36 19 6.6 3.6
23000 -22.9 -9.2 255 35 18 6.6 3.6 | -23.1 -9.6 250 35 18 6.7 3.7
22000 -21.0 -5.8 255 32 17 6.7 3.7 | -21.1 -6.0 250 33 17 6.7 3.7
21000 -18.8 -1.8 255 31 16 8.1 4.4 | -18.9 -2.0 250 31 16 8.0 4.4
20000 -16.4 2.5 255 30 15 8.1 4.5 | -16.6 2.1 250 31 16 8.0 4.4
19500 -15.2 4.6 255 29 15 8.1 4.5 | -15.4 4.3 250 30 16 8.0 4.4
19000 -14.0 6.8 255 28 15 7.8 4.3 | -14.2 6.4 250 30 15 8.0 4.4
18500 -12.9 8.8 255 28 14 7.3 4.0 | -13.0 8.6 250 29 15 7.9 4.3
18000 -11.8 10.8 255 27 14 7.3 4.0 | -11.9 10.6 245 28 14 7.9 4.3
17500 -10.7 12.7 255 26 13 7.6 4.2 | -10.7 12.7 245 27 14 7.7 4.2
17000 -9.6 14.7 250 25 13 7.6 4.2 | -9.6 14.7 245 26 13 7.8 4.3
16500 -8.5 16.7 250 25 13 7.6 4.2 | -8.5 16.7 245 25 13 7.9 4.3
16000 -7.4 18.7 250 24 12 7.6 4.2 | -7.3 18.9 245 24 12 7.9 4.4
15500 -6.3 20.7 250 23 12 7.6 4.2 | -6.1 21.0 245 23 12 8.0 4.4
15000 -5.1 22.8 255 22 11 7.9 4.3 | -4.9 23.2 245 22 11 8.4 4.6
14500 -3.9 25.0 255 20 10 7.8 4.3 | -3.7 25.3 245 20 10 8.4 4.6
14000 -2.7 27.1 255 19 10 8.7 4.8 | -2.4 27.7 245 19 10 8.8 4.8
13500 -1.4 29.5 260 18 9 8.6 4.7 | -1.1 30.0 245 17 9 8.8 4.8
13000 -0.1 31.8 260 17 9 8.7 4.8 | 0.2 32.4 245 16 8 8.8 4.8
12500 1.2 34.2 265 16 8 8.8 4.8 | 1.6 34.9 245 15 8 8.8 4.8
12000 2.6 36.7 265 15 8 8.6 4.7 | 2.9 37.2 245 14 7 8.7 4.8
11500 3.9 39.0 270 14 7 8.6 4.7 | 4.2 39.6 245 13 7 8.8 4.8
11000 5.1 41.2 270 13 7 7.7 4.2 | 5.4 41.7 250 12 6 7.3 4.0
10500 6.2 43.2 275 12 6 6.9 3.8 | 6.5 43.7 250 11 5 5.9 3.2
10250 6.8 44.2 275 11 6 9.5 5.2 | 7.0 44.6 250 10 5 11.9 6.5
10000 7.6 45.7 275 11 5 9.7 5.3 | 8.2 46.8 255 9 5 13.2 7.2
9750 8.2 46.8 275 10 5 7.1 3.9 | 8.9 48.0 255 9 5 7.7 4.2
9500 8.8 47.8 275 9 5 8.0 4.4 | 9.5 49.1 255 8 4 10.1 5.5
9250 9.3 48.7 280 8 4 6.8 3.7 | 10.2 50.4 255 8 4 6.1 3.3
9000 10.4 50.7 280 7 3 8.8 4.8 | 10.6 51.1 260 7 3 6.9 3.8
8750 11.1 52.0 275 6 3 9.0 4.9 | 12.1 53.8 260 6 3 10.6 5.8
8500 11.7 53.1 275 5 2 6.9 3.8 | 12.9 55.2 260 5 3 7.4 4.1
8250 12.1 53.8 270 4 2 5.5 3.0 | 13.3 55.9 275 4 2 6.2 3.4
8000 12.6 54.7 265 3 2 7.8 4.3 | 13.9 57.0 275 3 2 10.2 5.6
7750 13.2 55.8 260 2 1 8.2 4.5 | 14.7 58.5 275 3 2 10.7 5.9
7500 13.7 56.7 250 1 1 5.5 3.0 | 15.4 59.7 270 3 1 7.2 4.0
7250 14.0 57.2 230 1 0 3.8 2.1 | 15.8 60.4 285 2 1 5.4 2.9
