11/24/2017

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 Sunday night/Monday 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"...

 

GeminidMeteorShower2012_JeffDai

Image Credit: NASA

 

Geminids:


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"!

 

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11/23/2017

Spot the ISS This Weekend

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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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11/22/2017

WHAT ABOUT SNOW DURING LA NINA WINTERS?

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.

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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. 

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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.

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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

Rick

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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. 

Mars-recurring-slope-lineae-e1443455838123
Image Credit: NASA

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

Recurring-slope-linea-e1511279618975
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. 

Recurring-slope-lineae-Garni-crater-Mars-e1443458025185
Image Credit: NASA

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11/21/2017

UPDATED WINTER OUTLOOK: "Wetter-Than-Normal" Conditions Expected For Ohio River Valley...

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Text & Image Credit: NOAA

 

 

-Rick DeLuca

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11/20/2017

FROST FLOWERS: Rare Weather Phenomenon Spotted In Kentuckiana...

Frost flowers were spotted Monday morning in Kentuckiana! It's a pretty rare phenomenon that only happens in sub-freezing temperatures when a plant's stem hasn't frozen previously and the soil is wet, but not frozen. 

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What is a frost flower and where do you look?

The National Weather Service put together a very cool article about Frost Flowers. This rare phenomena is explained in an article by Glen Conner, a state Climatologist Emeritus for Kentucky:

Frost flowers are thin layers (perhaps credit card thickness) of ice that are extruded through slits from the stems of white or yellow wingstem plants, among others. Their formation requires freezing air temperature, soil that is moist or wet but not frozen, and a plant's stem that has not been previously frozen. (Practically speaking, a once per year event, although not all individuals produce frost flowers on the first day of good conditions). 

The water in the plant's stem is drawn upward by capillary action from the ground. It expands as it freezes and splits the stem vertically and freezes on contact with the air. As more water is drawn from ground through the split, it extrudes a paper thin ice layer further from the stem. The length of the split determines if the frost flower is a narrow or wide ribbon of ice. It curls unpredictably as it is extruded, perhaps from unequal friction along the sides of the split, to form "petals". These flowers, no two of which are alike, are fragile and last only until they sublimate or melt.

To find them, look for tall weeds, especially in locations that are seldom mowed. They seem to like the same habitat purple ironweed, blackberrries and wingstems with the actual frost flowers forming on the wingstems.

 

 

 

-Rick DeLuca

Rick

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11/19/2017

NWS Confirms Tornado in Meade County

The following information comes directly from the National Weather Service office in Louisville. 

...NWS Damage Survey for 11/18/2017 Tornado Event...

.Meade County, Kentucky Tornado...

EF Scale Rating: EF-1
Estimated Peak Wind: 100-105 mph
Path Length/Statue/: 1.8 miles
Path Width/Maximum/: 50 yards
Fatalities: 0
Injuries: 1

Start Date: 11/18/2017
Start Time: 4:32 PM EST
Start Location: 3 miles NNW of Irvington, KY
Start Lat/Lon: 37.9222 / -86.3086

End Date: 11/18/2017
End Time: 4:34 PM EST
End Location: 3 miles N of Irvington, KY
End Lat/Lon: 37.9287 / -86.2763

Survey Summary:

The tornado touched down just inside the Breckinridge-Meade County
line a mile north of Irvington. It pushed a large tobacco barn 15
feet eastward, tore off its roof, and collapsed several walls.
Debris from the barn was scattered over a half mile downwind. The
tornado moved east-northeast, skipping along a wooded area where
several trees were snapped or uprooted, then hit a mobile home on
Fackler Road, rolling the anchored unit several times, destroying
the home. The owner sustained only minor injuries as he rolled over
with his house, crawling out of a hole after it settled. A garage
on the property was also destroyed. The tornado continued skipping
along the northwest side of Sandy Hill Rd, damaging outbuildings on
another farm, before crossing KY highway 261 at Guston Rd. A split
level home on Guston Rd had part of its roof removed, with
insulation spattered on the lee side of the home. An occupant of
the home reported he was descending the stairs as the roof was torn
off, and was briefly drawn up the stairs as it occurred. Debris from
the split level home was dropped across the road, where a few more
trees were snapped and uprooted. The tornado then flattened a fence
and peeled a section of sheet metal on an outbuilding before
lifting. The NWS thanks Meade County EMA and Remote Aerial for their
assistance in this damage survey.

