Case Setting

Case Introduction

This case presents a blowing snow forecast challenge over north-central Canada. The time period of interest is from 04 to 10 February 2003. The case addresses specific low-level wind and snow conditions over the central mainland region of Nunavut. You'll be asked to assess the potential for blowing snow and blizzard conditions for the Baker Lake region of Nunavut.

Location of Interest: Baker Lake, Nunavut

Case Time Frame: 04 Feb - 10 Feb 2003

Phenomenon of Interest: Blowing Snow

Forecasting Challenges:

• Recognize common synoptic patterns of a blowing snow event
• Forecast wind speed and direction, and the duration of blowing snow events

About the Nunavut Territory

Nunavut spans across a vast stretch of northern Canada, covering 2 million square kilometers—a fifth of Canada's total landmass. Most of its land lies north of tree line. This sparsely populated territory stretches from the coast of the Beaufort Sea in the west, across the Hudson Bay to Baffin Island in the east, and from Manitoba in the south, to the northern-most Queen Elizabeth Islands. With all its islands and open stretches of tundra, there are few roads connecting the 29,000 residents. Air travel is the primary means of transport between communities, while snowmobiles and all-terrain vehicles are commonly used for local travel.

About Baker Lake

The specific area of interest for this case is Baker Lake, which is near the geographic center of Canada. Baker Lake is Canada's only inland Inuit community and has around 1,500 full time residents. Located in the central mainland region of Nunavut, it sits at the mouth of the Thelon River on the northwestern edge of Baker Lake. The lake stretches eastward towards an inlet of Hudson Bay, 320 km away. In the summer, the town is a jumping off point for hunting, fishing, and canoe trips. Year around, the town is dependent on air travel for supplies.

Baker Lake Winter Climatology

Located as far north as it is, Baker Lake experiences cold and dark winter months. The climatology listed here provides an overview of what to expect in Baker Lake during the winter months.

Baker Lake Climatology (sampling period: 1971 to 2000)
	Dec	Jan	Feb	March
Temperatures: daily average (°C)	-28.4	-32.3	-31.5	-27.2
Temperatures: daily maximum (°C)	-24.8	-28.7	-27.9	-22.9
Temperatures: daily minimum (°C)	-31.9	-35.8	-35.1	-31.5
Average snow depth (cm)	34	40	45	51
Days with snowfall >= 0.2 cm	8.6	6.9	7.3	8.3
Days with snowfall > 5.0 cm	0.46	0.23	0.29	0.59
Wind speed (km/h)	22.7	23.7	22.9	21.6
Most frequent direction	NW	NW	NW	NW
Days with wind >= 52 km/h (28 kt)	7.9	10.8	9.6	7.9
Visibility: hours with <1 km	82.4	118.9	89.7	68.1
Environment Canada

Winds and Blowing Snow in Baker Lake

During the winter, Baker Lake residents deal with fairly constant winds and frequent blowing snow conditions. Average winds in February blow at more than 12 knots.

Blizzards in Baker Lake

It is safe to say that Baker Lake is the blizzard capital of Canada. Between 1980 and 1999, residents there had to cope with an average of 91 blowing snow days and over 20 blizzard events per year!

Forecasting in the North

The MSC's Arctic Weather Centre in Edmonton issues forecasts for all of Nunavut. Given the sparse population and remote location of most communities, the forecasters in Edmonton have to deal with a number of limitations. Foremost, the network of surface stations is much sparser than in the south. A few of these remote stations can be viewed using a Webcam. The example shown here is located on the southeast coast of King William Island, where for much of the winter, the sun is low or below the southern horizon.

Given the latitude of the region, geostationary satellite (GOES) data is of limited use. Verification is much more dependent on the use of polar-orbiting sensors (POES). It's important to keep in mind that POES data does not come in as regularly as GOES data, and the availability of POES imagery is tied to the orbital paths of the satellites.

Case Exercise

Case Setup: Upper-level Pattern and Winds

With the Baker Lake area setting and forecast limitations in mind, let's take a look at conditions early on 04 February 2003.