7000 14.4 57.9 180 1 0 7.4 4.0 | 16.4 61.5 295 2 1 11.1 6.1
6750 15.0 59.0 135 1 0 8.0 4.4 | 17.3 63.1 285 2 1 11.4 6.3
6500 15.5 59.9 115 1 1 5.7 3.1 | 17.9 64.2 290 1 1 6.7 3.7
6250 15.9 60.6 105 2 1 5.2 2.9 | 18.4 65.1 310 1 1 5.8 3.2
6000 16.3 61.3 100 2 1 6.6 3.6 | 18.8 65.8 335 1 0 7.1 3.9
5750 17.0 62.6 115 2 1 11.3 6.2 | 19.5 67.1 000 0 0 14.3 7.8
5500 17.9 64.2 095 2 1 15.7 8.6 | 21.3 70.3 005 1 0 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
05/18/2024 at 1500 MDT | 05/18/2024 at 1800 MDT
|
CAPE... +80.3 LI... -0.7 | CAPE... +76.4 LI... -0.3
CINH... -3.9 K Index... +23.9 | CINH... -41.4 K Index... +26.5
|
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 -57.0 -70.6 250 40 21 1.6 0.9 | -56.7 -70.1 255 43 22 1.5 0.8
45000 -55.2 -67.4 245 42 22 -2.3 -1.3 | -55.2 -67.4 250 46 24 -2.8 -1.5
40000 -58.7 -73.7 240 42 21 -2.9 -1.6 | -59.5 -75.1 245 44 23 -3.0 -1.6
38000 -56.3 -69.3 240 42 22 5.3 2.9 | -57.2 -71.0 245 43 22 5.7 3.1
36000 -53.2 -63.8 240 42 22 5.3 2.9 | -53.8 -64.8 245 42 22 5.7 3.1
34000 -49.3 -56.7 240 42 21 7.7 4.2 | -49.1 -56.4 245 41 21 8.4 4.6
32000 -44.7 -48.5 240 40 21 7.7 4.2 | -44.1 -47.4 245 39 20 8.4 4.6
30000 -39.8 -39.6 240 39 20 8.3 4.6 | -39.1 -38.4 240 36 19 8.3 4.6
29000 -37.3 -35.1 245 39 20 8.3 4.6 | -36.6 -33.9 240 35 18 8.3 4.6
28000 -34.8 -30.6 245 39 20 8.3 4.6 | -34.1 -29.4 240 34 18 8.3 4.6
27000 -31.8 -25.2 245 38 20 7.8 4.3 | -31.7 -25.1 240 33 17 8.0 4.4
26000 -29.5 -21.1 245 37 19 7.8 4.3 | -29.3 -20.7 240 32 17 8.0 4.4
25000 -27.1 -16.8 245 36 18 7.8 4.3 | -26.9 -16.4 235 31 16 8.0 4.4
24000 -24.9 -12.8 245 35 18 7.1 3.9 | -24.6 -12.3 235 30 15 7.6 4.2
23000 -22.8 -9.0 245 33 17 7.1 3.9 | -22.4 -8.3 230 29 15 7.7 4.2
22000 -20.7 -5.3 245 31 16 7.1 3.9 | -20.1 -4.2 230 28 14 7.7 4.2
21000 -18.4 -1.1 245 30 15 8.0 4.4 | -17.3 0.9 225 27 14 7.7 4.2
20000 -16.1 3.0 240 29 15 8.0 4.4 | -15.0 5.0 225 26 13 7.8 4.3
19500 -14.9 5.2 240 28 15 8.0 4.4 | -13.9 7.0 225 26 13 7.8 4.3
19000 -13.7 7.3 240 28 14 8.1 4.5 | -12.7 9.1 225 25 13 7.8 4.3
18500 -12.5 9.5 240 27 14 8.2 4.5 | -11.6 11.1 225 24 13 7.8 4.3
18000 -11.3 11.7 240 27 14 8.3 4.5 | -10.5 13.1 225 24 12 7.9 4.3
17500 -10.1 13.8 240 26 13 8.1 4.5 | -9.3 15.3 225 23 12 7.7 4.2
