604
UXUS97 KPUB 221215
SRGPUB
SOARING FORECAST
NATIONAL WEATHER SERVICE PUEBLO, COLORADO
0615 MDT WEDNESDAY, OCTOBER 22, 2025
THIS FORECAST IS FOR VILLA GROVE, CO FOR WEDNESDAY, OCTOBER 22, 2025:
IF THE TRIGGER TEMPERATURE OF 57.5 F/14.2 C IS REACHED...THEN
THERMAL SOARING INDEX....................... GOOD
MAXIMUM RATE OF LIFT........................ 709 FT/MIN (3.6 M/S)
MAXIMUM HEIGHT OF THERMALS.................. 16376 FT MSL (7415 FT AGL)
FORECAST MAXIMUM TEMPERATURE................... 63.0 F/17.7 C
TIME OF TRIGGER TEMPERATURE.................... 1200 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................. 12898 FT MSL (3936 FT AGL)
THERMAL SOARING OUTLOOK FOR THURSDAY 10/23..... GOOD
WAVE SOARING INDEX............................. NOT AVAILABLE
REMARKS...
SUNRISE/SUNSET.................... 07:19:58 / 18:15:53 MDT
TOTAL POSSIBLE SUNSHINE........... 10 HR 55 MIN 56 SEC (655 MIN 56 SEC)
ALTITUDE OF SUN AT 12:47:56 MDT... 40.31 DEGREES
UPPER AIR DATA FROM NUMERICAL MODEL FORECAST VALID ON 10/22/2025 AT 0600 MDT
FREEZING LEVEL.................. 14053 FT MSL (5092 FT AGL)
CONVECTIVE CONDENSATION LEVEL... 22342 FT MSL (13381 FT AGL)
LIFTED CONDENSATION LEVEL....... 20765 FT MSL (11804 FT AGL)
LIFTED INDEX.................... +3.5
K INDEX......................... -11.6
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 -66.4 -87.5 275 57 29 2.1 1.2 M M M M M
45000 -62.8 -81.0 270 70 36 2.9 1.6 M M M M M
40000 -58.5 -73.3 275 67 35 4.0 2.2 M M M M M
38000 -54.6 -66.3 275 68 35 6.6 3.6 M M M M M
36000 -50.7 -59.3 275 69 35 6.6 3.6 M M M M M
34000 -46.3 -51.3 275 67 34 7.8 4.3 M M M M M
32000 -41.6 -42.9 275 63 32 7.8 4.3 M M M M M
30000 -36.3 -33.3 280 57 29 7.9 4.3 27.6 81.6 8.1 M M
29000 -34.0 -29.2 280 54 28 7.9 4.3 26.9 80.3 7.7 M M
28000 -31.6 -24.9 280 51 26 7.9 4.3 26.3 79.3 7.3 M M
27000 -29.3 -20.7 280 49 25 7.6 4.2 25.4 77.8 6.7 M M
26000 -27.0 -16.6 280 47 24 7.6 4.2 24.6 76.4 6.1 M M
25000 -24.7 -12.5 280 44 23 7.7 4.2 24.0 75.1 5.6 M M
24000 -22.4 -8.3 285 42 22 7.6 4.2 23.2 73.7 5.0 M M
23000 -20.2 -4.4 285 40 21 7.6 4.2 22.4 72.3 4.4 M M
22000 -17.9 -0.2 285 38 20 7.6 4.2 21.7 71.1 3.8 M M
21000 -15.6 3.9 290 35 18 7.5 4.1 20.9 69.6 3.2 M M
20000 -13.4 7.9 290 32 17 7.5 4.1 20.1 68.2 2.5 M M
19500 -12.2 10.0 290 31 16 7.5 4.1 19.8 67.6 2.2 M M
19000 -11.1 12.0 290 29 15 7.3 4.0 19.5 67.0 1.9 M M
18500 -10.1 13.8 290 28 14 7.2 3.9 19.0 66.2 1.5 M M
18000 -9.0 15.8 295 26 13 7.1 3.9 18.6 65.5 1.1 M M
17500 -7.9 17.8 295 24 13 7.8 4.3 18.2 64.8 0.8 M M
17000 -6.8 19.8 295 23 12 7.7 4.2 17.9 64.2 0.5 M M