• The GEM Regional model is used throughout this case.
• The 00-hour analysis will be used to show current conditions, while 48-hour forecasts are used to support forecast questions.
• Be sure to take note of the timeline as you progress through the case.

The upper-level pattern at 0000 UTC shows a high-amplitude ridge over the Yukon Territory that extends southward over the Pacific off the coast of British Columbia. Downstream of the ridge is a major trough.

A branch of the polar jet stream is rounding the base of the trough over southwestern U.S., and another branch of the polar jet stream defines the trough farther north over Hudson Bay, northwestern Ontario, and the midwestern U.S.

Surface Pattern and Temperatures

The MSLP pattern shows high pressured centered off Vancouver Island and another large area of high pressure over the eastern Canadian prairies and Nunavut. A 988 hPa low lies over southwestern Alaska, while a weak low has formed over the Beaufort Sea. Relatively low pressure extends from the southern Arctic Ocean across the Northwest Territories and into Alberta.

The temperatures in mainland Nunavut are very cold, in the -30 to -40ºC range.

Developing Frontal System

Take a look at the GEM Regional forecast for MSLP and the 1000-500 hPa thickness.

Note that the previously mentioned ridging, centered from Nunavut southward, is being squeezed from the north by a developing surface frontal system. From southern Nunavut northward, the MSLP gradient is generating westerly geostrophic winds and is tightening.

MSLP contours are becoming cyclonically curved ahead of a cold front located approximately over Victoria Island, just north of mainland Nunavut.

Snow Coverage

A look at a recent snow-water equivalent analysis shows snow coverage throughout most of Nunavut, including significant amounts to the north and southwest of Baker Lake.

Amplification of Upper Ridge and Trough

Not much has changed 8 hours later. Although aloft some amplification of the upper ridge and trough system is evident, with troughing in southeastern Canada intensifying and slowing. The gradient over western Canada is strengthening somewhat behind a short wave. Fairly strong north-northwesterly to north-northeasterly flow is present over the Northwest Territories, Alberta, and Saskatchewan.

At the surface, the intense low pressure system has moved over Lake Huron and is heading northeastward. The Beaufort Sea low pressure is still evident but relatively weak, and lee troughing is developing over the western Northwest Territories. Moderately strong high pressure dominates British Columbia, and weak high pressure extends up into southern and central Nunavut.

Forecast Question 1

Forecast Question 2

Intensification

As the day progresses, the anticyclonic flow around the ridge aloft continues to strengthen.

70 to 90 knot northwesterly to northerly flow at 500 hPa now extends from the Beaufort Sea through the Northwest Territories and Alberta. A wave and associated westerly jet streak are apparent over the Beaufort Sea. The cyclonic flow in the large long-wave trough extends from Saskatchewan eastward.

At the surface, an intensifying trough has developed in association with the wave aloft and is moving southeastward from Victoria Island. Significant ridging is now pushing southeast from the Beaufort Sea. The intense low is now over central Quebec, heading northeast, with blowing snow reports appearing over northern Quebec. Ridging persists between these two features, with a 1030 hPa high centered over southern Nunavut.

Forecast Question 3

Blizzard Conditions Set In

As predicted, by this time the trough has passed over Baker Lake. Observations for the past 12 hours show that there have been periods of snowfall and blowing snow conditions. And by 1100 UTC, winds passed the 22 knot threshold for blizzard conditions.

The surface trough over Nunavut is now intense. It extends from the low's center in the northeast, southwestward across the Territory. Behind the system, the high over the Arctic Ocean has strengthened slightly to 1039 hPa (just off the MSLP map). Northwest of the trough, strong northwesterly winds extend back across the Queen Elizabeth Islands, and the ice of the Arctic Basin to the North Pole.

At 500 hPa, the cutoff low is now at 4760 m and located just southwest of the western tip of Baffin Island. This is creating a strong northwesterly flow over Victoria Island and mainland Nunavut.

Satellite Verification

Looking at imagery from the polar-orbiting NOAA-12 satellite, the 11 micrometer IR shows the cold air mass making its way southeastward across Nunavut. At 1155 UTC, the leading edge of the air mass has not yet passed over Baker Lake. By 1335 UTC it is to the south of town. The surface observations at Baker Lake show a drop of 10ºC during that time.

