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58 posts from November 2017


Hurricane Season Ends Today

Sayonara! The 2017 Atlantic Hurricane season ends today! This is a relief to many.

The 2017 season had more than the average number of storms. There were 17 named storms compared to 12 and 10 hurricanes compared to the average six hurricanes. There were also six major hurricanes and the norm is only two major hurricanes. But it was not a record year and did not come close to the 2005 season, the year of Katrina, which had 28 named storms and 15 were hurricanes! But this season had the highest ACE (accumulated cyclone energy) Index since 2005 at 229.6.

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Other Facts and Records:

  • The names Harvey, Irma and Maria will likely be retired due to their impacts 
  • There was a record of 10 consecutive hurricanes. This tied a record that was set back in 1893
  • This is likely to be the costliest season ever 
  • Hurricane Harvey's duration resulted in record rainfall of more than 60'' and caused catastrophic flooding
  • Hurricane Irma had 185 mph winds for 37 hours. Which is a worldwide record 
  • Hurricane Maria caused what is to be considered the largest blackout in history 
  • More than half of Puerto Rico is still without power. Maria made landfall on September, 20th 
  • Ophelia tracked farther east than any other major hurricane ever in the Atlantic

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The tropical cyclone season is considered to be from June 1 to November 30th. However, there can, and have been, off-season cyclones. But they are pretty rare. Since 1870, there have been 32 storms out of season. 18 of those happened in May, 9 in December, 2 in April, and 1 each in January, February and March. That means cyclones can happen during the entire year. 

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-Katie McGraw 



Rain Returns: Timing it out

Tonight is going to be pretty mild with temps in the 40s because there will be a southerly wind as well as more clouds around the area as a stronger cold front approaches the area.

This front is currently out to the west and will push through the area on Thursday, bringing the return of rain to the area and will drop our temps from the 60s to the 50s by tomorrow and Friday. 

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Most of tonight will be dry, but we could see a few light showers very early tomorrow morning, especially in our western counties. 

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Scattered showers will continue to move east through daybreak and you could see a few for the morning commute. 

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On and off showers will continue through the morning... 

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And into the afternoon... 
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And will begin to taper off by the evening commute. 

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By Thursday evening, the cold front will be exiting the area and take the showers and clouds with it. High pressure will quickly build into the region by Friday and Saturday and clear out our skies.  

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This is not going to be heavy rain. Notice the projected rainfall totals from the GFS and EURO below. Roughly a tenth of an inch only. 
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Temperatures are going to drop following the front for Friday but will be mild again for the weekend. HOWEVER, there is a major pattern shift looking ahead to next week. It's going to get COLD! To learn more be sure to join Marc and Rick on WDRB News this evening. 

Let's connect! The links to my pages are below!  

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-Katie McGraw 



SHOWTIME! The ISS Will Fly Overhead Within The Hour...

Looking into the night sky and seeing the International Space Station fly overhead is mind-blowing! Just think, you are watching something that is 230 miles above you, flying at nearly 5 miles per second. If you've never taken the opportunity to check it out, it's worth a few minutes of your time...


How To View The International Space Station


When To Look...

The ISS will be visible in our area this evening at 6:25 pm for 3 minutes! 3 minutes should be more than enough to view it, but remember it will be moving FAST.

Where To Look...

At 6:25 pm, the ISS will appear about 29 degrees above the horizon in the southwest part of the sky and move toward the northeast. The ISS will reach a peak elevation of 79 degrees above the horizon, so look high in the sky...


Grab a light jacket and enjoy the show as temperatures fall into the 50's...




-Rick DeLuca




Wonder When Do We Normally See Our First Snow? Our First 4"+ Snow? Let's Discuss...

There is no question that snow lovers start to grumble this time of the year hoping for snow in our area. What you may not know is that we normally do not average our first measurable snow for another 2 weeks in the Louisville area. I wanted to share some of the snow climatology, so you can have some realistic expectations about what we normally see in our area.


When Do We Normally See Our First Measurable Snow Of The Year?


