WEATHERAmerica Newsletter, Sunday, July 6, 2008 at 10:45 P.M. CT

by LarryCosgrove | July 6, 2008 at 08:16 pm

233 views | 0 Recommendations | 0 comments

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, Isolated Tornadoes)
SE SK....S MB....W MN....W IA....NE....SD....ND

ISOLATED Severe Thunderstorms
(Microbursts, Gustnadoes)
W, C TX....NM....AZ....UT....CO....W KS

Some Thunderstorms May APPROACH Severe Limits
FL....GA....AL....MS....LA....E AR....SE MO....IL....WI....W Lower MI....C ON

Some Thunderstorms May APPROACH Severe Limits
SC....NC....TN....KY....VA....E WV....W MD....W PA....W NY

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

Scattered Locations In
SE SK....S MB....W MN....W IA....NE....SD....ND
(QPF 1 - 2")

Isolated Locations In
W, C TX....NM....AZ....UT....CO....W KS
(QPF 1 - 2")

Isolated Locations In
FL....GA....AL....MS....LA....E AR....SE MO....IL....WI....W Lower MI....C ON
(QPF 1 - 2")

Isolated Locations In
SC....NC....TN....KY....VA....E WV....W MD....W PA....W NY
(QPF 1 - 2")

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

Numerous Locations In
Interior CA....C, E OR....S ID....SW MT....WY....UT....AZ....NM....TX Panhandle
W OK....KS....NE....CO

Scattered Locations In
SD....S MN....WI....Lower MI....ON Peninsula....W OH....IN....IL....KY....TN....AL
MS....LA....AR....MO....IA

TROPICAL WEATHER SUMMARY
(review of disturbances over the Atlantic Basin and Eastern Equatorial Pacific Ocean)

Eastern Equatorial Pacific Ocean

Tropical Depression 5E may reach named storm status. Excessive rainfall will create widespread flooding as the depression exploits a connection to the ITCZ, which is bulging northward into Central America from Colombia and Venezuela. Much of Mexico could see devastating rainfall amounts. TD 5E may skirt Baja California before dissipating on Tuesday over the eastern Pacific Ocean.

Atlantic Basin

Tropical Storm Bertha will pass well to the north and east of the Lesser Antilles during the next 36 hours. Bertha will have an opportunity to reach Category 1 hurricane status before encountering a shear axis over the Sargasso Sea (associated with a lingering TUTT signature).

A convective circulation just below Brownsville TX may strengthen if the center remains over water. But in a worst-case scenario, only a depression would form with heavy rainfall, waterspouts and tornadoes an issue on Monday. Most forecast models show this feature moving into the lower Interstate 35 corridor and breaking apart.

African ITCZ And Cape Verde Vicinity

There are four outstanding ITCZ waves over the equatorial Atlantic Basin and central Africa. The chief concern are the lows 300 miles south of Cape Verde and another over Nigeria. Both of these impulses will encounter less dry, dusty air and minimal shear as the interlocking heat ridge complex extends from Morocco westward into the southeastern U.S. over the next two weeks.

SHORT RANGE OUTLOOK
(Through The Next 72 Hours)

High Heat Over Much Of The Lower 48 States....

With the shift in the polar westerlies into southern Canada, heat that has been building across the Intermountain Region will now translate into the rest of the U.S. A cold front over the Prairie Provinces will trigger cooling thunderstorms in the Upper Midwest, but by and large readings over the next 48 hours will be excessively hot anywhere between 45 N Latitude and Mexico or the Gulf of Mexico.

....While Humidity Increases Over The Midwest And South

Enough of a weakness exist in the heat ridge exists for northward transport of high dewpoints, and the practical result will be a hot and sultry condition anywhere east of the Rocky Mountains during the next two days. The air will be stagnant below 40 N Latitude, adding a smog hazard to the unrelenting high temperatures.

