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Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
000
UXUS97 KGJT 171307
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
707 AM MDT Wednesday, April 17, 2024
This forecast is for Wednesday, April 17, 2024:
If the trigger temperature of 64.8 F/18.2 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1218 ft/min (6.2 m/s)
Maximum height of thermals.................. 18260 ft MSL (13421 ft AGL)
Forecast maximum temperature................... 76.0 F/24.9 C
Time of trigger temperature.................... 1100 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................. 15541 ft MSL (10702 ft AGL)
Thermal soaring outlook for Thursday 04/18..... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:33:12 / 19:53:49 MDT
Total possible sunshine........... 13 hr 20 min 37 sec (800 min 37 sec)
Altitude of sun at 13:13:31 MDT... 61.58 degrees
Upper air data from rawinsonde observation taken on 04/17/2024 at 0600 MDT
Freezing level.................. 11289 ft MSL (6450 ft AGL)
Convective condensation level... 15057 ft MSL (10218 ft AGL)
Lifted condensation level....... 16581 ft MSL (11742 ft AGL)
Lifted index.................... +1.2
K index......................... +18.8
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 -58.5 -73.3 280 66 34 3.0 1.7 102.8 217.0 44.7 M M
45000 -54.7 -66.5 270 55 29 -3.0 -1.7 83.4 182.1 36.1 M M
40000 -56.2 -69.2 285 57 29 4.2 2.3 57.8 136.1 21.9 M M
38000 -55.2 -67.4 285 54 28 2.4 1.3 50.6 123.1 17.6 M M
36000 -54.4 -65.9 285 48 25 2.8 1.5 43.1 109.5 12.9 M M
34000 -51.9 -61.4 285 55 28 7.8 4.3 38.3 100.9 9.8 M M
32000 -46.8 -52.2 280 52 27 9.2 5.1 37.3 99.1 9.4 M M
30000 -40.8 -41.4 285 51 26 8.7 4.8 36.6 97.9 9.1 M M
29000 -38.2 -36.8 280 51 26 7.6 4.2 36.1 96.9 8.8 M M
28000 -35.9 -32.6 280 48 25 7.9 4.3 35.3 95.5 8.3 M M
27000 -33.4 -28.1 280 50 26 8.5 4.6 34.7 94.5 8.0 M M
26000 -31.0 -23.8 275 44 23 8.2 4.5 34.2 93.5 7.6 M M
25000 -28.4 -19.1 270 45 23 8.8 4.8 33.8 92.9 7.4 M M
24000 -26.3 -15.3 265 47 24 7.2 4.0 32.8 91.1 6.7 M M
23000 -24.1 -11.4 270 50 26 6.4 3.5 31.9 89.4 6.0 M M
22000 -22.3 -8.1 265 50 26 6.2 3.4 30.6 87.1 4.9 M M
21000 -20.6 -5.1 265 48 25 5.5 3.0 29.2 84.5 3.7 M M
20000 -19.0 -2.2 265 44 23 4.9 2.7 27.6 81.7 2.5 M M
19500 -18.3 -0.9 260 41 21 4.6 2.5 26.7 80.1 1.7 M M
19000 -17.6 0.3 255 40 20 4.5 2.5 25.8 78.5 0.9 M M
18500 -16.9 1.6 260 39 20 6.3 3.5 25.0 77.0 0.3 M M
18000 -15.8 3.6 260 35 18 6.8 3.7 24.5 76.1 -0.1 1204 6.1
17500 -14.8 5.4 260 34 17 7.0 3.8 24.0 75.2 -0.5 1157 5.9
