266
UXUS97 KPUB 141222
SRGPUB
SOARING FORECAST
NATIONAL WEATHER SERVICE PUEBLO, COLORADO
0621 MDT SUNDAY, SEPTEMBER 14, 2025
THIS FORECAST IS FOR VILLA GROVE, CO FOR SUNDAY, SEPTEMBER 14, 2025:
IF THE TRIGGER TEMPERATURE OF 51.7 F/11.0 C IS REACHED...THEN
THERMAL SOARING INDEX....................... EXCELLENT
MAXIMUM RATE OF LIFT........................ 1144 FT/MIN (5.8 M/S)
MAXIMUM HEIGHT OF THERMALS.................. 21264 FT MSL (12278 FT AGL)
FORECAST MAXIMUM TEMPERATURE................... 67.0 F/19.9 C
TIME OF TRIGGER TEMPERATURE.................... 0945 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................. 18577 FT MSL (9592 FT AGL)
THERMAL SOARING OUTLOOK FOR MONDAY 09/15....... EXCELLENT
WAVE SOARING INDEX............................. NOT AVAILABLE
REMARKS...
SUNRISE/SUNSET.................... 06:44:57 / 19:12:59 MDT
TOTAL POSSIBLE SUNSHINE........... 12 HR 28 MIN 2 SEC (748 MIN 2 SEC)
ALTITUDE OF SUN AT 12:58:58 MDT... 54.82 DEGREES
UPPER AIR DATA FROM NUMERICAL MODEL FORECAST VALID ON 09/14/2025 AT 0600 MDT
FREEZING LEVEL.................. 12521 FT MSL (3535 FT AGL)
CONVECTIVE CONDENSATION LEVEL... 15299 FT MSL (6313 FT AGL)
LIFTED CONDENSATION LEVEL....... 18024 FT MSL (9038 FT AGL)
LIFTED INDEX.................... -3.3
K INDEX......................... +9.5
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 -59.2 -74.6 270 21 11 3.1 1.7 M M M M M
45000 -54.2 -65.6 270 35 18 4.3 2.3 M M M M M
40000 -47.8 -54.0 280 44 23 4.1 2.2 M M M M M
38000 -45.8 -50.4 285 50 26 3.2 1.8 M M M M M
36000 -43.9 -47.0 290 57 29 3.2 1.8 M M M M M
34000 -41.7 -43.1 290 55 28 3.2 1.8 M M M M M
32000 -39.8 -39.6 285 45 23 3.2 1.8 M M M M M
30000 -36.8 -34.2 280 37 19 6.5 3.6 27.6 81.7 6.4 M M
29000 -34.8 -30.6 280 34 18 6.5 3.6 26.3 79.4 5.5 M M
28000 -32.9 -27.2 280 31 16 6.6 3.6 25.2 77.4 4.6 M M
27000 -30.7 -23.3 280 29 15 8.1 4.4 24.3 75.8 4.0 M M
26000 -28.2 -18.8 285 27 14 8.2 4.5 23.7 74.6 3.5 M M
25000 -25.8 -14.4 285 26 13 8.2 4.5 23.1 73.6 3.1 M M
24000 -23.5 -10.3 285 24 12 6.6 3.6 22.5 72.4 2.5 M M
23000 -21.5 -6.7 280 22 11 6.8 3.7 21.3 70.4 1.6 M M
22000 -19.4 -2.9 280 21 11 6.8 3.7 20.3 68.6 0.7 M M
21000 -17.5 0.5 280 20 10 6.2 3.4 19.3 66.7 -0.2 1127 5.7