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Cold Air Invades for Thanksgiving Week

There are two different cold fronts coming through Kentuckiana this week bringing bitterly cold air.  The first one will come through Tuesday night, which means Wednesday morning will be very cold.  That's a travel day for many people being the day before a holiday, so let's break down what you will see. 

AT5

Temperatures Wednesday morning will be in the upper 20s, but notice the direction the wind is coming from.  It's coming out of the north/northwest in the image below.  That means the wind chill values will be much lower than temperatures. 

AT5

Wind chills, according to the North American Model, will be in the teens across Kentuckiana.  The good news here: even with wind chills that cold, it will still take more than 30 minutes for frostbite to set in if you're exposed to this bitterly cold air.  Even as cold as it will be, this is not considered dangerous unless you are outside without a coat/gloves/hat, etc. for an extended period of time. 

AT5

Temperatures on Thanksgiving morning will be similar, but wind chills won't be quite as low.  Notice the wind pattern in the image below.  It's hard to pick one out near Louisville because there will be a High Pressure very near us Thursday and Friday.  Thanksgiving and Black Friday will start cold, but not with wind chills in the teens. 

AT5

If you're not spending the holiday in Louisvile, here's how you can figure out the wind chill for where you are traveling.  This chart is from NOAA.

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VIDEO: 2017 Hurricanes Simulation

How can you see the atmosphere?

The answer is blowing in the wind! Tiny particles, known as aerosols, are carried by winds around the globe. This visualization uses data from NASA satellites combined with our knowledge of physics and meteorology to track three aerosols: dust, smoke, and sea salt.

Video Credit: NASA Goddard

Sea salt, shown here in blue, is picked up by winds passing over the ocean. As tropical storms and hurricanes form, the salt particles are concentrated into the spiraling shape we all recognize. With their movements, we can follow the formation of Hurricane Irma and see the dust from the Sahara, shown in tan, get washed out of the storm center by the rain. Advances in computing speed allow scientists to include more details of these physical processes in their simulations of how the aerosols interact with the storm systems. The increased resolution of the computer simulation is apparent in fine details like the hurricane bands spiraling counter-clockwise. Computer simulations let us see how different processes fit together and evolve as a system.

By using mathematical models to represent nature we can separate the system into component parts and better understand the underlying physics of each. Today's research improves next year's weather forecasting ability. Hurricane Ophelia was very unusual. It headed northeast, pulling in Saharan dust and smoke from wildfires in Portugal, carrying both to Ireland and the UK. This aerosol interaction was very different from other storms of the season. As computing speed continues to increase, scientists will be able to bring more scientific details into the simulations, giving us a deeper understanding of our home planet.

Pretty cool, right?! Let me know your thoughts in the links below! 

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11/18/2017

Saturday Post-Storm Analysis

Saturday's cold front packed quite the punch! Our WDRB counties saw 12 Severe Thunderstorm Warnings and 1 Tornado Warning through the afternoon.  That cold front is now dropping our temperatures.  This temperature fall actually happened in about 3 hours. 

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Just as forecast, wind was the main threat today.  That's why there were so many thunderstorm warnings.  As the night continues and the sun rises tomorrow, it is likely more damage reports will come in. Measured wind gusts exceeded 50 mph in several places around Kentuckiana. 

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On Sunday the National Weather Service office in Louisville will do a damage survey for the one tornado warning they issued. 

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It was near Mount Washington in Bullitt County.  Above you can see the reflectivity.  This is the exact moment the tornado warning was issued.  Below is the velocity showing the rotation.  Because winds were so universally strong today, we did not see the normal reds and greens next to each other in these rotation couplets.  Instead you see dark red next to pink/orange. 

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There was a small debris signature near this area of rotation for only a couple radar scans.  However that debris signature wasn't as tight/organized as we normally see in a storm like this.  The strong winds, especially higher up in the atmosphere, could have scattered any debris making it look less organized.  I'm not convinced there was a tornado touch down in this area, but it is VERY possible.  The National Weather Service will let us know tomorrow, so watch for updates.  Katie and I will keep you posted through the day. 

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