17000 -13.9 7.0 265 28 15 5.2 2.9 23.3 74.0 -1.1 1116 5.7
16500 -12.4 9.7 265 27 14 10.5 5.8 22.6 72.6 -1.9 1050 5.3
16000 -11.1 12.0 265 27 14 2.2 1.2 22.4 72.4 -2.0 995 5.1
15500 -10.8 12.6 275 25 13 9.4 5.2 21.2 70.1 -3.2 972 4.9
15000 -9.4 15.1 280 24 12 9.2 5.1 21.3 70.3 -3.3 915 4.6
14500 -8.1 17.4 285 26 13 8.4 4.6 21.1 69.9 -3.5 863 4.4
14000 -6.9 19.6 280 24 12 8.3 4.6 20.8 69.5 -3.7 810 4.1
13500 -5.6 21.9 275 22 11 8.3 4.6 20.6 69.1 -4.0 758 3.9
13000 -4.4 24.1 270 20 10 8.3 4.6 20.4 68.7 -4.2 706 3.6
12500 -3.1 26.4 255 22 11 8.3 4.6 20.1 68.2 -4.4 654 3.3
12000 -1.9 28.6 255 22 11 9.0 4.9 19.9 67.8 -4.7 601 3.1
11500 -0.5 31.1 250 23 12 9.2 5.1 19.8 67.7 -4.8 546 2.8
11000 0.9 33.6 260 22 11 9.2 5.1 19.7 67.5 -4.9 490 2.5
10500 2.2 36.0 245 23 12 9.3 5.1 19.6 67.3 -5.0 434 2.2
10250 2.9 37.2 250 22 11 8.9 4.9 19.6 67.3 -5.1 406 2.1
10000 3.5 38.3 255 21 11 7.9 4.3 19.5 67.1 -5.2 380 1.9
9750 4.1 39.4 255 21 11 7.6 4.2 19.3 66.8 -5.4 356 1.8
9500 4.7 40.5 250 21 11 7.6 4.2 19.2 66.5 -5.5 332 1.7
9250 5.2 41.4 250 20 11 7.6 4.2 19.0 66.2 -5.7 307 1.6
9000 5.8 42.4 240 17 9 7.6 4.2 18.9 65.9 -5.9 283 1.4
8750 6.4 43.5 235 15 8 7.6 4.2 18.7 65.7 -6.0 258 1.3
8500 6.9 44.4 240 12 6 7.6 4.2 18.5 65.4 -6.2 234 1.2
8250 7.5 45.5 250 8 4 7.6 4.2 18.4 65.1 -6.4 209 1.1
8000 8.1 46.6 275 5 3 7.6 4.2 18.2 64.8 -6.6 185 0.9
7750 8.6 47.5 285 5 3 7.6 4.2 18.1 64.5 -6.7 161 0.8
7500 9.2 48.6 280 3 1 7.6 4.2 17.9 64.2 -6.9 136 0.7
7250 9.8 49.6 000 0 0 7.6 4.2 17.7 63.9 -7.1 112 0.6
7000 10.3 50.5 155 4 2 7.6 4.2 17.6 63.6 -7.3 87 0.4
6750 10.9 51.6 155 7 3 7.8 4.3 17.4 63.3 -7.5 63 0.3
6500 11.5 52.7 150 10 5 6.9 3.8 17.2 63.0 -7.7 39 0.2
6250 11.9 53.4 150 13 7 3.8 2.1 16.9 62.4 -8.0 19 0.1
6000 12.1 53.8 150 18 10 2.3 1.3 16.4 61.5 -8.6 6 0.0
5750 12.1 53.8 155 19 10 -4.1 -2.3 15.6 60.2 -9.3 M M
5500 11.4 52.5 155 21 11 -9.3 -5.1 14.3 57.7 -10.7 10 0.1
5250 10.8 51.4 150 18 9 -7.5 -4.1 12.9 55.3 -12.1 22 0.1
5000 10.2 50.4 140 16 8 -9.5 -5.2 11.6 52.9 -13.5 33 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/17/2024 at 0900 MDT | 04/17/2024 at 1200 MDT
|
CAPE... 0.0 LI... +2.2 | CAPE... +0.3 LI... +2.7
CINH... -0.0 K Index... +16.6 | CINH... -1.4 K Index... +18.5
|
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 -58.4 -73.1 265 49 25 2.9 1.6 | -59.0 -74.2 265 54 28 2.7 1.5
45000 -54.4 -65.9 265 60 31 -2.5 -1.4 | -55.3 -67.5 265 65 34 -2.4 -1.3
40000 -57.5 -71.5 290 67 35 -1.8 -1.0 | -58.1 -72.6 280 70 36 -1.6 -0.9
38000 -55.8 -68.4 295 69 35 4.9 2.7 | -56.0 -68.8 285 71 36 5.6 3.0