17000 -8.9 16.0 240 25 13 8.2 4.5 | -8.2 17.2 225 23 12 7.7 4.2
16500 -7.7 18.1 245 24 13 8.5 4.6 | -7.1 19.2 230 22 11 7.7 4.2
16000 -6.4 20.5 245 24 12 8.7 4.7 | -6.0 21.2 230 22 11 7.6 4.2
15500 -5.1 22.8 245 23 12 8.8 4.8 | -4.8 23.4 230 21 11 7.8 4.3
15000 -3.8 25.2 245 22 12 9.4 5.1 | -3.7 25.3 235 21 11 8.2 4.5
14500 -2.4 27.7 245 22 11 9.4 5.1 | -2.5 27.5 235 20 10 8.1 4.5
14000 -1.0 30.2 245 21 11 9.2 5.1 | -1.2 29.8 235 20 10 8.6 4.7
13500 0.4 32.7 245 21 11 9.2 5.1 | 0.0 32.0 235 19 10 8.5 4.7
13000 1.8 35.2 250 20 10 9.4 5.2 | 1.3 34.3 240 19 10 9.1 5.0
12500 3.2 37.8 250 20 10 9.4 5.2 | 2.7 36.9 240 18 9 9.1 5.0
12000 4.6 40.3 250 19 10 9.4 5.2 | 4.1 39.4 240 18 9 9.0 4.9
11500 6.0 42.8 250 18 9 9.5 5.2 | 5.4 41.7 240 17 9 9.0 4.9
11000 7.3 45.1 250 17 9 8.1 4.4 | 6.7 44.1 240 16 8 8.2 4.5
10500 8.5 47.3 250 16 8 6.7 3.7 | 7.9 46.2 240 15 8 7.3 4.0
10250 9.1 48.4 250 16 8 11.7 6.4 | 8.5 47.3 240 15 7 10.8 5.9
10000 10.2 50.4 250 15 7 12.6 6.9 | 9.4 48.9 240 14 7 11.2 6.1
9750 10.8 51.4 250 14 7 8.0 4.4 | 10.0 50.0 240 14 7 8.0 4.4
9500 11.5 52.7 250 13 7 9.8 5.4 | 10.7 51.3 240 13 7 9.0 4.9
9250 12.7 54.9 255 12 6 7.7 4.2 | 11.3 52.3 240 13 6 8.1 4.5
9000 13.4 56.1 255 11 6 10.1 5.6 | 11.9 53.4 240 11 6 8.0 4.4
8750 14.1 57.4 255 10 5 9.9 5.4 | 12.5 54.5 240 11 5 8.5 4.6
8500 14.8 58.6 255 10 5 8.3 4.6 | 13.1 55.6 235 10 5 8.4 4.6
8250 15.4 59.7 260 9 5 7.6 4.2 | 14.3 57.7 235 8 4 7.9 4.3
8000 16.1 61.0 260 8 4 9.3 5.1 | 14.9 58.8 235 7 4 8.0 4.4
7750 16.8 62.2 260 7 4 9.7 5.3 | 15.5 59.9 235 7 3 8.3 4.5
7500 17.5 63.5 255 6 3 8.2 4.5 | 16.1 61.0 230 6 3 7.5 4.1
7250 18.0 64.4 260 6 3 7.5 4.1 | 16.6 61.9 235 5 3 7.0 3.8
7000 18.7 65.7 265 6 3 10.5 5.7 | 17.1 62.8 235 5 3 8.2 4.5
6750 19.5 67.1 260 5 2 11.6 6.4 | 17.8 64.0 225 5 2 8.9 4.9
6500 20.4 68.7 255 4 2 10.6 5.8 | 18.4 65.1 225 4 2 9.3 5.1
6250 21.2 70.2 265 4 2 11.1 6.1 | 19.1 66.4 225 4 2 10.2 5.6
6000 22.0 71.6 265 4 2 8.0 4.4 | 19.8 67.6 225 3 2 7.2 4.0
5750 22.5 72.5 255 3 2 12.1 6.6 | 20.2 68.4 215 4 2 7.6 4.2
5500 25.3 77.5 270 3 2 80.9 44.4 | 21.9 71.4 220 2 1 49.7 27.3
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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