Forecast for Monday 20 April 1998 by Don Wylie

Don's Comments, Monday 20 April 1998, 13:00 UT

NOAA image reception is back to normal. The ship reports show the snow has ended and visibility has returned to 10 mi. i Taneil also noted the lack of cloud in her 00 UT report from yesterday. Some middle Trop. cloud cover is still present. A broken cloud field moving north toward the camp can be seen on the satellite images.

The boundary layer cloud appears to be very weak over the ship. The HRPT 1 km images show some cloud present with ice patterns visible through it. IR radiating temperatures of this cloud appear to be only 2 K warmer than neighboring clear areas.

Two weather features will dominate the ice camp today. A surface high is moving in from the east. This high covers a very large area and will continue to dominate through Thursday. The 2nd feature is a small shortwave in the upper air flow. There is a weak trough over the camp today. This is the reason for the clouds in the middle troposphere. This trough is a small feature but present in all models. It is expected to remain over the ice camp today and deepen tomorrow. Both the ECMWF and MRF agree that it will be over the camp tomorrow. Then Wednesday night, it will move to the east clearing out the middle trop. clouds.

If your wondering how a upper air trough (low) can exist over a surface high, the reason is cold temperatures in the lower trop. The air is more dense in this trough and the vertical change in pressure is greater over the cold air. Its a classic feature of mid-western winter weather (in those real winters of long ago).

Surface temperatures have dropped at the camp more than I or the NWS expected. They are running around -20 C and about 4 C colder than the NWS analysis chart. They stay around -15 to -25 today and tomorrow with little changes. A slight warming on Wednesday is possible.

Winds will be light and easterly today and tomorrow. I expect the boundary layer cloud to remain diffuse, but still present. Visibility will remain very good today. The difference between Tuesday and Wednesday will be increased middle trop. clouds as the upper air trough strengthens.

Thursday will see a change as the high moves past to the northeast. A small low is expected in the northern Beaufort Sea by the MRF. This feature is to small to understand on the hemispheric plots of the ECMWF that I have to look at. Expect the winds to increase on Thursday from the north to 10 - 15 kts. Temperatures will drop slightly. Middle trop. cloud cover should disappear during the day.

Barrow and the arctic coast

Barrow is having light snow this morning with some small reduction in visibility and ceiling. The NWS forecast calls for "Cloudy with light snow... and light and variable winds" Tuesday and Wednesday. Barrow is being affected by a low along the Siberian Coast of the Bering Sea. This is part of the Aluetian low system. Winds will be light and southerly to southeasterly because of the low. Now there is disagreement on what that low will do. The MRF and ECMWF have it moving into the southern Bering sea on Wednesday. The Canadian model moves it more northerly toward Barrow. I tend to believe the ECMWF and MRF.

The low won't go directly over Barrow, but be close enough to hold them in cloud cover Tuesday and Wednesday. Light snow will be intermittent at times. Visibilities should remained above 2 mi.

Prudhoe Bay and the Beaufort have some cloud cover now from the upper air trough that will affect the ice camp. The trough axis extends southeast into the Beaufort Sea. It will affect this area through Wednesday. Surface visibility and ceilings will not be adversely affected and should remain good. Winds decrease today and be variable in direction.

don