16500 -5.6 21.9 295 23 12 7.6 4.2 17.6 63.6 0.2 M M
16000 -4.5 23.9 300 22 11 7.6 4.2 17.2 62.9 -0.2 682 3.5
15500 -3.4 25.9 300 22 11 7.6 4.1 16.8 62.3 -0.5 634 3.2
15000 -2.3 27.9 300 22 11 7.4 4.0 16.5 61.6 -0.9 586 3.0
14500 -0.6 30.9 300 21 11 6.6 3.6 15.9 60.6 -1.5 515 2.6
14000 0.3 32.5 300 21 11 6.8 3.7 15.4 59.7 -2.0 471 2.4
13500 1.3 34.3 300 21 11 6.4 3.5 14.9 58.8 -2.4 426 2.2
13000 2.3 36.1 300 20 10 6.3 3.4 14.3 57.8 -3.0 384 1.9
12500 3.2 37.8 300 20 10 6.2 3.4 13.8 56.8 -3.5 341 1.7
12000 4.0 39.2 300 19 10 5.5 3.0 13.2 55.7 -4.2 301 1.5
11750 4.4 39.9 300 19 10 5.7 3.1 12.9 55.1 -4.5 282 1.4
11500 4.8 40.6 300 19 10 5.4 3.0 12.5 54.6 -4.9 262 1.3
11250 5.2 41.4 300 18 9 4.4 2.4 12.2 53.9 -5.3 245 1.2
11000 5.4 41.7 300 18 9 3.9 2.1 11.7 53.1 -5.8 229 1.2
10750 5.7 42.3 300 17 9 4.2 2.3 11.3 52.3 -6.2 214 1.1
10500 5.9 42.6 295 17 9 3.0 1.6 10.8 51.5 -6.8 200 1.0
10250 6.0 42.8 295 16 8 0.3 0.1 10.2 50.4 -7.4 190 1.0
10000 5.9 42.6 295 15 8 -1.9 -1.0 9.4 48.9 -8.3 185 0.9
9750 5.9 42.6 290 14 7 2.0 1.1 8.6 47.5 -9.1 179 0.9
9500 5.9 42.6 285 13 7 -6.6 -3.6 7.9 46.3 -9.8 170 0.9
9250 4.4 39.9 275 10 5 -35.9 -19.7 5.6 42.1 -12.1 209 1.1
9000 1.8 35.2 250 6 3 -16.5 -9.1 2.3 36.1 -15.4 280 1.4
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 * * * * * *
10/22/2025 AT 0900 MDT | 10/22/2025 AT 1200 MDT
|
CAPE... 0.0 LI... +2.1 | CAPE... 0.0 LI... +2.1
CINH... 0.0 K INDEX... -8.7 | CINH... 0.0 K INDEX... -6.9
|
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 -68.0 -90.4 280 49 25 1.5 0.8 | -66.9 -88.4 275 51 26 1.7 0.9
45000 -65.1 -85.2 275 56 29 4.0 2.2 | -63.9 -83.0 275 59 30 3.4 1.9
40000 -59.0 -74.2 270 51 26 5.9 3.2 | -58.7 -73.7 275 58 30 4.9 2.7
38000 -54.6 -66.3 275 48 25 7.4 4.1 | -54.8 -66.6 270 54 28 6.6 3.6
36000 -50.1 -58.2 275 45 23 7.4 4.1 | -50.8 -59.4 270 51 26 6.6 3.6
34000 -44.9 -48.8 275 44 23 8.0 4.4 | -45.7 -50.3 270 49 25 7.9 4.3
32000 -40.0 -40.0 275 45 23 8.0 4.4 | -41.0 -41.8 270 49 25 7.9 4.3
30000 -35.3 -31.5 285 45 23 7.8 4.3 | -36.2 -33.2 270 46 24 8.1 4.5
29000 -33.0 -27.4 290 45 23 7.8 4.3 | -33.7 -28.7 275 45 23 8.1 4.5
28000 -30.7 -23.3 290 46 24 7.8 4.3 | -31.3 -24.3 275 44 22 8.2 4.5
27000 -28.3 -18.9 295 46 23 7.9 4.4 | -28.8 -19.8 280 43 22 8.5 4.6
26000 -25.9 -14.6 295 45 23 7.9 4.4 | -26.2 -15.2 280 42 21 8.5 4.6
25000 -23.5 -10.3 295 45 23 7.9 4.3 | -23.7 -10.7 285 41 21 8.4 4.6
24000 -21.0 -5.8 300 44 23 8.5 4.7 | -21.1 -6.0 285 40 21 8.6 4.7
23000 -18.5 -1.3 300 43 22 8.5 4.7 | -18.5 -1.3 290 39 20 8.6 4.7
22000 -15.9 3.4 300 41 21 8.7 4.8 | -16.0 3.2 290 37 19 8.7 4.8
