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Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 211312
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0711 MDT Sunday, April 21, 2024
This forecast is for Sunday, April 21, 2024:
If the trigger temperature of 51.6 F/10.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 809 ft/min (4.1 m/s)
Maximum height of thermals.................. 14982 ft MSL (9664 ft AGL)
Forecast maximum temperature................... 61.0 F/16.6 C
Time of trigger temperature.................... 1300 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................. 10861 ft MSL (5543 ft AGL)
Thermal soaring outlook for Monday 04/22....... Good
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak NVA
Potential height of wave....................... 34657 ft MSL (29339 ft AGL)
Wave soaring outlook for Monday 04/22.......... Poor
Remarks...
Sunrise/Sunset.................... 06:11:58 / 19:44:05 MDT
Total possible sunshine........... 13 hr 32 min 7 sec (812 min 7 sec)
Altitude of sun at 12:58:02 MDT... 62.45 degrees
Upper air data from numerical model forecast valid on 04/21/2024 at 0600 MDT
Freezing level.................. 5457 ft MSL (139 ft AGL)
Convective condensation level... 11969 ft MSL (6651 ft AGL)
Lifted condensation level....... 13041 ft MSL (7723 ft AGL)
Lifted index.................... +2.1
K index......................... +9.2
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 -57.6 -71.7 295 49 25 0.6 0.3 M M M M M
45000 -56.6 -69.9 295 50 26 -0.6 -0.3 M M M M M
40000 -59.9 -75.8 300 56 29 -2.2 -1.2 M M M M M
38000 -59.2 -74.6 305 59 30 4.7 2.6 M M M M M
36000 -56.0 -68.8 310 61 32 4.7 2.6 M M M M M
34000 -52.6 -62.7 315 64 33 8.3 4.5 M M M M M
32000 -47.6 -53.7 315 64 33 8.4 4.6 M M M M M
30000 -42.7 -44.9 315 63 33 7.8 4.3 34.2 93.5 13.5 M M
29000 -40.3 -40.5 320 63 32 7.8 4.3 33.3 91.9 13.1 M M
28000 -38.0 -36.4 320 62 32 7.8 4.3 32.6 90.7 12.7 M M
27000 -35.6 -32.1 320 61 31 6.7 3.7 31.9 89.5 12.3 M M
26000 -33.8 -28.8 320 57 29 6.2 3.4 30.4 86.8 11.3 M M
25000 -31.9 -25.4 320 54 28 6.2 3.4 29.1 84.3 10.3 M M
24000 -30.1 -22.2 320 50 26 6.3 3.5 27.8 82.1 9.5 M M
23000 -28.1 -18.6 320 47 24 6.5 3.6 26.5 79.8 8.5 M M
22000 -26.2 -15.2 320 44 23 6.5 3.6 25.4 77.7 7.7 M M
21000 -24.2 -11.6 320 41 21 7.2 4.0 24.3 75.8 6.9 M M
20000 -22.0 -7.6 320 39 20 7.3 4.0 23.4 74.1 6.2 M M
19500 -20.9 -5.6 320 38 20 7.3 4.0 23.0 73.4 5.8 M M
19000 -19.2 -2.6 320 37 19 7.4 4.0 22.4 72.3 5.4 M M
18500 -18.3 -0.9 320 36 19 5.8 3.2 21.9 71.3 4.9 M M
