UPPER AIR CALCULATIONS AND PLOTTING (Ver 5.52-LINUX-X11) Current filename: /home/data/upa/2025050112.upa.cvt Date: 1200Z 1 MAY 25 Searching for PTKK... Searching the city database file for: PTKK ... Date:1200Z 1 MAY 25 Station: PTKK WMO ident: 91334 Latitude: 7.47 Longitude: 151.85 Elevation: 2.00 ------------------------------------------------------------------------------- LEV PRES HGHT TEMP DEWP RH DD WETB DIR SPD THETA THE-V THE-W THE-E W mb m C C % C C deg knt K K K K g/kg ------------------------------------------------------------------------------- SFC 1010 2 26.6 24.1 86 2.5 24.8 10 4 298.9 302.4 297.6 354.5 19.04 1 1000 97 26.4 23.5 84 2.9 24.3 115 13 299.5 302.9 297.4 353.8 18.53 2 996 133 26.4 23.5 84 2.9 24.3 112 13 299.9 303.3 297.6 354.4 18.61 3 995 141 25.8 23.4 87 2.4 24.0 111 13 299.4 302.8 297.4 353.5 18.51 4 973 339 24.2 23.0 93 1.2 23.3 94 13 299.7 303.1 297.4 353.8 18.48 5 965 411 24.8 20.1 75 4.7 21.5 92 16 301.0 303.8 295.9 346.6 15.53 6 957 485 25.0 20.0 74 5.0 21.5 89 19 301.9 304.8 296.1 347.8 15.56 7 949 559 24.8 18.8 69 6.0 20.6 87 23 302.4 305.1 295.6 345.4 14.54 8 925 784 23.4 18.4 74 5.0 19.9 95 22 303.2 305.9 295.8 346.4 14.55 9 863 1388 21.2 13.2 60 8.0 15.9 88 17 307.0 309.1 294.4 340.6 11.12 10 850 1520 20.2 13.2 64 7.0 15.5 90 16 307.3 309.4 294.7 341.4 11.29 11 832 1705 19.0 13.0 68 6.0 15.0 100 16 307.9 310.1 294.9 342.4 11.39 12 807 1967 17.6 10.6 64 7.0 13.1 115 17 309.1 311.0 294.2 339.6 10.00 13 794 2105 16.6 11.7 73 4.9 13.4 123 17 309.5 311.6 295.0 342.9 10.95 14 788 2170 16.4 9.4 63 7.0 12.0 126 17 310.0 311.7 294.0 338.8 9.44 15 781 2246 15.8 9.8 67 6.0 12.0 130 17 310.1 312.0 294.3 340.1 9.79 16 777 2290 15.2 12.0 81 3.2 13.1 132 17 309.9 312.1 295.4 344.8 11.42 17 774 2323 15.2 11.3 78 3.9 12.7 134 16 310.3 312.3 295.2 343.7 10.94 18 773 2334 15.2 9.2 67 6.0 11.4 135 16 310.4 312.2 294.2 339.5 9.49 19 763 2444 14.8 7.8 63 7.0 10.4 140 16 311.1 312.8 293.8 338.0 8.74 20 756 2522 14.2 9.2 72 5.0 11.0 139 17 311.3 313.1 294.6 341.1 9.71 21 727 2852 13.0 5.0 58 8.0 8.2 136 18 313.5 314.9 293.6 337.0 7.54 22 719 2946 12.4 5.4 62 7.0 8.2 137 17 313.8 315.3 293.9 338.3 7.85 23 718 2957 12.4 5.4 62 7.0 8.2 137 17 313.9 315.4 293.9 338.5 7.86 24 702 3146 10.8 7.2 78 3.6 8.6 140 16 314.2 315.9 294.9 342.6 9.12 25 700 3170 10.8 6.0 72 4.8 7.9 140 16 314.4 316.1 294.5 340.7 8.41 26 698 3194 10.6 5.6 71 5.0 7.6 141 16 314.5 316.1 294.3 340.1 8.20 27 692 3266 10.2 6.2 76 4.0 7.8 