21000 -13.7 7.3 305 40 20 6.9 3.8 | -13.6 7.5 290 36 19 7.7 4.2
20000 -11.7 10.9 305 38 19 6.9 3.8 | -11.3 11.7 295 35 18 7.7 4.2
19500 -10.6 12.9 305 37 19 6.9 3.8 | -10.1 13.8 295 34 17 7.7 4.2
19000 -9.6 14.7 305 36 18 6.4 3.5 | -9.0 15.8 295 33 17 6.9 3.8
18500 -8.7 16.3 305 34 18 6.2 3.4 | -8.0 17.6 295 32 16 6.6 3.6
18000 -7.8 18.0 305 32 17 6.2 3.4 | -7.0 19.4 300 30 16 6.6 3.6
17500 -6.9 19.6 305 31 16 6.1 3.3 | -6.1 21.0 295 29 15 6.2 3.4
17000 -6.0 21.2 300 29 15 6.0 3.3 | -5.2 22.6 295 27 14 6.2 3.4
16500 -4.5 23.9 300 27 14 6.7 3.7 | -3.8 25.2 295 24 13 6.1 3.3
16000 -3.5 25.7 305 25 13 6.6 3.6 | -2.9 26.8 295 23 12 6.1 3.3
15500 -2.5 27.5 305 23 12 6.7 3.7 | -2.0 28.4 295 21 11 6.2 3.4
15000 -1.5 29.3 305 21 11 6.8 3.7 | -1.0 30.2 295 20 10 6.2 3.4
14500 -0.5 31.1 310 20 10 6.7 3.7 | -0.1 31.8 295 18 9 6.4 3.5
14000 0.5 32.9 310 19 10 7.4 4.1 | 0.9 33.6 295 17 9 6.6 3.6
13500 1.6 34.9 310 18 9 8.8 4.8 | 1.9 35.4 295 15 8 7.1 3.9
13000 2.9 37.2 310 18 9 6.7 3.7 | 3.0 37.4 290 14 7 6.5 3.6
12500 3.9 39.0 310 17 9 6.6 3.6 | 3.9 39.0 290 13 7 6.4 3.5
12000 4.9 40.8 310 17 9 6.7 3.7 | 4.9 40.8 290 12 6 6.0 3.3
11750 5.4 41.7 305 16 8 6.5 3.6 | 5.3 41.5 290 12 6 5.9 3.2
11500 5.9 42.6 305 16 8 5.4 3.0 | 5.7 42.3 285 11 6 4.5 2.4
11250 6.2 43.2 305 16 8 3.7 2.0 | 5.9 42.6 280 11 6 1.8 1.0
11000 6.4 43.5 300 15 8 3.2 1.8 | 6.0 42.8 275 11 5 1.3 0.7
10750 6.7 44.1 300 15 7 3.7 2.0 | 6.0 42.8 270 10 5 1.4 0.7
10500 6.8 44.2 295 14 7 -0.6 -0.3 | 6.1 43.0 265 10 5 3.7 2.1
10250 6.5 43.7 290 13 7 -6.8 -3.7 | 6.4 43.5 260 10 5 7.1 3.9
10000 5.9 42.6 285 13 7 -6.6 -3.6 | 7.0 44.6 250 9 5 8.1 4.5
9750 5.3 41.5 285 13 7 -9.6 -5.3 | 7.5 45.5 240 9 5 6.3 3.5
9500 4.3 39.7 280 13 7 -9.1 -5.0 | 8.0 46.4 235 9 5 12.1 6.6
9250 4.0 39.2 270 10 5 3.1 1.7 | 9.5 49.1 230 8 4 27.4 15.0
9000 3.9 39.0 255 6 3 -12.8 -7.0 | 11.2 52.2 230 8 4 5.9 3.3
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
10/22/2025 AT 1500 MDT | 10/22/2025 AT 1800 MDT
|
CAPE... 0.0 LI... +1.9 | CAPE... 0.0 LI... +1.5
CINH... 0.0 K INDEX... -2.9 | CINH... 0.0 K INDEX... +7.9
|
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 -66.3 -87.3 275 58 30 1.4 0.8 | -67.0 -88.6 280 58 30 1.4 0.8
45000 -63.7 -82.7 275 67 35 3.5 1.9 | -64.1 -83.4 275 68 35 4.0 2.2
40000 -58.5 -73.3 280 66 34 4.6 2.5 | -58.1 -72.6 275 68 35 4.9 2.7
38000 -54.6 -66.3 275 62 32 6.4 3.5 | -54.4 -65.9 275 64 33 6.2 3.4
36000 -50.8 -59.4 275 58 30 6.4 3.5 | -50.7 -59.3 275 60 31 6.2 3.4
34000 -45.9 -50.6 275 55 28 7.7 4.2 | -45.8 -50.4 280 56 29 8.0 4.4
32000 -41.3 -42.3 275 53 27 7.7 4.2 | -41.0 -41.8 280 53 27 8.0 4.4
