WEATHERAmerica Newsletter, Saturday, July 19, 2008 at 6:35 P.M. CT

by LarryCosgrove | July 19, 2008 at 05:06 pm

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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)
STRONG WINDS
(From Tropical Storm Cristobal)
Coastal SC, NC

ISOLATED Severe Thunderstorms
(Microbursts, Large Hail, Isolated Tornadoes)
S MB....S ON....MN....N, C WI....MI....N OH....N PA....W, C NY....VT....MA....NH
W, C ME....QB Eastern Townships

Some Thunderstorms May APPROACH Severe Limits
S CA....NV....AZ....UT....W WY....W CO....W, C NM....W TX

ISOLATED Severe Thunderstorms
(Microbursts)
SE WY....N NE....IA

Some Thunderstorms May APPROACH Severe Limits
LA....AR....TN....KY....SE OH....WV....W VA....W NC....W SC....GA....FL....AL....MS

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

Scattered Locations In
Coastal SC, NC
(QPF 1 - 5")

Isolated Locations In
LA....AR....TN....KY....SE OH....WV....W VA....W NC....W SC....GA....FL....AL....MS
(QPF 1 - 2")

Scattered Locations In
S MB....S ON....MN....N, C WI....MI....N OH....N PA....W, C NY....VT....MA....NH
W, C ME....QB Eastern Townships
(QPF 1 - 3")

Isolated Locations In
S CA....NV....AZ....UT....W WY....W CO....W, C NM....W TX
(QPF 1 - 2")

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

Scattered Locations In
CA....C, E OR....E WA....ID....SE BC....S AB....MT....WY....UT....NV....AZ....NM....TX
OK....KS....W MO....W, C IA....NE....S SD

Scattered Locations In
KY....IL....IN....C, S OH....PA....S NY....NJ....DE....MD....DC....VA....W NC

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

Eastern Equatorial Pacific Theater

Remnants of former Hurricane Elida are spinning down in colder waters between Mexico and Hawaii.

Hurricane Fausto is moving westward about 850 miles below Cabo San Lucas Baja CA.

New tropical depression appears to be forming below Nicaragua and Honduras. This feature may soon reach named storm status with wind and rain threats to much of Mexico.
Atlantic Basin

Hurricane Bertha is approaching Iceland. Effects may be felt over the Orkney Islands and eventually Scandinavia.

Tropical Storm Cristobal is about 150 miles east of Myrtle Beach SC moving northeast. Dangers of flooding rains to the Eastern Seaboard are noted in the SHORT RANGE OUTLOOK below.

A strong tropical wave (termed Invest 94L) is absorbing a TUTT signature over the northwestern Caribbean Sea. When this process is completed on Sunday morning true warm-core cyclogenesis should get underway with threats to the Yucatan Peninsula, northeastern Mexico and perhaps Texas. More on the risk posed by Invest 94L in the paragraphs below.

Two other convective clusters are noted, in the Sargasso Sea and Windward Islands.

African ITCZ

Two very impressive tropical waves, with circulations and abundant convection, are noted over the Cameroons and in the northern portion of the Congo Basin. Both of these impulses may organize into tropical cyclones over the equatorial Atlantic Ocean in a week to ten days.

SHORT RANGE OUTLOOK
(Through The Next 72 Hours)

Midwest Thunderstorms Will End Northeast U.S. , But Great Plains, Dixie Will Bake

On average, it is turning out to be a fairly hot summer across the U.S. Heat and humidity have persistently worked into the Interstate 95 corridor, as far north as New England. A relatively weak cold front is accompanied by intense thunderstorms over the Upper Midwest, and in time this feature will ease heat concerns over the major cities. But the process will be slow, with the front not reaching the Atlantic shoreline of the Northeast until Wednesday morning. At that time, other "complications" may arise due to the possible interaction of the front with Tropical Storm Cristobal.