20000 -15.7 3.7 285 19 10 6.2 3.4 18.0 64.4 -1.4 1042 5.3
19500 -14.7 5.5 285 19 10 6.2 3.4 17.4 63.4 -1.9 1000 5.1
19000 -13.8 7.2 285 19 10 6.2 3.4 16.9 62.4 -2.4 957 4.9
18500 -12.9 8.8 285 19 10 6.4 3.5 16.3 61.4 -3.0 914 4.6
18000 -11.9 10.6 290 18 9 6.5 3.5 15.8 60.4 -3.5 871 4.4
17500 -11.0 12.2 290 18 9 6.9 3.8 15.2 59.4 -4.0 828 4.2
17000 -9.9 14.2 295 18 9 7.1 3.9 14.8 58.6 -4.5 782 4.0
16500 -8.4 16.9 300 17 9 7.0 3.9 14.2 57.5 -5.2 713 3.6
16000 -7.4 18.7 305 17 9 7.0 3.8 13.7 56.7 -5.7 668 3.4
15500 -6.4 20.5 310 17 9 7.4 4.1 13.3 55.9 -6.1 623 3.2
15000 -5.2 22.6 310 17 9 8.0 4.4 13.0 55.4 -6.5 573 2.9
14500 -4.0 24.8 315 17 9 7.0 3.8 12.7 54.9 -6.8 523 2.7
14000 -3.0 26.6 315 17 9 7.8 4.3 12.3 54.1 -7.3 479 2.4
13500 -1.9 28.6 315 17 9 7.7 4.2 11.9 53.4 -7.7 431 2.2
13000 -0.9 30.4 315 18 9 6.9 3.8 11.5 52.7 -8.2 385 2.0
12500 0.2 32.4 315 18 9 7.5 4.1 11.1 52.0 -8.6 338 1.7
12000 1.2 34.2 310 19 10 5.9 3.2 10.7 51.2 -9.2 294 1.5
11750 1.6 34.9 305 19 10 6.6 3.6 10.4 50.7 -9.5 273 1.4
11500 2.1 35.8 305 19 10 6.9 3.8 10.1 50.3 -9.7 251 1.3
11250 2.6 36.7 300 19 10 6.1 3.3 9.9 49.9 -10.0 229 1.2
11000 3.0 37.4 300 19 10 5.8 3.2 9.6 49.3 -10.4 210 1.1
10750 3.3 37.9 295 18 9 3.9 2.1 9.3 48.7 -10.8 191 1.0
10500 3.5 38.3 295 19 10 1.5 0.8 8.7 47.7 -11.4 179 0.9
10250 3.6 38.5 295 20 10 2.1 1.2 8.1 46.6 -12.0 169 0.9
10000 3.7 38.7 290 19 10 2.5 1.4 7.5 45.6 -12.7 158 0.8
9750 3.9 39.0 290 18 9 2.7 1.5 7.0 44.6 -13.3 146 0.7
9500 4.1 39.4 290 17 9 7.1 3.9 6.6 43.8 -13.8 130 0.7
9250 4.6 40.3 285 14 7 2.9 1.6 6.4 43.5 -14.1 108 0.5
9000 3.0 37.4 275 7 4 -63.6 -34.9 4.0 39.2 -16.4 149 0.8
8750 M M M M M M M M M M M M
8500 M M M M M M M M M M M M
8250 M M M M M M M M M M M M
8000 M M M M M M M M M M M M
* * * * * * NUMERICAL WEATHER PREDICTION MODEL FORECAST DATA VALID * * * * * *
09/14/2025 AT 0900 MDT | 09/14/2025 AT 1200 MDT
|
CAPE... +0.6 LI... +1.3 | CAPE... +40.1 LI... +0.6
CINH... 0.0 K INDEX... +4.2 | CINH... -0.2 K INDEX... -0.5
|
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 -59.8 -75.6 275 18 9 2.9 1.6 | -60.9 -77.6 260 21 11 2.2 1.2
45000 -55.1 -67.2 280 35 18 4.0 2.2 | -56.7 -70.1 270 34 18 4.8 2.6