18000 -17.4 0.7 320 35 18 6.0 3.3 21.2 70.2 4.4 M M
17500 -16.5 2.3 320 34 17 5.0 2.7 20.5 68.9 3.8 M M
17000 -15.8 3.6 320 32 17 4.6 2.5 19.6 67.3 3.0 M M
16500 -15.2 4.6 320 31 16 4.5 2.5 18.8 65.8 2.3 M M
16000 -14.5 5.9 320 30 15 4.5 2.5 17.8 64.1 1.4 M M
15500 -13.9 7.0 315 29 15 4.5 2.5 17.0 62.5 0.6 M M
15000 -13.1 8.4 315 28 14 6.3 3.5 16.2 61.2 -0.1 805 4.1
14500 -12.2 10.0 315 27 14 6.1 3.3 15.6 60.2 -0.7 763 3.9
14000 -11.2 11.8 315 26 13 7.9 4.3 15.2 59.3 -1.1 719 3.7
13500 -10.1 13.8 315 24 13 7.8 4.3 14.9 58.7 -1.5 670 3.4
13000 -8.9 16.0 320 23 12 8.5 4.7 14.6 58.3 -1.7 619 3.1
12500 -7.6 18.3 320 22 11 8.6 4.7 14.4 57.9 -2.0 567 2.9
12000 -6.4 20.5 320 21 11 7.9 4.3 14.2 57.5 -2.2 515 2.6
11500 -5.2 22.6 320 19 10 7.9 4.4 13.9 56.9 -2.5 465 2.4
11000 -4.1 24.6 320 17 9 7.1 3.9 13.5 56.3 -2.9 417 2.1
10500 -3.1 26.4 315 15 8 7.6 4.2 13.1 55.5 -3.3 372 1.9
10250 -2.6 27.3 315 14 7 4.6 2.5 12.9 55.1 -3.6 349 1.8
10000 -2.4 27.7 315 14 7 2.6 1.5 12.3 54.1 -4.1 336 1.7
9750 -2.1 28.2 315 13 6 6.2 3.4 11.9 53.4 -4.5 319 1.6
9500 -1.6 29.1 310 11 6 7.4 4.1 11.7 53.0 -4.8 296 1.5
9250 -1.1 30.0 300 9 5 4.6 2.5 11.4 52.5 -5.0 275 1.4
9000 -0.9 30.4 300 8 4 2.6 1.4 10.9 51.6 -5.6 261 1.3
8750 -0.7 30.7 295 7 4 3.7 2.0 10.4 50.7 -6.1 247 1.3
8500 -0.4 31.3 280 6 3 2.5 1.4 9.9 49.8 -6.6 233 1.2
8250 -0.4 31.3 270 5 3 -0.3 -0.2 9.2 48.5 -7.3 224 1.1
8000 -0.5 31.1 260 5 3 -0.6 -0.3 8.4 47.1 -8.2 219 1.1
7750 -0.5 31.1 250 5 3 -2.3 -1.2 7.6 45.6 -9.0 214 1.1
7500 -0.9 30.4 230 4 2 -5.0 -2.7 6.5 43.7 -10.1 216 1.1
7250 -1.2 29.8 215 4 2 -4.9 -2.7 5.4 41.6 -11.2 219 1.1
7000 -1.6 29.1 200 4 2 -5.4 -2.9 4.2 39.6 -12.3 223 1.1
6750 -2.0 28.4 190 5 2 -3.6 -2.0 3.1 37.6 -13.5 227 1.2
6500 -2.0 28.4 170 4 2 2.4 1.3 2.3 36.1 -14.3 222 1.1
6250 -1.7 28.9 160 4 2 5.3 2.9 1.9 35.4 -14.7 204 1.0
6000 -1.4 29.5 140 3 2 3.8 2.1 1.5 34.7 -15.2 187 0.9
5750 -1.0 30.2 120 3 2 6.6 3.6 1.1 34.0 -15.6 170 0.9
5500 -0.3 31.5 105 3 1 12.8 7.0 1.1 34.0 -15.7 141 0.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/21/2024 at 0900 MDT | 04/21/2024 at 1200 MDT
|
CAPE... +3.0 LI... +5.4 | CAPE... +0.1 LI... +4.5
CINH... 0.0 K Index... -2.1 | CINH... -0.1 K Index... -7.8
|
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 -57.1 -70.8 300 47 24 0.4 0.2 | -57.3 -71.1 295 44 22 0.8 0.4
45000 -56.5 -69.7 300 50 26 -0.5 -0.3 | -56.2 -69.2 295 45 23 -0.4 -0.2
40000 -60.9 -77.6 300 53 27 -2.9 -1.6 | -61.3 -78.3 300 52 27 -3.3 -1.8
38000 -59.9 -75.8 305 54 28 5.0 2.8 | -60.3 -76.5 305 54 28 5.1 2.8
36000 -56.9 -70.4 310 57 29 5.0 2.8 | -57.2 -71.0 310 55 28 5.2 2.8