High Humidity Keeps Temperatures Down In The Desert Southwest

Whereas there is no real relief from the heat in the forecast for the Great Plains and much of the Old South, the usually seared Desert Southwest is seeing readings actually come in below season normals, thanks to the vaunted "summer monsoon". The unwanted side effect of this cooling, however, is the presence of higher dewpoints and thus relative humidity, which acts to keep nocturnal temperatures high in areas not receiving convective rainfall. The monsoon will begin to erode in the medium range, and soon most of the Intermountain Region will be one vast atmospheric oven.

Tropical Concerns For The Eastern Seaboard And Deep South!

There are major alarm bells going off with respect to the tropics, which are getting an early jump and may involve U.S. targets. Tropical Storm Cristobal is forecast by some of the baroclinic models to merge with a slow moving upper low and frontal structure now over the Great Lakes and Upper Midwest. This interaction could trigger excessive rains and much cooler temperatures from E VA into New England beginning Monday and not ending until perhaps July 24.

Invest 94L must be watched carefully for three possibilities. One is rapid intensification over the climatologically favorable northwest Caribbean Sea and Gulf of Mexico, which could occur after the TUTT signature to the left of the impulse breaks down. Another is the chance of a U.S. landfall, which may happen if the ridge complex over the Deep South erodes (which is forecast by a few of the outlooks and ensembles). The third risk is the potential for a deadly flooding episode, if the system tracks into the Rio Grande Valley and slows down.

And a glance at the GOES 12 images over the Sargasso Sea and Windward Islands shows convective clusters which may develop further, and ride west or northwest with possible targets in the Greater Antilles and Gulf Coast late in the medium range.

MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)

Lots Of Heat From The High Plains Into The Old South....

The gradual cessation of the western U.S. monsoon will get underway next week, and the heat ridge which builds over the Intermountain Region will often extend into the Great Plains and much of the Old South. Before a weakness takes shape to the right of the Mississippi Valley (likely around July 28), routinely oppressive heat will be in store from the Continental Divide into Dixie and parts of the Midwest.

....But Temperate Over The Great Lakes And Northeast

The gap between the Sonoran heat ridge and Bermuda High has been located over the Great Lakes and Corn Belt for much of the summer so far. This discontinuity allows intrusions of cooler air, replete with thunderstorms, to slip south and eastward from Canada. This set-up may occur during the 6 - 10 day time frame, perhaps even reaching into the Northeast in the wake of Cristobal. If so, hot temperatures may be limited to the western half of the nation and the coastal Southeast in the medium range, barring any other arrivals of tropical disturbances.

EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)

Say "Yes" To El Nino!

Sea surface readings continue to climb over the western and central Pacific Basin, joining the cluster of warm values stretching from Ecuador to below the Hawaiian Islands. A look at MTSAT imagery will show low latitude southwest flow over the International Dateline, a surefire signal of an impending El Nino episode (that is, a warm SST anomaly in the ENSO oceanic sectors). During the next 60 days, TUTT signatures and shearing wind profiles will march eastward, eventually (by the first week of September) shutting down production of tropical cyclones from the African ITCZ (i.e. Cape Verde hurricanes). Also of interest is the warming noted over the Gulf of Alaska. This moderation trend, in lock-step with the +ENSO event, may favor a strong +PNA configuration as we head into fall and winter. Remember 1976?

Fluff up your pillow, and dream....

Combination Of Active Tropics And Lengthy 500MB Weakness Can Prove Disastrous

The coming separation of the Bermuda High and the Sonoran heat ridge presents two kinds of challenges for forecasters. One is persistent heat along the Interstate 95 corridor from FL to ME, and another long-lived spell of hot weather encompassing most of the Intermountain Region and Great Plains. The other is the possible corridor of entry for warm-core disturbances from the Atlantic Basin. If the ECMWF and GFS ensemble packages are correct with placement of the trans-ridge gap form the Gulf Coast into the St. Lawrence Valley, we may see persistent heavy rains in Appalachia, the Ohio Valley and Quebec. And the ongoing risk of landfalling tropical cyclones into the Deep South during the first week of August.

