IOP 6: 04-05 December 2001

Time Period of IOP

1630 UTC 4 Dec-0600 UTC 5 Dec

Overview of IOP

The fifth and sixth short waves in this multi-day sequence moved in rapidly from the west northwest on 3-4 December 2001. At 500 mb the first short wave trough was evident at 1200 UTC 3 December at about 145 ^oW (Fig. 1a). By 0000 UTC 4 December, this trough was at about 132 ^oW (Fig. 1b), and it was centered over the Washington and Oregon Cascades at 1200 UTC  4 December (Fig. 1c). The infrared satellite imagery shows a quasi-frontal cloud system associated with the first short wave trough moving into the S-Pol radar area in Oregon at 2300 UTC 3 December 2001 (Fig. 2a).  At 0500 UTC 4 December the cloud area of the short wave was centered over the radar area, with one major component still northwest of the radar, and another band of enhanced brightness east of the radar (Fig. 2b).  By 1100 UTC, the quasi-frontal cloud band had moved east of the radar, and postfrontal convective clouds were located in the western part of the radar area (Fig. 2c). By 1700 UTC , the enhanced cloud pattern of the second short wave trough was moving over the radar and had the appearance of a jet streak cloud system (Fig. 2d).  This feature strengthened and moved in and became centered over the southern portion of radar area (Fig. 2e). The S-Pol low-level PPI scans were picking up echoes of precipitation moving into the area at 0500 UTC 4 December (Fig. 3a). At 0800 UTC a solid frontal-like band of precipitation about 80 km in width was centered over the radar (Fig. 3b). By 1100 UTC this main band of echo had moved over the mountains to the east, and the echoes in the vicinity of the radar had begun to look more postfrontal in character (Fig. 3c). Cellular echoes were still present at 1400 UTC but were smaller and weaker (Fig. 3d).

The P-3 and Convair flew in the second short wave, as it continued to intensify over the radar area. At 0000 UTC 5 December the enhanced infrared cloud top image was covering the southwestern quadrant of the S-Pol radar area, and the cloud area was being cut off abruptly on its eastern edge, apparently, by orographically induced downward motion (Fig. 4a).  The P-3 entered the radar area at about 2300 UTC 4 December and was starting its dual-Doppler pattern at 0000 UTC 5 December (Fig. 5a).  At 0300 UTC the satellite infrared enhance cloud top formed a frontal-like band oriented SW-NE and centered over the S-Pol radar (Fig. 4b).  At this time the P-3 was flying a microphysical sampling pattern on an east-west track across the mountains east of the S-Pol radar (Fig. 5b). The Convair flew a vertical profile from 16,000 to 13,000 ft above the P-3 on west-east track over Santiam Pass. The ETL S-band profiler showed that the precipitation at this time was highly convective, with updrafts appearing at about 1.5 km AGL (Fig. 6).

Convair-580 Summary

UW Flight Number:

   1895

Period of Flight:

   2247 UTC 4 December-0151 UTC 5 December 2001

Main Accomplishment of Flight:

Vertical profile from 16,000 to 13,000 ft on west-east track over Santiam Pass. (P-3 flew below Convair-580.)  Landed in Eugene. 

 Instrument Problems:

Possible problems with PMS 1-D cloud probe

Flight Scientist:

Peter V. Hobbs

Approximate UTC Timeline (Local time= UTC-8 hours) Activity for UW Flight 1895:

P-3 Summary

P-3 Flight Number:

   011204H, IMPROVE 03

Period of Flight:

   2227 UTC 4 December-0327 UTC 5 December 2001

Main Accomplishment of Flight:

The P-3 took dual-Doppler and microphysical data in conjunction with the flight of the Convair.