143 15 314.8 316.5 294.7 341.8 8.63 28 684 3363 9.8 3.8 66 6.0 6.3 146 15 315.4 316.8 294.0 338.6 7.37 29 678 3436 9.4 5.4 76 4.0 7.0 148 14 315.8 317.4 294.8 341.9 8.33 30 672 3510 8.6 5.3 80 3.3 6.6 150 13 315.7 317.3 294.8 341.8 8.35 31 654 3734 6.6 4.6 87 2.0 5.4 157 12 315.9 317.4 294.7 341.5 8.16 32 633 4002 5.2 3.5 89 1.7 4.2 164 10 317.2 318.7 294.8 341.9 7.80 33 626 4093 4.8 2.3 84 2.5 3.4 159 9 317.8 319.2 294.5 340.8 7.24 34 609 4318 4.6 0.4 74 4.2 2.2 149 8 320.1 321.3 294.6 340.9 6.48 35 586 4631 2.0 -0.2 85 2.2 0.8 140 7 320.6 321.9 294.6 341.3 6.45 36 564 4940 0.8 -1.4 85 2.2 -0.4 131 5 322.7 323.9 295.0 342.6 6.14 37 530 5437 -2.7 -2.8 99 0.1 -2.7 116 3 324.3 325.5 295.1 343.6 5.89 38 529 5452 -2.7 -2.9 99 0.2 -2.8 115 3 324.5 325.6 295.2 343.6 5.85 39 527 5482 -2.1 -4.0 87 1.9 -3.1 114 3 325.5 326.6 295.1 343.4 5.41 40 520 5589 -1.9 -5.4 77 3.5 -3.7 111 3 327.0 328.0 295.1 343.4 4.93 41 506 5806 -3.7 -6.3 82 2.6 -5.0 99 2 327.4 328.4 295.1 343.2 4.72 42 500 5900 -4.1 -7.3 78 3.2 -5.6 50 4 328.0 328.9 295.0 342.9 4.43 43 488 6092 -5.1 -9.6 71 4.5 -7.1 48 5 329.1 329.9 294.8 341.9 3.79 44 478 6255 -6.7 -7.8 92 1.1 -7.2 46 5 329.1 330.0 295.3 344.1 4.45 45 460 6555 -8.5 -10.1 88 1.6 -9.2 43 7 330.5 331.2 295.2 343.6 3.86 46 449 6743 -9.5 -13.0 76 3.5 -10.9 41 8 331.5 332.1 294.8 342.3 3.13 47 439 6917 -10.5 -13.0 82 2.5 -11.5 39 8 332.4 333.0 295.1 343.4 3.20 48 437 6952 -10.5 -12.9 82 2.4 -11.5 39 8 332.8 333.5 295.3 344.0 3.24 49 421 7239 -12.3 -14.2 86 1.9 -13.0 36 10 334.1 334.7 295.4 344.6 3.03 50 416 7331 -12.5 -15.5 78 3.0 -13.6 33 10 335.0 335.5 295.4 344.6 2.75 51 400 7630 -14.9 -16.3 89 1.4 -15.4 340 8 335.6 336.2 295.5 345.0 2.68 52 388 7859 -16.9 -16.9 100 0.0 -16.9 310 9 335.9 336.5 295.6 345.2 2.63 53 383 7956 -17.5 -17.8 97 0.3 -17.6 298 9 336.4 336.9 295.6 345.1 2.46 54 382 7976 -17.5 -18.8 90 1.3 -17.9 295 9 336.6 337.1 295.4 344.7 2.27 55 300 9740 -29.9 -33.0 74 3.1 -30.4 270 18 343.2 343.4 295.8 346.3 0.79 56 250 11010 -40.1 -43.7 68 3.6 -40.4 280 16 346.4 346.5 296.1 347.7 0.32 57 200 12490 -53.3 -58.0 56 4.7 -53.4 280 12 348.4 348.4 296.3 348.7 0.08 58 150 14280 -67.7 -77.7 23 10.0 -67.8 330 10 353.5 353.5 297.4 353.5 0.01 59 104 16418 -80.9 -85.9 43 5.0 -80.9 295 6 367.3 367.3 300.1 367.3 0.00 60 100 16640 -80.3 -87.3 30 7.0 -80.3 300 12 372.6 372.6 301.0 372.6 0.00 61 94 16989 -80.1 -88.1 25 8.0 -80.1 263 11 379.6 379.6 302.2 379.6 0.00 62 84 17621 -81.9 -88.9 29 7.0 -81.9 287 