40000 -48.8 -55.8 290 56 29 3.9 2.1 | -49.2 -56.6 290 49 25 3.5 1.9
38000 -46.5 -51.7 290 61 32 3.9 2.1 | -47.1 -52.8 290 52 27 3.5 1.9
36000 -44.2 -47.6 295 67 34 3.9 2.1 | -45.0 -49.0 290 55 28 3.5 1.9
34000 -41.1 -42.0 295 67 35 6.1 3.4 | -41.5 -42.7 295 58 30 7.2 4.0
32000 -37.4 -35.3 295 64 33 6.1 3.4 | -37.2 -35.0 300 61 31 7.2 4.0
30000 -34.4 -29.9 295 54 28 4.0 2.2 | -33.2 -27.8 300 58 30 6.3 3.4
29000 -33.2 -27.8 295 46 23 4.0 2.2 | -31.3 -24.3 300 53 27 6.3 3.4
28000 -32.0 -25.6 290 37 19 4.1 2.2 | -29.0 -20.2 300 47 24 6.3 3.5
27000 -30.0 -22.0 290 31 16 6.6 3.6 | -27.2 -17.0 300 42 21 5.7 3.1
26000 -28.0 -18.4 290 29 15 6.7 3.7 | -25.5 -13.9 300 35 18 5.7 3.1
25000 -26.0 -14.8 290 27 14 6.7 3.7 | -23.8 -10.8 300 29 15 5.7 3.2
24000 -23.9 -11.0 290 26 14 7.3 4.0 | -22.0 -7.6 300 25 13 6.5 3.5
23000 -21.8 -7.2 295 27 14 7.3 4.0 | -20.1 -4.2 300 25 13 6.5 3.6
22000 -19.6 -3.3 295 27 14 7.3 4.0 | -18.1 -0.6 300 25 13 6.6 3.6
21000 -17.4 0.7 300 28 14 7.4 4.1 | -16.1 3.0 300 26 13 7.1 3.9
20000 -15.2 4.6 305 29 15 7.4 4.1 | -14.8 5.4 305 26 13 7.2 3.9
19500 -14.1 6.6 305 30 15 7.4 4.1 | -12.9 8.8 305 26 13 7.1 3.9
19000 -13.0 8.6 305 31 16 7.5 4.1 | -11.8 10.8 305 26 14 6.8 3.8
18500 -11.9 10.6 310 31 16 7.5 4.1 | -10.9 12.4 305 26 14 6.1 3.4
18000 -10.8 12.6 310 31 16 7.5 4.1 | -10.0 14.0 305 27 14 6.2 3.4
17500 -9.7 14.5 310 31 16 7.3 4.0 | -9.1 15.6 310 26 14 5.7 3.1
17000 -8.7 16.3 310 30 15 7.3 4.0 | -8.3 17.1 310 26 13 5.7 3.1
16500 -7.6 18.3 310 29 15 7.1 3.9 | -7.5 18.5 310 25 13 5.8 3.2
16000 -6.6 20.1 310 27 14 6.7 3.7 | -6.7 19.9 310 24 13 5.8 3.2
15500 -5.6 21.9 310 26 13 6.8 3.7 | -5.8 21.6 315 23 12 5.9 3.2
15000 -4.6 23.7 310 24 13 6.6 3.6 | -4.9 23.2 315 22 11 6.7 3.7
14500 -3.7 25.3 310 22 12 6.7 3.7 | -4.0 24.8 315 21 11 6.9 3.8
14000 -2.3 27.9 310 19 10 7.0 3.8 | -2.6 27.3 320 20 10 6.8 3.8
13500 -1.3 29.7 310 15 8 6.9 3.8 | -1.7 28.9 320 19 10 6.0 3.3
13000 -0.3 31.5 315 17 9 7.0 3.9 | -0.8 30.6 320 18 9 7.7 4.2
12500 0.8 33.4 315 20 10 7.4 4.1 | 0.3 32.5 320 17 9 8.0 4.4
12000 1.6 34.9 315 20 10 4.4 2.4 | 1.3 34.3 310 15 8 8.2 4.5
11750 1.9 35.4 315 20 10 5.4 3.0 | 2.0 35.6 310 15 8 10.6 5.8
11500 2.3 36.1 315 20 10 6.3 3.5 | 2.7 36.9 305 14 7 10.6 5.8
