Upcoming Winter May Prove Difficult With Strains On Energy

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The Operative Words Are "ACTIVE" And "COLD"; Upcoming Winter May Prove Difficult With Strains On Energy And Transportation, As Arctic Intrusions, North Atlantic Oscillation, And Vigorous Southern Branch Storm Track Combine For Harsh Conditions Along Southern And Eastern Tiers Of The U.S.

Prepared by Meteorologist LARRY COSGROVE on
October 31, 2005 at 4:05 A.M. ET

http://www.easternuswx.com/bb/index.php?showtopic=62640

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Interesting comments by Larry Cosgrove

MEDIUM RANGE OUTLOOK
(weather trends through the next 6 to 10 days)

Judging from comments I read on message boards and in emails sent to me, I suspect that many weather enthusiasts are having a hard time dealing with the reality of a very warm November in much of the U.S. I do not suspect the current 500MB longwave pattern will change sufficiently during the next two weeks, so more irritation for expectant snow hounds seems assured. But before you go writing off the chances for a cold and snowy winter, best to review the synoptic situation across the continent. Which, in truth, seems even more dire for energy consumers in much of the nation, and Canada, beginning about a month from now.

First of all, there is an abundance, prematurely, of cAk values in AK and to some degree in Canada. Various computer models build the persistent cAk+mA vortex near Kodiak Island AK to a 500MB core of 499dcm, complimenting another gyre over the far northern Atlantic Ocean which may deepen to 493dcm at midlevels today. Energy ejecting out of the Gulf of Alaska storm complex will pulsate three times, with the first two shortwaves deepening into cyclones that will take strong winds through the Great Lakes into QC and NL while spreading showers and thunderstorms through the Ohio and Tennessee Valleys into the Northeast. the first low should reach the NL/LBR shoreline on Monday. The second and probably stronger, low center may take a "Panhandle Hook" route toward James Bay, itself deepening into a cA motherlode with more unseasonably cold values from the Prairie provinces into the Laurentian Shield. Interestingly, neither disturbance will dislodge the heat ridge positioned over FL and the eastern Gulf of Mexico. So while communities along and north of the International Border turn chilly, an area stretching from OK and TX into southern New England will see mild air or only brief incursions of cP readings.

The third impulse in the sequence looks to carve a different path: into CA and NV before settling over the Sonoran Desert for a few days. If you think that you have seen such a storm track before, it is because a similar scenario has unfolded four times since late September. In each of the previous cases, the energy minored out into the Great Plains when the vortex to its north and west charged eastward. I suspect that the low and its parent closed low will operate the same way, bringing rain and thunder to parts of the lower Great Plains after the 168 hour time period. Despite the obviously semizonal appearance of the jet stream configuration in mean presentations to 240 hours, it seems probable that some buckling of the upper flow will get underway around November 14, with the effects (colder air in the Midwest and Great Plains) being felt after that date.

But just think what happens in later December and January, when the (by then) far deeper and stronger upper low drifts into the Intermountain Region, then towards the Midwest....

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Forecast and Analysis by Met Larry Cosgrove


The "All-Inclusive" Forecast Next 24 Hours: Near-Blizzard Conditions; Heavy Rain; Severe Weather Outbreak; Strong Winds (Oh, And Don't Forget The "Santa Ana" And Tropical Threats, Either!)

WEATHER SUMMARY THROUGH NEXT 72 HOURS

Although the current weather forecast period seems more like a disaster movie than a prognostication, the truth of the matter is that some very bizarre happenings are underway in the realm of North American meteorology. The most prominent player on the scene is the rapidly deepening low over the central Great Plains, ticketed to rocket into James Bay by Wednesday evening. As I stated yesterday, many will be watching this feature closely to see how much snow (with wind and cold) develop to the left of the storm track. But this sells the spectacular cyclone very short; ultimately, many more people will be affected by problems within the warm and overrunning sectors of the low. And it is the threat of severe thunderstorms, torrential rainfall, and strong winds (whipped up by the astounding pressure gradient between a 1042MB anticyclone and the 972MB low center) that will be on our minds for the next 24-48 hours.