10 388.4 388.4 303.5 388.4 0.00 63 81 17826 -78.9 -87.9 22 9.0 -78.9 318 11 398.6 398.6 305.0 398.6 0.00 64 78 18039 -80.3 -89.3 21 9.0 -80.3 349 11 400.0 400.0 305.2 400.0 0.00 65 77 18112 -78.7 -88.7 18 10.0 -78.7 0 11 404.8 404.8 305.9 404.8 0.00 66 75 18262 -79.1 -90.1 15 11.0 -79.1 22 11 407.0 407.0 306.2 407.1 0.00 67 73 18417 -75.3 -89.3 9 14.0 -75.3 339 11 418.2 418.2 307.5 418.2 0.00 68 72 18497 -74.7 -89.7 8 15.0 -74.7 312 10 421.2 421.2 307.9 421.2 0.00 69 71 18578 -74.7 -89.7 8 15.0 -74.7 285 10 422.9 422.9 308.0 422.9 0.00 70 70 18660 -75.3 -90.3 8 15.0 -75.3 270 21 423.3 423.3 308.1 423.3 0.00 71 69 18744 -75.7 -90.7 8 15.0 -75.7 272 22 424.2 424.2 308.2 424.2 0.00 72 67 18916 -73.5 -89.5 7 16.0 -73.6 275 24 432.5 432.5 309.1 432.5 0.00 73 62 19369 -75.1 -90.1 8 15.0 -75.2 283 30 438.7 438.7 309.7 438.7 0.00 74 54 20187 -68.7 -89.7 3 21.0 -68.9 255 21 471.1 471.1 312.7 471.1 0.00 75 54 20187 -68.7 -89.7 3 21.0 -68.9 255 21 471.1 471.1 312.7 471.1 0.00 76 50 20650 -68.1 -90.1 3 22.0 -68.3 240 2 483.0 483.0 313.7 483.0 0.00 77 48 20896 -66.5 -90.5 2 24.0 -66.8 328 6 492.5 492.5 314.4 492.5 0.00 78 47 21025 -60.9 -88.9 1 28.0 -61.4 360 0 508.9 508.9 315.6 508.9 0.00 79 41 21869 -63.1 -88.1 2 25.0 -63.6 301 21 523.7 523.7 316.5 523.7 0.00 80 37 22507 -59.3 -87.3 1 28.0 -60.1 316 18 549.0 549.0 318.1 549.1 0.01 81 32 23409 -62.5 -88.5 2 26.0 -63.1 128 10 563.8 563.8 318.8 563.8 0.00 82 31 23606 -60.3 -88.3 1 28.0 -61.2 162 12 574.8 574.8 319.4 574.9 0.01 83 30 23810 -60.5 -87.5 2 27.0 -61.4 70 18 579.7 579.7 319.6 579.7 0.01 84 29 24021 -60.7 -87.7 2 27.0 -61.6 82 15 584.8 584.8 319.9 584.8 0.01 85 28 24240 -60.5 -88.5 1 28.0 -61.4 74 17 591.3 591.3 320.2 591.3 0.01 86 28 24240 -58.7 -87.7 1 29.0 -59.8 74 17 596.3 596.3 320.5 596.3 0.01 87 27 24468 -58.5 -87.5 1 29.0 -59.7 69 20 603.1 603.1 320.7 603.1 0.01 88 26 24705 -59.3 -88.3 1 29.0 -60.4 79 24 607.3 607.3 320.9 607.4 0.01 89 26 24705 -56.7 -86.7 1 30.0 -58.2 79 24 614.7 614.7 321.3 614.8 0.01 90 26 24705 -55.9 -86.9 1 31.0 -57.5 79 24 617.0 617.0 321.3 617.0 0.01 91 24 25212 -58.1 -87.1 1 29.0 -59.5 79 30 624.9 624.9 321.7 624.9 0.01 92 22 25765 -54.1 -86.1 1 32.0 -56.3 91 44 652.5 652.5 322.8 652.6 0.01 93 21 26065 -52.3 -84.3 1 32.0 -55.1 93 47 666.7 666.7 323.3 666.8 0.02 94 20 26380 -52.9 -84.9 1 32.0 -55.6 90 47 674.3 674.3 323.6 674.4 0.01 95 17 27439 -48.7 -82.7 1 34.0 -53.0 87 50 719.8 719.8 325.1 720.0 0.03 96 17 27439 -49.3 -83.3 1 34.0 -53.4 87 50 717.9 717.9 325.0 718.1 0.02 97 16 27839 -46.3 -82.3 1 36.0 -51.7 86 51 740.2 740.2 325.7 740.5 0.03 98 16 27839 -46.1 -82.1 1 36.0 -51.5 86 51 740.9 740.9 325.7 741.1 0.03 99 15 28267 -46.9 -81.9 1 35.0 -52.2 76 56 752.0 752.0 326.0 752.3 0.03 100 13 29219 -45.3 -81.3 1 36.0 -51.8 85 71 789.0 789.0 327.0 789.3 0.04 101 12 29760 -39.5 -79.5 1 40.0 -49.2 95 68 827.8 827.8 327.9 828.4 0.06 102 11 30357 -39.1 -79.1 1 40.0 -49.4 95 66 850.1 850.1 328.4 850.8 0.07 103 10 31010 -39.1 -79.1 1 40.0 -49.8 95 65 873.6 873.6 328.9 874.4 0.08 104 7.4 33085 -36.3 -79.3 0 43.0 -50.3 87 72 963.5 963.6 330.6 964.7 0.10 105 7.0 33470 -36.9 -78.9 0 42.0 -50.8 85 73 976.5 976.6 330.8 977.8 0.11 106 6.8 33670 -37.3 -79.3 0 42.0 -51.1 983.0 983.0 330.9 984.2 0.11 107 6.0 34539 -35.0 -78.3 0 43.3 -51.0 85 76 1028.8 1028.9 331.6 1030.6 0.15 108 5.6 35022 -33.7 -77.7 0 44.0 -50.9 1055.0 1055.1 332.1 1057.1 0.17 TRP 104 16418 -80.9 -85.9 43 5.0 -80.9 295 6 367.3 367.3 300.1 367.3 0.00 WND 6.0 34539 -35.0 -78.3 0 43.3 -51.0 85 76 1028.8 1028.9 331.6 1030.6 0.15 Sounding variables and indices 1000-500 mb thick: 5803.00 m Freezing level: 556.23 mb = 5053.27 m = 16578.77 ft Wetbulb zero: 571.33 mb = 4835.35 m = 15863.81 ft Precipitable water: 2.26 inches Sfc-500 mean rel hum: 76.33 % Est. max temperature: 34.81 C = 94.66 F Sfc-Lift cond lev (LCL): 974.43 mb = 325.77 m = 1068.77 ft T: 24.30 C 700-500 lapse rate: 5.46 C/km ThetaE index: 7.15 C Layer 965.0- 957.0 mb Conv cond level (CCL): 816.57 mb = 1865.32 m = 6119.76 ft Mean mixing ratio: 16.24 g/kg Conv temperature: 36.40 C = 97.52 F Cap Strength: 3.07 C Lifted Index: -0.90 C Risk: Thunderstorms probable Lifted Index @300 mb: -1.15 C Lifted Index @700 mb: 0.41 C Showalter Index: 2.09 C Risk: Showers probable Total Totals Index: 41.60 C Risk: None Vertical Totals Index: 24.30 C Cross Totals Index: 17.30 C K Index: 32.70 Risk: 60-80 % chance of thunderstorms Sweat Index: 194.40 Risk: None Energy Index: 0.27 Risk: None Parcel Indices Parcel: using 100 mb layer CAPE (B+): 402.61 J/kg Max Up Vert Vel: 28.38 m/s Conv Inhibition (B-): 163.06 J/kg Cap Strength: 3.08 C Lift Cond Lev (LCL): 905.59 mb = 968.75 m = 3178.29 ft Lev Free Conv (LFC): 670.59 mb = 3527.12 m = 11571.77 ft Equ Level (EL): 190.59 mb = 12789.78 m = 41960.70 ft B at Equ Level: 398.46 J/kg Max Parcel Lev (MPL): 120.59 mb = 15554.08 m = 51029.83 ft Wind level data Storm motion: 149 at 9 knt ---------------------------------------------------------- TRUE/GROUND REL | STORM REL LEV P H DIR SPD U V | DIR SPD U V mb m knt m/s | knt m/s ---------------------------------------------------------- 0 1010 2 10 4 -0.7 -3.9 | 341 13 4.2 -12.0 1 1000 97 115 13 -11.8 5.5 | 70 7 -6.9 -2.5 2 977 305 95 11 -11.0 1.0 | 41 9 -6.1 -7.1 3 943 610 85 25 -24.9 -2.2 | 63 22 -20.0 -10.2 4 925 784 95 22 -21.9 1.9 | 70 18 -17.0 -6.1 5 911 914 80 21 -20.7 -3.6 | 54 20 -15.8 -11.7 6 850 1520 90 16 -16.0 0.0 | 54 14 -11.1 -8.0 7 850 1524 90 16 -16.0 0.0 | 54 14 -11.1 -8.0 8 791 2134 125 17 -13.9 9.8 | 101 9 -9.0 1.7 9 763 2438 140 16 -10.3 12.3 | 128 7 -5.4 4.2 10 736 2743 135 18 -12.7 12.7 | 121 9 -7.9 4.7 11 700 3170 140 16 -10.3 12.3 | 128 7 -5.4 4.2 12 635 3962 165 10 -2.6 9.7 | 234 3 2.3 1.6 13 611 4267 150 8 -4.0 6.9 | 321 1 0.9 -1.1 14 507 5791 105 2 -1.9 0.5 | 339 8 2.9 -7.5 15 500 5900 50 4 -3.1 -2.6 | 350 11 1.8 -10.6 16 417 7315 35 10 -5.7 -8.2 | 3 16 -0.9 -16.2 17 400 7630 340 8 2.7 -7.5 | 334 17 7.6 -15.5 18 369 8230 260 10 9.8 1.7 | 293 16 14.7 -6.3 19 354 8534 290 17 16.0 -5.8 | 304 25 20.9 -13.8 20 325 9144 260 15 14.8 2.6 | 285 20 19.6 -5.4 21 300 9740 270 18 18.0 -0.0 | 289 24 22.9 -8.0 22 287 10058 270 18 18.0 -0.0 | 289 24 22.9 -8.0 23 251 10973 285 16 15.5 -4.1 | 301 24 20.3 -12.2 24 250 11010 280 16 15.8 -2.8 | 298 23 20.6 -10.8 25 240 11278 275 15 14.9 -1.3 | 295 22 19.8 -9.3 26 219 11887 290 15 14.1 -5.1 | 305 23 19.0 -13.1 27 200 12490 280 12 11.8 -2.1 | 301 20 16.7 -10.1 28 200 12497 290 12 11.3 -4.1 | 307 20 16.2 -12.1 29 190 12802 265 11 11.0 1.0 | 294 17 15.8 -7.1 30 156 14021 285 5 4.8 -1.3 | 314 13 9.7 -9.3 31 150 14280 330 10 5.0 -8.7 | 329 19 9.9 -16.7 32 134 14935 350 16 2.8 -15.8 | 342 25 7.7 -23.8 33 127 15240 235 10 8.2 5.7 | 280 13 13.1 -2.3 34 115 15850 230 21 16.1 13.5 | 255 22 21.0 5.5 35 104 16418 295 6 5.4 -2.5 | 316 15 10.3 -10.6 36 103 16459 245 18 16.3 7.6 | 271 21 21.2 -0.4 37 100 16640 300 12 10.4 -6.0 | 313 21 15.3 -14.0 38 98 16764 300 12 10.4 -6.0 | 313 21 15.3 -14.0 39 93 17069 250 10 9.4 3.4 | 288 15 14.3 -4.6 40 88 17374 250 10 9.4 3.4 | 288 15 14.3 -4.6 41 75 18288 25 11 -4.6 -10.0 | 359 18 0.2 -18.0 42 71 18593 280 10 9.8 -1.7 | 304 18 14.7 -9.8 43 70 18660 270 21 21.0 -0.0 | 287 27 25.9 -8.0 44 61 19507 285 32 30.9 -8.3 | 294 39 35.8 -16.3 45 58 19812 250 19 17.9 6.5 | 274 23 22.7 -1.5 46 55 20117 250 22 20.7 7.5 | 271 26 25.5 -0.5 47 52 20422 270 20 20.0 -0.0 | 288 26 24.9 -8.0 48 50 20650 240 2 1.7 1.0 | 