34000 -53.4 -64.1 315 58 30 8.2 4.5 | -53.7 -64.7 315 55 28 8.1 4.4
32000 -48.4 -55.1 315 57 29 8.3 4.6 | -48.8 -55.8 315 50 26 8.2 4.5
30000 -42.8 -45.0 320 56 29 8.4 4.6 | -43.3 -45.9 315 47 24 8.2 4.5
29000 -40.3 -40.5 320 55 28 8.4 4.6 | -40.8 -41.4 320 46 24 8.2 4.5
28000 -37.8 -36.0 320 55 28 8.4 4.6 | -38.4 -37.1 320 45 23 8.2 4.5
27000 -35.4 -31.7 320 54 28 7.4 4.1 | -35.9 -32.6 320 45 23 8.3 4.5
26000 -33.1 -27.6 325 53 27 7.5 4.1 | -33.4 -28.1 320 44 23 8.3 4.5
25000 -30.9 -23.6 325 51 26 7.5 4.1 | -30.9 -23.6 325 44 23 8.3 4.5
24000 -28.7 -19.7 325 50 26 6.4 3.5 | -28.5 -19.3 325 43 22 7.2 3.9
23000 -26.9 -16.4 325 46 24 6.0 3.3 | -26.4 -15.5 325 41 21 7.0 3.8
22000 -25.1 -13.2 325 43 22 6.0 3.3 | -24.4 -11.9 325 39 20 7.0 3.8
21000 -23.2 -9.8 325 39 20 7.2 4.0 | -22.3 -8.1 325 37 19 6.5 3.6
20000 -21.1 -6.0 330 37 19 7.1 3.9 | -20.3 -4.5 325 33 17 6.6 3.6
19500 -20.0 -4.0 330 36 18 7.1 3.9 | -19.3 -2.7 325 32 16 6.6 3.6
19000 -19.0 -2.2 330 34 18 7.1 3.9 | -18.4 -1.1 325 30 15 6.5 3.6
18500 -17.9 -0.2 330 33 17 6.9 3.8 | -17.4 0.7 325 28 15 7.1 3.9
18000 -16.9 1.6 330 32 17 6.9 3.8 | -16.3 2.7 325 27 14 7.1 3.9
17500 -15.9 3.4 330 31 16 6.7 3.7 | -15.2 4.6 325 25 13 7.4 3.8
17000 -14.9 5.2 330 30 16 6.2 3.4 | -14.2 6.4 325 25 13 6.8 3.7
16500 -13.6 7.5 325 29 15 5.7 3.1 | -12.7 9.1 325 24 12 6.6 3.6
16000 -12.8 9.0 325 28 15 5.1 2.8 | -11.8 10.8 325 23 12 6.4 3.5
15500 -12.1 10.2 325 28 14 5.1 2.8 | -10.8 12.6 325 23 12 6.3 3.5
15000 -11.4 11.5 320 26 14 4.7 2.6 | -9.9 14.2 325 22 12 6.0 3.3
14500 -10.7 12.7 320 25 13 4.7 2.6 | -9.0 15.8 320 22 11 6.0 3.3
14000 -10.0 14.0 320 24 12 5.5 3.0 | -8.2 17.2 320 22 11 5.9 3.3
13500 -9.2 15.4 315 23 12 5.4 3.0 | -7.3 18.9 315 21 11 5.9 3.3
13000 -8.3 17.1 315 22 11 6.7 3.7 | -6.4 20.5 315 21 11 6.5 3.6
12500 -7.4 18.7 315 20 10 6.6 3.6 | -5.4 22.3 310 20 10 6.5 3.6
12000 -6.4 20.5 315 19 10 7.3 4.0 | -4.5 23.9 305 19 10 6.9 3.8
11500 -5.3 22.5 315 18 9 7.3 4.0 | -3.5 25.7 300 18 9 7.0 3.8
11000 -4.3 24.3 320 16 8 7.3 4.0 | -2.5 27.5 300 17 9 7.1 3.9
10500 -3.2 26.2 320 14 7 7.9 4.3 | -1.5 29.3 300 16 8 7.9 4.3
10250 -2.7 27.1 320 14 7 4.7 2.6 | -1.0 30.2 295 15 8 3.2 1.7
10000 -2.4 27.7 320 13 7 4.2 2.3 | -0.9 30.4 295 15 8 3.8 2.1
9750 -1.9 28.6 320 12 6 8.7 4.8 | -0.3 31.5 300 13 7 9.5 5.2
9500 -1.2 29.8 320 12 6 8.9 4.9 | 0.3 32.5 300 11 6 8.5 4.6
9250 -0.7 30.7 320 11 6 5.9 3.2 | 0.9 33.6 300 10 5 5.8 3.2
9000 -0.4 31.3 320 10 5 4.0 2.2 | 1.2 34.2 300 9 5 4.4 2.4
8750 -0.0 32.0 320 9 5 5.5 3.0 | 1.6 34.9 300 8 4 6.7 3.7
8500 0.4 32.7 315 8 4 5.0 2.7 | 2.1 35.8 305 6 3 6.2 3.4
