WEATHERAmerica Newsletter, Monday, Memorial Day, May 26, 2008

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WEATHERAmerica Newsletter, Monday, Memorial Day, May 26, 2008

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WEATHER HAZARDS (During The Next 24 Hours)

SEVERE WEATHER OUTLOOK
(potential for tornadoes, damaging winds, and large hail within the next 24 hours)
SCATTERED Severe Thunderstorms
(Microbursts, Large Hail, Tornadoes)
N TX....OK....C, E CO....KS....MO....C, S IL....S IN....KY....TN

ISOLATED Severe Thunderstorms
(Microbursts, Large Hail, Isolated Tornadoes)
S OH....WV....N VA....DC....MD....DE....C, E PA....NJ....S NY....CT....RI....MA....S NH
E ME....S NB

ISOLATED Severe Thunderstorms
(Microbursts, Large Hail, Isolated Tornadoes)
N CA....N NV....S ID....W MT....W WY


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

Numerous Locations In
N TX....OK....C, E CO....KS....MO....C, S IL....S IN....KY....TN
(QPF 1 - 5")

Isolated Locations In
S OH....WV....N VA....DC....MD....DE....C, E PA....NJ....S NY....CT....RI....MA....S NH
E ME....S NB
(QPF 1 - 2")

Isolated Locations In
N CA....N NV....S ID....W MT....W WY
(QPF 1 - 2")


EXCESSIVE HEAT OUTLOOK
(potential for maximum temperature to exceed 95 deg F within the next 24 hours)

Scattered Locations In
AZ....NM....S CO....S KS....OK....TX....W LA....W, C AR

Isolated Locations In
FL....GA....SC

SHORT RANGE OUTLOOK
(Through The Next 72 Hours)


Severe Weather Terror Continues In Parts Of Great Plains And Midwest



We live in violent, destructive times. As the death toll from an active tornado year continues to climb, perhaps the worst news to offer is that the scourge of severe weather will continue. With a still-strong jet stream cutting across the northern third of the U.S. and almost extreme temperature contrast and convergence in place from the Front Range into the Ohio Valley, intense convection is almost a given in the next 48 hours from CO to OK and then through OH and WV. Oklahoma and North Texas will be hardest hit on Tuesday, with some reduction of storm coverage by midweek as the frontal structure begins to wash out.

But yet another bombardment of twisters, large hail, and damaging winds is on tap during Days 4 and 5, as a storm couplet now over the Gulf of Alaska advances along the Canadian border. Notice that the impact zone of stronger dynamics and instability will occur a bit further north. By Friday night and Saturday, watch boxes and warnings could proliferate in much of the lower Great Lakes and Corn Belt.

Surge Of Cool Air Targets Great Lakes, Northeast....

Relief from the late spring heat and humidity will be in place across the northern tier states on Wednesday and Thursday. With the flow signature becoming increasingly semizonal, the Canadian air mass will not be anywhere near as chilled as in the recent past. So the states from the Pacific Northwest into the Northeast can shortly look forward to a 48-72 hour period of refreshing, low-dewpoint, no-air-conditioner weather.

....While Southern Tier Of U.S. Is Set On "BROIL"
Those nice, crisp readings in the northern U.S. will not be enjoyed by communities further south. Instead, a fetid mixture of haze, heat and high humidity will be the main weather course from parts of the Desert Southwest through the lower Great Plains and Deep South. The heat will be accompanied by growing drought that, with time, will begin to spread north and westward.

MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)

Is There An "Arthur" In Your Future?

There is growing concern over the potential for a tropical cyclone formation in the western Caribbean Sea or southern Gulf of Mexico within the next week. GOES satellite imagery shows a huge convective cluster below Central America, which is in the process of merging with a tropical wave over Panama. A weak steering current exists which could take this disturbed area northward across Nicaragua to just east of Belize and the resorts of the Yucatan Peninsula during the following six days. The various baroclinic models seem to lose the system after a growth period in either the Yucatan Channel or Bay of Campeche. Ensemble data, however, suggests a steady northward drift toward Texas late in the medium range. Waters in the Gulf of Mexico are warm enough for growth of a tropical depression or storm, but barely so and confined to the Bay of Campeche and the vicinity of southern Florida of Cuba. So it should be sufficient to say that a warm-core disturbance of some kind may threaten the Gulf Coast perhaps early next week.

