The 2 June 1993 stormCHARLES R. STEARNS, ROBERT E. HOLMES, and BRUCE B. SINKULA, Space Science and Engineering Center,

University of Wisconsin, Madison, Wisconsin 53706

severe wind storm struck McMurdo Station, Antarctica,etween 1800 UTC 1 June and 1800 UTC 2 June 1993

causing extensive damage. Presented here are some of theobservations from the automatic weather station (AWS) siteson the Ross Ice Shelf and near Ross Island, some of which suf-fered damage to the wind systems and antennas. The loca-tions of the AWS sites are given in figures 1 and 2 and thetable of Stearns, Weidner, and Holmes (Antarctic Journal, inthis issue).

Pegasus North AWS site is located at the north end of thePegasus Runway on the Ross Ice Shelf west of Williams Field.Figure 1 shows the air pressure and the wind speed as a func-tion of time starting at 0000 universal coordinated time (UTC)30 May and ending at 0000 UTC 4 June 1993. The wind speedstarted increasing in magnitude at 1200 UTC 1 June 1993reaching a maximum recorded speed of 46 meters per second(89 knots) at 1047 UTC 2 June 1993. The AWS unit did not

transmit data between 1047 UTC and 1640 UTC on 2 June1993. After 1640 UTC there were five transmissions received.Additional transmissions from Pegasus North site were notreceived between 1730 UTC 2 June 1993 and 14 January 1994,when repairs were made to the site.

Pegasus South AWS site is located at the south end andapproximately 300 meters east of the Pegasus runway. ThePegasus South AWS unit operated through the rest of 1993,but the recorded wind speed at that site only reached 36.3meters per second (70 knots) at 1352 UTC, 2 June 1993. Thewind speed is sampled every 10 minutes at the two sites. TheAWS unit at Pegasus South did not suffer any wind damageeven though it was just as susceptible to the wind damage asPegasus North. Therefore, the assumption that the windspeeds were relatively lower at Pegasus South is reasonable.

Examination of the antarctic composite infrared images(Stearns and Young 1993) from 31 May 1993 to 3 June 1993

Pegasus North Wind Speed and Pressure May30 .June3 1993

Cz c..1 C.,C')

50

45

40

35

- 30

125

20

15

10

5

0

1020

1010

1000

990

980

970

960

Day

-- Wind Speed•Pressure

Fig 1. Pegasus North wind speed and air pressure as a function of time starting at 0000 UTC 30 May and ending at 0000 UTC 4 June 1993.The t ,WS unit was damaged by the high wind speeds and did not transmit reliably after 1047 UTC on 2 June and did not transmit at all after 1730UTC )n 2 June. (m/s denotes meters per second. mb denotes millibars.)

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Ross Its Shift Area AWS Pressures May 30-Juno 3 1993

1010

1000

990

980

970

960

950

940

Day

— Elaine-- Marble Point—'— Scbwardtfegsc -0- Farrell

Figure 2. Elaine, Marble Point, Schwerdtfeger, and Ferrell air pressure as a function of time starting at 0000 UTC 30 May and endingat 0000 UTC 5 June 1993. The pressure minimum occurred very close to the same time for the four AWS sites. (mb denotes millibars.)

Ross Ic. Shelf Area AWS Temperatures May 30-Jun. 3 1993

0

.5

10

-15

-20

It -25isI.U.I-

.35

-40

.45

-50- -

Cn

Day

Elaine-s-- Marble Point— Schwardtfeger- Farrell

Figure 3. Elaine, Marble Point, Schwerdtfeger, and Ferrell air temperature as a function of time starting at 0000 UTC 30 May andending at 0000 UTC 5 June 1993. The air temperature maximum occurred very close to the same time for the four AWS sites.