36000 -52.9 -63.2 295 69 35 4.9 2.7 | -52.7 -62.9 285 71 36 5.6 3.0
34000 -49.4 -56.9 300 66 34 7.6 4.2 | -48.9 -56.0 290 69 36 7.7 4.2
32000 -44.9 -48.8 295 57 29 7.6 4.2 | -44.3 -47.7 285 65 34 7.7 4.2
30000 -40.4 -40.7 285 50 26 7.0 3.9 | -39.8 -39.6 285 60 31 7.1 3.9
29000 -38.3 -36.9 280 49 25 7.0 3.8 | -37.6 -35.7 280 56 29 7.1 3.9
28000 -36.2 -33.2 280 48 25 7.0 3.9 | -35.5 -31.9 275 53 27 7.1 3.9
27000 -34.1 -29.4 275 47 24 7.5 4.1 | -33.4 -28.1 275 50 26 7.1 3.9
26000 -31.8 -25.2 275 47 24 7.7 4.2 | -30.8 -23.4 270 48 25 7.1 3.9
25000 -28.9 -20.0 275 46 23 7.7 4.2 | -28.6 -19.5 270 46 24 7.1 3.9
24000 -26.6 -15.9 275 45 23 7.1 3.9 | -26.5 -15.7 270 45 23 7.5 4.1
23000 -24.5 -12.1 275 44 23 7.1 3.9 | -24.3 -11.7 270 43 22 7.5 4.1
22000 -22.4 -8.3 270 43 22 7.1 3.9 | -22.0 -7.6 270 41 21 7.5 4.1
21000 -20.4 -4.7 270 42 22 5.7 3.1 | -19.9 -3.8 270 40 20 6.6 3.6
20000 -18.7 -1.7 270 41 21 5.8 3.2 | -17.9 -0.2 270 39 20 6.6 3.6
19500 -17.9 -0.2 265 40 21 5.8 3.2 | -16.9 1.6 270 38 20 6.7 3.7
19000 -17.0 1.4 265 40 20 5.8 3.2 | -15.9 3.4 270 38 19 6.8 3.7
18500 -16.2 2.8 265 39 20 6.0 3.3 | -15.1 4.8 270 37 19 5.0 2.8
18000 -15.3 4.5 265 37 19 6.0 3.3 | -14.3 6.3 265 37 19 5.1 2.8
17500 -14.4 6.1 265 36 18 6.1 3.3 | -13.6 7.5 265 36 19 5.1 2.8
17000 -13.5 7.7 260 34 18 6.2 3.4 | -12.8 9.0 265 35 18 5.1 2.8
16500 -12.6 9.3 260 33 17 6.2 3.4 | -12.1 10.2 260 35 18 5.1 2.8
16000 -11.6 11.1 260 31 16 6.7 3.7 | -11.3 11.7 260 34 17 5.7 3.2
15500 -10.6 12.9 260 29 15 6.6 3.6 | -10.5 13.1 260 32 17 5.6 3.1
15000 -9.6 14.7 255 28 14 7.5 4.1 | -9.6 14.7 255 31 16 7.2 4.0
14500 -8.5 16.7 255 27 14 7.6 4.1 | -8.5 16.7 255 30 15 7.4 4.0
14000 -7.4 18.7 255 26 13 7.8 4.3 | -7.4 18.7 255 28 15 7.8 4.3
13500 -6.2 20.8 255 25 13 8.0 4.4 | -6.2 20.8 250 27 14 8.0 4.4
13000 -5.1 22.8 255 25 13 8.1 4.4 | -5.1 22.8 250 26 13 8.2 4.5
12500 -3.9 25.0 250 24 12 8.2 4.5 | -3.8 25.2 250 24 13 8.4 4.6
12000 -2.6 27.3 250 24 12 8.3 4.6 | -2.6 27.3 250 23 12 8.7 4.8
11500 -1.4 29.5 250 23 12 8.5 4.6 | -1.2 29.8 250 23 12 9.0 5.0
11000 -0.1 31.8 250 22 11 7.9 4.3 | 0.2 32.4 250 22 11 8.5 4.7
10500 1.0 33.8 250 21 11 6.8 3.7 | 1.3 34.3 250 21 11 7.2 3.9
10250 1.5 34.7 245 21 11 8.8 4.8 | 1.9 35.4 250 21 11 10.3 5.7
10000 2.3 36.1 245 20 10 9.4 5.1 | 2.8 37.0 245 21 11 11.3 6.2
9750 2.9 37.2 245 19 10 7.5 4.1 | 3.5 38.3 245 20 10 8.6 4.7
9500 3.5 38.3 245 18 9 7.8 4.3 | 4.2 39.6 245 20 10 9.5 5.2
9250 4.1 39.4 240 17 9 7.7 4.2 | 4.9 40.8 245 19 10 8.1 4.5
9000 5.1 41.2 240 15 8 6.5 3.6 | 5.5 41.9 250 18 10 8.1 4.5
