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WEATHERAmerica Newsletter, Saturday, November 7, 2009 at 5:25 P.M. CT
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TODAY'S FUN LINKS:
WEATHER HAZARDS (During The Next 24 Hours)
SEVERE WEATHER OUTLOOK
(potential for tornadoes, damaging winds, and large hail within the next 24 hours)
(potential for tornadoes, damaging winds, and large hail within the next 24 hours)
STRONG WINDS
(Pressure Gradient Derived, Orographically Enhanced)
W BC....WA Olympic Peninsula
STRONG WINDS
(Pressure Gradient Derived)
N, C QB....NL (Labrador)
HEAVY RAINFALL OUTLOOK
(potential for an inch or more total rainfall within the next 24 hours)
(potential for an inch or more total rainfall within the next 24 hours)
Scattered Locations In
W BC....WA Olympic Peninsula
(QPF 1 - 3")
WINTER WEATHER OUTLOOK
(potential for minimum temperature to drop below 20 deg F, or for snow and/or ice impeding travel within the next 24 hours)
Scattered Locations In
BC....NW WA
(Snow; Above 4500 Feet; 4 - 16")
Isolated Locations In
N MN
(Snow, Sleet, Freezing Drizzle; up to 1" Ice, Slush Cover)
Scattered Locations In
N, C QB....NL Labrador
(Snow; Ground Blizzard; 4 - 8")
SHORT RANGE OUTLOOK (Through The Next 72 Hours) Is Ida Really That Big Of A Deal?
NASA
WEATHERAmerica
Yes, in fact Ida is a major player on the weather scene, and not just because of the lateness of its genesis. Ida will soon begin to combine with a TUTT signature over Mexico and the Bay of Campeche, also with a convective circulation that has been lingering below the Gulf of Tehuantepec. The combinant system should begin to transform to a cold-core entity over the Gulf of Mexico on Sunday night and Monday morning, bringing heavy rainfall and gusty (pressure gradient derived) winds along the Gulf Coast on November 9 and 10.
What happens afterward may actually play a critical role in apparent weather over much of the U.S. for the remainder of November. Does the combinant Ida-derived low pressure area contort the jet stream wind field and bring in colder air (the scenario championed by the GGEM and GFS model suites)? Or is the track and intensity profile suggested by the ECMWF package (weak, no big deal) likely to verify? Going by the idea of four outlook series against two (operational and variant European schemes), I think that Ida will become a stronger mid-latitude cyclone, drawing in enough cPk values to offer some potential for snowfall in New England (away from the coastal plain) before the storm moves eastward off of Nova Scotia and Newfoundland on November 12. While not having the same effect as Hurricanes Opal (1995) or Ike (2008), I believe that the Ida-related system will ultimately suppress mean 500MB ridging over the Southeast, leading to a somewhat cooler medium range forecast east of the High Plains.
Indian Summer Reigns Over The Great Plains And Midwest....
Plymouth State University Weather Server
Before the "Ida" disturbance affects the 500MB longwave pattern, however, most locations to the right of the Rocky Mountains are going to experience some unusually warm and dry weather. Afternoon readings exceeding 80 deg F may reach as far north as the Ohio Valley and the Mason-Dixon Line through Tuesday, ahead of the aforementioned storm. Humidity will be low as well, owing to the fact that the air mass will be a combination that is derived from the Desert Southwest and northern Mexico.
....While Colder Air Grips The Pacific Northwest
Plymouth State University Weather Server
There IS colder air present in the U.S., although not where one would expect to see in a moderate El Nino episode. Energy from a deep mA vortex over the western Gulf of Alaska continues to find a home over the Pacific Northwest, bringing abundant snows to higher elevations in British Columbia and Washington. Repeated intrusions of mPk air masses and 500MB vorticity look to keep the mountain snows (and chilly lowland rains) going in BC, WA, and ID through early next week.
MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)
Overall Outlook: Mild, But Transitional
ECMWF
While I am not certain about the ECMWF depiction of a strong heat ridge over Georgia, Florida, and the southwestern Atlantic Ocean, the idea that no truly harsh polar or Arctic values occupying the U.S. in the 6 - 10 day range has merit. A formative trough over the Intermountain Region should create a window for southwesterly flow aloft from the Interstate 25 corridor through the Eastern Seaboard. So while California and other parts of the West turn chilly (especially WA, OR, and ID), the mild spell may rebuild in the central and eastern parts of the nation between November 13 - 17.
....With Potential For A Panhandle Hooker Storm?
