Monday, January 31, 2005

FEBRUARY WILL ROCK...AND STORMS ARE GONNA ROLL

MONDAY EVENING UPDATE: BIG CHANGES ON HORIZON FOR THE NORTHEAST
Next post Tuesday morning about 6:30 AM

Based on your comments from Monday, which I can't read at school, many of you have picked up on the 180-reverse course-about face-egg in your face change in NWS forecasts today. The computer models are all haywire on this system, hence the consternation in forecasting. As for the big warmup? Yeah, okay...whatever. I don't mind above normal temps in early February, because it is like waving a red flag at a hungry bull in heat inside a china closet. Whatever warmup was on the table for late this week is now gone, as Baltimore NWS has..surprise! Chance of Rain and Snow, high 41 for Friday. Either way, you have to agree that restricting Arctic air in Canada for an entire week in the dead middle of winter can only mean that once it is unleashed again, the retaliation will be swift and powerful.

This has happened several times this winter already, and gives my forecast even more impetus. The storms we've had thus far were only salvos across your bow, pipsqueaks compared to what I think is on the horizon. Granted the folks in the Deep South don't think the 3/4 inch ice in Atlanta was pipsqueaky, but winter is far from done. Groundhog Phil WILL see his shadow Tuesday, and you are in for a wild ride the next 3 weeks.

Now that we are going back into "Storm Mode" I will focus attention the rest of this week on our developing winter storm situations for the Mid-Atlantic and New England.

1. BASIC FORECAST: A SERIES OF STORMS FOR FIRST 15 DAYS OF FEBRUARY.

Storm 2 : Eastern New England, Thu night-Friday. This system is really just an older version of Storm 1 that just exited the coast Sunday. It is becoming clear from a multitude of models, especially the GFS, that a re-energized version of Storm 1 will retrograde toward New England on Thursday and has the potential to deliver a roughly 3-6" in downeast Maine, and 2-4" in Eastern Massachusetts, with up to 6 inches along the Cape. nUThis will be in combination with very gusty winds and heavy wave action as you'll have a strong northerly fetch across the Gulf of Maine. This is clearly indicated on the current QPF for that time period. Why is this happening? The negative NAO, blocking in the North Atlantic due to a westward expansion of the Icelandic Low prevents storms from heading merrily out to sea. Read this simple explanantion of the North Atlantic Oscillation.

Storm 3A : Gulf/Southeast, Tue-Thu. is a system in the desert southwest and crossing Texas as of Monday night into Tuesday. There could be wet snow and freezing rain across Arkansas, Tennessee, North Georgia and NC Mountains early Tuesday morning and late Tuesday night. The Raleigh, NC Forecast Office wins the big prize for being first out of the gates with a Special Weather Statement on this system. The latest QPF (Quantitative Precipitation Forecast) shows considerable moisture as you would expect from a Gulf system. The current NAM (North American Model) shows the rain/snow line with this system by Wednesday running from eastern Tennessee to southern Virginia, so it seems plausible those areas would have an early morning snow and rain mix Thursday. This system SHOULD go out to sea near the Carolinas, right? Not so fast.

In the face of a strongly negative NAO, this beast has the potential to stall, and then spawn a secondary Low which may try to turn up the coast late this week. Meanwhile, the monkey wrench in all of this is retrograding Storm 2 heading to New England Thursday. Remember air moves counter-clockwise around a Low Pressure. The wrap-around warm air coming on the backside of Storm 2 will clash with low-level cold air over eastern New England, producing moderate snows accumulating no more than 6” in any one location. So the wrap-around moisture from Storm 2 will continue to stream southward after snowing in Mass and Rhode Island. Concurrently, a strong trough is forecast to develop over the Mid-Atlantic at upper levels. When surface moisture is injected into a developing trough, it usually spawns a new Low pressure system, which I will name Storm 3B. The only wrinkle is what effect the cooler than normal water would have on this developing Low.