8750 5.6 42.1 235 14 7 6.8 3.7 | 6.9 44.4 250 17 9 9.5 5.2
8500 6.1 43.0 235 13 7 6.5 3.6 | 7.6 45.7 245 16 8 9.1 5.0
8250 6.6 43.9 230 12 6 6.0 3.3 | 8.2 46.8 250 15 8 8.8 4.8
8000 7.0 44.6 230 11 6 6.2 3.4 | 8.9 48.0 250 15 8 9.7 5.3
7750 7.5 45.5 220 10 5 6.7 3.7 | 9.7 49.5 250 14 7 10.5 5.7
7500 8.0 46.4 215 9 5 5.8 3.2 | 10.4 50.7 250 14 7 9.4 5.2
7250 8.4 47.1 210 9 4 4.7 2.6 | 11.1 52.0 250 14 7 8.5 4.6
7000 8.8 47.8 205 8 4 7.1 3.9 | 11.8 53.2 255 13 7 10.4 5.7
6750 9.4 48.9 195 8 4 8.6 4.7 | 12.6 54.7 250 13 7 11.6 6.4
6500 10.0 50.0 185 7 4 7.1 3.9 | 13.5 56.3 250 12 6 10.9 6.0
6250 10.5 50.9 180 7 3 6.8 3.7 | 14.3 57.7 255 12 6 11.8 6.5
6000 11.0 51.8 165 6 3 6.7 3.7 | 15.1 59.2 255 12 6 8.1 4.5
5750 11.5 52.7 175 6 3 10.7 5.9 | 15.7 60.3 255 11 6 11.7 6.4
5500 13.1 55.6 160 5 2 35.9 19.7 | 18.6 65.5 260 10 5 87.2 47.9
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
04/17/2024 at 1500 MDT | 04/17/2024 at 1800 MDT
|
CAPE... +1.0 LI... +1.9 | CAPE... +2.8 LI... +1.0
CINH... -1.6 K Index... +17.5 | CINH... -0.1 K Index... +18.8
|
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 -74.6 265 58 30 2.6 1.4 | -58.5 -73.3 270 60 31 2.3 1.3
45000 -55.6 -68.1 270 68 35 -1.9 -1.0 | -55.4 -67.7 270 72 37 -1.4 -0.8
40000 -57.7 -71.9 275 72 37 -1.2 -0.7 | -57.6 -71.7 275 77 40 -1.4 -0.7
38000 -55.7 -68.3 280 73 38 5.3 2.9 | -55.6 -68.1 275 78 40 5.4 2.9
36000 -52.4 -62.3 280 73 38 5.3 2.9 | -52.4 -62.3 280 79 40 5.4 2.9
34000 -48.7 -55.7 280 72 37 7.7 4.2 | -48.7 -55.7 280 77 40 7.6 4.2
32000 -44.1 -47.4 280 68 35 7.7 4.2 | -44.1 -47.4 280 72 37 7.6 4.2
30000 -39.5 -39.1 275 64 33 7.2 4.0 | -39.6 -39.3 275 66 34 7.1 3.9
29000 -37.4 -35.3 275 61 32 7.2 4.0 | -37.5 -35.5 275 63 33 7.1 3.9
28000 -35.2 -31.4 275 59 30 7.2 4.0 | -35.4 -31.7 275 61 31 7.1 3.9
27000 -33.1 -27.6 275 56 29 6.7 3.7 | -32.7 -26.9 275 57 29 6.8 3.7
26000 -30.6 -23.1 275 53 27 6.5 3.6 | -30.7 -23.3 275 54 28 6.8 3.7
25000 -28.7 -19.7 270 50 26 6.5 3.6 | -28.7 -19.7 275 51 26 6.8 3.7
24000 -26.6 -15.9 270 47 24 7.3 4.0 | -26.6 -15.9 275 48 25 6.8 3.7
23000 -24.5 -12.1 270 44 23 7.3 4.0 | -24.6 -12.3 270 46 24 6.8 3.7
22000 -22.3 -8.1 270 42 21 7.3 4.0 | -22.6 -8.7 270 43 22 6.8 3.7
21000 -20.1 -4.2 270 39 20 7.1 3.9 | -20.5 -4.9 270 41 21 7.1 3.9
20000 -18.0 -0.4 270 37 19 7.1 3.9 | -18.4 -1.1 270 39 20 7.1 3.9
19500 -17.0 1.4 270 36 18 7.1 3.9 | -17.3 0.9 270 38 19 7.1 3.9
19000 -15.9 3.4 265 35 18 7.2 4.0 | -16.3 2.7 270 37 19 7.2 4.0
18500 -14.9 5.2 265 34 17 6.1 3.3 | -15.3 4.5 270 35 18 5.8 3.2
18000 -14.0 6.8 265 33 17 6.2 3.4 | -14.5 5.9 270 34 17 6.0 3.3