Pacific Northwest Cold Front Makes Move Toward The Great Lakes

While the vigorous NAM solution may prove to be too aggressive, there is a high degree of confidence that the strong shortwave and cold front over the Gulf of Alaska wills weep through the northern third of the U.S. during the near term. Severe thunderstorms may be followed by a day or so of cooler air and lower humidity in the Great Lakes region. But the overall strength and durability of the heat ridge complex will ultimately return the heated regime to most of the Midwest by the start of the medium range.

MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)

Conjoined Heat Ridge East Of The Rocky Mountains?

There is unity among the numerical models concerning the possibility of a conjoined heat ridge stretching from the Rio Grande Valley into the central Atlantic Ocean. This type of positive height anomaly can mean only one thing: widespread heat over the U.S. east of the Rocky Mountains. Indeed, extremely hot air may reach threatening levels in the major metropolitan areas such as Dallas TX, Atlanta GA, Washington DC, St. Louis MO and many other highly populated regions between July 11 and 16.

Could Tropical Storm Bertha Be A Factor Along The Eastern Seaboard?

For its entire lifetime thus far, the various numerical models have been steadfast on a weak and out-to-sea solution for Tropical Storm Bertha. The most likely scenario for the first "Cape Verde" tropical cyclone is still one which remains at or below Category 1 strength and recurving well east of the U.S., or for that matter Bermuda. An outlier possibility with such a strong, inter-connected heat ridge complex: Bertha is forced southwestward toward the Bahamas. So far, however, the presence of a TUTT signature and prominent upper southwest flow (shearing direction) would imply that Bertha never becomes a threat to any populate area.

Western Pacific Quiets Down, Favoring Hot Weather In Lower 48 States

During the winter and spring of this year, and even as late as 10 days ago, a sporadic connection has existed between the tropical realm of the Orient and the polar westerlies. As the linkage of energy has dwindled and finally ended, more and more heat has appeared across the lower 48 states. This "energy boost" to the jet stream has resulted in periods of greater amplitude for progressive troughs, and enabled some fairly impressive shots of colder air into the U.S. What likely happens now is that the disturbances and fronts in the stronger upper level winds will pass through southern Canada, while heat ridges and higher temperatures control the U.S.

EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)

Developing Window For Increased Tropical Activity
Bertha may or may not have any direct impact on weather in North America or the surrounding islands. But the second named storm seems to have exploited a key change in the overall atmospheric configuration. Saharan air is shifting northward, winds aloft have shifted to east and have lightened. All of this at a time when water temperatures are rising across the Atlantic Basin, to levels which will allow for intensification of ITCZ impulses. The window for development of "Cape Verde" disturbances will be shortened, however. Warming continues along all of the ENSO sectors, favoring the re-formation of lower latitude westerlies between South America and western Africa. The possibility for systems originating over the African tropics should end during the first week of September.

+PNA Configuration May Develop; Similarity To 1976?
There seems to be a general, but not outstanding, consensus among the numerical models on the transition to a non-blocking +PNA configuration during the third week of July. Since the transition to a weak El Nino episode is apparently nearing completion, the possibility of increasing upper level westerlies over a ridge complex in the western U.S. would enable a classic "northwest flow" thunderstorm pattern to unfold over the Great Lakes and Northeast. Without mentioning anything about the succeeding winter (and at this point you should not, as every year has its own character with regard to the atmosphere and seasonal weather), the possibility exists for a rapid series of cold frontal passages through the northern tier states that would bring to mind the middle and late summer of the U.S. bicentennial year. While the longer term predictions may look similar to that year of wild extremes, keep in mind that two important distinctions are cropping up: a stronger than normal Bermuda High (implying warmer readings along the Interstate 95 corridor) and the tendency for a 500MB weakness to appear over or near the Mississippi Valley. The most likely solution for the July - September period: a cross between 1976 and 1993. This summer will be a hot one with normal precipitation along the coastline of the Mid-Atlantic and New England states.

Prepared by Meteorologist LARRY COSGROVE on
Sunday, July 6, 2008 10:45 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

All rights reserved.

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