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The Thaw Breaks

A. Camden Walker @ 2:02 AM

UPDATE 1:00pm - Flurries have now made inroads into downtown DC.  The back-building of clouds and instability behind the exiting low pressure system are fairly relentless this afternoon.  Look for mostly cloudy skies and flurries through mid-afternoon.  Temperatures will fall into the mid-30s, below 30 in the far N&W parts of the region.  Bundle up!

Forecast: FrioFriday

A brief respite from the relentless January Thaw. 42 degrees today for a high, can you believe it? With the pattern shift kicking into high-gear today, confidence can't be higher'Filtered sunshine should return around midday... and clearing could complete before sunset to allow full view of the sky. Look for 15mph wind out of the NNW behind the storm that last night passed to our South & East. Take the coat today, not just the windbreaker since we'll not be used to cold wind chills this morning.

This is the reason for our steady NE breezes today!

Graphic of the Northeast courtesy of Accuweather

How Appropriate We End on Z:
or not?

Shortwave Infrared of Zeta early on 1/6 *CLICK FOR LARGER VIEW*Despite severe shearing of Zeta's convection (especially on the East side), the final 2005 tropical system breathes ...still. Used to scratching their heads this season, The National Hurricane Center Tropical Prediction Center (NHC-TPC) is begrudgingly watching Zeta defy death with 40 mph winds-- remaining 1000 miles from any land. Zeta will likely succumb to the hostile environment (which has simultaneously provided enough lift and divergence in the atmosphere) before long dying down into a Remnant Low by this weekend. No major strengthening is forecast before this occurs, but the lovengevity of this Tropical Storm can't be forecasted with high confidence.

A "Remnant Low" is all that is left of a tropical system wherein a low-level atmospheric swirl is still visible; But, the system is devoid of any and all convection.  It is thought that these vortices produce little if any sustained wind pattern.  Zeta, however, still has convection associated with its evident, well-banded Low Pressure swirl.

The January Thaw: Indian Summer's evil twin

There are several angles to explore with this topic.  Socially, the meaning of "The January Thaw" portrays any warm period experienced in January.  Some people stick by the guideline that December had to be cold, or at least there had to have been a protracted, hard freeze prior to the perceived January warmth.  The January Thaw has similar debate surrounding it just as the usage of the term "Indian Summer" during the early- to mid-Autumn timeframe.  Sometimes Social and Meteorological conceptions do not match up.  Or, perhaps there is indeed data to support folklore?

Kevin Ambrose catches a Smithsonian Sunrise on The MallThere is some veracity that meteorological & climatological data can provide.  While neither the January Thaw nor Indian Summer comprise true meteorological singularities, they do provide labels for burps in clear, downward seasonal temperature trends.  They do not necessarily occur every year.  The atmosphere does not dictate that they must-- in fact with clear solar reduction in Winter, the atmosphere has a lot to overcome to produce mild temperatures. 

Climate records still solidly demonstrate downward trends with little visible quantitative evidence of Indian Summer or January Thaw rearing their heads enough to disrupt Climatological curves.  These two names help identify seasonal anomalies-- but how should we scientifically classify "calendaricities"? (Brier 1963)

It has been hypothesized to be associated with anomalies in atmospheric parameters such as sea-level pressure (Wahl 1952; Brier 1954; Lanzante and Harnack 1982; Kalnicky 1987), zonal and meridional indices (Duquet 1963), upper-level geopotential height (Dickson 1959; Duquet 1963; Lanzante 1983), and ocean wave directions on the East Coast (Hayden 1976). 

Again, it could be said, there is no yet-found physical mechanism--but the above ideas are fascinating.  Perhaps it is the lack of understanding and the timing during the coldest portion of some Winters that captures the fascination of meteorologists and soccermoms alike.  However, it appears likely that natural, harmonic fluctuations occur in the annual temperature patterns--as with the one we are seeing now.  In fact, with a "finite" climate record (Godfrey&Wilks 2001) of +/-150 years, do we really know what long-term behaviors are to be found?

In Washington D.C., by January 23, records indicate we expect to experience the coldest average temperatures in our Winter.  It has been observed that in this time frame of latter January, temperatures may maintain a +10 degrees above average (around 52 degrees F) for one week.  This in and of itself could be deemed The [quintessential] January Thaw.  Temperatures, which on-average are expected to slowly rise a couple of average degrees into February, instead make a marked jump.  Temperatures then resume their cold, seasonal state (as if rudely interrupted in some years) by February.

There is difficulty proving or disproving the January Thaw due to our limited data.  Humans naturally look at the environment around them and find patterns.  Yet with all the conflicting papers out there, and even our "limited" climate data (that has higher resolution than ice cores), the search continues.  Scientists try to classify January Thaw or Indian Summer as "anomalies" but they assume there are limits to what might be expected to occur by chance alone in a stationary climate during any random period.  January might actually behave in the way it currently is in 2006 OR it may be brutally cold except for the pronounced "thaw period" of January 23-26 OR neither of these. 

So, in conclusion, I am arguing for statistical variations in so far as timing, place, and length-of-thaw. I myself place a lot of credence in multi-decadal phenomena in climate or meteorological studies.  But I must admit our high-resolution data didn't really begin until the middle of the 18th Century, and that prevents hyper-evaluation of one week of time in the Pleistocene or even the current Holocene epoch of Geologic time.

Our current warm temperature trend is notable for its length.  However, our averaging 5 degrees above average is not quite in the Thaw category.  Nor have we had much in the way of cold in latter December or January thus far (until this current 48 hour period).  I have been satisfied that the more socially-used jargon of "January Thaw" hasn't been used with our present weather pattern--for now, meteorology and conversational lexicon do agree.

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