The Limits of Long Range Forecasting
“Paul, please help. My little girl is having an outdoor wedding on October 11. Any idea what the weather will be?” Yes I do. Changeable. It might be easier to predict where the stock market will be on October 11.
There is (some) forecast skill going out 1-2 weeks for a specific location. Beyond that it’s mostly hand-waving and ruminating about trends. The reason? Chaos Theory.
Over 210 million current observations from weather stations, balloons, satellites, ships and planes provide the raw fuel for weather models that simulate what the atmosphere SHOULD look like in the future. The harsh reality? A butterfly fluttering its wings in Japan MIGHT impact the weather thousands of miles downwind; tiny errors and omissions become magnified over time and computers become useless after a couple of weeks. In spite of faster supercomputers we don’t yet have the technology to peer out, with any
accuracy, beyond 2 weeks. Sobering, but true.
Ever Wonder Why Trees Ditch Their Leaves Every Fall? The Washington Post (paywall) has a good explainer geared toward kids; here’s an excerpt: “…Trees are solar-powered. Each leaf is loaded with a pigment called chlorophyll (pronounced CLORE-o-fill), which absorbs light and helps convert water and carbon dioxide into energy. The process is called photosynthesis (fo-toe-SYN-thuh-sis). But there’s a problem. In parts of the world that experience seasons, winter means less and less sunlight each day. It also comes with biting cold that can freeze the liquids inside leaves. These two factors hamper the tree’s ability to make energy. A full-grown oak tree might have more than 60,000 leaves, and each one requires valuable nutrients. So when fall turns into winter, trees discharge their leaves as a cost-cutting measure. If it had to spend resources on all those leaves through the winter, not only would the leaves freeze, but the tree would die...”
“Crazy” 2020 Hurricane Season Matches 2005 in Activity, But Not Storm Intensity. Some perspective from USA TODAY: “…The big difference between the two seasons, Sudduth said, is “we haven’t had the very long lasting, powerful hurricanes like we did in ’05.” In that regard, Klotzbach said, it’s unlikely 2020 will catch up to 2005. In terms of the intensity and duration of the strongest storms, 2020 is unlikely to equal 2005, Klotzbach said. By the end of 2005, the accumulated cyclone energy – measured by the intensity and duration of all the storms combined – was 250, he said. Right now, the Atlantic’s accumulated energy is around 90…”
Briefing: Issued: Monday morning, September 21st, 2020:
Tropical Storm Beta
Beta Is Struggling. It appears that Beta, sitting not even a hundred miles off the Texas coast, is struggling a bit this morning as showers/storms and winds associated with the system have decreased. Dry and stable air has been wrapped into the system, and upper level winds remain strong, preventing any strengthening. As of 7 AM CDT, the center of Sally was about 70 miles southeast of Port O’Connor, TX, or 120 miles south-southwest of Galveston, TX, and moving west at 6 mph. Beta had 50 mph winds and tropical-storm force winds extend outward 175 mph, mainly on the north side of the system.
Beta Track. Beta will slowly continue to move off to the west/west-northwest today into tonight, which will bring Beta to the Texas coast tonight along or south of Matagorda Bay. Many models show Beta slowing down even more or stalling out near/just inland over Texas Tuesday before an approaching system finally kicks Beta off to the northeast late Tuesday into Wednesday and Thursday. Due to unfavorable atmospheric conditions, and eventually its proximity to land, additional strengthening is not expected, with weakening expected through the middle of the week. It should become post-tropical by Friday.
Tropical Storm Watches and Warnings. With Beta approaching the western Gulf Coast, Tropical Storm Watches and Warnings have been issued inland and along the coast. Cities that are under Tropical Storm Warnings include Houston, Galveston, Beaumont, and Victoria (TX), as well as Morgan City (LA). Tropical Storm Watches include Corpus Christi. Here are where these watches and warnings are in place along the coast:
A Tropical Storm Warning is in effect for…
* Port Aransas Texas to Morgan City Louisiana
A Tropical Storm Watch is in effect for…
* Baffin Bay to Port Aransas Texas
Heavy Rain. One of the main risks with Beta will be heavy rain across portions of Texas and Louisiana. Near and along the track of Beta, rainfall amounts of at least 5-10” (isolated 15” amounts) are possible from the middle Texas coast to southeastern Louisiana. This heavy rain could lead to flash flooding across the region. 3-5” are possible from Beta north of these regions up into the ArkLaTex and east into the lower Mississippi Valley.
Flooding Expected. Due to the heavy rain threat, flash flooding is expected the next few days across portions of Texas and Louisiana. Today/tonight the greatest risk is along the middle and upper Texas Coast, where widespread one-day totals of 3-6”+ are expected with hourly rainfall rates of up to 3” possible. On Wednesday, models are showing a band of rain occurring across portions of southeastern Louisiana with hourly rainfall rates of 2”+ possible. This could lead to rainfall amounts of 5”+ in a day, which will lead to flooding.