8250 0.7 33.3 310 7 4 2.7 1.5 | 2.5 36.5 305 5 2 4.3 2.4
8000 0.9 33.6 310 7 4 4.2 2.3 | 2.8 37.0 305 4 2 3.8 2.1
7750 1.1 34.0 305 6 3 -2.3 -1.2 | 3.1 37.6 305 3 1 5.5 3.0
7500 0.5 32.9 275 4 2 -7.6 -4.2 | 3.5 38.3 285 2 1 2.6 1.4
7250 0.1 32.2 260 4 2 -4.9 -2.7 | 3.5 38.3 255 1 0 -0.4 -0.2
7000 -0.4 31.3 240 3 2 -5.6 -3.1 | 3.4 38.1 200 1 1 -1.0 -0.6
6750 -0.8 30.6 220 4 2 -5.3 -2.9 | 3.4 38.1 175 2 1 4.5 2.5
6500 -1.1 30.0 200 4 2 0.7 0.4 | 3.9 39.0 170 2 1 6.9 3.8
6250 -0.8 30.6 190 4 2 5.6 3.1 | 4.1 39.4 155 1 1 3.7 2.0
6000 -0.5 31.1 180 3 2 2.9 1.6 | 4.4 39.9 125 1 1 1.9 1.1
5750 -0.2 31.6 170 3 2 7.0 3.8 | 4.5 40.1 100 1 1 8.5 4.7
5500 0.7 33.3 165 2 1 17.0 9.3 | 5.9 42.6 090 1 1 29.2 16.0
04/21/2024 at 1500 MDT | 04/21/2024 at 1800 MDT
|
CAPE... 0.0 LI... +2.0 | CAPE... +14.8 LI... +1.0
CINH... -0.0 K Index... -0.2 | CINH... -15.4 K Index... +3.5
|
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 -57.1 -70.8 295 40 21 1.2 0.6 | -58.0 -72.4 290 42 22 0.4 0.2
45000 -55.6 -68.1 295 44 23 -3.9 -2.1 | -57.3 -71.1 295 48 24 -0.9 -0.5
40000 -62.0 -79.6 305 55 28 -4.3 -2.4 | -62.5 -80.5 310 56 29 -3.4 -1.9
38000 -61.0 -77.8 310 56 29 5.7 3.1 | -61.1 -78.0 315 57 30 6.1 3.3
36000 -57.6 -71.7 315 56 29 5.7 3.1 | -57.5 -71.5 315 57 30 6.1 3.3
34000 -53.7 -64.7 315 55 28 8.4 4.6 | -53.5 -64.3 310 56 29 8.2 4.5
32000 -48.7 -55.7 315 52 27 8.5 4.6 | -48.5 -55.3 310 52 27 8.3 4.5
30000 -43.1 -45.6 315 48 25 7.8 4.3 | -43.0 -45.4 310 47 24 8.0 4.4
29000 -40.8 -41.4 315 45 23 7.8 4.3 | -40.6 -41.1 310 45 23 8.0 4.4
28000 -38.5 -37.3 315 42 22 7.8 4.3 | -38.2 -36.8 310 42 22 8.0 4.4
27000 -36.1 -33.0 315 40 20 7.9 4.4 | -35.9 -32.6 310 40 20 7.5 4.1
26000 -33.7 -28.7 315 39 20 7.9 4.4 | -33.7 -28.7 310 38 20 7.5 4.1
25000 -31.4 -24.5 320 38 19 7.9 4.4 | -31.4 -24.5 310 36 19 7.5 4.1
24000 -29.0 -20.2 320 37 19 8.1 4.4 | -29.1 -20.4 310 34 18 8.3 4.6
23000 -26.6 -15.9 320 36 19 8.1 4.4 | -26.6 -15.9 310 33 17 8.3 4.6
22000 -24.1 -11.4 325 35 18 8.1 4.4 | -24.1 -11.4 315 32 16 8.3 4.6
21000 -21.8 -7.2 325 34 18 7.1 3.9 | -21.7 -7.1 315 31 16 8.1 4.5
20000 -19.6 -3.3 325 32 17 7.2 3.9 | -19.2 -2.6 315 29 15 8.1 4.5
19500 -18.6 -1.5 325 31 16 7.2 3.9 | -18.0 -0.4 315 29 15 8.1 4.5
19000 -17.5 0.5 325 30 15 7.3 4.0 | -16.8 1.8 315 28 15 8.2 4.5
18500 -16.4 2.5 320 29 15 6.7 3.6 | -15.6 3.9 315 28 14 7.2 4.0
18000 -15.4 4.3 320 28 14 6.7 3.7 | -14.6 5.7 315 27 14 7.3 4.0
17500 -14.4 6.1 320 26 14 6.7 3.7 | -13.5 7.7 315 26 14 7.1 3.9
17000 -12.9 8.8 320 25 13 6.8 3.7 | -12.4 9.7 315 26 13 7.0 3.8
