06-15-2008, 12:01 AM
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)
extreme N OK....C, E KS....W, C MO....SE NE....C, E IA....N IL....WI....W Lower MI
Some Thunderstorms May APPROACH Severe Limits
extreme E TX....LA....C, S MS....C, S AL....FL....GA....SC....C, E NC
Some Thunderstorms May APPROACH Severe Limits
CT....RI....MA....VT....NH....QC Eastern Townships
HEAVY RAINFALL OUTLOOK
(potential for an inch or more total rainfall within the next 24 hours)
Scattered Locations In
extreme N OK....C, E KS....W, C MO....SE NE....C, E IA....N IL....WI....W Lower MI
(QPF 1 - 4")
Isolated Locations In
extreme E TX....LA....C, S MS....C, S AL....FL....GA....SC....C, E NC
(QPF 1 - 3")
Isolated Locations In
CT....RI....MA....VT....NH....QC Eastern Townships
(QPF 1 - 2")
EXCESSIVE HEAT OUTLOOK
(potential for maximum temperature to exceed 95 deg F within the next 24 hours)
Numerous Locations In
CA....SE OR....S ID....NV....UT....AZ....NM....CO....C, S WY....W NE....W, C KS....OK
TX....LA....W MS....AR....S MO
TROPICAL WEATHER SUMMARY
(review of disturbances over the Atlantic Basin and Eastern Equatorial Pacific Ocean)
TROPICAL WAVE along ITCZ 700 miles south of Manzanillo Mexico; Threat: NONE
TROPICAL WAVE along ITCZ below Panama; Threat: Minor (Flooding Central America)
TROPICAL WAVE northeast of Brazil, Guyane; Threat: NONE (Vertical Wind Shear)
TROPICAL WAVE 350 miles south of Cape Verde Islands; Threat: NONE (Dust Intrusion)
ENSO Status: Neutral with warming in sectors 1,2; signature may act to limit season of African ITCZ wave development
SHORT RANGE OUTLOOK
(Through The Next 72 Hours)
Who'll Stop The Rain?
If you look at the rainfall chart further down the page, you can envision the staggering amount of precipitation that has fallen over sections of the Great Plains and Midwest in recent days. Yet another dose of severe thunderstorms, tornadoes, and torrential rainfall is on tap for the worst hit areas of the Corn Belt. A cold front dropping southeast from the upper Missouri Valley will again pull up some moisture from the Gulf of Mexico, with an unstable regime settling into place to the right of the frontal structure. As a result, intense thunderstorms will spring up from N OK into the Great Lakes on Sunday, then slowly spread through Appalachia into the Eastern Seaboard on Monday. A convective complex with flooding rains and damaging winds could impact the Mid-Atlantic states on Monday night. More limited rains from diurnal convection may help to ease drought over the Southeast, and this moist air mass may increase the threat for heavy rains and thunder along the Interstate 95 corridor before the front eases offshore on Tuesday afternoon.
Cool Air Advances From The Midwest....
The potential for record cool weather exists as the aforementioned front and parent 500MB low drops into the Northeast from Ontario during the near term. Latest model forecasts place the southern extent of the cooler regime along a line from Amarillo TX to Brunswick GA by Wednesday morning. Daytime high temperatures in the Great Lakes, upper Appalachia, and New England may be limited by convective showers and thunderstorms (note steep lapse rates associated with the presence of the 500MB cold dome).
....While The Southwest Suffers In The Heat
While suppressed over the next 72 hours, high heat (and in some cases sweltering humidity) will continue to be a problem across the southern third of the nation. The heat ridge will actually be building during this time, so a belt stretching from California into the Gulf Coast may actually experience an INCREASE in temperature at a time when locations further to the north are feeling like April!
MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)
Transitioning From Cool To Hot....And Back Again?
The heat will be heard from again! As the Sonoran heat ridge begins to advance eastward during the medium range (note the strong storm complex over the Gulf of Alaska setting up a warm advection phase over the U.S.), hot air (cTw) will spread north and east. While the operational GFS scheme is quite limited with the expansion of the subtropical high, the ECMWF outlook from 12z June 14 is very bullish on the high heat area reaching as far north as a Chicago IL to New York NY line by Day 11. There is a chance, however, that a breakaway shortwave from the northern Pacific Ocean could dent the ridge complex, especially over the eastern third of the country, by June 23 - 24.
Severe Weather, Heavy Rain Concerns For Great Lakes, Northeast
Even if the ECMWF model suite is correct, severe weather and heavy rainfall is still a looming threat over the Great Lakes and Northeast during the 6-10 day time frame. A semi-stationary frontal structure is predicted by all of the versions to stretch from Montana to Michigan and then toward Long Island NY. Waves forming along this front will have plenty of surface convergence and unstable air to work with, and severe thunderstorm clusters and even derechoes are a likely result! The situation is analogous in some ways to the summer of 1976. Ensemble forecasts appear to be pointing away from the storm and flood laden 1993 summer season, hinting at a drying period for much of the Corn Belt west of Interstate 75.
EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)
Looking At Drought Vs. Excessive Rainfall
Sometimes recurrent dry spells and ensuing drought are a good indicator of developing subtropical high patterns in early summer. While California and portions of Nevada and Arizona have areas of extreme dryness, it is worth noting that the formerly drenched Mid-South is now joining the Southeast and lower Great Plains in lacking rainfall. This display of dry weather would seem to point toward a fairly massive, conjoined Sonoran and Great Smokies heat ridge from the Golden State eastward to the Virginias and Carolinas. If so, tropical cyclone threats may tend to increase over time in the Gulf States while the severe weather potential lines up from the north central U.S. into the Northeast.
Merger Of The Heat Ridges?
About a week ago, the GFS model suite kept pointing toward an elongated, conjoined heat ridge across the southern two-thirds of the U.S. during the last week of June. The ECMWF scheme and its ensemble members have, for the most part, picked up on this theme as we approach the longer term. Note this Day 10 forecast, which shows a sprawling subtropical high, a virtual merger of the Sonoran and Bermudan anticyclones. A conclusion that can be drawn from the American and European variants: a heat wave along and below the Interstate 80 corridor (Cheyenne WY to Tenafly NJ) during June 25 - 30.
Powerful Saharan Heat Ridge, Upper Wind Shear Limit Atlantic Basin Tropical Threats
The powerhouse Saharan heat ridge that has been on view since December is beginning to make a move toward the Mediterranean Sea. So strong is this anticyclone that dust and hot air have been projected as far west as North Carolina and to the east in Iran. The advection of the searing hot and dry air has limited tropical wave growth; note that while the ITCZ has FIVE impressive impulses, the disturbances are either eaten up by the desert air mass or sheared by westerlies in a trough over much of the Atlantic Basin. If we are to assume that the ridging and shearing may not relax for the next two weeks, the threat for tropical cyclone development from this theater (even outside of ENSO considerations) will likely not start until sometime in July.
Prepared by Meteorologist LARRY COSGROVE on
Saturday, June 14, 2008 at 5:45 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.
SEVERE WEATHER OUTLOOK
(potential for tornadoes, damaging winds, and large hail within the next 24 hours)
SCATTERED Severe Thunderstorms
(Microbursts, Large Hail, Isolated Tornadoes)
extreme N OK....C, E KS....W, C MO....SE NE....C, E IA....N IL....WI....W Lower MI
Some Thunderstorms May APPROACH Severe Limits
extreme E TX....LA....C, S MS....C, S AL....FL....GA....SC....C, E NC
Some Thunderstorms May APPROACH Severe Limits
CT....RI....MA....VT....NH....QC Eastern Townships
HEAVY RAINFALL OUTLOOK
(potential for an inch or more total rainfall within the next 24 hours)
Scattered Locations In
extreme N OK....C, E KS....W, C MO....SE NE....C, E IA....N IL....WI....W Lower MI
(QPF 1 - 4")
Isolated Locations In
extreme E TX....LA....C, S MS....C, S AL....FL....GA....SC....C, E NC
(QPF 1 - 3")
Isolated Locations In
CT....RI....MA....VT....NH....QC Eastern Townships
(QPF 1 - 2")
EXCESSIVE HEAT OUTLOOK
(potential for maximum temperature to exceed 95 deg F within the next 24 hours)
Numerous Locations In
CA....SE OR....S ID....NV....UT....AZ....NM....CO....C, S WY....W NE....W, C KS....OK
TX....LA....W MS....AR....S MO
TROPICAL WEATHER SUMMARY
(review of disturbances over the Atlantic Basin and Eastern Equatorial Pacific Ocean)
TROPICAL WAVE along ITCZ 700 miles south of Manzanillo Mexico; Threat: NONE
TROPICAL WAVE along ITCZ below Panama; Threat: Minor (Flooding Central America)
TROPICAL WAVE northeast of Brazil, Guyane; Threat: NONE (Vertical Wind Shear)
TROPICAL WAVE 350 miles south of Cape Verde Islands; Threat: NONE (Dust Intrusion)
ENSO Status: Neutral with warming in sectors 1,2; signature may act to limit season of African ITCZ wave development
SHORT RANGE OUTLOOK
(Through The Next 72 Hours)
Who'll Stop The Rain?