11250 2.7 36.9 315 19 10 2.9 1.6 | 3.5 38.3 305 14 7 9.6 5.3
11000 2.6 36.7 315 19 10 -0.9 -0.5 | 4.1 39.4 300 14 7 8.3 4.5
10750 2.5 36.5 310 19 10 1.2 0.7 | 4.8 40.6 300 13 7 9.9 5.4
10500 2.6 36.7 305 18 9 1.1 0.6 | 5.6 42.1 300 13 7 11.3 6.2
10250 2.7 36.9 295 16 8 5.9 3.2 | 6.4 43.5 300 13 7 10.8 5.9
10000 3.3 37.9 295 15 8 10.3 5.6 | 7.2 45.0 300 13 6 10.9 6.0
9750 4.0 39.2 290 14 7 8.9 4.9 | 8.0 46.4 300 12 6 10.3 5.6
9500 4.7 40.5 285 13 7 10.5 5.8 | 8.8 47.8 300 12 6 12.9 7.1
9250 5.6 42.1 285 11 6 16.2 8.9 | 10.1 50.2 300 11 6 24.5 13.5
9000 7.2 45.0 285 10 5 29.1 16.0 | 12.5 54.5 295 10 5 40.9 22.5
8750 M M M M M M M | M M M M M M M
8500 M M M M M M M | M M M M M M M
8250 M M M M M M M | M M M M M M M
8000 M M M M M M M | M M M M M M M
09/14/2025 AT 1500 MDT | 09/14/2025 AT 1800 MDT
|
CAPE... +105.7 LI... -0.1 | CAPE... +15.0 LI... +1.2
CINH... 0.0 K INDEX... +8.5 | CINH... -0.4 K INDEX... -0.7
|
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 -61.5 -78.7 260 22 11 2.0 1.1 | -61.8 -79.2 275 20 10 1.8 1.0
45000 -57.6 -71.7 265 36 19 4.7 2.6 | -58.2 -72.8 280 33 17 4.4 2.4
40000 -50.3 -58.5 280 43 22 3.4 1.8 | -51.3 -60.3 290 46 24 3.6 2.0
38000 -48.2 -54.8 285 44 23 3.5 1.9 | -49.1 -56.4 290 46 24 3.7 2.0
36000 -46.2 -51.2 285 46 23 3.5 1.9 | -46.9 -52.4 290 46 24 3.7 2.1
34000 -42.6 -44.7 290 47 24 7.1 3.9 | -43.1 -45.6 290 44 23 7.5 4.1
32000 -38.4 -37.1 295 48 25 7.1 3.9 | -38.6 -37.5 290 41 21 7.5 4.1
30000 -33.6 -28.5 300 50 26 8.7 4.8 | -34.0 -29.2 290 39 20 8.0 4.4
29000 -30.9 -23.6 300 50 26 8.7 4.8 | -31.0 -23.8 295 39 20 8.0 4.4
28000 -27.7 -17.9 300 51 27 8.6 4.7 | -28.6 -19.5 295 38 20 8.0 4.4
27000 -25.7 -14.3 300 48 25 6.1 3.3 | -26.2 -15.2 295 39 20 7.9 4.3
26000 -23.9 -11.0 300 44 23 6.1 3.3 | -23.9 -11.0 300 40 20 7.9 4.3
25000 -22.1 -7.8 300 40 21 6.1 3.3 | -21.5 -6.7 300 41 21 8.0 4.4
24000 -20.3 -4.5 300 36 19 5.8 3.2 | -19.5 -3.1 300 39 20 6.2 3.4
23000 -18.6 -1.5 300 32 17 5.8 3.2 | -17.6 0.3 305 36 18 6.2 3.4
22000 -16.9 1.6 300 28 14 5.8 3.2 | -15.8 3.6 305 32 17 6.2 3.4
21000 -14.9 5.2 300 25 13 7.0 3.8 | -13.9 7.0 305 29 15 6.3 3.5
20000 -12.9 8.8 305 23 12 7.0 3.8 | -12.0 10.4 300 26 13 6.4 3.5
19500 -11.8 10.8 305 22 11 6.9 3.8 | -11.0 12.2 300 25 13 6.3 3.5