317 10 6.6 -7.0 49 49 20726 285 14 13.5 -3.6 | 302 22 18.4 -11.6 50 47 21031 0 0 -0.0 -0.0 | 329 9 4.9 -8.0 51 43 21641 270 10 10.0 -0.0 | 298 17 14.9 -8.0 52 41 21946 310 24 18.4 -15.4 | 315 33 23.3 -23.4 53 39 22250 300 21 18.2 -10.5 | 309 30 23.1 -18.5 54 33 23165 355 12 1.0 -12.0 | 343 21 5.9 -20.0 55 32 23470 160 10 -3.4 9.4 | 227 2 1.5 1.4 56 30 23774 165 14 -3.6 13.5 | 193 6 1.3 5.5 57 30 23810 70 18 -16.9 -6.2 | 40 19 -12.0 -14.2 58 29 24079 85 14 -13.9 -1.2 | 44 13 -9.1 -9.2 59 27 24384 65 19 -17.2 -8.0 | 38 20 -12.3 -16.0 60 25 24994 90 28 -28.0 0.0 | 71 24 -23.1 -8.0 61 24 25298 75 31 -29.9 -8.0 | 57 30 -25.1 -16.0 62 22 25908 95 47 -46.8 4.1 | 85 42 -41.9 -3.9 63 20 26380 90 47 -47.0 0.0 | 79 43 -42.1 -8.0 64 16 28042 85 51 -50.8 -4.4 | 75 48 -45.9 -12.5 65 15 28346 75 57 -55.1 -14.8 | 66 55 -50.2 -22.8 66 13 29261 85 71 -70.7 -6.2 | 78 67 -65.9 -14.2 67 12 29566 95 68 -67.7 5.9 | 88 63 -62.9 -2.1 68 10 31010 95 65 -64.8 5.7 | 88 60 -59.9 -2.4 69 7 33470 85 73 -72.7 -6.4 | 78 69 -67.8 -14.4 Wind Parameters Mean winds (0-6000m): 118.7 at 12.5 knts Storm direction: 148.7 at 9.4 knts Shear (0-3000m) pos: 3.7 neg: 0.4 tot: 4.1 10-3/s Storm rel Dir Shear (0-3000m): 144.4 deg Storm rel helicity (0-3000m) pos: 88.9 neg: -33.3 tot: 55.6 m^2/s^2 ave: 18.5 10^-3 m/s^2 rel: 0.39 Storm rel vorticity (0-3000m) horiz: 11.4 stream: 4.5 10^-3/s Energy-Hel index: 0.19 Bulk Rich Number: 140.07 Bulk Shear: 2.87 m/s Storm Parameters ------------------------------------------------------------------------------- Depth Mean Inflow| Shear | Helicity | Vorticity AGL Dir Spd Dir Spd| Pos Neg Tot| Pos Neg Tot Ave Rel | Hor Strm m knt knt| 10^-3/s | m^2/s^2 m/s^2 | 10^-3/s ------------------------------------------------------------------------------- 500 97 13 51 10| 20.2 0.0 20.2| 38.6 -8.8 29.8 59.6 0.52| 30.9 16.1 1000 90 18 58 15| 10.1 1.3 11.4| 52.4 -31.5 20.9 20.9 0.31| 22.8 7.0 1500 88 18 57 15| 5.7 0.9 6.6| 53.4 -31.9 21.5 14.3 0.28| 16.9 4.7 2000 92 17 59 15| 5.2 0.6 5.8| 75.1 -31.9 43.2 21.6 0.36| 14.7 5.3 2500 99 17 67 13| 4.4 0.5 4.9| 87.9 -31.9 56.0 22.4 0.41| 13.1 5.4 3000 106 17 74 12| 3.7 0.4 4.1| 88.9 -33.3 55.6 18.5 0.39| 11.4 4.5 4000 115 16 83 10| 2.0 0.3 2.3| 96.5 -33.3 63.2 15.8 0.44| 9.8 4.3 5000 118 14 81 8| 1.6 0.9 2.5| 97.9 -33.4 64.5 12.9 0.44| 8.5 3.8 6000 119 13 72 6| 1.4 1.3 2.6|102.9 -35.3 67.5 11.3 0.42| 7.7 3.2 Wrote GIF file: /home/apache/climate/data/raob//PTKK/skewt/PTKK.skewt.20250501.12.gif