Friday, April 5, 2013

Spring Showers (heavier, steadier rain possible next week - latest tornado research)

44 F. high on Friday in the Twin Cities.
52 F. average high for April 5.
59 F. high on April 5, 2012.

.07" rain fell yesterday at KMSP as of 7 pm.
Trace of snow fell Friday in the cities.

Pushing The Envelope

I'm at a Severe Storms & Doppler Conference in Des Moines, focused on best practices for tornado prediction. We've made progress: advanced lead-time for tornadoes has gone from 6 minutes in the 70s to 13 minutes today. Predicting polygon tracks means fewer people have to be warned, cutting down on confusion. But the false alarm rate is still 75 percent. In other words, 3 out of 4 warnings don't produce an actual tornado.

NOAA will use more emphatic wording in 2013, especially when there is confirmation of a tornado on the ground. Expect to hear words like "catastrophic", even "you could be killed if you aren't in a basement or underground shelter" if there is a large, violent tornado on the ground, moving into a populated area. New, high-res models, capable of a 40-60 minute tornado probability, are probably 4-8 years away. Hospitals and businesses may get advance notice of a high probability of tornadoes before general consumers, giving them more time to prepare, move patients and employees, etc. The WSR-88D "NEXRAD" Doppler radars are almost 25 years old, and at some point they will be replaced, possibly with "phased-array radars" that can take a 3-D snapshot of the atmosphere within seconds vs. minutes, speeding up the tracking and warning process.

One problem: many people still wait to get confirmation from multiple sources (TV, radio, apps, a phone call) before they do the right thing and head for shelter. Waiting for confirmation can cost you your life; apathy and delay (along with a lack of basements) resulted in 161 deaths from Joplin's EF5 tornado on May 22, 2011.

A major severe outbreak is shaping up for the Southern Plains early next week. Closer to home the risk of Red River flooding will rise in coming weeks.

Rain is likely today, but a major southern storm may drop over 1" rain Monday & Tuesday; possibly ending as midweek slush.

Something to look forward to.
NOAA Needs Your Help. The local Twin Cities National Weather Service is interested in knowing whether the ground is still frozen in your neighborhood. Why does this matter? The extent and depth of lingering frost in the ground will help to determine rainfall run-off rates next week, when we may see a significant storm. This will impact not only the potential for minor flash flooding in the Twin Cities, but more significant river flooding, especially on the Red River in the weeks to come. Details: "As we head in to Spring, potential flooding is a primary concern across Minnesota and Wisconsin.  We could use your help in determining if the ground is still frozen, or if there has been some partial thaw of the ground.  As you can see on the map below, we have quite a large area with no data across southern MN and western WI.  Visit our Facebook Page or send us a message via Twitter @NWSTwinCities and let us know what the ground condition is like at your location."

Median Lake Ice Out Dates. The interactive map above shows median dates when most of the ice is off Minnesota's lakes. For Nokomis the date is April 5. Not this year. Map courtesy of the Minnesota DNR.

Scary Numbers. Data from the Minnesota Climate Office reminds us just how harsh 1983 was in the Twin Cities. That "spring" we picked up a whopping 21.8" of snow during April. I had just arrived in Minnesota the previous month to work at WTCN-TV (now KARE-11), and I remember wondering what I had gotten myself into. Yes, it can always be worse.

Dueling Models. The uncertainty over next week's forecast is even greater than usual. Most of the U.S. and Canadian models bring very significant rain north as an intense area of low pressure pushes across the Plains into the Upper Mississippi River Valley, maybe a couple inches of rain nearby. But the (normally reliable) ECMWF/European model keeps the heaviest rain just south of Minnesota, bringing showery rains in Monday, maybe a rain-snow mix by Thursday. It's too early for specifics, but here are some of the model solutions. Graphic above: Iowa State.

Full Latitude Storm. We haven't seen this for some time. The GFS spins up a major storm over the Central Plains early next week, pushing a shield of heavy rain (and possible T-storms) northward. The availability of Gulf moisture coupled with the slow forward motion of the storm could spell out significant amounts of rain, changing to wet snow across the Dakotas. Map above valid midnight Tuesday night of next week courtesy of WSI.

GEMS Model. The Canadian model has a similar solution, not quite as intense, but showing a surge of southern moisture pushing into Minnesota Monday - Wednesday of next week, possibly ending as wet snow from the Dakotas into portions of western and central Minnesota. WSI model data above valid next Tuesday evening.

