Happy Leap Day! 5 simple things to know about a (surprisingly complicated) moment in time

Once every four years, today happens: Feb. 29. But why do we have leap days, and leap years? With the help of Keely Finkelstein, a University of Texas astronomer, we have five things you should know about leap days:

  1. The Western calendar, which uses leap days, is based on the Earth’s rotation around the sun. It takes the Earth 365 days to complete a circuit around the sun. Thus 365 days in a year.
  2. Well, it takes roughly 365 days. The actual number is 365.2422 days. Back in 46 BC, when Julius Caesar ordered the creation of a new calendar, his astronomers knew this. The discrepancy meant that every four years, a day was missing, which could mess with endeavors such as agriculture.
  3. There was a solution, though. Every four years, that missing day should be added back. Thus, today: February 29.
  4. But wait – Caesar’s solution doesn’t quite work. Leap day actually adds too much time to the calendar. Pope Gregory’s people noticed this, too. To account for that discrepancy, the pope decided in the 1580s that every so often we should skip a leap year. So as part of the Gregorian calendar, which we use today, we skipped leap year at the start of every century: in 1700, in 1800, and again in 1900.
  5. But wait … wasn’t 2000 a leap year? Yes, it was, actually. That’s because the pope’s astronomers also figured out that skipping leap year every 100 years would take too much time off the calendar. So to account for that discrepancy, some leap days were added back. We observed Feb. 29 in 2000, and we will again in 2100, 2200 and 2300. But to make the math work, there will be no Feb. 29 in 2400 – at least for those people still living on Earth that point.

leap year

Foggy start leads to warm, mild Monday; small chance of rain on Super Tuesday

feb 29 planner

Monday forecast for Austin: Let’s just call off winter already. Above-normal highs dominate the forecast for the work week and into the first weekend of March. The biggest weather news this week is the small chance of rain possible on Tuesday just as voters head to the polls for primary elections.

At 5 a.m., it’s already warm enough in Austin to be within a few degrees of the normal daily high for this time of year. Monday’s outlook also calls for patchy fog throughout Central Texas before 10 a.m., the National Weather Service says. Mostly cloudy skies will keep conditions muggy as temperatures climb all the way to 78 — peaking 10 degrees above normal for this time of year.

At night, cloud cover increases, it traps radiant surface heat and — coupled with warm south winds — will keep the evening low a balmy 63, the weather service says.

Super Tuesday in Central Texas will start off mostly cloudy before a cold front blows through and gradually turns skies sunny, forecasters say. A small chance of rain in the morning remains in the forecast, but shifting winds of 10 to 15 could gust as high as 20 mph. Once the front passes, the nighttime outlook calls for clear skies and decreased humidity, which will sink the evening low temperature to around 46. Winds are likely to remain gusty.

Wednesday and the rest of the work week are expected to be sunny with high temperatures in the 70s, possibly near 80 on Thursday.


 

Statesman Weather app keeps Central Texans forewarned

The all-new American-Statesman weather app is available for iPhone and Android devices. Statesman Weather features include radar, a 7-day forecast, real-time severe weather alerts, as well as the latest weather news and social sharing. Download for free in the Apple iTunes and Google Play stores by searching for “Statesman Weather.”

Ever asked, ‘What the heck is an upper-level trough?’ Let us explain

You’ll hear it fairly often in forecasts, any may have heard it right before it rained: an “upper-level trough” is on the way. The news may be accompanied by colorful charts. It may not be apparent what a trough actually is, or what it means, aside from some weather being on the way.

We’re here to help translate, along with the good folks the National Weather Service, those running the TravisCountySevereWx Twitter feed, and Troy Kimmel, a forecaster who teaches meteorology at the University of Texas.

The short, short version is that a trough means colder and sometimes wetter weather — and tends to be associated with storms.

First, let’s learn how atmospheric pressure works

The longer version starts with a brief explanation of atmospheric pressure (bear with us):

In low pressure, air way up in the sky is colder than it usually is at that height. Being unusually cold makes it unstable, which then makes air in that part of the atmosphere want to rise. These low-pressure situations are called troughs. The word trough — as in, horse trough — is just a metaphor used to describe a line of low pressure stretching from one place to another. This phenomenon is important partly because sometimes a trough passes over a low-hanging front (the front end of a mass of air moving into an area).

