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Rainshadow

Meteorological Autumn Pattern Discussion, Desperately Seeking September

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All guidance pointing to :abomsnow: making his annual migration south around the turn of the month.  Will be nice to have an early season cool snap for a change

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00z/19th GEFS

Above normal 500mb heights (what else?) return on the 20th as the Southeast CONUS ridge slides offshore and is outlooked to remain there for a while. We have a Gulf of Alaska ridge / Central Conus Trof / East Coast Ridge, so there will be some cooler air arriving in NOAM.  Back in the day this was a stable autumn climo pattern because of the ocean waters still relatively warm. Anyway this pattern is outlooked to progress slight east toward the end of the month with the ridge more centered on the west coast and trof in Great Lakes. After the 29th we never get below normal heights, but above normal 500mb heights are gone.  From the 29th til the end (October 4th), the WAR flexes every once in a while edging above normal heights back into our area.  

 

00z/22nd GEFS

-EPO pattern, but shorter wavelength & SE Conus/SW Atlantic ridge keeps us in above normal 500mb heights the rest of September, any colder dump west.  Not much change the first week of October either, above normal heights with a flatter but still present southeast ridge and ridging through Alaska.  FWIW this is not just a 500mb pattern being misleading, very little of the next 384 hours outlooking below normal 850mb anomalies either.

4indices.png.be7b510a5ab3c4bb88fda17e3a03620d.png

Pretty dramatic one day NAEFS change even if the days are not exactly the same:

 

2018092100_054@007_E1_north@america_I_NAEFS@TEMPERATURE_anomaly@probability@combined@week2_198.png

2018092200_054@007_E1_north@america_I_NAEFS@TEMPERATURE_anomaly@probability@combined@week2_198.png

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51 minutes ago, Rainshadow said:

00z/19th GEFS

Above normal 500mb heights (what else?) return on the 20th as the Southeast CONUS ridge slides offshore and is outlooked to remain there for a while. We have a Gulf of Alaska ridge / Central Conus Trof / East Coast Ridge, so there will be some cooler air arriving in NOAM.  Back in the day this was a stable autumn climo pattern because of the ocean waters still relatively warm. Anyway this pattern is outlooked to progress slight east toward the end of the month with the ridge more centered on the west coast and trof in Great Lakes. After the 29th we never get below normal heights, but above normal 500mb heights are gone.  From the 29th til the end (October 4th), the WAR flexes every once in a while edging above normal heights back into our area.  

 

00z/22nd GEFS

-EPO pattern, but shorter wavelength & SE Conus/SW Atlantic ridge keeps us in above normal 500mb heights the rest of September, any colder dump west.  Not much change the first week of October either, above normal heights with a flatter but still present southeast ridge and ridging through Alaska.  FWIW this is not just a 500mb pattern being misleading, very little of the next 384 hours outlooking below normal 850mb anomalies either.

 

Pretty dramatic one day NAEFS change even if the days are not exactly the same:

 

 

 

Noticed this trend with eps over last couple days. Trending away from that big cool shot and more towards more bermuda high influence. We aren't fully in it, but kind of inbetween the cool shot and the sw flow around that high. So you know what that means, probably a wet pattern developing. The -epo isn't in the ideal spot to deliver the cool temps to us, more central plains. Really lost that stout +pna look they had 5 days ago. It's centered further offshore which puts the meat of the trough in the plains into the rockies with some pieces that tries to come east

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