At first glance it may be tempting to think the 11 micrometer IR is showing low-level cloud or blowing snow as the front heads southeast. But in this situation, the 11 micrometer IR is showing sensitivity to differences in temperatures between the very cold air moving in from the northwest and the air mass ahead of it.

How could this be? Especially since the 11 micrometer IR is commonly referred to as an atmospheric "window" channel, supposedly only seeing energy from cloud top and surface? It is true that the 11 micrometer is relatively insensitive to atmospheric gases, but there is just enough sensitivity to low-level water vapor to bias the observed brightness temperatures toward the temperature of the low-level air mass. The larger the temperature contrast between air masses and the more moist the air masses, the greater the effect on the 11 micrometer IR brightness temperatures.

Forecast Question 4

Gradient Continues Strengthening

The deep surface low continues to develop into 07 Feb, with a center at less than 972 hPa. To the northwest, the high pressure over the Arctic Ocean builds to 1046 hPa (just off the map). The gradient between the low and the high is strengthening, as are the northerly winds.

The main surface trough sweeps south to southwest, across central Hudson Bay, and continues west across northern Manitoba and northern Saskatchewan. This elongated trough is evidence of the extensive nature of the conditions favorable for strong winds. With snow on the ground in most parts of the region, blizzard conditions persist for most communities behind the trough.

At 500 hPa, a strong 4630 m cutoff is over the extreme northern portion of Hudson Bay, with continued strong northwesterly flow over the eastern Northwest Territories, southern Nunavut, and the northern Hudson Bay region. To the east, the western portion of the long-wave trough is weakening rapidly—“shearing off”—and becoming more positively-tilted. The new, digging cutoff is new reinforcement for the old long-wave trough.

Continued Strengthening

And things just continue to build. Strong northwesterly surface flow now reaches well into the Hudson Bay as the tight surface gradient moves southward and southeastward.

The surface low is just northeast of Southampton Island and nearly stationary. The strong high has built from the Arctic Basin southeastward to eastern Great Bear Lake, and continues south-southeastward into northern Manitoba. The intense pressure gradient, with isobars oriented pretty much north-south, is creating high winds consistently above 22 knots across the region. Baker Lake reports blizzard conditions with gusts over 40 knots.

To the south, in central Manitoba, a secondary low pressure system is evident along the trough and is moving southward fairly rapidly. This secondary low is located on the arctic front.

At 500 hPa, the still-strengthening cutoff low, now 4580 m, is nearly stationary. The strong northwesterly flow is entrenching itself west and southwest of the cutoff, with strong flow sagging into northern Alberta and Saskatchewan.

Forecast Question 5

Slight Weakening of Surface Gradient

By 1200 UTC on 08 Feb, the surface systems have weakened somewhat. But enough gradient has moved west to give blowing snow to Ekati and Lupin, two communities in western mainland Nunavut.

The surface low is now 978 hPa, moving slowly east, and is over Baffin Island. The surface high to the northwest has essentially split, with a portion remaining over the Arctic Ocean and a second part over western Canada. Weak troughing is occurring between these highs.

At 500 hPa, the strong cutoff has also drifted a bit to the northeast, but strength is maintained. The most energetic portion of the western region of this large trough is moving into the northern plains of the U.S.

Further Weakening of Surface Gradient

But there is still blowing snow observed at Arviat and Churchill. 15-25 knot north-northwesterly flow is still common from northern Saskatchewan and Alberta, north-northwestward. In the southern portion of this region, significant cyclonic flow persists and extends into the Hudson Bay.

Aloft, persistence is again noted, with even some reinforcing flow enhancement, slightly cyclonic, over north-central Nunavut.

Forecast Question 6

A Lull Before the Next Round

Between 0000 and 1200 UTC on 10 Feb, the winds start letting up. Most stations are no longer reporting blizzard conditions, though winds are still above 15 knots in Baker Lake with periods of blowing snow.

Is it over? Not really. Note the gradient that persists to the northwest through central Nunavut. There is also an embedded wave in this flow. The blowing snow threat in the region won't be over anytime soon.