If you look at the rainfall chart further down the page, you can envision the staggering amount of precipitation that has fallen over sections of the Great Plains and Midwest in recent days. Yet another dose of severe thunderstorms, tornadoes, and torrential rainfall is on tap for the worst hit areas of the Corn Belt. A cold front dropping southeast from the upper Missouri Valley will again pull up some moisture from the Gulf of Mexico, with an unstable regime settling into place to the right of the frontal structure. As a result, intense thunderstorms will spring up from N OK into the Great Lakes on Sunday, then slowly spread through Appalachia into the Eastern Seaboard on Monday. A convective complex with flooding rains and damaging winds could impact the Mid-Atlantic states on Monday night. More limited rains from diurnal convection may help to ease drought over the Southeast, and this moist air mass may increase the threat for heavy rains and thunder along the Interstate 95 corridor before the front eases offshore on Tuesday afternoon.
Cool Air Advances From The Midwest....
The potential for record cool weather exists as the aforementioned front and parent 500MB low drops into the Northeast from Ontario during the near term. Latest model forecasts place the southern extent of the cooler regime along a line from Amarillo TX to Brunswick GA by Wednesday morning. Daytime high temperatures in the Great Lakes, upper Appalachia, and New England may be limited by convective showers and thunderstorms (note steep lapse rates associated with the presence of the 500MB cold dome).
....While The Southwest Suffers In The Heat
While suppressed over the next 72 hours, high heat (and in some cases sweltering humidity) will continue to be a problem across the southern third of the nation. The heat ridge will actually be building during this time, so a belt stretching from California into the Gulf Coast may actually experience an INCREASE in temperature at a time when locations further to the north are feeling like April!
MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)
Transitioning From Cool To Hot....And Back Again?
The heat will be heard from again! As the Sonoran heat ridge begins to advance eastward during the medium range (note the strong storm complex over the Gulf of Alaska setting up a warm advection phase over the U.S.), hot air (cTw) will spread north and east. While the operational GFS scheme is quite limited with the expansion of the subtropical high, the ECMWF outlook from 12z June 14 is very bullish on the high heat area reaching as far north as a Chicago IL to New York NY line by Day 11. There is a chance, however, that a breakaway shortwave from the northern Pacific Ocean could dent the ridge complex, especially over the eastern third of the country, by June 23 - 24.
Severe Weather, Heavy Rain Concerns For Great Lakes, Northeast
Even if the ECMWF model suite is correct, severe weather and heavy rainfall is still a looming threat over the Great Lakes and Northeast during the 6-10 day time frame. A semi-stationary frontal structure is predicted by all of the versions to stretch from Montana to Michigan and then toward Long Island NY. Waves forming along this front will have plenty of surface convergence and unstable air to work with, and severe thunderstorm clusters and even derechoes are a likely result! The situation is analogous in some ways to the summer of 1976. Ensemble forecasts appear to be pointing away from the storm and flood laden 1993 summer season, hinting at a drying period for much of the Corn Belt west of Interstate 75.
EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)
Looking At Drought Vs. Excessive Rainfall
Sometimes recurrent dry spells and ensuing drought are a good indicator of developing subtropical high patterns in early summer. While California and portions of Nevada and Arizona have areas of extreme dryness, it is worth noting that the formerly drenched Mid-South is now joining the Southeast and lower Great Plains in lacking rainfall. This display of dry weather would seem to point toward a fairly massive, conjoined Sonoran and Great Smokies heat ridge from the Golden State eastward to the Virginias and Carolinas. If so, tropical cyclone threats may tend to increase over time in the Gulf States while the severe weather potential lines up from the north central U.S. into the Northeast.
Merger Of The Heat Ridges?
About a week ago, the GFS model suite kept pointing toward an elongated, conjoined heat ridge across the southern two-thirds of the U.S. during the last week of June. The ECMWF scheme and its ensemble members have, for the most part, picked up on this theme as we approach the longer term. Note this Day 10 forecast, which shows a sprawling subtropical high, a virtual merger of the Sonoran and Bermudan anticyclones. A conclusion that can be drawn from the American and European variants: a heat wave along and below the Interstate 80 corridor (Cheyenne WY to Tenafly NJ) during June 25 - 30.
Powerful Saharan Heat Ridge, Upper Wind Shear Limit Atlantic Basin Tropical Threats
The powerhouse Saharan heat ridge that has been on view since December is beginning to make a move toward the Mediterranean Sea. So strong is this anticyclone that dust and hot air have been projected as far west as North Carolina and to the east in Iran. The advection of the searing hot and dry air has limited tropical wave growth; note that while the ITCZ has FIVE impressive impulses, the disturbances are either eaten up by the desert air mass or sheared by westerlies in a trough over much of the Atlantic Basin. If we are to assume that the ridging and shearing may not relax for the next two weeks, the threat for tropical cyclone development from this theater (even outside of ENSO considerations) will likely not start until sometime in July.
Prepared by Meteorologist LARRY COSGROVE on
Saturday, June 14, 2008 at 5:45 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.