This is a pretty popular question in our area. While we average our first trace of snow in November, we normally don't measure our first snow of the year until December 7th. Of course we have had years where we had measurable snow earlier and later than this date, but statistically this is our average first measurable snow.


When Do We Normally See Our First 1" Snow Of The Year?


This is the time of the year that we start to talk about the real snow. As you know, an inch of snow in our area can cause some real problems. I think many that have lived in snow belts think that 1" is not much, but our area definitely has problem with any 1"+ snows. The average first 1"+ snow of the year for our area is December 26. Think about that for a second... we don't average our first 1" snow for the area until AFTER Christmas.


What Is Our Chance For A White Christmas


Since we normally don't see our first 1" snow of the year until after Christmas, this kind of brings up a good question... what is our chance of a white Christmas in Kentuckiana based on climatology. Children of the 70s and 90s probably remember many years with a White Christmas, but statistically speaking that is not the norm for our area. 


Probabilty Of White Christmas


As you can see, the chance is not good for Louisville. The chance of a white Christmas in Louisville is only about 5% to 10%. That means we have a 90% to 95% chance on average that we do not see a white Christmas. That may surprise some, but these are the stats.


When Do We Normally See Our First 4"Snow Of The Year?



This is really the stat that speaks to when we have our first "big" snow of the year on average. 4" of snow in our area can cause a whole lot of problems so this one is important. On average, we normally see our first 4" snow on January 19 or about half way through the meteorological winter. We absolutely can get some before, but it is clearly not the norm.



Any Snow Chances In The Near Future?


Honestly, I know that people will try to forecast snow 2, 3, or 4 weeks into the future. We all know those forecasts are rubbish. The bottom line is that we will likely average above normal through around the first week of December. There are some signals pointing toward us turning sharply colder after that, but that is still quite a long way off. To be honest, virtually all of the long range data shows that shift to sharply colder in the December 7th range and could last quite a while. It that verifies, we know that could open that door and it is something we will be watching.




Remember it is Winter storm season and if you want to be one of my storm spotters, you can join me on my facebook or twitter page. Just follow the link below and click "like" or "follow".






The Power Of The Persimmon Seed: What Are They Are Saying About The Upcoming Winter Season?

"When cut into two pieces, the persimmon seed will display one of three symbols. A knife shape will indicate a cold icy winter (where wind will cut through you like a knife). A fork shape indicates a mild winter. A spoon shape stands for a shovel to dig out the snow."

Tracy Mount
Image Courtesy: Tracy Mount

For the last 5 years (including now), we have seen spoons (and some knives) when cutting open persimmon seeds.  That proved an accurate prediction a few years, but not every year. This year we are seeing all spoons. 

Tasha Masters
Image Courtesy: Tasha Masters
Tasha Masters
Image Courtesy: Justin Case
Tasha Masters
Image Courtesy: Debree Underwood
Tasha Masters
Image Credit: Janet Goodman
Tasha Masters
Image Credit: Brooklyn LaPlant
Tasha Masters
Image Credit: Diana Evans
Tasha Masters
Image Credit: Ron Line

My Thoughts

According to legend, this should be a snowy year since we are seeing spoons inside the seeds.  You can click here to see our official winter outlook, but I think this persimmon prediction is half right. I think we will see a wet winter, but not specifically a snowy winter.  I actually think we will see pretty normal snow amounts (10-15 inches this season), but likely more rain than normal especially early in the season. The coldest air and best snow chances won't come until later this winter. 

I couldn't find a ton of research on how accurate persimmon seeds are in general for predicting winter weather, but they seem to be right about half the time.  Share your pictures of seeds and your winter prediction with me to see if you can beat the seeds! 

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-Hannah Strong




20 YEARS IN A FEW MINUTES: Check Out The Changing Colors Of Our Living Planet...

NASA satellites can see our living Earth breathe.

In the Northern Hemisphere, ecosystems wake up in the spring, taking in carbon dioxide and exhaling oxygen as they sprout leaves — and a fleet of Earth-observing satellites tracks the spread of the newly green vegetation.

Meanwhile, in the oceans, microscopic plants drift through the sunlit surface waters and bloom into billions of carbon dioxide-absorbing organisms — and light-detecting instruments on satellites map the swirls of their color.