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The 2 June 1993 storm: Pressure and temperature change over 24 hours and magnitude and time of the minimum pres-sure and the maximum temperature on the Ross Ice Shelf, around Ross Island and at three remote AWS sites, are shown

Mount SipleByrdLettauElaineGill

SchwerdtfegerFerrellMinna BluffLindaWillie

Pegasus SouthPegasus NorthMarble PointPossession IslandYoung Island

+8.2+8.0-7.4+9.9+7.1--7.5+34.5+24.7-9.5+34.5+21.9

-19.8+35.7+14.4

-28.1+42.7+26.5-32.4+40.4+21.1-23.0+35.5+8.5-+42.1-

-29.0+39.2+27.8

-34.3+40.0+25.6-37.1 +23.6-30.0+24.8+15.3-19.0+19.6+7.7-5.6+1.3+4.6

+1.0- --823.12002

-12.0969.21028-17.8968.91349-0.6950.20817

-9.3950.61132-3.3947.71216-9.4848.51200+7.3951.01228-952.91004

-6.4951.11332

-0.6943.01224-2.7951.31647-2.4970.30324

-12.81108

-12.61210

-5.90817

-14.51152

-15.41345

-24.41350

-14.01315

-13.91332

-8.91612

-16.31647

-14.40234

NOTE: The "Before" column under pressure change is the pressure at 1200 UTC 2 June minus the pressure at 1200 UTC 1 June 1993. The"After" column under pressure change is the pressure at 1200 UTC 3 June minus the pressure at 1200 UTC 2 June 1993. The temperaturechanges in the "Before" and "After" columns are for the same time periods as the pressure changes. (The pressure units are millibars and thetemperature units are degrees Celsius. The remaining columns are the pressure minimum and temperature maximum for the universal timeson 2 June 1993.)

showed that a low-pressure system moved onto the Ross IceShelf over Roosevelt Island from the northwest and thenmoved westward toward the Transantarctic Mountains. Theclouds moved over the Transantarctic Mountains onto theplateau. At 1500 UTC on 2 June 1993, the infrared imagesshowed decreased cloudiness on the Ross Ice Shelf and nearRoss Island corresponding to the decrease in wind speedobserved at Pegasus North and South.

Figure 2 shows the air pressure at four sites as a functionof time. Elaine, Schwerdtfeger, and Ferrell are along a roughlysouth-to-north line, and all had the pressure minimum atclose to the same time. Figure 3 shows the air temperature forthe same AWS sites as a function of time. There is rapidwarming at the four sites starting 1200 UTC on 1 June andreaching a maximum temperature at about 1200 UTC on 2June 1993. The pressure minimum, the temperature maxi-mum, and the wind speed maximum occur essentially togeth-er. The temperature maximum in figure 3 is not as welldefined as the pressure minimum is in figure 2. The tablegives the times of the actual pressure minimum and the tem-perature maximum for the AWS sites where they occurred.Mount Siple and Byrd pressure rose throughout the periodwhen pressure was falling at the other sites. This indicatesthat the system did not extend to Mount Siple or Byrd sites.The low-pressure system associated with the extreme wind

speeds had a warm core and passed east of Gill site as itmoved onto the Ross Ice Shelf. Gill site had the highest maxi-mum air temperature.

The pressure decrease over 24 hours prior to 1200 UTCon 2 June and the pressure rise over 24 hours after 1200 UTCon 2 June 1993 are similar for the AWS sites around McMurdoStation and on the Ross Ice Shelf as are the air-temperatureincrease and decrease, respectively.

Forecasting this high-wind-speed event would haverequired the installation of AWS units along the edge of theRoss Ice Shelf between Ross Island and Cape Colebeck. Atbest, the lead time for the forecast would have been less than24 hours based on the satellite imagery. The satellite imageryindicated areas of both very cold and very warm cloud tem-peratures in the system.

The AWS program and the Antarctic MeteorologicalResearch Center are supported by the National Science Foun-dation grants OPP 93-03569 and OPP 92-08864.

References

Stearns, C.R., G.A. Weidner, and R. Holmes. 1994. Antarctic automaticweather stations: Austral summer 1993-1994. Antarctic Journal ofthe U.S., 29(5).

Stearns, C.R., and J.T. Young. 1993. Antarctic Meteorological ResearchCenter: 1992-1993. Antarctic Journal of the U.S,, 28(5), 335-336.

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