Monday, September 19, 2011

So that was summer
5:50 PM EDT 9/22/11 A summer-like sunset from Southeast Baltimore County taken last week, shown here to commemorate the final day of Summer 2011. The Autumnal Equinox arrives at 5:05 AM EDT Friday 9/23/11, and with it we expect a classic, cool early fall pattern to take us right into October. If you are part of a snow sports resort or a snow removal company, things might be looking up: A recent bump in Arctic Sea Ice extent, though on track for a near-record melt off, does show interesting signals for what may come in the winter ahead. 

Here we go again...Part Trois

5:30 PM EDT 9/22/2011 | With today as last full day of Summer 2011, Star Wars aficionados, upon seeing NOAA's latest 5-day precipitation projections, might be compelled to say "there is a great disturbance in the force." Is it  Tropical Storm Ophelia? Not yet, no worries there for at least another 5-6 days. But as Baltimore's ABC-2's Meteorologist Justin Berk reminds us, "the atmosphere has a 'memory' " and after all, don't bad things usually go in threes? (Let's hope it forgets about this whole idea outlined below)

The Eastern U.S. situation is simple, but troubling: If you experienced flooding rains in Hurricane Irene or Tropical Storm Lee, it might be wise to prepare for the third installment (but perhaps not last) installment of this prolonged heavy rain pattern. As outlined in the previous post, the atmospheric arrangement from the Northern Pacific, across North American and into the Atlantic has locked into a more fall- and winter-like "trough-ridge-trough" pattern. Evidence of this is clear on the precip projections: Virtually no precip in the west from now to Saturday, with all the action confined to places needing it the least... Eastern North Carolina, the Delmarva, New Jersey, Eastern Pennsylvania, New York and southern New England.  

SO WHAT GIVES? Why can't Mother Nature just donate all the rain to Texas and balance things out?  While that would be nice, the laws of physics are just not going to cooperate so amicably for you. The unfortunate possibility of the current pattern can be best summed up by the famous line from 1942's Casablanca: "Here's lookin' at you kid" (Youtube). For the foreseeable future (read: To Halloween), we think you'll be looking at weather headlines that sound  like a corrupted remix  (millennial version of broken record): Flooding rains in the Mid-Atlantic, Drought and wildfires in Texas, cold pre-season air in the Northern Plains, and near-tropical warmth in the Pacific Northwest. 

We think the causes of this pattern could include warmer-than-normal waters in Gulf of Mexico and along the Eastern seaboard, enhancing moisture transport along fronts, an active storm pattern in the Pacific locking in the trough and the return of La Nina in the equatorial central Pacific, locking in the southern U.S. high.  

Hey, for all the powderhounds out there, at least winter is still on the way, right?
(Forecaster Foot)

Here we go again?

12:30 PM EDT 9/19/2011 | On this day after the eighth anniversary of Hurricane Isabel's trek across the Carolinas and Mid-Atlantic, our Tropical Team is watching not only Tropical Storm Ophelia developing in the Eastern Atlantic... but also some mischievous atmospheric activity in the Pacific. Our Winter Stormcast Team recently released a preliminary statement on the expected trends and teleconnections we believe will be influential for the upcoming season (Facebook). If the future climate patterns of the next three months were a mystery to be unraveled, the atmosphere is about to deliver a significant set of clues on how the pattern may play out. While many focus on the Atlantic, the real driver of events this year has been changes in the Pacific, and specifically, a resurgent La Nina as reported by NOAA's Climate Prediction Center.  

SO WHAT'S GOING ON? The energy from two typhoons in the western Pacific are, over the next week to 10 days, expected to be absorbed into a strong cyclone in the of Alaska, as shown in this satellite image of the Northwest Pacific. NOAA's Hydrometeorological Prediction Center (HPC) is monitoring this possibility in their Preliminary Extended Forecast Discussion. The significance of this "synoptic" or large-scale atmospheric process cannot be understated:

1. The Gulf of Alaska Low, by ingesting energy from the Pacific systems, may "lock in place" the current pattern in place across much of the U.S.: A strong western ridge responsible for the late season warmth in the Pacific Northwest, little or no break from the drought in the southern U.S. and a persistent trough in the Eastern U.S. This arrangement would lead to continued dry conditions in places which don't need them, and a cool, rainy, wet pattern in places that don't THAT either. 

2. The potential long range implications: Although conditions are supposed to begin "cooling" with the approach of Fall,  amplification of the long range pattern could drive more chilly,damp weather into the Eastern U.S. sooner and longer than expected. This could throw off the usual step-down into traditional cool weather, making for a much colder and stormier early- to mid-October than we might expect. After all, it was less than one year ago, October 26-27, 2010 that a record Extratropical Cyclone across the Great Lakes (NOAA report) became so strong it was dubbed the equivalent of an "inland Category 3 hurricane" due to the historically low pressures observed.  We believe that system was an influential factor which may have led to the January 26, 2011 "snow monsoon" among other extreme events of the past year. 

3. What about the Atlantic tropical system?  Long range tropical forecasts are notoriously difficult to pinpoint with any precision. The best we can tell you at present is the Atlantic pattern suggests this system as shown in the Tropical Cyclone Guidance from Colorado State University, is a westward track for the next 5 days with slow development. After that, it is anyone's guess what clues the atmosphere will let us be privy to by for the next analysis. (Forecasters Foot, Long Range Coordinator Nic R. and the Long Range Team)