IOP 16, 22-23 Dec 2001

IOP 16: 22-23 December 2001

Time Period of IOP

1200 UTC 22 Dec-0000 UTC 23 Dec 

Overview of IOP

A nearly cut-off short wave at 500 mb moved into Oregon during 1200 UTC 22 December and 0000 UTC 23 December 2001 (Fig. 1a, Fig. 1b). The wind at 500 mb turned from southerly to southeasterly during this period. The wind at 850 mb was southerly and weakening during this period (Fig. 2a, Fig. 2b). The tongue of high relative humidity reached southwestward to only about 20 deg north (Fig. 3a, Fig. 3b). The west-east gradient of sea level pressure was very strong at 1200 UTC but decreased during the period (Fig. 4a, Fig. 4b). This west-east gradient favored easterly flow through the Columbia Gorge.

The satellite imagery showed an occluded frontal cloud band moving across western Oregon from 1200-1500 UTC 22 December (Fig. 5a, Fig 5b, Fig. 5c). At 2100 UTC, a comma cloud was moving over western Oregon (Fig. 5d).

The Convair flew two flights between 1400 UTC and 2300 UTC. The Medford radar showed warm-frontal rainbands oriented NW-SE moving through western Oregon from 0900-1200 UTC (Fig. 5e, Fig. 5f). At 1500 UTC, the Medford radar showed the last warm-frontal rainband to the northeast of the radar, while the rainbands over and to the southwest of the radar were changing over to north-south oriented cold frontal rainbands (Fig. 5g). By 1800 UTC the cold-frontal rainbands were still evident but much weaker (Fig. 5h). At 2100 UTC postfrontal convective echoes, located just ahead of the comma cloud were detected to the southwest of the radar (Fig. 5i).

Convair-580 Summary

UW Flight Number:

   1905

Period of Flight:

  1459-1752 UTC, 22 December 2001

Main Accomplishment of Flight:

Weak warm-frontal rainband from 20,000 to 18,000 ft.  Landed in Eugene, Oregon.

Instrument Problems:

PMS 1-D cloud probe (?).

 

Flight Scientist:

 

Nick Bond

 

Approximate UTC Timeline (Local time= UTC-8 hours) Activity for UW Flight 1905:

 

1459 

Engines on.

1509 

Takeoff.

1547 

Hit clouds at ~46˚ north/123˚9'.

1603 

Broke out of clouds; still some small crystals from aloft.

1612 

Back in clouds; 2-DC temporarily out.

1614 

44˚31'/123˚35'. 

Winds 155-160˚ @ ~22 m s–1.  (~5 m s–1 greater than forecast).

1631 

Turning for start of first leg; popped into clear briefly.

1633 

Start of leg 1 (northeast at 20,000 ft).  Wind 168˚ @ 31 m s–1.  T ~–27˚C.  Sun dimly visible; only small crystals implying not much growth above.

1648 

End of leg 1; brighter here.

1650 

Start of leg 2 (southwest 20,000 à18,000 ft).

1651 

Dropping down to 18,000 ft due to traffic.

1703 

Ground becoming visible.

1710 

End of leg 2; shallow CBs ahead.

1712 

Start leg 3 (northeast 18,000-20,000 ft). 

1719 

Intercepted cloud/precipitation.  Wind 167˚ @ 25 m s-1.  T ~–26˚C.

~1728 

End of leg 3.

1732 

After conversations with S-Pol radar operator decided to break off pattern and land at Eugene to wait for surface front.

1749 

Landed at Eugene Oregon

1752 

Engines off.

 

UW Flight Number:

   1906

Period of Flight:

  1909-2300 UTC, 22 December 2001

Main Accomplishment of Flight:

1)   Takeoff from Eugene, Oregon.  North-south oriented profile from 20,000 to 10,000 ft in same system as UW Flight 1905. 

2)   Wind profile in Columbia Gorge.  Landed at Paine Field, Washington.

Instrument Problems:

PMS 1-D cloud probe (?).

 

Flight Scientist:

 

Nick Bond

 

Approximate UTC Timeline (Local time= UTC-8 hours) Activity for UW Flight 1906:

 

1909 

Engines on.

1916 

Takeoff.

1931 

In precipitation in vicinity of Santiam Pass.  LWC = 0.1-0.2 g m-3.  Descent in precipitation east of crest.

1937 

Beginning spiral ascent to 20,000 ft.

1941 

Leveling at 12,000 ft for traffic.

2002 

Getting bright above 18,000 ft.

2004 

First north-south run (north at 20,000 ft) near top.  Wind 150˚ @ 16 m s–1.  T ~–29˚C. 

2010 

At north end; turning.

2012 

Start of second (south, 20,000 à 18,000 ft).

2021 

End of second; turning.

2023 

Third north-south (north at 18,000 ft).  Wind 165˚ @ 18 m s-1.  T ~–24˚C.

2030 

End of third; turning.

2032 

Start of fourth (south, 18,000-16,000 ft).

2043 

End of forth; turning.

2045 

Fifth north-south (north at 16,000 ft).  Wind 170˚ @ 14 m s-1.  T ~–20˚C.

2052 

End of fifth leg; turning.

2054 

Start of sixth (south, 16,000-14,000 ft).

2104 

Broke into clear slot.

2106 

Hit liquid H2O cloud at south end.

2107 

End of sixth; turning.

2109 

Start of seventh north-south (north at 14,000 ft).  Wind 175˚ @ 12 m s-1.  T ~–17˚C.

2117 

End of seventh leg (somewhat greater precipitation at north end.

2119 

Start eighth (south 14,000-12,500 ft).

2126 

Hit clear zone.

2131 

End of seventh leg.

2134 

Start eighth leg north-south (north 12,500 ft).  Wind 225˚ @ 8 m s-1.

2145 

End of eighth leg.

2146 

Proceeding northeast and descending to 10,000 ft in very light precipitation.

2152 

Heading for Troutdale to do a missed approach.

2202 

Crossing crest at 45˚10'.  Little precipitation reaching surface.

2209 

Winds into Troutdale at 4,000 ft, 185˚ @ 10 m s-1; 2,500 ft, 110˚ @ 15 m s-1.

2213 

Over runway 080˚ at 10 m s-1.

2215 

Rapid wind shift at 2,000 ft. with some turbulence.

2216 

Ferry to Paine Field.

2257 

Landed.

2300 

Engines off.

 

P-3 Summary

No flight

 

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

 

1720 UTC 22 Dec

1856 UTC 22 Dec

2016 UTC 22 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

 

1500 UTC 22 Dec

1800 UTC 22 Dec

2100 UTC 22 Dec

 

Summary of NWS Sonde Launches from Salem (SLE)

 

Launch times:

 

1200 UTC 22 Dec (standard)

0000 UTC 23 Dec (standard)

 

Summary of Snow Crystal Ground Measurements

 

Measurement times: Every 15 minutes from

1500 UTC 22 Dec-2115 UTC 22 Dec (at Corbett Sno Park, Hoodoo Ski Lodge)