Penn State University E-Wall
I suspect that the energy closing off over the Intermountain Region may yield a storm, with the track being of the Panhandle Hooker B variety. 500MB heights are forecast to rise through the Prairie Provinces into Greenland, making a path through the Great Plains into Lake Superior unlikely. Again, using the GFS/GGEM template, cyclogenesis near Lubbock TX would be followed by a trajectory through northwestern Pennsylvania by November 17. Colder air would then occupy the Midwest by the end of the medium range.
Keep in mind that there is good agreement on very high surface pressures moving southeastward from MB and ON during this time frame, which might enable enough cold advection for frozen precipitation in parts of the Great Lakes as well as northern NY and interior New England. Otherwise, another moderate/heavy rainfall episode appears likely for the Old South and the Atlantic Coastal Plain on November 16 - 17..
EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)
Kelvin Wave Enters Indonesia; Major Influence On North American Weather?
NOAA/CPC
INSAT
Many of you probably wonder why I frequently mention Kelvin waves in the longer term forecast discussions. These eastward-moving equatorial impulses are critical to weather prediction for a number of reasons. For one, these thermally-derived areas of disturbed weather can affect conditions over higher latitudes if and when the energy and moisture that accompany them is tapped by systems in the polar westerlies. Should a trough dig far enough south and equatorial convection is fed northward into a linkage with a shortwave, a "boost" effect is created which enables warm advection to reach far northern locations. So if a ridge complex forms in this manner, the downstream trough which forms to the right of said ridging will deliver colder air. That is why the "Pineapple Express" is cited as a forebear to important cold advection when the tropical teleconnection is delivered into Alaska and British Columbia. When the energy/moisture fetch aims at California, ridging generally will not penetrate the Arctic Circle. In such situations temperature forecasts above 35 N Latitude are often mild or warm.
Kelvin waves can also be critical to developing and maintaining +ENSO events. Three weeks ago we saw a rather vigorous perturbation move from Indonesia to the International dateline. Anomalous westerly wind flow and downwelling occurred, enabling the SST pattern to undergo prominent warming. The current strong wave complex over the Indian Ocean is slower to move, and is NOT connected to a higher latitude trough. Will this feature be like the last one, or follow the pattern seen in September and October (minoring out near the Philippines)? If you see reports in the next week or two of heavy rainfall in the Philippines, Indonesia and Malaysia, or maybe multiple tropical cyclone formation, then El Nino 2009-10 will strengthen yet again. Or, if the southwestern Pacific Ocean remains quiet and a cold wave enters the Orient from Siberia, it could be that a -EPO or +PNA ridge complex will form and a distinctly wintry period will envelop Canada and the U.S.
Blocking Signature Over Northern Canada Holds Key To U.S. Longer Term Forecast
Penn State University E-Wall
Environment Canada
This will be one of the tougher extended forecasts seen in years, due to the unusual 500MB configuration shown during an El Nino episode so far. The subtropical jet stream has not entered California, but has found a home in Mexico and the Gulf Coast into the westernmost Atlantic Ocean. If this southern branch windfield becomes re-oriented along 30 N Latitude (think CA....TX....GA....FL), then a mild winter will ensue. If, however, the STJ locks in and favors a storm track over or just below the Deep South and Eastern Seaboard, and a ridge complex straddles Hudson bay and Greenland, middle and late November is likely to be cold and stormy from the lower Great Plains through the Great Lakes and Atlantic Coastal Plain. As stated above, the GFS and GGEM packages strongly favor the latter option, while the ECMWF panels spell doom for lovers of winter weather. The NAEFS clustered ensemble prediction is no help here; notice that while Canada is quite warm, the entire U.S. is a vast shade of neutral!
From what I can gather, there will be a substantial intrusion of either IcA or cPk values into the eastern half of the country, starting November 18. Oddly enough, the Pacific Northwest will have weather more common to La Nina episodes: continued cold and wet with high elevation snows. It appears that a new storm could generate in the TX/OK Panhandle Region by November 23, as the first installment of a cold regime starts to slacken and move eastward.
The motto of this forecast: if you want a replay of 1976 or 2002, pray for that positive height anomaly to reach (at least) into Baffin Island. On the other hand, if you wish for 1991 or 1994 redux, hope that the ridge complex straddles a belt from BC and WA into the St. Lawrence Valley. As of now, I am leaning toward the "mixed bag" approach (1957, 1965, 1992; maybe a bit colder thn those winters) which straddles the two configurations.
Prepared by Meteorologist LARRY COSGROVE on
Saturday, November 7, 2009 at 5:25 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 2009 by Larry Cosgrove
Saturday, November 7, 2009 at 5:25 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 2009 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.
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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