WEATHERAmerica Newsletter, Saturday, April 20, 2024

[Larry Cosgrove]

WEATHER HAZARDS (During The Next 24 Hours)

 

SEVERE WEATHER OUTLOOK
(potential for tornadoes, damaging winds, and large hail within the next 24 hours)

 

Some Thunderstorms May APPROACH Severe Limits

S LA....S MS....S AL....N FL....GA....E SC....Coastal NC

 

HEAVY RAINFALL OUTLOOK
(potential for an inch or more total rainfall within the next 24 hours)

 

Isolated Locations In

S LA....S MS....S AL....N FL....GA....E SC....Coastal NC

(QPF 1 - 2")

 

EXCESSIVE HEAT RISK

(Potential For Temperature To Exceed 95 deg F)

 

Isolated Locations In

S CA....S NV....S UT....AZ....W NM

WINTER WEATHER POTENTIAL

(potential for Moderate Icing, Snow 2 - 4" or more, and/or temperatures below 10 deg F)

 

Isolated Locations In

N, C ON....W, C QC

(Intense Cold)

Isolated Locations In

QC Laurentian Shield

(Wet Snow; 3- 6")

GLOBAL WEATHER SUMMARY

(a review of important weather features around the world)

 

IODC

ECMWF; METEOBLUE; EUMETSAT

 

Still dealing with intense thunderstorms, but a bit further north. While the heat demons approach from the Suda, Saudi Arabia, and India....

Devastating heavy rain and severe weather can occur in the (usually) dry Middle East, and the numerical models over the past few weeks have proven that point with accurate predictions of excessive rainfall (such as the Dubai case). Most of the forecast guidance shows large and cold upper disturbances migrating from the Balkan Peninsula and Anatolia through the Middle East and Persia through the first week of May. I suspect that the transition to extreme heat is about three weeks away. Between now and mid-May, the 500MB disturbances and weak frontal structures will continue to pound the stretch from Egypt to Pakistan with bouts of intense convection, with the occasional instance of hail, high winds and tornadoes. But it is the torrential rain that will leave its mark on the Levant and Persia before the vast heat ridge network (note high temperatures and dryness in the Sahel and South Asia) makes its jump northward, and sticks southwestern and central Asia with hellish heat and aridity.

 

HIMAWARI 8

METEOBLUE; Kochi University

 

Since the storm sequence across the Pacific Basin reaches back into central Asia, I am leery of forecasting any changes to the course of weather in North America much before mid-May. Colder air has largely dissipated and retreated to the Siberian shoreline. Hot air is slowly locking in from India through Southeast Asia and the Philippines Archipelago, which will cut back on typhoon potential and overall rainfall chances in the tropical areas of the Pacific Basin. Note the dissipation of the Madden-Julian Oscillation, and lack of connection to the polar westerlies to the left of the International Dateline.

Except for some convection along the northern and eastern shorelines, Australia is drying out after a rather bizarre wet and stormy summer. A stronger cold front has passed New Zealand, and may interact with a tropical feature in Oceania.

 

GOES WEST

METEOBLUE; NOAA/NESDIS

 

It is a waiting game across the western states, as a broad trough complex with cold air aloft is moving slowly, but steadily toward California. Linked to a deep subtropical jet stream from the equatorial Pacific Basin, there could be a significant heavy rainfall event in lower elevations of the Golden State and into the Great Basin. Most importantly, the disturbed area will set up a cool West vs. warm Central/East alignment with increased threats for severe weather from Texas into the middle and lower Missouri Valley.

 

GOES EAST

ECMWF; METEOBLUE; NOAA/NESDIS

 

After a cold frontal passage through the Eastern Seaboard into the Deep South, a shortwave is progressing through Texas with heavy rain and thunderstorms. An MCS is trying to organize, and the convective aspect of this impulse should continue along the Gulf Coast an into the Southeast on Sunday before moving out into the open waters of the Atlantic Ocean. Colder air behind the frontal structure has so far been underwhelming, with the lowest temperatures remaining in Ontario and Quebec (with snow possible in association with the diminished vortex breaking up across Hudson Bay). Another cold front out of the Prairie Provicnes may set up showers and thunder in the Midwest/Great Lakes/Northeast at midweek.

The lower half of South America appears to be drying out, with cooler air across southern Chile and Argentina. But a wide swath from Brazil to the Pacific shoreline has a humid air mass populated by both diurnal thunderstorms and MCCs, again typical of a La Nina influenced atmosphere.

 

METEOSAT

ECMWF; METEOBLUE; EUMETSAT

 

All eyes are on a vast, cold full-latitude trough over the northern Atlantic Ocean. This feature will likely hold intact as it approaches the British Isles/western Europe, probably arriving there on Tuesday. This feature is significant because of the likelihood of intense convection across France and the Iberian Peninsula and points eastward during the new week, along with a temporary sharp temperature drop through the northern portions of the subcontinent. Eastern European nations and western Russia could see a sizable warm-up.

There are signs of the imminent takeover of La Nina. Heat and drought are slowly inching northward from the Sahel, and will occupy most of the Sahara Desert later in the ne week. The Kalahari heat ridge is in firm control of the southern third of Africa. But note the thunderstorm complex in the eastern half of the equatorial zone. The convective group will likely expand westward, associated with the reformation of the ITCZ (with larger/broader coverage associated with a -ENSO episode).