WEATHERAmerica Newsletter, Saturday, June 29, 2024; EXTENDED PERIOD FORECAST

[Larry Cosgrove]

EXTENDED PERIOD FORECAST

(Between Day 11 And Day 15)

 

Tropical Question Marks....And Elongated Heat Ridges....

CIMSS

TropicalTidbits.Com (Dr. Levi Cowan) (3)

NOAA/PMEL

NOAA/CPC

HPRCC/University Of Nebraska (2)

ECMWF (3)

TropicalTidbits.Com (Dr. Levi Cowan) (5)

NOAA/CPC

The battle for forecasting weather from here on out through the summer will be if you end up covered by a heat ridge complex, or fall into a scenario where deep tropical moisture,eventually disturbances and cyclones make an impact. The June forecast has largely been verified, with the coolest values close to the border with Canada and the vast bulk of the lower 48 states under a warm/hot realm. I suspect that we will maintain such a set-up through July, but at some point, probably in August, breaches in the network of heat ridging will allow moisture advection. The first example of this phenomenon will be the monsoon across the Desert and Intermountain Regions. And the next alteration would be coastal thunderstorms with the eventual approach of tropical storms and hurricanes. But for now, the Saharan Air Layer will also be influential in limiting larger storms while creating haze displays over the southern half of the lower 48 states.

The idea of weakness and eventual breaching of the subtropical highs covering the USA into the Atlantic Basin falls under La Nina climatology. Core 500MB heights in the CFS and ECMWF model variations seem to hover between 35 and 40 N Latitude through July. That would keep out tropical systems, but would of course allow for occasional surges in dewpoints form the Gulf of Mexico, Caribbean and Sargasso Seas. So if a trough and cold front did drop in from Canada, such as the operational European version is showing at 216-240 hours over the Mississippi Valley,the hot air that floods Appalachia and the Eastern Seaboard would be accompanied by very high dewpoints. And, most likely, strong thunderstorms.

Most of Canada appears to be in for the continuation of a cool or changeable temperature regimen, with energy ejecting from the Gulf of Alaska Low. That feature has been ever present during late spring and now the summer, and could continue through autumn and winter. Rather than have wildfires like last year, there is a sizable threat for severe weather in the Prairie Provinces, Ontario and much of Quebec. The cold pools associated with the shortwaves moving across the southern third of the dominion will enable enhanced risks for large hail and tornadoes.

 

Prepared by Meteorologist LARRY COSGROVE on 
Saturday, June 29, 2024 at 11:15 P.M. CT

Disclaimer: 
The previous statements are my opinions only, and should not be construed as definitive fact. Links provided on this newsletter are not affiliated with WEATHERAmerica and the publisher is not responsible for content posted or associated with those sites.

Copyright 2024 by Larry Cosgrove

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