Saturday, March 5, 2005

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HEY NOW, HEY NOW...DON'T DREAM IT'S OVER

HEADING INTO THE WEEKEND, THERE IS MUCH TO TALK ABOUT AS THE ATMOSPHERE IS ALIGNING ITSELF FOR ANOTHER PERIOD OF COLD AND STORMY WEATHER NEXT WEEK AND BEYOND. The first in a long series of clippers will dash across the Southern Mid-Atlantic on today delivering 1-3" of snow in higher elevations from western PA to western MD to the Virginia mountains. Beyond that things get very interesting, and I have updated the Storm Analysis and Week Ahead Sections below. I will be away skiing today so no updates until later tonight. I am very sorry however that I cannot seem to get my graphics on line. This is the second day it has happened and I have no idea why. I am using Picasa/Hello as my image upload programs, so if you have any advice on this, please let me know.

FIRST, JUST THE WEATHER

SATURDAY: This clipper has changed it's tune as you notice I am doing also. The GFS WAS right in that it would head farther south, in fact VERY much farther south...to the Carolinas. As you can plainly see on TWC, there is no high pressure system nearby thus the reason you see hardly any snow at all on the map. Snowfall will be limited to higher elevations, and a dusting to 1" at best.

SUNDAY: A welcome respite from the cold as west-southwest winds in advance of the next cold front sweep in much warmer air. Highs near 50 south of Philly, in the 40's north.

MONDAY: that cold front and accompanying system approaching the Great Lakes will continue to surge warm air on the heels of southwest winds across the Northeast. Temperatures could actually crack ABOVE normal for a day. For example DC is normally 54 by now, and could see 60. Baltimore is normally 52, and will push into the upper 50's. It will be a delightful two day period during which I hope the plants in our school's greenhouse can get recharged from the warmth and sunlight. Showers are expected late in the day as the front sweeps to the coast.

TUESDAY: Now it gets interesting. The second in a long series of clippers heads for the coast, and moisture left behind the front clashes with a new surge of cold air coming SE from the nearby polar vortex in Ontario and Quebec. I notice over the past few days that the Tuesday forecast has been jumping all over the place, from rain to cloudy to now rain/snow showers. It is a good bet that the reintroduction of fresh cold air will turn anything left over behind that front to snow. However warm roads and ground surfaces will limit or negate any accumulation.

WEDNESDAY: Proverbial calm before the storm. The third clipper coming east from the southern Lakes is being depicted by a variety of computer models as intensifying as is revolves around the south side of the Polar Vortex. This is known as "surface reflection" of the upper level Low. This storm will undoubtedly be the first of several that may make a permanent mark in your memory as one of the great March snowstorms of the past 10 years or so. If not, it only raises the stakes for the next system

THURSDAY-FRIDAY: This is the current timeframe targeted for development and impact of Kahuna 3, as indicated on this site almost a week ago. This system will likely be the Coastal version of the Wednesday system, arriving in the evening, and lasting into Thursday. Cold air having recharged behind the Tuesday system will allow for snow to quickly break out along the I-95 corridor. Liquid equivalents being pegged for this event are .75 – 1.25 for the major cities. With a snow ratio of 10 to perhaps 15:1…the potential exists for 12 to 18 inches to fall out of the SKY. The difference between our last big storm is that there much colder air is expected to accompany this storm, so snowfall rates will be higher. However sun angle and warmer road and ground surfaces may negate 3-4 inches or more. What would appear to be a 12-18 inch storm may be cut down to an 6-12 inch storm. Temperatures on Wednesday 3/9 will start out mild, but will head lower as the cold air encroaches.

Remember the March 1993 Blizzard occurred on 3/12-13, and despite higher sun angle and several days of 50 F in advance of the storm, every major city from Atlanta, GA to Portland, ME got many many inches of snow, ON THE ROADS. While that scenario is unlikely in this particular storm, it does serve to remain naysayers that March can produce BIG TIME snow in a short period of time.

WHAT EFFECT WILL THIS HAVE ON THE MONTH IN GENERAL? This over-abundance of cold which should have been spent in December, January and February is now being worked out of the system. Hence the statement, "Welcome Back to January." I would not expect a consistent return to normal temperatures until at least the weekend AFTER St. Patty’s Day. But I do think March will follow it’s traditional route… in like a lion, out like a lamb. It is not impossible to see much-above normal temperatures by Easter, maybe 70 F? Maybe 80 F ? It has happened before, and this March I believe will go to the extremes for both sides of the aisle. As for the rest of spring and into summer, a overly cold March would argue for a warmer April, a cooler May, and a warmer June according to the theory I use for how the months see-saw the variables until temperature anomalies balance out.

ANALYSIS OF THIS PATTERN

Our last big storm from Monday the 28th pumped heat northeast into the combined double barrel air flow of Labrador Low and Azores High near Greenland. This warm air enhances both systems, creating a continous stream of air flow into far northeast Canada. When this warm air intrudes into higher latitudes, it has the logical effect of redirecting the polar vortex usually located much farther north down into in SE Canada or even over the Northeast US. When that happens, the vortex often gets "locked in" as shown by the Accuweather graphics in the previous post. This is why we have observed Negative NAO values as low as they have been in the past 50 years. As shown on my graphics, the PNA is already heading for the stratosphere, and forecasters at HPC as well as those from Baltimore to Boston are becoming noticeably concerned in their discussions that the -NAO and +PNA setup cannot go on much longer without a major phasing event on the East Coast.

Now think about the downstream consequences. Each subsequent Low pressure system which passes on by uses it’s counterclockwise motion to enhance the double barrel effect which puts increasing pressure on the 500 mb Polar Vortex swirling about. Meanwhile a strong west coast ridge forces the split jet stream to ridge up over the Rockies and Canadian Coast Range and into far northwestern Canada. A Low pressure system off the California coast, and a sharply digging trough in the Gulf of Alaska helps lock this pattern in place as these two work in conjunction with a persistent high over the Rockies to continue directing the Pacific Polar Jet northeast. Any cold air lurking way up there in the Northwest Territories can also be tapped, as well as create the setup necessary to even have "cross polar flow" from Siberia. The polar jet then comes charging southeast across Canada, approaches the vortex in Quebec, and that continues to direct the jet south and underneath it...right across the Northeast U.S. This setup will continue to rule our weather for at least the next 7-10 days if not longer.

There are about 4-5 distinct clipper type systems on the map, lined up clear out into the Pacific that will follow the Polar Jet according to the setup described in the previous paragraph. Any one or more of these systems has the potential to become a major Northeast snowmaker over the next 10 days.

I believe the “front runner” low on Tuesday is going to be little boy who pulls his finger out of the dam, allowing the Polar Vortex air to come charging in behind that system right into the face of the newly energized southern stream riding along the southwest winds ahead of the front runner cold front. The Tuesday storm is not going to be the major event, but rather will deal the cards onto the table that the Thursday-Friday system is going to play. You would have to agree that many, many of the best possible cards are already on the table, the Queen of Spades is safely buried at the bottom of the down pile, and the game is about to get real fun real soon.




WELCOME BACK TO JANUARY

Water break during Thursday afternoon lacrosse practice in Dundalk, MD

Conditions: Winds northwest at 15-25 mph. Wind chill 25 F.