WEATHERAmerica Newsletter, Saturday, June 22, 2024; EXTENDED PERIOD FORECAST

[Larry Cosgrove]

EXTENDED PERIOD FORECAST

(Between Day 11 And Day 15)

Pattern At 500MB Favors Changeable Canada, Mostly Hot USA....And No Major Tropical Disturbances For A While

CIMSS (3)

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

NOAA/PMEL

NOAA/CPC

Columbia University/IRI

HPRCC/University Of Nebraska (2)

Environment Canada

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

ECMWF (3)

NOAA/CPC

So far, even with a slow progression of cooling in the Pacific Basin, the evolving weather pattern "fits the routine '' of what you would expect in a La Nina summer.  There is a mean 500MB Gulf of Alaska Low, semizonal jet stream hugging the U.S./Canada border, and a tendency for a conjoined (Sonoran + Bermudan) heat ridge that sets up repeated cases of hot air to the right of the Continental Divide. We have seen one ill-defined tropical cyclone (Alberto, though I question if a name was needed for a very weak-looking disturbance), and a slow tendency for weaknesses in the Mississippi Riverwatershed and Appalachia to dissolve. Telltale heat waves have formed in the lower High Plains and the Mid-Atlantic, with forecast cool spells in the Pacific Northwest and the New England states.

Seeing how stable the mapped model guidance is, hot air will build up from Texas into the Heartland, then pulse out as storms ride through the Prairie Provinces into Ontario and Quebec. Use the 588dcm height contour at 500MB for an idea how far north the +90 deg F readings will be. Severe thunderstorms look to be an issue every few days about 250 miles either side of the Canadian border. Given the coldness of the upper levels, there are concerns for tornadoes and large hail from BC and WA into the Great Lakes, St. Lawrence Valley and the Northeast.

Careful review of the Atlantic Basin and Africa shows an impressive Saharan heat ridge complex. There are still low latitude westerlies aloft, so even with a strong pulse ITCZ at work through the equatorial regions, we are not likely to see any meaningful tropical cyclones for the next two months. It is either shear or the vast amount of sand and hot/dry air that will diminish these systems. But when the subtropical high begins to parcel and shift toward the Mediterranean Sea, the cTw air mass will suspend and there will be less infiltration on impulses as each passes Cape Verde into the Atlantic Ocean. This will be a very active and probably dangerous hurricane season with impacts on the major islands, USA, and Canada. But I think that the main action waits until gaps in the ridge appear in Mid-August. Once here, the action will probably continue until just after Halloween. The numbers: 18 named storms, 10 hurricanes, 6 major cyclones, with strike probabilities for both Gulf and Atlantic coasts. The equatorial Pacific theater could see 11 named storms, 7 hurricanes, and 3 major events.

And of course, invests in fans and air conditioners.

 

Prepared by Meteorologist LARRY COSGROVE on 
Saturday, June 22, 2024 at 10:05 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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