This fall marks 20 years since NASA has continuously observed not just the physical properties of our planet, but the one thing that makes Earth unique among the thousands of other worlds we’ve discovered: Life.

Satellites measured land and ocean life from space as early as the 1970s. But it wasn't until the launch of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) in 1997 that the space agency began what is now a continuous, global view of both land and ocean life. A new animation captures the entirety of this 20-year record, made possible by multiple satellites, compressing a decades-long view of life on Earth into a captivating few minutes.

“These are incredibly evocative visualizations of our living planet,” said Gene Carl Feldman, an oceanographer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s the Earth, that is it breathing every single day, changing with the seasons, responding to the Sun, to the changing winds, ocean currents and temperatures."


Since the fall of 1997, NASA satellites have continuously and globally observed all plant life at the surface of the land and ocean. Twenty years of satellite data has helped scientists track phytoplankton populations in the ocean, study changing vegetation in the Arctic reaches of North America, monitor crop yields and more.
Credits: NASA's Goddard Space Flight Center

The space-based view of life allows scientists to monitor crop, forest and fisheries health around the globe. But the space agency's scientists have also discovered long-term changes across continents and ocean basins. As NASA begins its third decade of global ocean and land measurements, these discoveries point to important questions about how ecosystems will respond to a changing climate and broad-scale changes in human interaction with the land.

Satellites have measured the Arctic getting greener, as shrubs expand their range and thrive in warmer temperatures. Observations from space help determine agricultural production globally, and are used in famine early warning detection. As ocean waters warm, satellites have detected a shift in phytoplankton populations across the planet's five great ocean basins — the expansion of "biological deserts" where little life thrives. And as concentrations of carbon dioxide in the atmosphere continue to rise and warm the climate, NASA's global understanding of plant life will play a critical role in monitoring carbon as it moves through the Earth system.

Life on Earth, from space


From space, satellites can see Earth breathe. A new NASA visualization shows 20 years of continuous observations of plant life on land and at the 
ocean’s surface, from September 1997 to September 2017. On land, vegetation appears on a scale from brown (low vegetation) to dark green (lots 
of vegetation); at the ocean surface, phytoplankton are indicated on a scale from purple (low) to yellow (high). This visualization was created with 
data from satellites including SeaWiFS, and instruments including the NASA/NOAA Visible Infrared Imaging Radiometer Suite and the Moderate 
Resolution Imaging Spectroradiometer.
Credits: NASA

Sixty years ago, people were not sure that Earth’s surface could be seen clearly from space. Many thought that the dust particles and other aerosols in the atmosphere would scatter the light, masking the oceans and continents, said Jeffrey Masek, chief of the Biospheric Sciences Laboratory at NASA Goddard.

The Gemini and Apollo programs demonstrated otherwise. Astronauts used specialized cameras to take pictures of Earth that show the beauty and complexity of our living planet, and helped kickstart the era of Earth science research from space. In 1972, the first Landsat mission began its 45-year record of vegetation and land cover.

“As the satellite archive expands, you see more and more dynamics emerging,” Masek said. “We’re now able to look at long-term trends.”

The grasslands of Senegal, for example, undergo drastic seasonal changes. Grasses and shrubs flourish during the rainy season from June to November, then dry up when the rain stops. With early weather satellite data in the 1970s and '80s, NASA Goddard scientist Compton Tucker was able to see that greening and die-back from space, measuring the chlorophyll in the plants below. He developed a way of comparing satellite data from two wavelengths, which gives a quantitative measurement of this greenness called the Normalized Difference Vegetation Index.

“We were astounded when we saw the first images. They were amazing because they showed how vegetation changed annually, year after year,” Tucker said, noting that others were surprised as well when the study came out in 1985. “When we produced this paper, people accused us of ‘painting by numbers,’ or fudging data. But for the first time, you could study vegetation from space based on their photosynthetic capacity.”

When the temperature is right, and water and sunlight are available, plants photosynthesize and produce vegetative material. Leaves strongly absorb blue and red light but reflect near-infrared light back into space. By comparing the ratio of red to near-infrared light, Tucker and his colleagues could quantify the vegetation covering the land.