Storm 3B : Mid Atlantic, Friday. This system should begin to form sometime Thursday night near the Virginia Capes. At the same time, we have moisture streaming northeastward ahead of Storm 3A. The formation of Storm 3B will absorb moisture from 3A, helping to intensify it under the trough. Now this system has TWO sources, one is warm moist air from the southeast, the other is moderated moist air from the northeast. Link all this up with an arriving High pressure from Canada, and you have the makings of a surprise late week snowstorm for the Mid-Atlantic from DC to Boston. I know it sounds very complicated. If you think I am making this up for ratings sake, check the Japanese Model (JMA) which I will put online in my links column.

The scary part is that I pretty much made up this idea today as a “what if” brainstorm, while I was trying to figure how Storm 2 and 3 would interact if they go close enough to each other. Then I learned after the fact from other discussions that I have learned from other discussions that the JMA this model has been depicting just such a scenario for sometime now.

So what we have is a BLUE BANDWAGON ALERT, I think many forecasters along the East Coast from Norfolk to Boston will find themselves hastily revising their predictions for the Thursday-Sunday period. Looks like they already started. I’ve already begun to see this reflected in the Thursday-Friday forecasts for Philly, NYC and Boston. The JMA is printing out up to .75 liquid for the Mid-Atlantic from Virginia up to southern New England. (Also need to issue a Bass-O-Meter alert to find out how much himming and hawing Marty Bass will do in Baltimore over this storm.)

The Forecast Discussions put out by Boston NWS Office are the most objective and forward-thinking of any NWS office on the East Coast. This one in particular is worth your time reading. Although I originally said Storm 3 would not turn into a Nor’easter, I now have to change my tune and make the bold call that you can kiss goodbye the 40’s on Friday, for it might actually be snowing in DC, Baltimore and Philly instead. This system is going to make forecasters very nervous this week as computer models will waffle quite a bit on this until they can resolve the energy differences between retrograding Storm 2 and the encroaching Storm 3. Will we see forecasts creep toward precip this week for the Mid-Atlantic?

Big Warmup Alert: The 48 degrees advertised by TWC for Friday in Baltimore is now 41. Wonder where the big warmup went? Hmmmm.

Storm 4 : Feb 8-10, Northeast U.S. This has been advertised on some of the computer models now for a couple days. As of Monday morning, it appears to be two separate systems. One looks to be in the February 8-10 period, and the other February 12-14 period. Either of these could become the BIG KAHUNA... like a 2005 version of the March 1993 Storm of the Century. As you would expect, there will be all kinds of model meandering over the next 2 weeks with this. I can be confident of this forecast because of the plethora of scientific data available that points to one or two very significant winter storm events brewing for February.

HOW SIGNIFICANT? Oh you had to ask... well it's your run-of-the-mill paralyzing coastal snowstorm for the Northeast... 12-24" in the major cities, airports shut down, that kind of thing, nothing you can't handle. This description is called reverse hyping. We know it will be big, so we're downplaying it's big-ness now to compensate for all the real hype later.

2. ANALYSIS BEHIND THE FORECAST
The time period from February 7 to 20 is going to be a powderhound's dreamworld, because the atmospheric signals are all beginning to align in the way we observed inJanuary 2003, which ultimately led to the legendary Blizzard of 2003. My forecasts are based on my interpretation of the models, a consideration of how NWS and Accuweather Forecasters are reading them, my study of how similar situations and storms developed, as well as my experience and intuition over the past 20 years in forecasting big winter storms.
The two graphics at top are from Accuweather, and the ones on the bottom from NOAA's Climate and Meteo Centers.

A. The North Atlantic Oscillation. Look carefully at the charts on the lower left. I apologize for them being hard to read, but just take a closer look. You will notice little black dots along the O base line. I placed these dots there to show that in the case of the January 22-23 Blizzard, the NAO immediately flipped to negative right before the storm. This is why I had a sixth sense it was coming farther north, and hence called it a Blizzard before that idea went public.

