Re: November 2022
Posted: Sat Nov 26, 2022 7:40 pm
From Larry Cosgrove posted at 6:50pm CST 11/26/22
Overview
James Bay Vortex, check. Strong dual blocking ridge in the Arctic Circle, check. Active southern branch storm track, check.
The ingredients for a wintry period of weather are all present for a long period of cold air and frozen precipitation potential across the lower 48 states. As stated before, the start of December will be relatively mild outside of the Pacific Northwest and the Prairie Provinces. But the immense, widespread chill in those regions is symptomatic of how conditions will evolve across the lower 48 states starting in about a week or so. The only protection against an Arctic invasion, so to speak, is the development of a subtropical high over the Greater Antilles and Strait of Yucatan. This heat ridge formation was overdone by the numerical model groups when the last big cold shot struck. Given that the positive 500MB height anomalies over Greenland, Northern Canada, and the Gulf of Alaska are so strong and well-situated, storm energy will consolidate into a cAk vortex over or near James Bay. That feature is classic in winter synoptic climatology, associated with widespread bitter cold, most especially in the Midwest, Great Lakes and Northeast. Think back to the winters of 1993-94 and 2013-14 for examples.
Now if for some reason the ECMWF panels are right with a summer-like heat ridge over the Gulf of Mexico, the cold would not get any further than an Interstate 40 line (Albuquerque NM to Wilmington NC). But that broad area of snow cover, the deepest in many years and about to get a lot deeper, will be an air mass refrigerant. Cold air is heavier and denser than the tropical regime, and if a storm comes along between the two late next week, the ridge complex will be crushed. I know that the various computer schemes have been erratic as of late. But when all of the numerical models show that familiar high-latitude warmth in the upper atmosphere, the most recent cold projections of the GFS and GGEM series, with the cold working down to the Gulf Coast, should verify in the December 7 - 21 period.
BOTTOM LINE
I also suspect that a widespread, and potent, ice and snow event will occur in the 11-15 day period. Track and coverage scenarios at this distance, of course, would be hard to define, though I am leaning toward a Colorado/Trinidad path of some sort with a wide variety of precipitation types from the Rocky Mountains into the Mid-Atlantic and New England states. As that system interacts with the likely presence of the aforementioned James Bay vortex, the cold numbers you see now in far northern Canada will be displaced. California and Florida should avoid the cold regime. But areas of North America to the right of the Rocky Mountains will be re-acquainted with the need for heating, heavy clothes, boots and hot chocolate.
Overview
James Bay Vortex, check. Strong dual blocking ridge in the Arctic Circle, check. Active southern branch storm track, check.
The ingredients for a wintry period of weather are all present for a long period of cold air and frozen precipitation potential across the lower 48 states. As stated before, the start of December will be relatively mild outside of the Pacific Northwest and the Prairie Provinces. But the immense, widespread chill in those regions is symptomatic of how conditions will evolve across the lower 48 states starting in about a week or so. The only protection against an Arctic invasion, so to speak, is the development of a subtropical high over the Greater Antilles and Strait of Yucatan. This heat ridge formation was overdone by the numerical model groups when the last big cold shot struck. Given that the positive 500MB height anomalies over Greenland, Northern Canada, and the Gulf of Alaska are so strong and well-situated, storm energy will consolidate into a cAk vortex over or near James Bay. That feature is classic in winter synoptic climatology, associated with widespread bitter cold, most especially in the Midwest, Great Lakes and Northeast. Think back to the winters of 1993-94 and 2013-14 for examples.
Now if for some reason the ECMWF panels are right with a summer-like heat ridge over the Gulf of Mexico, the cold would not get any further than an Interstate 40 line (Albuquerque NM to Wilmington NC). But that broad area of snow cover, the deepest in many years and about to get a lot deeper, will be an air mass refrigerant. Cold air is heavier and denser than the tropical regime, and if a storm comes along between the two late next week, the ridge complex will be crushed. I know that the various computer schemes have been erratic as of late. But when all of the numerical models show that familiar high-latitude warmth in the upper atmosphere, the most recent cold projections of the GFS and GGEM series, with the cold working down to the Gulf Coast, should verify in the December 7 - 21 period.
BOTTOM LINE
I also suspect that a widespread, and potent, ice and snow event will occur in the 11-15 day period. Track and coverage scenarios at this distance, of course, would be hard to define, though I am leaning toward a Colorado/Trinidad path of some sort with a wide variety of precipitation types from the Rocky Mountains into the Mid-Atlantic and New England states. As that system interacts with the likely presence of the aforementioned James Bay vortex, the cold numbers you see now in far northern Canada will be displaced. California and Florida should avoid the cold regime. But areas of North America to the right of the Rocky Mountains will be re-acquainted with the need for heating, heavy clothes, boots and hot chocolate.