Summary

This is the end of the "Blowing Snow: Baker Lake Case Exercise." This case exercise revisited an extended blowing snow event in northern Canada.

The Case Setting presented the climatology of the region of interest and provided various blowing snow and blizzard condition thresholds.

The Case Exercise addressed the synoptic patterns and existing snow conditions leading up to the event. It tracked the synoptics and low-level wind conditions as the event evolved through the use of model analysis, observations and satellite data. Forecast questions focused on:

• identifying the synoptic pattern that led to blowing snow conditions
• the timing of the passing of an arctic front across the area of interest
• forecasting surface winds and blowing snow conditions at varous time points after frontal passage
• the use of satellite feature identification for verification of blowing snow conditions
• forecasting the persistence of a large-scale pressure gradient

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Contributors

COMET Sponsors

The COMET^® Program is sponsored by NOAA National Weather Service (NWS), with additional funding by:

• Air Force Weather Agency (AFWA)
• Meteorological Service of Canada (MSC)
• National Environmental Satellite Data and Information Service (NESDIS)
• Naval Meteorology and Oceanography Command (NMOC)
• National Oceanic and Atmospheric Administration (NOAA)
• National Polar-orbiting Operational Environmental Satellite System (NPOESS)
• National Weather Service (NWS)

Project Contributors

Principal Science Advisors

• Patrick Dills — UCAR/COMET
• Ron Goodson — MSC
• Ed Hudson — MSC
• Garry Toth — MSC
• Doug Wesley — UCAR/COMET

Project Lead/Instructional Design

• Bruce Muller — UCAR/COMET

Multimedia Authoring

• Bruce Muller — UCAR/COMET
• Dan Riter — UCAR/COMET

Audio Editing/Productionn

• Seth Lamos — UCAR/COMET

Audio Narration

• Matt Kelsch — UCAR/COMET

Computer Graphics/Interface Design

• Heidi Godsil — UCAR/COMET

Software Testing/Quality Assurance

• Linda Korsgaard — UCAR/COMET
• Michael Smith — UCAR/COMET

Copyright Administration

• Lorrie Fyffe — UCAR/COMET

Data Provided by

• MSC
• NASA
• NWS — NOAA

COMET HTML Integration Team 2021

• Tim Alberta — Project Manager
• Dolores Kiessling — Project Lead
• Steve Deyo — Graphic Artist
• Ariana Kiessling — Web Developer
• Gary Pacheco — Lead Web Developer
• David Russi — Translations
• Tyler Winstead — Web Developer

COMET Staff, December 2004

Director

• Dr. Timothy Spangler

Deputy Director

• Dr. Joe Lamos

Meteorologist Resources Group Head

• Dr. Greg Byrd

Business Manager/Supervisor of Administration

• Elizabeth Lessard

Administration

• Lorrie Fyffe
• Heather Hollingsworth
• Bonnie Slagel

Graphics/Media Production

• Steve Deyo
• Heidi Godsil
• Seth Lamos
• Dan Riter

Hardware/Software Support and Programming

• Tim Alberta (Supervisor)
• James Hamm
• Karl Hanzel
• Ken Kim
• Mark Mulholland
• Carl Whitehurst

Instructional Design

• Patrick Parrish (Supervisor)
• Dr. Alan Bol
• Lon Goldstein
• Dr. Vickie Johnson
• Bruce Muller
• Katherine Olson
• Dwight Owens
• Dr. Sherwood Wang

Meteorologists

• Dr. William Bua
• Patrick Dills
• Tom Dulong
• Kevin Fuell
• Dr. Stephen Jascourt
• Matthew Kelsch
• Dolores Kiessling
• Wendy Schreiber-Abshire
• Dr. Doug Wesley

Software Testing/Quality Assurance

• Michael Smith (Coordinator)

National Weather Service COMET Branch

• Anthony Mostek (NWS COMET Branch Chief [acting] and Satellite Training Leader)
• Brian Motta
• Dr. Robert Rozumalski (SOO Science and Training Resource [SOO/STRC] Coordinator)
• Shannon White (IFPS Training)

Meteorological Service of Canada Visiting Meteorologists

• Peter Lewis
• Garry Toth