European Solution. The ECMWF keeps the brunt of the moisture south of Minnesota, just brushing southern counties with a cold rain next Tuesday, a second surge next Thursday bringing rain and even a period of wet snow. I normally lean toward the "Euro", but all the U.S. and Canadian models are suggesting a more northward track, so I suspect we may wind up with more rain than the ECMWF is printing out. We'll see.

High Bust Potential. That's meteorological slang for "there's much that can go wrong with this forecast". Confidence levels are low for next week, but the ECMWF guidance (above) for MSP shows mostly light showers today, heavier rain late Sunday into Monday morning, with next week's storm tracking too far south for heavy rain across most of Minnesota. A period of rain/snow is predicted for next Thursday. Let's hope the Euro is wrong on this call.

Close To Throwing In The Towel On April. What happened to the 60s Paul? Good question. That's what I want to know too. After a few runs/row of 60s after April 18 the latest GFS run keeps us chilly (40s, maybe some 50s) into at least April 21. Wet and cool. Maybe May will be better.

Red River Flooding Likely To Peak After Mid-April In Fargo-Moorhead Area, USGS Says. INFORUM has the story; here's an excerpt: "Peak flooding on the Red River in the Fargo-Moorhead metro area will likely occur sometime after April 15, according to the U.S. Geological Survey and National Weather Service. USGS stream gauges indicated that on Wednesday the Red still had not begun its spring rise. That means this year’s flood will be much later than the large floods of 2009 and 2011. This year’s flood also likely will be later than the 1997 flood, which was exacerbated by an early April blizzard, USGS predicts. “The large floods at Fargo that have previously occurred in April – 1952, 1965, 1969, 1979, and 1997 – peaked from April 15 to April 19,” said Gregg Wiche, director of the USGS North Dakota Water Science Center. “Above-normal snowpack and cold March temperatures have contributed to this year’s late melt...”

HydroClim Update. Here are a few bullet points from the latest update, courtesy of the Minnesota State Climate Office and the Minnesota office of the DNR:
  • Snow depths range from zero in the southern one-third of Minnesota to over 20 inches west central Minnesota, north central Minnesota, and in the Lake Superior highlands.
    [see: NWS Snow Depth Estimation Map  |  Snow Depth Maps]
  • The amount of water content in the snow pack is estimated to be in excess of five inches in some west central and north central Minnesota counties. The large amount of water on the landscape, lying upon an impervious frozen surface, has led to a high risk for major flooding in the Red River basin.
    [see: NWS Snow Water Equivalent Estimation Map]
  • The U.S. Geological Survey and Minnesota DNR report that stream discharge values vary widely across the state. After the initial flush of snow melt runoff recedes, stream discharge values will quickly fall below historical medians unless there is a very wet spring.
    [see: USGS Stream Flow Conditions  |  MNDNR Weekly Stream Flow Maps and Tables]
  • Water levels on most Minnesota lakes are low due to the dry summer and autumn of 2012. Lake Superior's water level is approximately one foot lower than its historical average for this time of year.
* latest modeled snow depth from NOAA is here.

Criticism After Sandy Leads To Changes In The Way Hurricane Warnings, Watches Are Issued. Technically, Sandy wasn't a hurricane (warm core storm) when it hit New Jersey and metro New York. NOAA discontinued Hurricane Warnings, which caused many coastal residents to lower their guard a little. Big mistake. Changes are coming, as documented in this Washington Post story; here's an excerpt: "...Under the new policy, the hurricane center in Miami will continue to put out warnings and advisories if a storm threatens people and land, even if a hurricane or tropical storm loses its name and becomes something different. “Our forecasters now have more flexibility to effectively communicate the threat posed by transitioning tropical systems,” said Louis Uccellini, the director of the National Weather Service, which is part of the National Hurricane Center. “Sandy’s forecast was remarkably accurate and under a similar situation in the future, forecasters will be able to choose the best option to underscore the urgency involved...”