Prepared by Meteorologist LARRY COSGROVE on
Saturday, July 19, 2008 at 6:35 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. WEATHER HAZARDS (During The Next 24 Hours)

SEVERE WEATHER OUTLOOK
(potential for tornadoes, damaging winds, and large hail within the next 24 hours)
STRONG WINDS
(From Tropical Storm Cristobal)
Coastal SC, NC

ISOLATED Severe Thunderstorms
(Microbursts, Large Hail, Isolated Tornadoes)
S MB....S ON....MN....N, C WI....MI....N OH....N PA....W, C NY....VT....MA....NH
W, C ME....QB Eastern Townships

Some Thunderstorms May APPROACH Severe Limits
S CA....NV....AZ....UT....W WY....W CO....W, C NM....W TX

ISOLATED Severe Thunderstorms
(Microbursts)
SE WY....N NE....IA

Some Thunderstorms May APPROACH Severe Limits
LA....AR....TN....KY....SE OH....WV....W VA....W NC....W SC....GA....FL....AL....MS

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

Scattered Locations In
Coastal SC, NC
(QPF 1 - 5")

Isolated Locations In
LA....AR....TN....KY....SE OH....WV....W VA....W NC....W SC....GA....FL....AL....MS
(QPF 1 - 2")

Scattered Locations In
S MB....S ON....MN....N, C WI....MI....N OH....N PA....W, C NY....VT....MA....NH
W, C ME....QB Eastern Townships
(QPF 1 - 3")

Isolated Locations In
S CA....NV....AZ....UT....W WY....W CO....W, C NM....W TX
(QPF 1 - 2")

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

Scattered Locations In
CA....C, E OR....E WA....ID....SE BC....S AB....MT....WY....UT....NV....AZ....NM....TX
OK....KS....W MO....W, C IA....NE....S SD

Scattered Locations In
KY....IL....IN....C, S OH....PA....S NY....NJ....DE....MD....DC....VA....W NC

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

Eastern Equatorial Pacific Theater

Remnants of former Hurricane Elida are spinning down in colder waters between Mexico and Hawaii.

Hurricane Fausto is moving westward about 850 miles below Cabo San Lucas Baja CA.

New tropical depression appears to be forming below Nicaragua and Honduras. This feature may soon reach named storm status with wind and rain threats to much of Mexico.
Atlantic Basin

Hurricane Bertha is approaching Iceland. Effects may be felt over the Orkney Islands and eventually Scandinavia.

Tropical Storm Cristobal is about 150 miles east of Myrtle Beach SC moving northeast. Dangers of flooding rains to the Eastern Seaboard are noted in the SHORT RANGE OUTLOOK below.

A strong tropical wave (termed Invest 94L) is absorbing a TUTT signature over the northwestern Caribbean Sea. When this process is completed on Sunday morning true warm-core cyclogenesis should get underway with threats to the Yucatan Peninsula, northeastern Mexico and perhaps Texas. More on the risk posed by Invest 94L in the paragraphs below.

Two other convective clusters are noted, in the Sargasso Sea and Windward Islands.

African ITCZ

Two very impressive tropical waves, with circulations and abundant convection, are noted over the Cameroons and in the northern portion of the Congo Basin. Both of these impulses may organize into tropical cyclones over the equatorial Atlantic Ocean in a week to ten days.

SHORT RANGE OUTLOOK
(Through The Next 72 Hours)

Midwest Thunderstorms Will End Northeast U.S. , But Great Plains, Dixie Will Bake

On average, it is turning out to be a fairly hot summer across the U.S. Heat and humidity have persistently worked into the Interstate 95 corridor, as far north as New England. A relatively weak cold front is accompanied by intense thunderstorms over the Upper Midwest, and in time this feature will ease heat concerns over the major cities. But the process will be slow, with the front not reaching the Atlantic shoreline of the Northeast until Wednesday morning. At that time, other "complications" may arise due to the possible interaction of the front with Tropical Storm Cristobal.

