2018-19 NPP Operating Season Events

Michael D. JohnsonMeteorologistDIGITALiBiz

NIWC Office of Polar Programs

N65236-18-D-8002 Jun 27, 2019

Overview

ØThe “14-Day” Storm

ØThe “Joe” Low

ØSouth Pole Ridging

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The “14-Day” Storm

§ Series of low pressure systems brought strong winds, snow, and blowing snow to McMurdo region over 12 day period.

§ Periods of calm between storm systems allowed barely enough time for runway clearing, but not enough time to allow for flight operations.

§ From the morning of 01 Oct 2018 to mid-day 13 Oct 2018, Phoenix Field was Condition One or Two (Visibility less than 400m, or winds greater than 48 knots, or wind chill greater than -75°Fahrenheit for roughly 8 days, 18 hours.

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The “14-day” Storm

§ First scheduled flight of Mainbody for 01 Oct 2018 delayed until 16 Oct 2018.

§ 10 missions were delayed or canceled, along with a 4 day delay to the annual airfield certification mission.

§ The delay in personnel equipment delayed the opening of Williams Field until 05 Nov 2018, and the subsequent arrivals of 109AW aircraft until 09 Nov 2018.

5Photo Credit: J. Meyer

The “14-day” Storm

§ From the forecaster’s point of view, these events were relatively straight forward; only three amendments for category were issued between 30 Sep 2018 and 16 Oct 2018.

§ From the customer point of view, the delay seemed unending, and led to some creative modification to our products.

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The “Joe” Low

§ A large low pressure system moved SSE from Cape Adare on 04 Dec 2018, bringing high winds, snow, and blowing snow to McMurdo Region.

§ System was under-forecasted, and delayed/diverted two South Pole missions.

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The “Joe” Low

§ The struggle with this forecast came with the apparent shift in track and intensity of the storm.

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AMPS 8km SLP/Precip Init 02/00z Fcst 04/00z AMPS 8km SLP/Precip Init 03/00z Fcst 04/00z

The “Joe” Low

§ As successive model runs came in, the forecast changed from predominant below minimum conditions to marginal temporary conditions…

…Until

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Using the 02/12z Run:TAF NZWD 0221/0321 VRB04KT 9999 FEW020 FEW050BECMG 0318/0320 12015G25KT 2400 -SN BLSN SCT010 BKN020 OVC040 620208 510005

Using the 03/00z Run:TAF NZWD 0309/0409 09015G25KT 9999 DRSN SCT010 SCT030 SCT040BECMG 0319/0321 14018G28KT 4800 -SN BLSN SCT020 BKN030 OVC100 620302 510002TEMPO 0322/0403 2000 -SN BLSN BECMG 0403/0405 07010G20KT 8000 -SN DRSN SCT030 BKN100

Using the 03/12z Run:TAF NZWD 0321/0421 12017KT 9999 DRSN SCT010 BKN020 OVC150 620205BECMG 0321/0323 18020G30KT 1600 -SN BLSN SCT010 BKN020 OVC120 620208 510002TEMPO 0323/0403 0800 -SN BLSN BKN008 OVC020 BECMG 0406/0408 11015G20KT 8000 -SN DRSN BKN030 BKN100 620307BECMG 0411/0413 07012KT 9999 NSW SCT030 BKN100

SPECI NZWD 032326Z 11017KT 0800 SN BLSN M06/M07 A2937SPECI NZWD 032213Z 10020KT 1600 -SN BLSN M06/M08 A2937SPECI NZWD 032243Z 10022KT 1200 -SN BLSN M06/M08 A2936SPECI NZWD 032144Z 10021KT 8000 -SN BLSN M06/M09 A2937

The “Joe” Low

§ The finest AMPS grid struggled…

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USAP Williams Field (NZWD) Forecast initialized at 2018120300AMPS 0p89km domain