Instrument Problems:

-

Flight Scientist:

Nick Bond

Approximate UTC Timeline (Local time= UTC-8 hours) Activity for P-3 Flight 03:

2:27pm  Engine Start

2:32pm  Block Out

2:39 pm  Takeoff

Actual takeoff

entered cloud base

224526 UTC (47.72373, -122.51717) 230.612°, 781.3 mb, 2035.0 m  wind 250^o at 15 kts

224807 UTC (47.60429, -122.62686) 192.210°, 718.2 mb, 2596.0 m  tail radar up 5 minutes ago.

225854 UTC (46.91788, -122.93411) 185.375°, 569.8 mb, 4345.0 m  radar down. Convective tops around aircraft to 4.5 km.

230331 UTC (46.59182, -123.05453) 196. 23  cloud station up and working.

230640 UTC (46.36724, -123.11476) 175.418°, 571.0 mb, 4140.0 m  radar back up 5 minutes ago.

231136 UTC (45.99902, -123.06897) 172.824°, 572.2 mb, 4064.0 m  radar down. Within widespread echo at mid-levels. Radar was filling in before it went down. Temp -25.2 ^oC

231741 UTC (45.57755, -123.00696) 175.738°, 572.0 mb, 4368.0 m  all radars up again. Within widespread/uniform ice cloud from 5 km to surface. Echoes surprisingly uniform even if with steep lapse rates.

231904 UTC (45.48827, -123.02010) 189.826°, 594.5 mb, 4087.0 m  started decent to 6 k ft one minute ago.

232448 UTC (45.11684, -123.04106) 178.609°, 810.6 mb, 1759.0 m  at 6 kt feet. Widespread echo around the aircraft to 75 km. Echoes light < 25 dBZ

232735 UTC (44.94235, -123.03590)  just south of point A. To 25 dBZ over foothills 20 km west of aircraft. Nice gradual sloping echo field over foothills. 4.5 km deep. Temp        -5.5 ^oC,  winds 250^o at 37 kts.

234707 UTC (43.76271, -123.02628) 162.932°, 797.9 mb, 1619.0 m  At point F, starting climb to 8kt. Radar echo was weakening as we approached point F. Just light echo to15 dBZ within 20 km of aircraft.

235138 UTC (43.73425, -122.61497) 56.622°, 753.0 mb, 1457.0 m  At point G, starting northbound leg at 8kt ft. Temp -8C, winds 242/38kts. Echoes below aircraft to 24 dBZ.

000510 UTC (44.68037, -122.56819) 359.471°, 752.7 mb, 1741.0 m  Stratiform precip has filled in more around aircraft. Getting great doppler coverage and microphysics at -9 ^oC, winds 244/31kts.

000955 UTC (45.01089, -122.56090) 9.463°, 743.5 mb, 2009.0 m  At point B, starting climb to 11 kft. Got some nice dendrites around –10 ^oC.

001155 UTC (45.12153, -122.43289) 70.908°, 669.9 mb, 2837.0 m  reached 11 kft. Winds 255^o/43kts, temp-15.7 ^oC, dewpoint-16.7 ^oC.

001425 UTC (45.10608, -122.16867) 136.625°, 669.8 mb, 2585.0 m  stratiform precip to 24 dBZ. Some evidence of a secondary bright band around 2.5 km, probably within max dendrite growth region.

001630 UTC (44.97415, -122.10022) 176.733°, 669.9 mb, 2680.0 m  reached point C a couple minutes ago. Winds 250^o/42kts. temp-17 ^oC

002758 UTC (44.22675, -122.08504) 179.899°, 669.9 mb, 2282.0 m  temps have gradually increased to -15.2 ^oC. winds 257^o/42kts. Right at top of enhanced precip to 22 dBZ.

003435 UTC (43.78763, -122.08191) 164.033°, 666.3 mb, 1788.0 m  At point H, climbing to 13 kft. Still in widespread precip. Did not notice any distinct precip enhancements over individual peaks during past leg. At 13kt temp=-19 ^oC, 283^o/43kts.

003906 UTC (43.74596, -121.63779) 14.105°, 618.3 mb, 2583.0 m  At point G at 13kft. Winds 270^o/41kts. Precip covereage drops off significantly 15 km to the west of plane.

005110 UTC (44.59812, -121.61647) 359.603°, 617.8 mb, 2882.0 m  radar down.

005151 UTC (44.64896, -121.61702) 359.558°, 617.9 mb, 2952.0 m  radar quickly back up. Echoes only to the left of plane. Some evidence of sloping echo along the lee slope. Temp -19.5 ^oC, wind 270^o/43kts

005700 UTC (45.022011447 UTC (44.53233, -121.59709)  at point D, descending back down to 10kt. Encountered some lee wave turbulence just before point D.