If you look to the right of the first big NAO chart, there are two smaller charts. The top smaller chart is the NAO archive for Winter 02-03. I have 5 small dots placed where major snow or cold events occured in the Mid-Atlantic and Northeast, all right around the time period when the NAO either flipped to negative, or trended back to neutral, then retreated strongly negative again. The best case for this setup was the February 2003 Blizzard. The NAO after being mostly positive the first 10 days of that month, did a quick reversal around the 15th, a day before forecasters caught on to what had been up to that point a very hard storm to peg. And everyone but Accuweather was howling that this puppy would go south, sure thing it did, huh York County?

For big nor'easters, the NAO is quite simply, the fingerprints on the smoking gun. It gives you a heads up about 2 days before a major event, or an unanticipated shift in the pattern. Any meteorologist, or member of the general public, can easily find and read the NAO chart on the NOAA websites. So if you consider where the NOAA computer ensembles are taking the index for the next 14 days, you can see why Accuweather has the cold and stormy forecast they do. Look at the general trend..heading toward strongly negative as the month progresses. As of Monday afternoon, it has resumed a much stronger negative signal. This can only mean a return to much below normal temperatures for the Northeast throughout February.

B. Water Temperature Analysis
I have visited this topic several times since October, and it is worth refreshing. The key to our weather this winter has been where the above and below normal water temperatures are located.

Below Normal: Off U.S. Southeast coast, Florida and Pacific Northwest. This lends stability to the High pressure ridge already in place, as the cooler than normal water allows sinking air above it, continually re-strengthening the High. The placement of that high helps send southern stream storms up toward the Northeast. Notice how Storm #1 trended more NE than ENE like computer models predicted? Cool water off the Pacific Northwest tends to lend stability to the ridge parked over the Rockies. This forces the northern branch of the jet stream (the northern stream) up over the western U.S., and the negative NAO signal with the blocking Icelandic Low and Greenland High FORCE the northern stream southeast across the Great Lakes and into the Northeast. The cool water adjacent to the East Coast is also a very good sign, for it was the reason our High pressure this weekend was so stubborn in leaving. The cooling, sinking air over the water tends to stabilize the pressure, keeping the High in place.

Above normal: Large patches of 4-6 C water off New England coast, 1-2 deg C water in Gulf of Mexico and extending southwest into the Pacific tropics from the west Mexico coast. That is the El Nino signal, for it keeps the southern jet stream continually fed with moisture as it traverses across Mexico, and into the Gulf.

The correlation? The confluence of all these events has to come together in the right orientation to get a big East Coast snowstorm. At present, it sure looks like everything is starting to dance according to the music. Later this week, the blocking signal from the NAO will send the northern stream southeast, just in time for the southern stream to get squeezed north by the Atlantic ridge. Where the two streams meet will be above normal water in the Northwest Atlantic, and cooler water just to it’s southwestern flank. That cooler water allows cold Arctic highs to set up show right along the coast. When the two streams meet, or PHASE over that water and in this atmospheric orientation I have described, you have the Perfect Storm(s). We had a very similar setup in February 2003… a warm start to the month, followed by a surprise snowstorm on the 6th, then a second but shorter quiet period leading up to the BIG KAHUNA which began on the 14th and continued until the 17th.

So when is this BIG KAHUNA? I think the time frame looks to be February 8-10, when all the elements will be in place for something very very big to happen along the East Coast. When this occurs, I’m sure that the A.P.P.L.E. will be brightly beaming with pride. (That’s an special, exclusive branch of the powderhound association, kind of like the Red Hat Society. Membership is given only to those with three full cans of snowblower gas, 32:1 mix.

3. THE PHILOSOPHY BEHIND THE ANALYSIS
Sometime Tuesday or Wednesday, for now we will focus on the evolution of Storm 2 and 3A/3B.

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