FCST UTC UTC T Td Altim Spd Gust Dir ACCUMHR DAY HR (C) (C) (inHg) (kts) (kts) (deg)(mm/100)18 3 18 -9.1 -12.0 29.41 14 25 84 00019 3 19 -8.7 -11.3 29.43 14 24 82 00020 3 20 -7.4 -11.0 29.40 16 25 93 00021 3 21 -6.6 -11.3 29.39 18 26 128 00022 3 22 -6.1 -11.0 29.40 16 24 140 00023 3 23 -5.5 -10.6 29.40 12 22 152 00024 4 00 -5.4 -10.7 29.40 14 24 145 00025 4 01 -5.3 -11.2 29.39 13 25 163 00026 4 02 -4.4 -10.4 29.38 17 24 140 00027 4 03 -4.3 -9.8 29.37 15 22 154 00028 4 04 -4.6 -10.5 29.38 17 24 160 00029 4 05 -5.0 -9.4 29.38 7 22 109 00030 4 06 -6.1 -8.7 29.37 10 19 46 00031 4 07 -5.8 -8.8 29.39 10 20 32 00132 4 08 -5.8 -9.0 29.37 10 20 33 00033 4 09 -5.9 -8.8 29.38 8 9 28 00034 4 10 -6.3 -9.1 29.38 5 8 30 00035 4 11 -6.4 -9.3 29.38 4 5 15 00036 4 12 -6.1 -10.0 29.37 3 6 16 00037 4 13 -6.0 -10.9 29.35 3 4 296 00038 4 14 -6.0 -12.8 29.35 2 10 22 00039 4 15 -5.8 -14.2 29.33 2 15 0 000

METAR NZWD 031855Z 09016KT 9999 DRSN M06/M09 A2939 METAR NZWD 031955Z 09020KT 9999 DRSN M06/M09 A2938METAR NZWD 032059Z 10021KT 9999 DRSN M06/M09 A2938 METAR NZWD 032155Z 10020KT 3200 -SN BLSN M06/M09 A2937METAR NZWD 032255Z 10022KT 1200 -SN BLSN M06/M08 A2936 METAR NZWD 032355Z 12018KT 0800 -SN BLSN M05/M07 A2936 METAR NZWD 040055Z 14024G27KT 0800 -SN BLSN M06/M08 A2934 SPECI NZWD 040108Z 14024G27KT 0400 SN BLSN M06/M08 A2934SPECI NZWD 040123Z 14028KT 0200 SN BLSN M07/M09 A2934SPECI NZWD 040145Z 14030G35KT 0200 SN BLSN M07/M09 A2934

Spd (kts) Aug-Nov Vis (m) Dec-Feb Vis (m)

LT 15 9999 – 4800 9999

15 – 20 4800 – 2400 9999 – 9000

20 – 25 2400 – 1600 9000 – 4800

25 – 30 1600 – 0800 4800 – 1600

30 – 35 0800 – 0000 1600 – 0800

The “Joe” Low

§ This low resembled the low(s) and resultant weather impacts described by Bromwich et. al. in 2003.

§ Terrain shadowing may have influenced the AMPS forecast to delay onset of winds and under-estimate the intensity, especially in the finer resolution grids.

§ The transition from spring to summer usually marks a change in snow and blowing snow characteristics; this storm had early-spring characteristics.

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South Pole Ridging

§ Point

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South Pole Ridging

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South Pole Ridging

§ Abnormally extensive ridging from the grid NW extended from the Weddell Sea through the South Pole, with an associated jet extending across the continent.

§ Impacts to operations to South Pole and McMurdo were noted throughout the period, although no incidents were reported.

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References

Bromwich, D. H., A. J. Monaghan, J. G. Powers, J. J. Cassano, H.-L. Wei, Y.-H. Kuo, and A. Pellegrini, 2003: Antarctic MesoscalePrediction System (AMPS): A case study from the 2000–01 field season. Mon. Wea. Rev., 131, 412–434.

National Aeronautics and Space Administration, 2019: Earth Observing System Data and Information System Worldview. [Available online at https://worldview.earthdata.nasa.gov]

Space and Naval Warfare Systems Center Atlantic, Office of Polar Programs, 2017: Antarctic Weather Forecasting Handbook, OPSEA 2017-18. 94 pp.

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Questions?

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