High Humidity Keeps Temperatures Down In The Desert Southwest

Whereas there is no real relief from the heat in the forecast for the Great Plains and much of the Old South, the usually seared Desert Southwest is seeing readings actually come in below season normals, thanks to the vaunted "summer monsoon". The unwanted side effect of this cooling, however, is the presence of higher dewpoints and thus relative humidity, which acts to keep nocturnal temperatures high in areas not receiving convective rainfall. The monsoon will begin to erode in the medium range, and soon most of the Intermountain Region will be one vast atmospheric oven.

Tropical Concerns For The Eastern Seaboard And Deep South!

There are major alarm bells going off with respect to the tropics, which are getting an early jump and may involve U.S. targets. Tropical Storm Cristobal is forecast by some of the baroclinic models to merge with a slow moving upper low and frontal structure now over the Great Lakes and Upper Midwest. This interaction could trigger excessive rains and much cooler temperatures from E VA into New England beginning Monday and not ending until perhaps July 24.

Invest 94L must be watched carefully for three possibilities. One is rapid intensification over the climatologically favorable northwest Caribbean Sea and Gulf of Mexico, which could occur after the TUTT signature to the left of the impulse breaks down. Another is the chance of a U.S. landfall, which may happen if the ridge complex over the Deep South erodes (which is forecast by a few of the outlooks and ensembles). The third risk is the potential for a deadly flooding episode, if the system tracks into the Rio Grande Valley and slows down.

And a glance at the GOES 12 images over the Sargasso Sea and Windward Islands shows convective clusters which may develop further, and ride west or northwest with possible targets in the Greater Antilles and Gulf Coast late in the medium range.

MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)

Lots Of Heat From The High Plains Into The Old South....

The gradual cessation of the western U.S. monsoon will get underway next week, and the heat ridge which builds over the Intermountain Region will often extend into the Great Plains and much of the Old South. Before a weakness takes shape to the right of the Mississippi Valley (likely around July 28), routinely oppressive heat will be in store from the Continental Divide into Dixie and parts of the Midwest.

....But Temperate Over The Great Lakes And Northeast

The gap between the Sonoran heat ridge and Bermuda High has been located over the Great Lakes and Corn Belt for much of the summer so far. This discontinuity allows intrusions of cooler air, replete with thunderstorms, to slip south and eastward from Canada. This set-up may occur during the 6 - 10 day time frame, perhaps even reaching into the Northeast in the wake of Cristobal. If so, hot temperatures may be limited to the western half of the nation and the coastal Southeast in the medium range, barring any other arrivals of tropical disturbances.

EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)

Say "Yes" To El Nino!

Sea surface readings continue to climb over the western and central Pacific Basin, joining the cluster of warm values stretching from Ecuador to below the Hawaiian Islands. A look at MTSAT imagery will show low latitude southwest flow over the International Dateline, a surefire signal of an impending El Nino episode (that is, a warm SST anomaly in the ENSO oceanic sectors). During the next 60 days, TUTT signatures and shearing wind profiles will march eastward, eventually (by the first week of September) shutting down production of tropical cyclones from the African ITCZ (i.e. Cape Verde hurricanes). Also of interest is the warming noted over the Gulf of Alaska. This moderation trend, in lock-step with the +ENSO event, may favor a strong +PNA configuration as we head into fall and winter. Remember 1976?

Fluff up your pillow, and dream....

Combination Of Active Tropics And Lengthy 500MB Weakness Can Prove Disastrous

The coming separation of the Bermuda High and the Sonoran heat ridge presents two kinds of challenges for forecasters. One is persistent heat along the Interstate 95 corridor from FL to ME, and another long-lived spell of hot weather encompassing most of the Intermountain Region and Great Plains. The other is the possible corridor of entry for warm-core disturbances from the Atlantic Basin. If the ECMWF and GFS ensemble packages are correct with placement of the trans-ridge gap form the Gulf Coast into the St. Lawrence Valley, we may see persistent heavy rains in Appalachia, the Ohio Valley and Quebec. And the ongoing risk of landfalling tropical cyclones into the Deep South during the first week of August.

Prepared by Meteorologist LARRY COSGROVE on
Saturday, July 19, 2008 at 6:35 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.

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