WEATHERAmerica Newsletter, Saturday, April 27, 2024

[Larry Cosgrove]

EXTENDED PERIOD FORECAST

(Between Day 11 And Day 15)

 

The Approaching La Nina Favors A Sudden Pattern Shift For North America

CIMSS

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

NOAA/PMEL

NOAA/CPC

IRI/Columbia University

HPRCC/University Of Nebraska (2)

Environment Canada

ECMWF (3)

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

NOAA/CPC

If you look at the equatorial Pacific Basin, the La Nina episode has basically started. Colder water temperatures are streaking west from the Galapagos Islands, and the current positive neutral ENSO should be on the negative side by the middle of May. We may reach a La Nina threshold in sector 3.4 in June, and most projections favor a moderate designation (-1.0 deg C deviation) by October 1. I suspect that the peak of this session will be in January before a possible upturn in hydrothermal measures at mid-ocean in January 2025.

Put in practical terms, the climatology for these changes in the sea surface temperature anomalies will favor a hot summer east of the Continental Divide, with likely dryness below Interstate 90 and to the right of the Rocky Mountains. The Mexican heat ridge will start its northward ascent, and likely join with the Bermuda High. The question in timing deals with when will we lose the current very stormy set-up in between both coasts? The ECMWF weeklies do not want to give up on the pattern next month. But the presence currently of the strong subtropical high in Oaxaca state, with occasional expansions into the Gulf of Mexico, tells me that after perhaps one more week of intense convection in Texas, the Great Plains through the Mississippi River watershed, that the leading edge of the ridge complex (588dcm at 500MB) will reach past the Interstate 10 corridor around May 15 or so. Note that overall, weather after last January has been very warm overall. I suspect that we will keep that trend going next month.

One other issue to talk about: it will probably take about three months before we lose the "El Nino Upper Wind Hangover". I am predicting an active hurricane season with multiple threat zones to the major islands, the Gulf Coast, and Eastern Seaboard. Because we may not start until Saharan heat and dust infiltration lessens and the shearing westerlies aloft depart, the core tropical cyclone period looks to be August 15 to October 31.

More later....

Prepared by Meteorologist LARRY COSGROVE on 
Saturday, April 27, 2024 at 1:95 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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