Foul. After a promising start clouds streamed in yesterday; the atmosphere just cold and dry enough for a period of wet snow, that changed over to rain. The atmosphere should we warm enough for rain today, although the Minnesota Arrowhead may pick up a plowable snowfall. Friday highs ranged from 32 at Grand Marais to 38 St. Cloud, 44 in the Twin Cities.
TODAY: Showery rains. Wet roads. Winds: S 7-12. High: 48

SATURDAY NIGHT: Showers taper off - clouds linger. Low: 34

SUNDAY: Some sun, nighttime rain likely. High: 48

MONDAY: Showery rains expected. Wake-up: 39. High: 54

TUESDAY: Potentially heavier rain. Wake-up: 46. High: 56

WEDNESDAY: Rain may mix with or change to wet snow, especially west of MSP. Wake-up: 40. High: 42

THURSDAY: Mostly cloudy, cool breeze. Wake-up: 33. High: 47

FRIDAY: Peeks of sun, still brisk. Wake-up: 31. High: 48

Climate Stories....

Federal Study: Global Warming Means More "Extreme" Rains. Basic physics: warm up the atmosphere, even by a few degrees, and you increase the capacity of the sky overhead to hold more water vapor (which is itself another greenhouse gas). The result? More fuel for extreme rains (and snows). The Hill has the story; here's the intro: "Global warming will make cases of “extreme” rainfall even more intense and worsen flood risks, federal researchers say in the latest warning that climate change will likely worsen violent weather. A new federally led study explores how growing amounts of atmospheric water vapor due to global warming will affect what is called probable maximum precipitation. The report, released by the National Oceanic and Atmospheric Administration, forecasts an “accelerated water cycle with heavier extreme rains.” The study shows “a 20-30 percent expected increase in the maximum precipitation possible over large portions of the Northern Hemisphere by the end of the 21st century if greenhouse gases continue to rise at a high emissions rate,” NOAA said..."

Photo credit above: "The flooded Red River surrounds houses near Fargo, N.D., in 2010. Scientists say climate change will produce more intense storms, increasing the risk of damaging floods." (M. Spencer Green / Assoicated Press / March 21, 2010)

* The Los Angeles Times has another perspective on the potential for more extreme rains here.

Rising Seas Swallow 8 Cities In These Climate Change GIFS. Mashable has the story; here's an excerpt: "Climate change and global warming may cause sea levels to rise and flood coastal cities across the world. Over the past century, the Global Mean Sea Level has risen by 4 to 8 inches. And according to estimates by the National Oceanic and Atmospheric Administration (PDF), it will keep rising between 8 inches and 6.6 feet by 2100. How will the world look if that happens? In November of 2012, The New York Times published interactive maps displaying the effects of the sea level rising, in a series titled "What Could Disappear?" The maps show how much land the sea will claim in the future, if it rises by 5, 12, and 25 feet. Nickolay Lamm, a 24-year-old researcher and artist saw the interactive maps and wondered: "What would this actually look like in real life?" Lamm told Mashable in an email interview that "the only imagery I had of sea level rise came from Hollywood." So he decided to put his skills to work..."

Spring Leaf-Out Comes 6 Days Earlier Than It Did In 1982. Here's an excerpt of some new research from Climate Central that caught my eye: "...The map shows that leaves are coming earlier in some parts of the country, like the Rocky Mountains and Appalachians, but that spring leaf-out has been delayed over time in parts of the Southeast, Northeast and Midwest. This is consistent with climate research that shows that many types of plants have not been blooming uniformly earlier over time. We looked at the difference between when this time arrived during the first five years and the last five years of the study. In the Minneapolis area, this date is coming about six days earlier on average since 1982. Rising temperatures may actually be behind the way this date shifts in both directions. New research suggests that the response of spring leaves to warming temperatures may not be linear, due to the effects of reduced winter chilling, and increased vulnerability to late-winter freezes. A continuing trend of warming winters may lead to further changes in the familiar timing of the seasons..."

Keystone XL Stirs Montana Farmer's Climate And Crop Concerns. Huffington Post reports; here's an excerpt: ".."In terms of carbon emissions, Alberta tar sands are among the worst of the worst," said John Abraham, an engineering profesor at the University of St. Thomas. The other problem, he added, is the massive quantity of that crude oil. A study published last year in Nature Climate Change found that if all the oil in Alberta was harvested -- now only a theoretical possibility unless new technology emerges as fracking did for tapping previously hard-to-reach reserves of natural gas -- global temperatures would rise nearly 0.4 degrees Celsius (about 0.7 F), without taking into account emissions from energy used during the extraction, upgrading and refining of the heavy crude. That figure is arguably significant in the context of keeping any increase in global temperatures below the 2-degrees Celsius benchmark world leaders have agreed is critical for avoiding the most dangerous effects on the climate system. The planet has already warmed by 0.8 degrees Celsius..." (graphic: U.S. State Department).

No comments:

Post a Comment