Expanding these observations to the rest of the globe, the scientists could track the impact on plants of rainy and dry seasons elsewhere in Africa, see the springtime blooms in North America, and the after-effects of wildfires in forests worldwide.

But land is only part of the story. At the base of the ocean’s food web are phytoplankton — tiny organisms that, like land plants, turn water and carbon dioxide into sugar and oxygen, aided by the right combination of nutrients and sunlight.


The SeaWiFS satellite was launched in late 1997, just in time to capture the phytoplankton that bloomed in the Eastern Equatorial Pacific as conditions changed from El Niño to La Niña, seen here in yellow.
Credits: NASA

Satellites that can monitor the subtle changes in color of the ocean have helped scientists track changes in phytoplankton populations across the globe. The first view of ocean color came from the Coastal Zone Color Scanner, a proof-of concept instrument launched in 1979. Continuous observations of ocean color began with the launch of SeaWIFS in late 1997. The satellite was just in time to capture the transition from El Niño to La Niña conditions in 1998 — revealing just how quickly and dramatically phytoplankton respond to changing ocean conditions.  

“The entire Eastern Pacific, from the coast of South America all the way to the dateline, transitioned from what was the equivalent of a biological desert to a thriving rainforest. And we watched it happen in real time,” Feldman said. “For me, that was the first demonstration of the power of this kind of observation, to see how the ocean responds to one of the most significant environmental perturbations it could experience, over the course of just a few weeks. It also showed that the ocean and all the life within it is amazingly resilient — if given half a chance.”

Tracking change from satellites

With 20 years of satellite data tracking ocean plant life on a global scale, scientists are investigating how habitats and ecosystems are responding to changing environmental conditions.

Recent studies of ocean life have shown that a long-term trend of rising sea surface temperatures is causing ocean regions known as “biological deserts” to expand. These regions of low phytoplankton growth occur in the center of large, slow-moving currents called gyres.

“As the surface waters warm, it creates a stronger boundary between the deep, cold, nutrient-rich waters and the sunlit, generally nutrient-poor surface waters,” Feldman said. This prevents nutrients from reaching phytoplankton at the surface, and could have significant consequences for fisheries and the marine ecosystem.

In the Arctic Ocean, an explosion of phytoplankton indicates change. As seasonal sea ice melts, warming waters and more sunlight will trigger a sudden, massive phytoplankton bloom that feeds birds, sea lions and newly hatched fish. But with warming atmospheric temperatures, that bloom is now happening several weeks early — before the animals are in place to take advantage of it.

“It’s not just the amount of food, it’s the location and timing that are just as critical,” Feldman said. “Spring bloom is coming earlier, and that’s going to impact the ecosystem in ways we don’t yet understand.”

The climate is warming fastest in Arctic regions, and the impacts on land are visible from space as well. The tundra of Western Alaska, Quebec and elsewhere is turning greener as shrubs extend their reach northwards.

The neighboring northern forests are changing as well. Massive fires in 2004 and 2015 wiped out millions of acres of forests in Alaska, including spruce forests, noted Chris Potter, a research scientist at NASA’s Ames Research Center in California’s Silicon Valley.

“These fires were amazing in the amount of forest area they burned and how hot they burned,” Potter said. “When the air temperature hits 90 degrees Fahrenheit in late May up there, and all these lightning strikes occurred, the forest burned very extensively — close to rivers, close to villages — and nothing could stop it.”


Satellites help scientists routinely map fires, deforestation and other changes, and to analyze their impact on the carbon cycle, Potter said. Giant fires release many tons of carbon dioxide into the atmosphere, both from the charred trees and moss but also, especially in northern latitudes, from the soils. Potter and colleagues went to the burned areas of Central Alaska this year to measure the underlying permafrost — the thick mossy layer had burned off, exposing the previously frozen soils.

“It’s like taking the insulating layer off a cooler,” he said. “The ice melts underneath and it becomes a slushy mess.”