We can probably break down this system into two concerns: winter weather and convective. On the "cold" side of the low, moderate to heavy snowfall is likely along and about 250 miles either side of a line from Omaha NE to Kenora ON. Interactions between the incoming cAk regime and the developing low will increase threats in south central Canada, while the near-blizzard that erupts in the Upper Midwest will be a function of the neutral-tilt 500MB low closing off and accelerating north-northeastward. Most of the NWP schemes depict an inverted trough just to the left of the center of lowest pressure, which would enhance forcing and lifting in parts of IA, MN, and eventually NW WI and W ON. An interesting side effect with the snowfall will be the howling winds, worthy of some of the worst storms of January. This will be the first meaningful snow episode of the season in the Minneapolis-St. Paul and Duluth MN metro areas.

Now on to the thunderstorm potential. In a word, vast! Consider that Arctic values are pushing out a warm, unstable (mT) layer from TX into S ON and NY. With the sharp PVA gradient and high UVV display present, there will be a threat for a diverse array of heavy to severe thunderstorms, individually accompanied by tornadoes, microbursts, large hail, and of course heavy rainfall. Instability may appear marginal in panels of the NAM and GFS schemes, but the extreme upper dynamic parameters will allow for supercell and bow echo formation. Even though the vorticity and thermal measures will weaken somewhat on Wednesday, cumulonimbi will trigger heavy rainfall along the Atlantic coastal Plain with some transport of strong winds aloft down to the surface. By tomorrow evening, colder readings should reach as far south as Brownsville TX and into C FL, where the temperature boundary may stall out by becoming parallel to a weakening upper flow.

The rapid intrusion of Arctic air into the High Plains will have a side effect across parts of the Desert and Intermountain Regions. With pressures increasing to the right of the Continental Divide, downslope flow will accelerate and be prone to channeling through local orography. This means that a ferocious "Santa Ana" wind will scour through the southwestern U.S., bringing warm, dry, but often dust/sand laden conditions below the Salt Lake Valley. The building 500MB ridge should push incoming shortwaves from the Gulf of Alaska into BC and AB, keeping WA and OR out of gales and heavy precipitation while inundating the Canadian side with awful weather.

MEDIUM RANGE OUTLOOK
(weather trends through the next 6 to 10 days)

I have to admit that there are some intriguing possibilities with regard to apparent weather, late in the medium range. You may recall that the previous runs of the GGEM scheme suggested an interaction of a 500MB trough (closing off in the Southeast) with the tropical cyclone (TD 27) over the Caribbean Sea. Now the latest run of the Canadian version has backed off of that idea somewhat, the 0z Nov 15 ECMWF has stepped up to the plate to endorse such a scenario! The upper trough complex appears stronger and colder over the eastern states, with a neutral-tilt disturbance phasing with the warm-core feature to create a Nor'easter (of sorts; perhaps a surface low moving up the coastline just to the left of shore) during the 144-192 hour time frame. Since the European equation is an outlier in the mix (which, oddly, has occurred a fair amount of times since late August), I will be careful not endorse it just yet. However, the possibility for a coastal low with tropical elements involved seems to be increasing as of now.

Another potential issue to take about is the fate of the PNA-styled ridge over the western states. While this anticyclone is NOT a blocking feature, its presence and potential sharpening along a 105 W Longitude axis COULD aid in renewing cold advection into the states to the right of the Rocky Mountains next week. The 0z Nov 15 GFS and GGEM versions endorse this change; even though the bitter cAk realm stays in northern Canada, readings from the Mississippi Valley into the Appalachian Mountains on Days 7 and 8 are decidedly chilly. Should an NAO-styled block take shape by November 25 (which would only happen if the ECMWF version verifies in creating a vigorous coastal storm), then it will feel like winter in the eastern half of the nation.

But it is best to wait a while to see just how amplified the jet stream becomes on the upcoming numerical model runs.

TROPICAL WEATHER OUTLOOK
(systems to watch in the lower latitudes in and near North America)

Tropical Depression 27 has been struggling with vertical wind shear, associated with the weakening IcP/mTw frontal structure that cuts across the central Atlantic Ocean. A prominent heat ridge will take shape over the Sargasso Sea within the next day or so. This positive height anomaly will steer the depression westward while aiding in convective outflow. later in the forecast period (around this weekend), the storm may be nearing hurricane status and advancing toward western Cuba. If so, the prospect for linkage or phasing with a trough complex across the eastern half of the U.S. (seen by the latest run of the ECMWF forecast) cannot be ignored.