Flood Watches. Due to the heavy rain threat, Flood Watches are in place from the mid-Texas coast to southern Louisiana.
Storm Surge Threat. Beta will continue to produce a storm surge threat over the next few days, with coastal flooding already ongoing this morning. The combination of the storm surge and tide will cause normally dry areas to be flooded by water moving inland from the Gulf of Mexico. The following levels could be reached if the peak surge occurs at high tide:
Peak Winds. The strongest winds – up to around 50 mph – are expected along the Texas coast, particularly near where the center makes landfall. The strongest winds are expected overnight tonight as Beta approaches and makes landfall.
Other Tropical Activity
Other Tropical Activity. We are also watching the following systems in the Atlantic:
D.J. Kayser, Meteorologist, Praedictix.
Summer of U.S. Disasters Set Records, Left Trail of Ruins. Bloomberg summarizes some of the biggest weather stories of 2020: “…Other parts of the U.S. saw record temperatures, too. Arizona, California, Colorado, Nevada, New Mexico and Utah all had their warmest August on record. Phoenix had its hottest month ever in August, with an average temperature of 99.1. And it was the hottest July ever across the Northern Hemisphere. Derechos: A line of violent storms known as a derecho cut electricity to more than 1 million customers last month in the U.S. Midwest and destroyed more than 550,000 acres of corn in Iowa. It was 160 miles (260 kilometers) wide, bringing lightning, hail and deadly, 100 mile-per-hour winds that cut a path of destruction across Iowa, Illinois and Indiana. It was one of the most damaging storms ever for Eastern Iowa’s power grid, leaving some areas without power for more than a week...”
File image above: NOAA.
Smoke from Western Fires Reported As Far Away as the Netherlands. Mental Floss has details: “For those not living in California, Oregon, or Washington, the raging wildfires in those states that have consumed more than 4 million acres might seem slightly abstract. But over the past week, the intensity of those blazes, coupled with specific weather patterns, has made it possible for people in New York—and even as far away in Europe as the Netherlands—to look up and see smoke in the skies. According to both NASA and the National Weather Service, jet streams have allowed the smoke to migrate across the Northeast and Mid-Atlantic regions, with the plume strong enough to actually blot out the sun and lower the temperature by a few degrees...”
Monday smoke visualization courtesy of NOAA.
The Limits of “Forest Management”. Can we do more to clear out brush and dead trees, less fuel to combust during a mega-fire? Absolutely. But other factors are in play, according to a story at The Washington Post: “…The scale of this year’s fires have horrified even those who saw them coming. As of Tuesday, 3.2 million acres in California have been incinerated — almost double the previous record of 1.9 million, set in 2018. In Oregon, blazes have erupted in parts of the wet Western Cascades that have not burned in years. On a single day last week, red-flag warnings on fire weather stretched along the entire West Coast from the U.S. border with Mexico to Canada. “It really is a shocking escalation,” said Daniel Swain, a climate scientist at the University of California at Los Angeles. “Characterizing it as a phase change, a new era of megafire — as dramatic as that sounds, ultimately I think it’s accurate…”
The Most Important Number for the West’s Hideous Fire Season. I did not know this; more analysis from The Atlantic: “...The vapor-pressure deficit indexes two other measurements: the air temperature and the relative humidity. Both measurements affect the air’s sponginess. Hotter air is more likely to bump water into a gas state, while drier air can hold more water vapor overall. The vapor-pressure deficit measures the overlap. “It’s the difference between the amount of water vapor that’s in the air and the amount of water vapor that the air can possibly hold,” Williams said. When the vapor-pressure deficit is high, it means the atmosphere has become an immense, six-mile-high sponge. The arid air will induce water to evaporate from wherever it’s hiding—the soil, the wooden boards of houses, the limbs and leaves of trees and underbrush...”
Graphic credit: “The vapor-pressure deficit in August in California, as calculated by Park Williams.”
The Most Destructive Tornado in Minnesota History? Star Tribune follows up on a very good question: “…National Weather Service meteorologist Todd Krause noted that those tornadoes of a century ago tended to be more deadly because warning systems were rudimentary. Finally, if we consider property damage, the 1965 outbreak was the worst. Because it struck densely populated areas, it caused tens of millions of dollars in damage within a few hours. Some larger tornado systems may have caused more physical destruction, but fewer homes were lost because they took place in rural areas. The 1992 tornado system that hit Chandler, for example, spawned 27 total tornadoes. Even more were recorded on June 17, 2010, when 48 twisters walloped 22 counties, from Wadena to Albert Lea…”