Forest types can change too, whether it’s after wildfires, insect infestations or other disturbance. The Alaskan spruce forests are being replaced with birch. Potter and his colleagues are also keeping an eye on California forests burned in recent fires, where the concern is that pines will be replaced by oaks.

“When drought is accentuated with these record high temperatures, nothing good seems to come from that for the existing forest type,” he said. “I think we’re seeing real clear evidence of climate causing land-cover change.”


Keeping an eye on crops

Changing temperatures and rainfall patterns also influence crops, whether they are grown in California or Africa. The “greenness” measurement that scientists use to measure forests and grasslands can also be used for agriculture, to monitor the health of fields throughout the growing season.

Researchers and policy makers realized this potential early. One of the first applications of Landsat data in the 1970s was to predict grain yields in Russia and better understand commodities markets. In 1985, food security analysts from USAID approached NASA to incorporate satellite images into their Famine Early Warning Systems Network, to identify regions where food production has been limited by drought. That partnership continues today. With rainfall estimates, vegetation measurements, as well as the recent addition of soil moisture information, NASA scientists can help organizations like USAID direct emergency help.

With improved data from Landsat, the MODIS instruments on NASA's Terra and Aqua spacecraft and other satellites, and by combining data from multiple sensors, researchers are now able to track the growth of crops in individual fields, Tucker said.

“This moves things down to the field sizes for probably 80 percent of the fields globally — this is a huge advancement,” Tucker said.

The view from space not only helps monitor crops, but can help improve agricultural practices as well. A winery in California, for example, uses individual pixels of Landsat data to determine when to irrigate and how much water to use.

The next step for NASA scientists is actually looking at the process of photosynthesis from space. When plants undergo that chemical process, some of the absorbed energy fluoresces faintly back, notes Joanna Joiner, a NASA Goddard research scientist. With satellites that detect signals in the very specific wavelengths of this fluorescence, and a fine-tuned analysis technique that blocks out background signals, Joiner and her colleagues can see where and when plants start converting sunlight into sugars.

“It was kind of a revelation that yes, you can measure it,” Joiner said. An early study looked at the U.S. Corn Belt and found it fluoresces “like crazy,” she said. “Those plants have some of the highest fluorescence rates on Earth at their peak.”

Joiner and Tucker are using both the fluorescence data and vegetation indices to get the most information possible about plant growth at regional and global scales: “One of the big questions that still remains is how much carbon are the plants taking up, why does it vary year to year, and which areas are contributing to that variability,” Joiner said

Whether it’s crops, forests or phytoplankton blooms, NASA scientists are tracking life on Earth. Just as satellites help researchers study the atmosphere, rainfall and other physical characteristics of the planet, the ever-improving view from above will allow them to study the interconnected life of the planet, Feldman said.

“This is the capability that will allow us to understand how Earth’s biology responds to a changing planet,” he said.

-Rick DeLuca




Gearing Up For The Geminid Meteor Shower! Let's Discuss When Things Ramp Up...

Meteor showers are probably one of my favorite night sky events. At the same time, these can be frustrating because it feels like many times you just look at dark sky. The Geminid meteor shower is one of our best late year events and will be ramping up over the next couple of weeks.


Geminid Meteor Shower

The Geminids will be ramping up on December 7th and peak Wednesday night / Thursday morning December 13 - 14! Most meteor showers come from comets, which spew ample meteoroids for a night of 'shooting stars.' The Geminids are different. The parent is not a comet but a weird rocky object named 3200 Phaethon that sheds very little dusty debris—not nearly enough to explain the Geminids. 3200 Phaethon was discovered in 1983 by NASA's IRAS satellite and promptly classified as an asteroid. What else could it be? It did not have a tail; its orbit intersected the main asteroid belt; and its colors strongly resembled that of other asteroids. Indeed, 3200 Phaethon resembles main belt asteroid Pallas so much, it might be a 5-kilometer chip off that 544 km block. Another part of the Geminids that makes it so intriguing is the raw number of meteors. Astronomers are calling for a peak of "up to 120 per hour"...