30000 -36.3 -33.3 275 51 26 8.4 4.6 | -36.2 -33.2 280 50 26 7.9 4.4
29000 -33.8 -28.8 275 49 25 8.4 4.6 | -33.8 -28.8 280 49 25 7.9 4.4
28000 -31.3 -24.3 275 48 25 8.4 4.6 | -31.5 -24.7 280 47 24 8.0 4.4
27000 -28.8 -19.8 280 46 24 8.3 4.5 | -29.0 -20.2 280 45 23 8.4 4.6
26000 -26.3 -15.3 280 45 23 8.3 4.5 | -26.4 -15.5 280 44 22 8.4 4.6
25000 -23.8 -10.8 280 43 22 8.3 4.5 | -23.9 -11.0 280 42 22 8.5 4.6
24000 -21.3 -6.3 280 41 21 8.4 4.6 | -21.4 -6.5 280 40 21 8.0 4.4
23000 -18.8 -1.8 280 39 20 8.4 4.6 | -19.0 -2.2 280 38 19 8.0 4.4
22000 -16.3 2.7 280 36 19 8.5 4.7 | -16.6 2.1 280 36 18 8.1 4.4
21000 -14.1 6.6 285 34 17 7.3 4.0 | -14.4 6.1 280 33 17 7.2 4.0
20000 -11.9 10.6 290 32 16 7.3 4.0 | -12.3 9.9 285 31 16 7.2 4.0
19500 -10.8 12.6 290 31 16 7.3 4.0 | -11.2 11.8 285 30 15 7.2 4.0
19000 -9.7 14.5 290 30 15 7.2 4.0 | -10.1 13.8 290 29 15 7.2 3.9
18500 -8.6 16.5 295 29 15 7.2 4.0 | -9.0 15.8 290 28 14 7.2 3.9
18000 -7.5 18.5 295 27 14 7.2 4.0 | -8.0 17.6 290 27 14 7.2 3.9
17500 -6.5 20.3 300 26 14 6.6 3.6 | -6.9 19.6 295 26 13 6.8 3.7
17000 -5.5 22.1 300 26 13 6.7 3.7 | -5.9 21.4 295 25 13 6.8 3.7
16500 -4.0 24.8 295 24 13 6.9 3.8 | -4.9 23.2 295 25 13 6.9 3.8
16000 -2.9 26.8 295 24 12 6.9 3.8 | -3.3 26.1 295 24 12 6.9 3.8
15500 -1.9 28.6 295 23 12 6.4 3.5 | -2.3 27.9 295 23 12 7.1 3.9
15000 -1.0 30.2 295 23 12 6.3 3.4 | -1.2 29.8 295 23 12 7.1 3.9
14500 0.0 32.0 295 22 11 6.6 3.6 | -0.2 31.6 295 23 12 7.0 3.8
14000 0.9 33.6 290 22 11 6.0 3.3 | 0.8 33.4 295 23 12 6.8 3.8
13500 1.8 35.2 290 22 11 6.0 3.3 | 1.9 35.4 290 23 12 6.8 3.7
13000 2.7 36.9 285 20 11 6.5 3.6 | 2.9 37.2 290 21 11 7.1 3.9
12500 3.6 38.5 280 18 9 6.8 3.7 | 3.9 39.0 285 18 9 7.3 4.0
12000 4.6 40.3 270 14 7 7.4 4.1 | 4.9 40.8 280 15 8 7.7 4.2
11750 5.2 41.4 270 13 7 7.5 4.1 | 5.5 41.9 275 14 7 8.1 4.4
11500 5.7 42.3 265 12 6 7.8 4.3 | 6.1 43.0 270 13 7 8.0 4.4
11250 6.3 43.3 260 11 6 8.5 4.7 | 6.6 43.9 265 12 6 7.5 4.1
11000 6.9 44.4 255 10 5 8.5 4.6 | 7.2 45.0 260 11 6 7.4 4.1
10750 7.5 45.5 250 10 5 9.5 5.2 | 7.7 45.9 255 10 5 7.5 4.1
10500 8.3 46.9 245 10 5 10.6 5.8 | 8.2 46.8 250 10 5 7.6 4.2
10250 9.1 48.4 245 10 5 10.2 5.6 | 8.8 47.8 245 9 5 7.9 4.3
10000 9.8 49.6 245 9 5 10.5 5.7 | 9.4 48.9 240 9 5 7.6 4.2
9750 10.6 51.1 240 9 5 9.5 5.2 | 10.0 50.0 235 8 4 8.7 4.8
9500 11.4 52.5 240 9 5 13.0 7.1 | 10.6 51.1 225 8 4 6.1 3.4
9250 12.7 54.9 235 8 4 22.9 12.5 | 10.7 51.3 220 7 3 -2.6 -1.4
9000 14.3 57.7 235 8 4 14.1 7.8 | 10.5 50.9 210 4 2 3.7 2.0
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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