Never-Ending Heat In The Much Of The West And Old South....


The advertised build-up of heat has been ongoing across the southern tier states, and the medium range will see an expansion of hot temperatures into both the Desert Southwest and the Southeast. The chief culprit of this excessive warming is the formation, and expansion, of a 500MB heat ridge over northern Mexico. As a fast jet stream and storm complex races across the northern tier of the U.S. after May 31, the cTw regime in northern Mexico will build northeastward, forming a subtropical high across the Lone Star State. This anticyclone will cap the atmosphere, producing unrelenting sunshine and readings which may exceed 100 deg F even near the Gulf Coast.

And the bad news is, this hot spell will be lasting well into the month of June....

....But Stormy Northern Tier Of U.S. May Dodge The Hot Bullet

The two intense disturbances in the polar jet stream over the northern Pacific Ocean will have another side effect besides advecting hot temperatures into the southern and central U.S. Moving along a frontal structure straddling the Canadian border, both impulses are likely to produce what has become the normal for much of the Great Plains and Midwest: severe weather featuring large hail, damaging winds, and tornadoes. The first shortwave should impact the area from WY and CO into the Ohio Valley during the coming weekend. The second, and more potent, area of low pressure is likely to hit the same regions around June 3 - 5.

EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)


Tropical Weather Discussion
INDOEX

As is the case with Africa, the ITCZ is active across the length of the Indian Ocean. Two disturbances, both over the Arabian Sea, stand out as possible impact players. The broad convective circulation centered just east of Somalia should bring heavy rainfall over most of the Horn of Africa as well as the lower Nile Basin. The other, more tightly compacted impulse may briefly threaten Yemen or the United Arab Emirates before dry air entrainment lessens thunderstorm, and wind, development.

MTSAT


A tropical depression is forming between Iwo Jima and the Philippines. Due to impulses moving off of the Chinese mainland, there is relatively little danger that this feature will threaten the Japanese main islands. That said, the storm very likely will reach typhoon status within 48 hours, and will join/bolster the polar westerlies later this week. As a result, yet another major-impact severe weather outbreak is probable across the northern and/or central tiers of the U.S. at some point in the first week of June.

METEOSAT

Although it is far too early to contemplate threats from the wave train of the ITCZ over equatorial Africa, the above pictured satellite image shows that the sequence of tropical waves is already potent, displaying massive areas of convection as well as vorticity or circulatory maxima. When shearing winds and rising SSTs in the Atlantic Basin permit warm-core cyclogenesis to occur from this source region (sometime in late June or July), we may be facing a sudden onslaught of tropical development which in time could threaten North America and the nearby islands. Note that those waves not compromised by dry air are already present between Cape Verde and northernmost Brazil.

Heat Ridges Set To Expand
With all of the numerical models and ensemble sets showing a northward relocation of the polar jet stream, it should be no surprise that said versions are also showing the formation of a durable heat ridge configuration along and below 40 N Latitude. The European and Canadian outlooks and variants would seem to favor the worst of the heat between June 6 and 11 as occurring over the Southwest, while the American schemes bring the highest 500MB heights to Oklahoma by late in the extended period. After the tropical cyclone threat ends (around 288 hours), the procession of strong shortwaves across the northern tier will almost certainly bring the hottest of the cTw regime (with increasing dewpoints from the Gulf of Mexico) into the south central U.S. Bottom line: the cities across the southern third of the U.S. are going to be involved in a prolonged heat wave. Above the Interstate 70 corridor, strong thunderstorms and tornadoes will once again rule the landscape.

Prepared by Meteorologist LARRY COSGROVE on
Monday, Memorial Day, May 26, 2008 at 9:40 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 2008 by Larry Cosgrove

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This publication may not be reproduced or redistributed in whole or in part without the expressed written consent of the author.