11:50 AM (Thursday) | *An impressive cold shot coming to the central and eastern US…a quiet period for the Atlantic Basin (albeit temporary)*
Paul Dorian
A colder-than-normal air mass will drop from Canada into the central and eastern US later next week at the same time it becomes hotter-than-normal in the western states. The hotter weather conditions in the western US will likely lead to an increase in the threat for wildfires. Map courtesy Weather Bell Analytics, ECMWF
Overview
It looks like September will end and October will begin with an unusually cold air mass in much of the central and eastern US as a deep upper-level trough forms overhead. There may be two different cold frontal systems that will produce a “step-down” to the colder-than-normal conditions with the first pushing through early in the week and the second around mid-week. Once established, it looks like the colder-than-normal conditions will last right into the first full weekend of October. On the tropical scene, the Atlantic Basin has actually begun a quiet period with no activity currently over the tropical Atlantic, Caribbean Sea or Gulf of Mexico. This quiet stretch is very likely only a temporary phenomenon as October will no doubt feature more tropical activity in these still quite warm water regions of the Atlantic Basin.
A deep upper-level trough will form over the central/eastern US later next week at the same time strong high pressure ridging develops along the US west coast. Map courtesy NOAA, tropicaltidbits.com
Cold air outbreak
It has been cooler-than-normal so far this month in much of the Mid-Atlantic region with some spots in the I-95 corridor recording four consecutive nights with low temperatures in the 40’s – something that hasn’t happened in many decades during the month of September. For the month so far, DC is averaging 1.6 degrees below-normal, Philly 1.3 degrees below-normal and Central Park in New York City has a monthly average temperature of 0.8 degrees below-normal.
Looking ahead, an even colder air mass is destined to reach the central and eastern US next week as a deep upper-level trough forms overhead. This cold air outbreak for the central and eastern US will roughly coincide with the calendar transition from September to October with a couple of cold fronts ushering in a “step-down” to the colder-than-normal conditions. Once the colder-than-normal air mass becomes established, it looks like it’ll stick around right into the first full weekend of October. In terms of rainfall, a decent chance of rain will come early next week for the Mid-Atlantic region and much of the eastern US as the first of the two cold fronts advance southeastward from the north-central part of the nation. A second cold front at the leading edge of even colder air could also result in some rainfall at mid-week as it crosses the eastern states on its way to the western Atlantic.
At the same time the central and eastern US chill down, high pressure ridging will intensify along the west coast of the US and this is not good news. It’ll become warmer-than-normal in the same western US areas that experienced numerous wildfires in recent days. In fact, this unfolding weather pattern for early October suggests the threat of wildfires will likely go back up significantly in much of the western US.
The remnants of Tropical Storm Beta are currently located over Mississippi and moving to the east-northeast at 17 mph. Elsewhere in the Atlantic Basin, it is quiet for the first time in several weeks. Map courtesy NOAA/NHC
The tropical scene
The remains of Tropical Storm Beta are now located over the state of Mississippi and will contribute to some decent rainfall over the Tennessee Valley during the next 24 hours. Some of the moisture from Beta’s remains will, in fact, make it all the way into the Mid-Atlantic region by the weekend albeit in a weakened form and it can result in a shower from time-to-time in the Friday night to Saturday night time period. Elsewhere in the Atlantic Basin, it is quiet for the first time in weeks and this quiet stretch is likely to last several days. This quieter stretch in the Atlantic Basin will very likely be only temporary and at the same time, the Pacific Basin is likely to become much more active after a very subdued month of September in the world’s largest ocean.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
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