Image Credit: NASA



Comet of Origin: 3200 Phaethon
Radiant: constellation Gemini
Active: Dec. 7-16, 2017
Peak Activity: Dec. 13-14, 2017
Peak Activity Meteor Count: 120 meteors per hour
Meteor Velocity: 22 miles (35 kilometers) per second

-- Try to view the Geminids away from city lights. The city lights can make it much more difficult to see the streaking meteors. Inside the city, the bright lights may only allow you to see one or two meteors per hour.

-- Allow your eyes to adapt. Don't just go outside and expect to see a dazzling show. It normally takes about 20 minutes for your eyes to adapt to the low light.

-- This year we will have a waning crescent moon. This is important because it will mean the moon light will not spoil the show.



If you ever have any question, please remember I can be reached on facebook or twitter easily! Just follow the link below to my facebook or twitter page and click "LIKE/FOLLOW"!






Spot the ISS This Weekend


You will have several chances to see the International Space Station this weekend. 

1) Friday it will be visible for less than a minute, but if you want to see it, it will pass by at 6:42 PM.  Look up about 10 degrees to the South/Southeast. 

2) Saturday it will be visible for 2 minutes starting at 7:24 PM.  Look Southwest this time about 10 degrees up. 

3) Sunday is your best chance to see it; the Space Station will be visible for 4 minutes beginning at 6:32 PM.  Again, look South/Southwest about 10 degrees up. 

4) Monday will be another short sighting.  Look up about 26 degrees and toward the West.  It will only be visible for about a minute starting at 7:17 PM. 

Check in with us to see the forecast on WDRB News each of these days; some will have better viewing weather than others.  

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-Hannah Strong




Recent cold air outbreaks over the north-central and northwestern U.S., along with record cold on Veterans Day in parts of the Northeast and Mid-Atlantic, should have people excited about (or dreading) the upcoming winter. My colleagues and I at the Climate Prediction Center have just issued our final outlook for the upcoming “meteorological winter,” that is, December through February. Right now, our official outlook covers only temperature and total precipitation, with the latter combining both liquid and frozen precipitation. However, what about the frozen stuff? What about snow?

Because many people remember winters that were either exceptionally snowy or not snowy at all, we get a lot of questions about what the winter forecast portends for seasonal snowfall accumulation. In many parts of the country, snowfall also has major economic and societal ramifications, including water resource management and winter tourism, among others.

Snow Way!

Tackling this problem is not easy, though. Part of the issue boils down to the technical difficulties of snowfall measurements—a real “problem child” as Deke Arndt (NCEI) puts it. The other issue is related to the difficulties with prediction. As many people in the Northeast corridor are aware, snowfall with any given storm system is a function of the dreaded rain-snow line that separates air masses that are below or above freezing.

For any given storm system, the exact boundaries between rain and snow can be hard to predict even days in advance. Luckily, at CPC, we aren’t trying to predict specific events, but the climate instead. We take a step back and see how seasonal temperature and precipitation forecasts might play a role in determining seasonal snowfall accumulation.

In regions that receive a large percentage of their cold-season precipitation in the form of snow, increased seasonal precipitation is intuitively related to increased snowfall accumulation. In more temperate areas that receive a relatively small percentage of frozen precipitation, temperature becomes important. Anomalously cold temperatures are, more or less, a necessary condition for snow in those areas. Therefore, a region with a relatively cold winter may find itself on the cold side of storm systems more often.

In more mountainous areas, where temperature varies as a function of elevation, colder systems result in snow falling at lower altitudes and more total snowfall coverage over a given region. This is where the long-term warming trends, recently discussed by Tom, become important over western North America. Drier and warmer climate signals will generally result in lower snow coverage.

Because a La Niña Advisory was recently issued, we will take a look at how La Niña, in general, affects snowfall across North America. This analysis is part of a broader effort at CPC to better understand and potentially predict seasonal snowfall, made possible in part by a new snowfall dataset (1).