010607 UTC (44.75910, -121.13535) 180.062°, 693.3 mb, 2301.0 m  no much precip arround plane. Just to 5 DBUTC.

010857 UTC (44.57002, -121.13284) 189.086°, 692.4 mb, 2176.0 m  Breaking southbound leg at lat of point Q. To start west leg at 13 kft. Very little echo here.

011024 UTC (44.53767, -121.23328) 270.525°, 642.2 mb, 2788.0 m  reached 13kft. Temp -17.7 ^oC, winds 270^o/40kts.

011512 UTC (44.53263, -121.63080) 271.160°,  radar down for a couple minutes.  Nice wave length structure in vertical velocity and a few good bumps.

011913 UTC (44.53313, -121.95842) 269.604°, 642.0 mb, 2321.0 m  more widespread precip and dendrites. Started descent at 0121 UTC.

012522 UTC (44.53279, -122.46231) 269.800°, 752.2 mb, 1842.0 m  ambient temperature about –9 ^oC; with large rimed dendrites and what appears to be some liquid water in cloud.

013023 UTC (44.52911, -122.87538) 268.495°, 752.3 mb, 2036.0 m  Convair headed home about 1:20 UTC (lost air speed indicator).

013241 UTC (44.52745, -123.06622) 271.598°, 750.7 mb, 2317.0 m  started climb and turn; uniform precip to west before we initiated turn.

014011 UTC (44.46234, -122.61966) 237.720°, 645.4 mb, 2943.0 m  Very obvious secondary bright band extending across tail radar display; well below level of aircraft

014430 UTC (44.40684, -122.90321) 32.776°, 645.7 mb, 3296.0 m  about over point M.  Will hold 12k ft until point 0. -16.5 ^oC ambient. rimed dendrites.

015501 UTC (44.43151, -121.71146) 90.902°, 643.4 mb, 2572.0 m  Wind holding right near 50 kt.  Precip very steady state with little horizontal variation.

020030 UTC (44.39371, -121.61902) 282.060°, 644.9 mb, 1948.0 m  Started descent to 10k ft. Very close to crest of Cascades - westbound.

020344 UTC (44.38945, -121.87445) 267.629°, 694.7 mb, 1544.0 m  10k ft ambient temp -13.5 ^oC; plenty of dendrites.

021522 UTC (44.37776, -122.82436) 270.147°, 694.6 mb, 2747.0 m  Very near point M. 10K ft ambient temp as warmed to about -12.5C. Wind 256^o at 35kt.

021825 UTC (44.37933, -123.07571) 277.089°, 693.7 mb, 2922.0 m  End of leg west bound beginning climb....up up and away.  Heading home....a keeper!

025838 UTC (47.32586, -122.73151) 8.994°, 808.0 mb, 1747.0 m  radar taken down.

032237 UTC (47.90707, -122.28560) 178.341°, 985.6 mb, 9.0 m  landed.

032705 UTC (47.90024, -122.28056) 176.644°, 985.6 mb, 6920.0 m  Engine off and block in

S-Pol Radar Summary

The S-Pol radar was run continuously in the same mode of operation for the length of the field project.

Summary of Mobile Upstream Sonde Launches

Launch times at: Rowland, OR, Lat: 44.2800, Lon: -123.0650, Elev: 97 m

1630 UTC 4 Dec

2059 UTC 4 Dec

0131 UTC 5 Dec

0327 UTC 5 Dec

Summary of Leeside Sonde Launches

Launch times at: Black Butte Ranch, OR (a.k.a. ISS-3), Lat: 44.379, Lon: -121.679, Elev: 1027 m

2255 UTC 4 Dec

0055 UTC 5 Dec

0250 UTC 5 Dec

0450 UTC 5 Dec

Summary of NWS Sonde Launches from Salem (SLE)

Launch times:

0000 UTC 5 Dec (standard)

0300 UTC 5 Dec (special)

0600 UTC 5 Dec (special)

Summary of Snow Crystal Ground Measurements

Measurement times:Every 15 minutes from

2145 UTC 4 Dec-0300 UTC 5 Dec (at Santiam Pass, Corbett, and Tombstone Sno Park)