16500 -11.9 10.6 315 24 12 6.6 3.6 | -10.9 12.4 315 25 13 6.8 3.7
16000 -11.0 12.2 315 23 12 6.6 3.6 | -9.9 14.2 310 24 12 6.8 3.7
15500 -10.0 14.0 315 23 12 6.7 3.7 | -8.9 16.0 310 23 12 7.0 3.8
15000 -9.0 15.8 310 22 11 7.0 3.8 | -7.8 18.0 305 23 12 7.3 4.0
14500 -8.0 17.6 310 22 11 7.0 3.8 | -6.8 19.8 300 23 12 7.4 4.0
14000 -6.9 19.6 305 22 11 7.0 3.9 | -5.6 21.9 300 23 12 7.9 4.3
13500 -5.9 21.4 300 21 11 7.0 3.8 | -4.5 23.9 295 23 12 7.9 4.3
13000 -4.8 23.4 300 21 11 8.0 4.4 | -3.3 26.1 290 22 12 8.3 4.5
12500 -3.7 25.3 295 21 11 7.9 4.4 | -2.2 28.0 290 22 11 8.3 4.6
12000 -2.6 27.3 290 21 11 7.9 4.3 | -1.0 30.2 285 20 11 8.4 4.6
11500 -1.5 29.3 290 20 10 7.9 4.4 | 0.3 32.5 285 19 10 8.5 4.7
11000 -0.3 31.5 285 18 9 8.1 4.5 | 1.5 34.7 285 17 9 7.7 4.2
10500 0.9 33.6 285 16 8 9.3 5.1 | 2.6 36.7 280 15 8 8.9 4.9
10250 1.5 34.7 285 15 8 3.3 1.8 | 3.1 37.6 280 14 7 3.3 1.8
10000 1.5 34.7 285 16 8 3.4 1.9 | 3.2 37.8 275 14 7 4.1 2.2
9750 2.1 35.8 285 14 7 9.5 5.2 | 3.8 38.8 270 13 7 10.1 5.5
9500 2.7 36.9 280 12 6 8.0 4.4 | 4.5 40.1 265 11 6 8.9 4.9
9250 3.2 37.8 280 10 5 5.3 2.9 | 5.1 41.2 255 10 5 6.6 3.6
9000 3.5 38.3 275 9 4 3.9 2.1 | 5.5 41.9 250 10 5 5.6 3.1
8750 3.9 39.0 270 7 4 6.4 3.5 | 6.0 42.8 240 9 5 7.9 4.3
8500 4.4 39.9 260 5 3 5.7 3.1 | 6.5 43.7 230 8 4 7.4 4.1
8250 4.7 40.5 240 4 2 3.7 2.0 | 7.0 44.6 220 7 4 6.2 3.4
8000 4.9 40.8 210 3 2 3.2 1.8 | 7.4 45.3 210 7 3 5.7 3.1
7750 5.3 41.5 185 3 2 7.1 3.9 | 7.9 46.2 200 6 3 7.4 4.1
7500 5.9 42.6 170 3 2 6.7 3.7 | 8.4 47.1 185 5 3 6.7 3.7
7250 6.2 43.2 150 3 2 4.1 2.2 | 8.8 47.8 175 5 2 5.0 2.7
7000 6.4 43.5 130 3 2 4.0 2.2 | 9.1 48.4 165 4 2 4.8 2.7
6750 6.8 44.2 115 3 2 9.8 5.4 | 9.5 49.1 150 4 2 8.4 4.6
6500 7.7 45.9 105 3 2 12.3 6.7 | 10.2 50.4 145 3 2 10.4 5.7
6250 8.4 47.1 105 3 2 9.4 5.2 | 10.9 51.6 140 3 2 9.1 5.0
6000 9.1 48.4 100 3 2 9.0 5.0 | 11.6 52.9 130 3 1 9.2 5.0
5750 9.8 49.6 095 3 2 12.7 7.0 | 12.3 54.1 125 3 1 10.1 5.6
5500 11.1 52.0 090 3 2 23.2 12.7 | 13.1 55.6 125 2 1 13.0 7.2
________________________________________________________________________________
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 near the old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 meters)
and may not be representative of other areas along the Front Range of the
Colorado Rocky Mountains. 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
- San Juan, PR Weather Forecast Office
- 4000 Carretera 190
- Carolina, PR 00979
- 787-253-4586
- Page Author: SJU Webmaster
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- Page last modified: Sep 19th, 2023 19:10 UTC