Archive for large scale
Eastern ridge return for next week, but for how long?
Posted by: | Comments9:04 AM
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There can be no doubt that change is in the air as the Arctic Oscillation relaxes and the Sub Tropical jet stream gets some breathing room to flex its muscles now. The result of which is a pattern that by next week leads to a ridge moving through the East and a deep trough extending from the Gulf of Alaska to the West coast. This pattern will bring a significant amount of rain into California and a threat of severe weather for the Plains, but is this the end of winter? Is it time for those in the northern Mid Atlantic to throw their hands up in despair as another winter exits without everyone getting into the “party” of snow and cold?
Well, while it is true that the pattern is trending towards a return to warmer temperatures for the Philadelphia and New York City metropolitan area, I don’t think this pattern has much legs beyond a few days and I’m going to explain why.
-- Weather When Posted --
- Temperature: 26°F;
- Humidity: 49%;
- Heat Index: 26°F;
- Wind Chill: 15°F;
- Pressure: 30.25 in.;
A dry start to September
Posted by: | Comments5:15 AM
The start of September is going to be unlike any weather conditions seen this summer, namely dry. High pressure over the Great Lakes will dominate the
Mid Atlantic and New England through the next several days. The high pressure system is from central Canada and is bringing a dry, cool air mass into the forecast area. The biggest difference in the air mass will be the significant drop in dew points compared to the last 48 hours. Dew points will barely break 50 degrees in some locations while temperatures will hold in the lower to mid 70′s.
The cold front from Sunday morning is positioned well off the coast, far enough to keep any lingering precipitation well east of the forecast area. While waves of low pressure will develop along this cold front, the precipitation is not expected to even reach the coastal waters.
High pressure will remain in control through much of this week. A week upper level trough will remain in place over the eastern third of the nation, but will not have much influence on the surface conditions. The large scale pattern will become more zonal in nature, which will feature fast moving cold fronts clipping the northern portions of the forecast area later in the week with a few isolated showers. However, most locations will remain dry.
A stronger disturbance will attempt to move through on Saturday with a few scattered showers, but nothing organized. High pressure will return on Sunday with dry and clearing conditions.
Temperatures through the forecast period will average below to near normal with very low humidity.
-- Weather When Posted --
- Temperature: 62°F;
- Humidity: 72%;
- Heat Index: 62°F;
- Wind Chill: 62°F;
- Pressure: 30.05 in.;
The Key Positions Of Ridges And Troughs
Posted by: | CommentsAs you may have read, I am not all that impressed with the potential for a Nor’ Easter this weekend. The thoughts on this potential are covered in the technical forecast discussion.
I do want to point out though that I think the theme I am discussing today will become a key issue this winter for storms along the coast. The position and strength of the ridge over the Western United States and the state of the North Atlantic Osscilation (NAO) will be key this winter. I am expecting a weakening Pacific jet stream this winter, which should allow for a ridge to develop over the West. However, the teleconnections that seem to continue to show up to this point can be dated back to the position of troughs and ridges over the western Pacific. The trough that develops over Japan has the axis of the trough over the Japan Sea. The progression of this large scale wave would suggest a trough axis along the East coast. The position of the trough axis slightly off the coast has lead to a compel of close calls already. Note the storm that has potential to develop off the East coast in late September and the potential storm for this weekend.
Now, there are indications of the Pacific setting up so that the ridge, trough positions would focus storms closer to the coast line. I am watching the changes in the Pacific and the Indian Ocean very carefully and it is these changes why I am holding off on issuing the winter forecast at this time.
I do think that there will be a better chance for storms along the East coast this year. The question now comes into whether the position of the troughs and ridges will allow the storms to develop close enough to the coast. If they do develop, will a progressive pattern from a weakening PNA ridge allow the storms enough time to develop. These questions are still unresolved and will likely be the main questions through the winter.
-- Weather When Posted --
- Temperature: 57°F;
- Humidity: 87%;
- Heat Index: 57°F;
- Wind Chill: 57°F;
- Pressure: 30.28 in.;


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