WEATHERAmerica Newsletter, Saturday, September 21, 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)

 

ISOLATED Severe Thunderstorms

(Microbursts, Large Hail, Isolated Tornadoes)

W TX....W OK....KS....SE NE....S IA....MO....Far N TN....W KY....W IN....IL....E WI....N MI....C ON

 

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

 

Isolated Locations In

Coastal BC

(QPF 1 - 3")

Scattered Locations In

W TX....W OK....KS....SE NE....S IA....MO....Far N TN....W KY....W IN....IL....E WI....N MI....C ON

(QPF 1 - 3")

 

EXCESSIVE HEAT RISK

(Potential For Temperature To Exceed 95 deg F)

 

Isolated Locations In

CA....NV....AZ....NV....UT....W CO....W, S NM....TX....SE OK....AR....LA....MS....AL....FL....GA....SC....W NC....TN....Far W KY

GLOBAL WEATHER SUMMARY

(a review of important weather features around the world)

 

IODC

ECMWF; METEOBLUE; EUMETSAT

 

The slow demise of the Middle East/Persian heat ridge complex....

In what may be ascribed to the current La Nina episode, the large subtropical high straddling Saudi Arabia and southern Iran is only slowly giving ground to cold fronts and associated shortwaves running along a line from the Balkan Peninsula, Asia Minor and the Caucasus/Caspian Sea. A Rex blocking signature over western Russia is forecast to extend into the Central Asia Republics, so the cP vs. mT boundary will drop in latitude, possibly bringing Baghdad Iraq and Tehran Iran into the polar air mass by the first day of October. Many of the forecast models have been reluctant to increase precipitation potential, but there should be cool stratiform rain above 35 N Latitude in the medium range, with renewed severe weather threats in convection from Israel/Jordan on the west to Pakistan on the east starting next weekend.

 

HIMAWARI 8

METEOBLUE; Kochi University

 

As almost always happens in autumn, the Madden-Julian Oscillation starts to link with the polar westerlies and subtropical jet stream. The MJO is incoherent right now, with one convective formation in the Bay of Bengal through Indochina, and another grouping across the Marianas Chain to the International Dateline. There are some signs that the southern branch will link with the more eastward impulse, which could prove very interesting if that interaction was maintained through the coming winter. For now, the repeated formation of a Gulf of Alaska Low favors a cool Russia and Canada vs. warm PRC and USA as we move through the fall.

Very stormy conditions are now enveloping parts of Australia. The recent tendency of very warm and dry conditions seems gone, and the approach of summer may be marked by a return of "The Wet" across the northern half of the subcontinent.

 

GOES WEST

NOAA/NESDIS

 

The linear presentation of thunderstorms stretching below Central America and Mexico is the ITCZ. This disturbed area may still generate some tropical depressions and storms, some of which may move north into the Caribbean Sea and Bay of Campeche. Most, however, will graze the Mexican Riviera before heading westward out to sea. The Gulf of Alaska Low continues the autumn pattern of weakening upon reaching the Pacific Northwest and rebuilding below the Aleutian Islands. Ridging is returning to the Intermountain Region, allowing for very warm, but not hot, temperatures there.

 

GOES EAST

NOAA/NESDIS

 

The Atlantic Basin is becoming tropically active, even with no declared warm-core systems. Note that there are five disturbances across various parts of the ocean that remain very warm between North America and Africa. Also note that the westerlies are beginning to impinge on the subtropical regions, and should prevent "Cape Verde" ITCZ waves from threatening the U.S. after mi-October. From that point onward, systems will eject out of the Caribbean Sea, Gulf of Mexico, or the western Sargasso Sea, in cases where weaknesses and TUTT signatures form.

There is a great deal of hot and dry weather in South America. Frontal structures continue to press eastward from Chile to Argentina, with most of the important rainfall and thunderstorms now occurring near the shoreline of the Atlantic Basin.

 

METEOSAT

ECMWF; METEOBLUE; EUMETSAT

 

The polar westerlies have begun to edge into the European subcontinent. The heat ridge over northern Africa is beginning to erode, which will allow for more shortwaves to move from England, France, and Spain into eastern Europe, where a blocking ridge should force energy to cut off. The resultant temperature pattern will be mild, but rainfall may, at times, become heavy again from the Danube Valley into the Balkan Peninsula.

See also that the ITCZ. is quite energetic, with numerous convective clusters throughout the equatorial regions of Africa. A cold front has penetrated into Mozambique, but for the most part the Kalahari heat ridge is still controlling apparent weather across the southern third of the continent.