*Hints of an “omega” blocking pattern as we approach Labor Day weekend...an upper-level trough centered over the NE US would limit chances of sustained heat as summer winds down*
Paul Dorian
There are hints of an “omega” blocking pattern in the upper part of the atmosphere as we approach the Labor Day weekend with an intensifying ridge centered over north-central Canada and troughs of low pressure over the NE US and NW US. Map courtesy NOAA, tropicaltidbits.com
Overview
Labor Day is still two weeks away and that puts this outlook in the “speculation” phase; however, there are interesting and somewhat consistent signs of an “omega” blocking pattern in the upper atmosphere over North America which is more typical of winter or spring seasons. An “omega” blocking pattern typically features an upper-level ridge sandwiched in between two upper-level troughs and these systems tend to linger for several days. If indeed this pattern unfolds with an upper-level trough centered over the Northeast US, then any chance for sustained heat for summer’s unofficial end would be quite low in that part of the nation. However, if the ridge sets up over the Northeast US then 90+ degree heat would certainly remain on the table in those urban areas along the I-95 corridor.
If an upper-level ridge sets up the central part of Canada in early September with troughs over the NE US and NW US then cooler-than-normal conditions could be the result for a several day time period in the Mid-Atlantic region. However, if the ridge is centered farther to the east and over the northeastern states then 90+ degree heat will be on the table for Labor Day weekend. Map courtesy Canadian Met Centre, tropicaltidbits.com
Details
Labor Day comes late this year and is still two weeks away from today, but many are wondering what kind of weather there will be in the unofficial ending to the summer season. Some computer forecast models hint at an “omega” blocking pattern in the upper part of the atmosphere, which is more typical of winter or spring, but cannot be ruled out for early September. In this potential scenario, an upper-level ridge is projected to intensify over the north-central part of Canada and be sandwiched in between two upper-level troughs of low pressure with one centered over the Northeast US and the other near the Pacific Northwest.
The month of August has been warmer-than-normal across much of the nation including across the northeastern states, but that pattern could change in early September if an “omega” block sets up with upper-level trough centered over the Northeast US. Map courtesy NOAA, Prism-OSU
If this type of pattern unfolds, then cooler-than-normal conditions would be possible across portions of the northern US; especially in the Pacific Northwest and across the northeastern states. However, if these systems were to form slightly to the east with the ridge centered over the northeastern states then 90+ degree heat will certainly be on the table for the Labor Day weekend…just too early to say where the “block” will set up.
In addition to potential effects on temperatures for the Labor Day weekend, another interesting facet to monitor in coming days would be potential impacts of a western US trough - should it develop in that location - on moisture associated with eastern Pacific Ocean tropical systems. One possibility in this active season in the Pacific Basin will an influx of tropical moisture into the Southwest US and a trough of low pressure centered over the western US could help to “steer” such moisture northward during that first part of September...all in the speculation phase but something interesting to monitor as August winds down and September gets underway.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com
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