September 22, 2017

  GFS Forecast: analysis time: 18Z 2017-09-21 :: valid time: 21Z 2017-09-22

Links to plots Below

Sea ice contours: 15% (blue), 50% (black), 90% (red)

2-m temperature contour: -1.8 ℃

U/V transect contour: 0 m/s 

Update [17:20AM, Thur. Sep 21, 2017 PST] : 28-hour forecast. Mostly consistent with previous forecast. The weak high is further weakened and moved to southeast.  

Update [14:40AM, Wed. Sep 20, 2017 PST] : 58-hour forecast. Sea ice edge is still at about 77.6 °N now. The weak high is shrinking and moving to the southeast compared to the forecast of 24 hours ago. Mostly, cold, dry, and clear. The low level jet at the northern end is moving south to 76 °N. Low cloud from 76 °N to 80°N. Cloud at 70 °N, with base around 700 m and top at 1200 m. 

Update [09:50AM, Tue. Sep 19, 2017 PST] : 82-hour forecast. Sea ice edge is still north of 77.5N, but the 50% contour is retreating further back north.  Along 150W, 70N to 80N is dominated by a weak high. Westerly winds at the north and easterly at the south. Low level wind jet of around 15 m/s centered at 77N at 500 m. Cold, dry, and clear sky. Weak norhterly winds to help save maybe a little fuel on the way north.

Update [10:20AM, Fri. Sep 15, 2017 PST] : 177-hour forecast. The 90% sea ice area grow a lot compared to Sep 12 in the pan-Arctic but the 15% and 50% contours are still loitering. The 15% sea ice edge is still around 78N and 50% sea ice concentration is around 79.5N. Large scale pattern changed a lot. Still cold. BCSIZ is under a weak high centered over the Canadian Archipelago, with a low to the west and a low to the south. Moist south of 74N and dry northward. Cloud patterns are similar. Low level easterly wind jet along the coast. Southwesterly wind to the north. 

Update [10:20AM, Thur. Sep 14, 2017 PST] : 201-hour forecast.

Update [10:30AM, Wed. Sep 13, 2017 PST] : 225-hour forecast. Clod, moist, and cloudy. Southeasterly winds south of 74.5N and northwesterly north of 74.5N. Looks like the cold advection low pressure state in the north but with a low to the southwest as well, which is too far south to have significant warm air advection from the south. Interestingly, the 15% ice edge moved slightly to the south compared to a day ago, likely due to ice drift from the west. 

Update [10:30AM, Tue. Sep 12, 2017 PST] : 252-hour forecast. Cold, moist, easterly winds. Likely cloudy. A high north of 75N brings in cold and dry air and the low to the southeast brings warmer and moister air from the Bering Strait. The pattern can still change a lot at this point. The wind shifts from northerly winds from the forecast 24 hours ago. The change of wind pattern brings the -1.8C isotherm from around 72N to 75N at 200 m height. At the surface, the -1.8C is at 73N.

  • Pan-Arctic maps

Sea ice concentration at analysis time

Mean sea leve pressure at valid time

700 hPa Geopotential Height

700 hPa temperature

700 hPa relative humidity

700 hPa wind speed

Pressure on 2PVU surface

Pressure on 2PVU surface

Low-level cloud cover

Mid-level cloud cover


  • Beaufort and Chukchi seasonal ice zone (the map is centered at 150W)

Sea ice concentration at analysis time

Mean sea leve pressure at valid time

2-m air temperature

2-m relative humidty

low cloud fraction

middle cloud fraction


  • Transects along 150 °W

  • Flight conditions at different altitudes along 150 °W