17500 -13.1 8.4 265 31 16 5.8 3.2 | -13.6 7.5 270 32 17 6.5 3.5
17000 -12.3 9.9 260 30 16 5.5 3.0 | -12.6 9.3 270 31 16 6.9 3.8
16500 -11.5 11.3 260 29 15 5.5 3.0 | -11.6 11.1 270 30 15 7.0 3.8
16000 -10.6 12.9 260 28 15 6.6 3.6 | -10.5 13.1 265 29 15 7.7 4.2
15500 -9.7 14.5 255 28 14 6.4 3.5 | -9.4 15.1 265 28 15 7.6 4.2
15000 -8.7 16.3 255 27 14 7.9 4.3 | -8.2 17.2 265 28 14 8.5 4.7
14500 -7.5 18.5 255 27 14 7.9 4.3 | -6.9 19.6 265 27 14 8.5 4.7
14000 -6.3 20.7 250 26 13 8.6 4.7 | -5.6 21.9 265 27 14 8.9 4.9
13500 -5.0 23.0 250 26 13 8.8 4.8 | -4.3 24.3 260 27 14 9.1 5.0
13000 -3.7 25.3 250 26 13 8.9 4.9 | -2.9 26.8 260 26 13 9.2 5.0
12500 -2.4 27.7 250 25 13 9.0 4.9 | -1.6 29.1 260 26 13 9.2 5.1
12000 -1.0 30.2 250 25 13 9.2 5.0 | -0.2 31.6 260 26 13 9.3 5.1
11500 0.4 32.7 250 24 13 9.4 5.2 | 1.2 34.2 260 25 13 9.4 5.2
11000 1.8 35.2 250 24 12 8.6 4.7 | 2.6 36.7 260 25 13 8.7 4.8
10500 2.9 37.2 255 23 12 6.5 3.6 | 3.8 38.8 260 25 13 6.9 3.8
10250 3.5 38.3 255 23 12 11.2 6.2 | 4.4 39.9 260 25 13 11.4 6.3
10000 4.5 40.1 255 23 12 13.0 7.1 | 5.4 41.7 260 24 13 12.5 6.8
9750 5.3 41.5 255 23 12 9.0 4.9 | 6.1 43.0 260 24 12 8.4 4.6
9500 6.0 42.8 255 23 12 10.3 5.7 | 6.8 44.2 260 24 12 8.5 4.6
9250 6.7 44.1 255 22 12 7.8 4.3 | 7.4 45.3 260 24 12 10.6 5.8
9000 7.2 45.0 255 22 12 8.5 4.7 | 9.0 48.2 260 23 12 9.0 5.0
8750 8.9 48.0 255 22 11 10.7 5.9 | 9.8 49.6 260 22 12 9.7 5.3
8500 9.7 49.5 255 22 11 10.1 5.6 | 10.5 50.9 260 22 11 9.2 5.0
8250 10.4 50.7 260 22 11 9.1 5.0 | 11.1 52.0 260 22 11 9.1 5.0
8000 11.1 52.0 260 22 11 10.1 5.5 | 11.8 53.2 260 22 11 9.9 5.4
7750 11.9 53.4 260 21 11 11.1 6.1 | 12.6 54.7 260 21 11 10.5 5.8
7500 12.7 54.9 260 21 11 9.5 5.2 | 13.4 56.1 260 21 11 9.3 5.1
7250 13.3 55.9 260 21 11 7.9 4.3 | 14.0 57.2 260 21 11 7.8 4.3
7000 14.0 57.2 260 21 11 10.3 5.6 | 14.6 58.3 260 21 11 9.9 5.4
6750 14.8 58.6 260 20 10 11.9 6.6 | 15.5 59.9 260 20 10 11.5 6.3
6500 15.7 60.3 260 19 10 10.8 5.9 | 16.3 61.3 260 19 10 10.5 5.7
6250 16.5 61.7 260 19 10 11.0 6.0 | 17.1 62.8 260 19 10 10.6 5.8
6000 17.3 63.1 265 19 10 8.8 4.8 | 17.8 64.0 260 19 10 8.7 4.8
5750 18.0 64.4 260 18 9 14.8 8.1 | 18.4 65.1 260 17 9 9.9 5.4
5500 21.0 69.8 265 16 8 82.6 45.3 | 20.2 68.4 260 15 8 47.5 26.0
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.
042613
- National Weather Service
- Rapid City, SD Weather Forecast Office
- 300 East Signal Drive
- Rapid City, SD 57701-3800
- 605-341-9271
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- Page last modified: Sep 19th, 2023 19:10 UTC