US Weather Commentary Location: New York Author: Weather 2000, Inc Date: Friday, February 8, 2008 Hemispheric Teleconnections realigning to tweak North American pattern..... Bottom-line U.S. impacts you'll notice as a 'change' when we proceed deeper into February 2008, include: * Milder Southwestern quadrant of Nation than experienced past several weeks. * New England and Mid-Atlantic to participate more in Midwest Polar Waves (a la December 2007). For those who care about some of the technical footnotes behind the upcoming patterns: * Solid La Niña (and not for the reasons circulating), North American snow-pack (>51 percent coverage), as well as the AO, TNH and WP patterns. This of course downplays the MJO, NAO and EP patterns others have been referencing. Comments on recent Volcanic Eruption: * For a few days we have been monitoring Mount Tungurahua in Ecuador. This active volcano has recently erupted, but far below the thresholds to have any climate implications. Tungurahua, already situated 3 miles above sea level, ejected an ash plume an additional 3 miles into the atmosphere (which may confuse you as ash eruptions were listed as 6 miles, but that is above sea level). Regardless, this is a good opportunity to review Volcano-Climate impacts, so fears don't compensate the science: 1.) In order for Volcanoes to have weather/climate impacts beyond its region of the World, the erupted particles need to be forcefully ejected through the Tropopause and into the Stratosphere (> 15k m/9 mi. for mid-Latitudes and > 18 km/11 mi. closer to the Equator), where they can diffuse and eventually have a global reach. The ash ejection yesterday, located 1.5°S Latitude, only reached about 60 percent of this threshold. 2.) Separately, keep in mind that any Volcanoes located Poleward of 30° have only small impacts on Hemispheric climate. Unlike Pinatubo and Tungurahua (located in the Tropics), Volcanoes closer to the Poles will have their contents advected toward the Northeast/Poles. 3.) Regionally, larger soot and erupted particles (> 2.2 µm) are more effective at keeping in Infrared radiation and can impart some warming effects. Smaller particles (usually containing lots of sulfur) are less effective in the IR spectrum, but stay aloft longer and increase Albedo and hence lead to cooling. (FYI, Volcanic Ash is not actually ash, but tiny jagged particles of rock and natural glass). After the infamous 1980 Mount Saint Helens eruption it took several weeks to cart away all the Ash & Soot, and until that is done in any future events, could be blown around obscuring visibility in much the same way a Forest Fire would. 4.) At the lower levels of the Troposphere, Soot & Ash (if fine enough) could also act as condensation nuclei and perhaps help "feed" regional storm systems during an upcoming Season. Ionization of the atmosphere is a tertiary impact of this particulate matter that could translate into increased lightning events also during the upcoming Season. Such particles were detected as far away as New England following the 1980 Helens eruption. 5.) Mount Tungurahua in Ecuador has the potential to erupt again more violently/explosively in the coming days and weeks, and we will monitor this closely. If it does so, achieving stratospheric penetration, there are large lag times involved in global dispersion. Thus, it could have profound implications for (but not before) the 2008-2009 Winter and 2009 Spring weather predictions around the World including North America, which we of course factor into our research.