19000 -10.8 12.6 305 21 11 5.2 2.9 | -10.1 13.8 295 23 12 5.8 3.2
18500 -10.4 13.3 305 21 11 2.9 1.6 | -9.3 15.3 295 22 11 5.5 3.0
18000 -10.0 14.0 305 21 11 2.7 1.5 | -8.5 16.7 290 21 11 5.8 3.2
17500 -9.4 15.1 310 20 11 6.0 3.3 | -7.9 17.8 290 19 10 3.5 1.9
17000 -8.6 16.5 310 21 11 6.0 3.3 | -7.4 18.7 290 17 9 3.9 2.2
16500 -7.8 18.0 315 21 11 7.1 3.9 | -6.9 19.6 285 14 7 6.6 3.6
16000 -6.7 19.9 315 19 10 8.0 4.4 | -5.8 21.6 290 13 7 7.9 4.4
15500 -5.6 21.9 315 18 9 8.3 4.5 | -4.6 23.7 290 12 6 8.4 4.6
15000 -4.3 24.3 310 17 8 9.3 5.1 | -2.6 27.3 290 11 6 9.9 5.4
14500 -2.4 27.7 305 14 7 8.4 4.6 | -1.4 29.5 285 11 6 8.1 4.4
14000 -1.0 30.2 300 14 7 9.6 5.3 | -0.0 32.0 285 11 6 9.2 5.0
13500 0.4 32.7 300 13 7 8.8 4.8 | 1.4 34.5 290 11 6 9.1 5.0
13000 1.8 35.2 300 13 7 10.5 5.7 | 2.8 37.0 285 11 5 10.3 5.6
12500 3.3 37.9 300 13 7 10.1 5.6 | 4.3 39.7 290 10 5 9.9 5.4
12000 4.7 40.5 300 13 7 9.3 5.1 | 5.5 41.9 285 10 5 9.0 4.9
11750 5.4 41.7 300 13 7 11.0 6.0 | 6.3 43.3 285 10 5 11.5 6.3
11500 6.2 43.2 300 13 6 10.6 5.8 | 7.1 44.8 290 10 5 10.8 5.9
11250 7.0 44.6 300 12 6 10.1 5.6 | 7.9 46.2 290 10 5 9.9 5.5
11000 7.8 46.0 300 12 6 9.6 5.3 | 8.6 47.5 285 10 5 9.2 5.1
10750 8.5 47.3 300 12 6 10.1 5.5 | 9.3 48.7 285 9 5 9.7 5.3
10500 9.3 48.7 305 12 6 10.4 5.7 | 10.1 50.2 285 9 5 10.0 5.5
10250 10.0 50.0 305 12 6 10.3 5.7 | 10.8 51.4 285 9 5 10.1 5.5
10000 10.8 51.4 305 11 6 10.5 5.8 | 11.6 52.9 285 9 5 10.3 5.7
9750 11.6 52.9 305 11 6 10.1 5.6 | 12.3 54.1 285 9 4 9.9 5.4
9500 12.4 54.3 305 11 5 12.4 6.8 | 13.1 55.6 285 8 4 9.9 5.4
9250 13.6 56.5 305 10 5 21.8 12.0 | 13.9 57.0 285 7 4 13.0 7.2
9000 15.7 60.3 300 9 5 36.1 19.8 | 15.0 59.0 285 7 3 19.6 10.7
8750 M M M M M M M | M M M M M M M
8500 M M M M M M M | M M M M M M M
8250 M M M M M M M | M M M M M M M
8000 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). 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 VILLA GROVE, COLORADO AT:
NORTH LATITUDE: 38 DEG 16 MIN 03 SEC
WEST LONGITUDE: 105 DEG 53 MIN 37 SEC
ELEVATION: 7986 FEET (2434 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.
CIN (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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