Wednesday, October 28, 2009

YOU HAVE 3 WEEKS


6:00 AM Friday, 10/30/09. [Supporting details added in conclusion] In continuing with our symposium on the upcoming winter pattern, this starts the second set of topics as outlined in the previous post (Part 2: Identifying the climate data ; Part 3: Laying out a storm projection calendar). For starters, we can ferret out some important FYI's for planning purposes:


1. HURRICANE RICK and the EARLY WINTER PATTERN: The Saturday 10/24 frontal passage, which delivered up to 1.5 inches of rain in a few hours across the Northeast I-95 corridor, was associated with remnants of once-Category 5 Hurricane Rick. Prior to making landfall along the Baja peninsula, Rick's maximum sustained winds were clocked at 180 mph for at least 12 hours, making this the strongest East Pacific Hurricane in 10 years. Why is that crucial to the winter forecast? I hypothesize that Rick's rapid intensification was driven by El Nino-influenced sea surface temperature anomalies SSTA's off the west Mexican coast. Both the hurricane and the system currently moving through the eastern U.S. featured rapid and expansive moisture transport from the eastern Pacific and Gulf of Mexico. There remain a multitude of other important climate influences driving the potential for a snowier winter in the Eastern US (including the Pacific Decadal Oscillation, the Quasi-Biennial Oscillation, among others.) Effect of those indicators will be outlined in greater detail within the next several weeks.


As other forecasters and weather outlets have suggested, an active southern storm track combined with a below-normal temperature regime for December across the Eastern US increases probability the Mid-Atlantic experiences several large, disruptive winter storms. My analysis of the pattern evolution suggests that Hurricane Rick's October 20-24 impact launched a second 6-week pattern (as outlined in the previous post), which would conclude by December 5. I propose that at least one significant snow event occurs in the Mid-Atlantic and by 12/5, ending a stormy pattern and transitioning to a long period period of below normal temperatures for most of December.


2. THE TEMPERATURE YO-YO: The chilly, rainy period from October 15-18, which made Baltimore's daytime highs of 43-45 seem more like December set in motion the temperature pattern which continues to play out. This was followed by the seasonal to above-normal temperature regime of October 19 to 23 prior to Hurricane Rick's rain. This out-of-balance temperature activity may also have contributed to the pattern shift which I believe will bring winter weather to the Eastern U.S. more quickly than we are accustomed. A recent time frame for comparison would be October to December 2002 as one example of long-duration unstable temperatures during a moderate El Nino in Autumn. What followed was a December 4 to March 1 period delivering 55 inches of snow to the Baltimore region.

CONCLUSION: I believe residents of the Mid-Atlantic region have 3 weeks to complete their usual winterizing preparations (notwithstanding central PA of course). Time is getting very short to finish remaining outdoor/summer cleanup, winterizing the home, switching out your clothes, getting your vehicle and transportation procedures in order. I project the region's first winter storm arrives anytime after mid-November (11/15) to early December (12/5). I also expect this event to be significant, drop a lot of snow quickly over a large area, and leave a long stretch of very cold weather in it's wake. For reference, this first event may bear similarity with three early season Mid-Atlantic storms: the Veteran's Day Storm of November 1987, the White Thanksgiving of 1989 or the December 1992 Appalachian Storm. The 1989 event was followed by a multi-week Arctic outbreak which set many eastern U.S. records for one of the coldest Decembers. Additional sources: 2000 AMS Online Journal article, Data table. In deference to meteorologists and weather-enthusiasts whom follow this site, it should be noted that reference to these three storms does not imply this year's winter pattern will resemble the year in which they occured. Those events are provided for climatological reference for readers looking for comparison of current ideas with previous events. With a moderate-to-strengthening El Nino and an already active subtropical jet, Mother Nature is giving us a clear heads up that the game is about to begin. Is your team ready?


Note to new readers: This site is operated as an on-going symposium where teachers, meteorologists, snow enthusiasts, students and parents alike share or compare ideas on the analyses presented. Your input, for or against, is welcome anytime in the comment section below.

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