Compendium of recent questions posed by clients, with answers:

WEATHER FAQ BEFORE DECEMBER COMMENCES

Q: I heard that the pending early-December cold will eventually moderate?

A: That is not a forecast as much as it is obvious logic. Nothing lasts forever, and cold waves ebb & flow, build back up in Canada and cycle down into the U.S. This volatility will be particularly pronounced this year, but the net results and net temperatures and net monthly HDD's will be anomalously colder in the populated Northern U.S. than people realize. Even the coldest Winters ever in history had numerous mild days, several mild weeks and even a mild month thrown in there as well. So don't let inherent climate fluctuations throw off your expectations for a Winter Month or the Winter Season as a whole.

Q: Why do forecast services now seem more bearish about December/Winter Cold than they were about November/Autumn Cool?

A: When the Summer Heat and Hurricane Season winds down, people's attention shifts to the upcoming Winter. As far as large National CDD or HDD totals, the Autumn can be quite benign, so short-term forecasters can become bored, antsy, or anxious for Winter. And what better way to garner headlines on a 64°F Halloween day, than to discuss major Polar Air invasions? But when a truly Wintery November (the likes of 2000, 1997 or 1995) does NOT materialize, and on the other side of the table you have a stance for a Warm Winter, something has to give. So one of two things was going to happen towards late-November: Either forecast services try to downplay December Cold (as their Winter Outlooks would then begin to be questioned), or they acknowledge Winter's arrival and substantially revise their Winter forecasts issued earlier in the Autumn.

We emphasized this disparity (or spread) between forecast service rhetoric Vs. meteorological reality, with the following summation as a guide, since psychology can often be as powerful as Mother Nature:

* Autumn, October - November 2007: Net results will be much milder than colder-themed models/outlooks insinuate.

* Winter, December 2007 - April 2008: Net results much colder (in the North) than warmer-themed models/outlooks insinuate.

Q: What psychological references might be used to spin the perception of a month in one direction or another?

A: For services rooting for a Warm Winter: eliciting memories December 2005 (starting off frigid and then fizzling), or mild Southern weather, or the fact that energy supplies are so high, will get people to overlook any cold occurrences in the North. For services rooting for a Cold Winter: eliciting memories of the most recent La Niña conditions in 2000, or the fact that December 2006 was so warm in comparison, will get people to pay attention to any cold occurrences in the North.

They will often use individual model runs as their ammunition, but as outlined in the next response, you can anticipate some of these "moves" before they make them.....

Q: I realize the short-falls and capriciousness of computer models, but considering they influence people, are there any useful tips or tricks?

A: The following pointers should help you navigate your own use of models or to help anticipate what others might say:

* During the Autumn, you will often see services go colder in their medium-range opinions during the morning (as the 00-Z model runs algorithms use an older climatological reference-set), and then they "pull-back" or "retreat" their medium-range opinions when they emulate the 12-Z model runs. Later in the Winter, this morning-to-midday 'switcheroo', will tend to go in the other direction.

* For better or worse, if you are impacted by computer models, know that both the transient patterns (like now) as well as the more amplified blocked regimes, are typically best quantified and qualified by the European [ECMWF] model suite.

* Debating model predictions 7 days out is fair game, as is the 8-14 day period, but maps/projections of individual days beyond 300 hours is pure Chaos Theory and should never be referenced by a scientist.

* 06-Z and 18-Z model run times do not include the valuable input of upper-air data from Balloon launches, so these typically have some of the more bizarre and erroneous predictions and are best relegated to storm track expectations within 3-5 days.

* While Lake-Effect snows, Up-Slope Rockies snows and Clippers, etc. might illicit minimal interest in November, it becomes an increasingly bigger topic this Season and snag for computer models. Soil moisture and surface heat fluxes are poorly handled by computer models so considering snow-pack (latent heat of Sublimation in 2,833 Joules/gram) extracts 13% more energy from the lower atmosphere than even wet ground (latent heat of Evaporation is 2,500 Joules/gram), you end up with a huge hemispheric parameter force largely ignored. {Correspondingly, Northern regions with abnormally minimal or absent snow-pack will tend to not chill off as much as model expectations, particularly at night.}

Q: I've generally seen nothing but warm Winter Outlooks from NOAA and Weather Services; will there be any surprises?

A: It is true that since the Summer and through most of the Autumn, NOAA and all mainstream forecasting firms had predicted a warm (to very warm) Winter Season this year. In fact, the NOAA/CPC Climate Outlooks have not predicted Below Normal Temperatures for any State or Region, for any month, all the way through 2008! Now, on the eve of the Winter Season with colder air in sight, some services may begin to back-peddle and revise their outlooks colder.

While we do anticipate mild conditions for much of the Southern U.S., our research conversely has always believed there will be cold weather propensity for Northern States extending from the Pacific to the Atlantic (oscillating westward and eastward throughout the Winter). Not only will several States end up with a Cold Winter [December-March], but some of the corresponding monthly HDD tallies across the Mid-West/North-Central, could be the largest this region has seen since last Decade.

Q: Why are all the prevailing outlooks so similar to each other?

A: Forecast services heavily rely on computer models, but model output only extends out 15 Days. So when it comes to monthly and seasonal predictions, they don't like to stray too far from NOAA maps. In the past 3 years, NOAA began issuing a 30-Day update map on the last day of every month, so on November 30th they will probably include their very first forecast of Below Normal temperatures in their December outlook. It will be curious to see if services then follow suit and revise their December thoughts colder.

Q: Is La Niña and La Niña composites all we need to know?

A: La Niña and El Niño are complex phenomena, but have also become whittled down to handy buzz words; and lumping a few of these recent ENSO Events together makes for convenient composites, but it is far from the full picture. Forecast services' practice of grouping recent ENSO (El Niño) events together led to disastrous results in 2002 when their composite indicated very warm Winter signals for the Northeast, and New England went on in 2002-2003 to have one of their largest HDD totals in the past Century.

The timing, intensity, and interaction of ENSO Events with various Teleconnections and Hemispheric Oscillations can lead to a wide range of weather scenarios which is tedious to analyze, but all part of climate science.

Q: So what exactly is going on with the 2007-2008 La Niña Event?

A: Forecast services unfamiliar with climate science often get mislead by the weekly fluctuations in Sea Surface Temperatures Anomalies (where ENSO events are measured), or they will miss the forest for the trees by comparing large anomalies early in the Event to the same month in history. Back in the Summer, this lead some services to declare that "La Niña was unlikely to develop this year", only to over-compensate by recently stating that this is one of the strongest La Niña Events of all time.

The fact of the matter is, is that the 2007-2008 La Niña Event has been developing, strengthening and intensifying precisely on schedule since this Summer. Proper analysis of multi-month running SSTA averages and the ONI value indicate that the 2007-2008 Event is the first true La Niña episode since the 1990's, and while it may have been stronger in October than other events in October, it still has a long way to go to become even one of the Top-5 strongest La Niña's of the 12 officially documented La Niña's since 1950.

Q: I sometimes hear forecast services throw out climate acronyms; how do I know if they are legitimate or being properly referenced?

A: There are indeed numerous Teleconnections and Hemispheric Oscillations that are instrumental in seasonal climate prediction, any they vary based on the time of year, their interaction with each other, and the weather impact in question. Unfortunately a lot of these terms have been bandied about as if they were randomly plucked from a text book, which confuses the user and hurts the science.

If you have questions about a particular climate term being tossed around (NAO, AO, AAO, PNA, EPO, WPO, PE, SCAND, PDO, MJO, QBO, etc.) we'd be pleased to set the academic record straight on how it works, and what it does and does not actually do.