La Niña = Skiers Delight over the Northern United States

In a nutshell, La Niña is associated with a retracted jet stream over the North Pacific Ocean. The retreat of the jet stream results in more blocking high pressure systems that allow colder air to spill into western and central Canada and parts of the northern contiguous U.S. At the same time, storm track activity across the southern tier of the U.S. is diminished under upper-level high pressure, which also favors milder-than-normal temperatures. The storm track is in turn shifted northward across parts of the Ohio Valley and Great Lakes (2).

Based on climate analysis (3) from this new snow dataset, we see that La Niña favors increased snowfall over the Northwest and northern Rockies, as well as in the upper Midwest Great Lakes region. Reduced snowfall is observed over parts of the central-southern Plains, Southwest, and mid-Atlantic.


Snowfall departure from average for all La Niña winters (1950-2009). Blue shading shows where snowfall is greater than average and brown shows where snowfall is less than average. Climate.gov figure based on analysis at CPC using Rutgers gridded snow data

This La Niña footprint is pretty intuitive. Given the northward shift of the storm track, relatively cold and wet conditions are favored over the northern Rockies and northern Plains, resulting in the enhancement of snowfall. Warmer and drier winters are more likely during La Niña over more southern states, and this is exactly where seasonal snowfall tends to be reduced (4). The more vigorous storm track and slight tilt toward colder temperatures over the northern tier of U.S. during La Niña modestly increases the chance of a relatively snowy winter.

Snow and Strength

We can break up the snow pattern further and look at the weakest and strongest La Niña events. Splitting La Niña events into strength reveals some interesting differences worth investigating further. In this preliminary analysis below, there is a suggestion that weaker events are snowier over the Northeast and northern and central Plains on average. 


Snowfall departure from average for weaker La Niña winters (1950-2009). Blue shading shows where snowfall is greater than average and brown shows where snowfall is less than average. Climate.gov figure based on analysis at CPC using Rutgers gridded snow data

On the other hand, stronger La Niña events (see below) are snowier across the Northwest, northern Rockies, western Canada, and the Alaska panhandle. Also, there is a tendency toward below average snowfall over the mid-Atlantic, New England, and northern and central Plains, which is not seen during weak La Niña.


Snowfall departure from average for stronger La Niña winters (1950-2009). Blue shading shows where snowfall is greater than average and brown shows where snowfall is less than average. Climate.gov figure based on analysis at CPC using Rutgers gridded snow data

Overall, stronger La Niña events exert more influence on the winter climate pattern over western North America. Weaker events appear to be associated with more widespread above-average snow over the northern United States. Because a weak La Niña means that the forcing from the Pacific is weaker than normal, it may imply other mechanisms (e.g. Arctic Oscillation) may be at play and is worth further investigation.

The predictability of seasonal snowfall may be somewhat similar to precipitation in that one or two big events can dramatically affect the seasonal average. Thus, in general, the expected prediction skill is likely to be lower than for temperature. However, because temperature also plays an important role in snowfall, some predictability is likely nonetheless. And like for seasonal temperature and precipitation, knowing the state of ENSO is a pretty reasonable place to start.

Lead editor: Michelle L’Heureux / Text Credit: Dr. Stephen Baxter


TAKE HOME MESSAGE: For reference, Louisville receives around 12.5" of snow on average each winter season. During La Niña years, our area typically sees a couple inches below the average snowfall. That would put us near 10" during a normal La Niña winter.


-Rick DeLuca



Not Water on Mars

These dark lines seen on Mars have been used by scientists to point to the existence of water, and possibly life, on the planet. However, the latest research shows the dark lines are likely the result of moving sand and dust, not seeping water as previously thought. 

Image Credit: NASA

Without the presence of water, the search for life as we know it on Mars is coming to a screeching halt.

Image Credit: NASA

These dark lines grow during the Martian summer and shrink during winter.  That cyclical movement has been pointed to as evidence for water on the Red Planet.  According to an article from EarthSky magazine, "The steepness of more than 150 of these features has now been assessed with a powerful telescopic camera on NASA’s Mars Reconnaissance Orbiter. The streaks are now being interpreted as grains of sand and dust slipping downhill, rather than as ground being darkened by seeping water." The new information shows the streaks only exist on dunes steep enough for sand to slide, not on flatter dunes. 

Image Credit: NASA

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