A front pushes air upward, and if there is a trough overhead, the air goes up into the trough. If that air in front of that trough has significant amounts of moisture, that moisture collects as clouds, with those clouds sometimes dropping rain as they pass.

Here is a visual explanation, via the weather service:

tstorm2

A trough usually shows up on weather maps as dashed red or brown lines, Kimmel said.

The counterpart to a trough is a ridge. They tend to be less exciting. A ridge is a line of high pressure, where the air way up in the sky is heavier than usual. It pushes down on the air underneath it. The weight makes the air below it stable. That produces the less-exciting kind of weather. A ridge is usually depicted with a zigging line, Kimmel said.

Think of them as water ripples

Paul Yura, the second-in-command of the National Weather Service’s New Braunfels office, compared troughs and ridges to the ripples in water. The atmosphere, like water, has ripples that roll through it. The cold ripples are the troughs. The warm ones, the ridges.

Things get a little more complicated when talking about “lower level” versus “upper level,” which refers to how high in the sky the trough or ridge is happening. For our purposes, an upper-level trough is two to five miles above the Earth’s surface.

Got it? Let’s now use a real-world example

The nice, clear, stable weather we had been enjoying recently here in Central Texas — suck it, Buffalo! — had been coming from a ridge hanging overhead, Kimmel said. We’d had a few cold fronts come through in recent weeks, but they didn’t bring rain because there hasn’t been much moisture in the air. The majority of the moisture around here generally comes from the Gulf of Mexico, but the gulf had not sent moisture this way in a while.

“When (troughs have) gone through, there’s been nothing to lift,” Kimmel said.

Early Tuesday morning, there was moisture in the air. That moisture arrived, from the gulf, just ahead of the trough and the front. The trough therefore had something to lift. Voila: thunderstorms, and more than an inch-and-a-half of rain.

Sunny, mild Friday; flip from heater to A/C this weekend; small chance of rain on primary day

National Weather Service
National Weather Service

Friday forecast for Austin: A chilly start to Friday will give way to sunshine and mild temperatures in the 60s this afternoon, but forecasters expect the weekend to be even warmer. A small possibility of rain early next week might complicate a trip to the polls on Tuesday.

Friday’s outlook calls for sunny skies, with a high near 64. Winds will shift from the north-northeast to become south-southeast breezes in the afternoon, the National Weather Service says. The nighttime should see clear skies with a low around 43.

Clouds may increase over the weekend, but not enough to bring rain just yet, forecasters say: Saturday will be mostly sunny, with a high near 71. At night, skies will turn partly cloudy, with a low around 53.

Sunday’s forecast also calls for partly sunny skies, with a high near 77. But the prevailing south-southwest winds of 10 to 15 mph may see gusts as high as 20 mph. On a mostly cloudy night, the low falls to around 56, the weather service says.

So far, Monday should just be partly sunny, with a high near 78, forecasters say. Clouds increase Monday night, which should keep the evening low a comfortable 61.

On primary day in Texas, the forecast calls for a 30 percent chance of showers and thunderstorms. Tuesday will see an above-normal high near 75, the weather service says. Skies will clear up at night, and the humidity will diminish, resulting in a nighttime low around 46.

Watch: 35 tornadoes hit Texas, Gulf states, Virginia, Carolinas

At least six of the 35 tornadoes to have touched down in the Gulf Coast states, the Carolinas and Virginia in the last few days were rated EF2 or stronger. This includes two tornadoes, one in Convent, Louisiana and one in County, Mississippi, which proved deadly. The area has been ravaged by severe weather this past week, the Weather Channel reports, with over 300 reports of wind damage and strong wind gusts reported to the Storm Prediction Center as of Thursday morning. This is the most reports to have been submitted in a 24-hour period since July 2015. According to Weather Underground meteorologist Bob Henson, the past two days have been the deadliest (with four people reported dead by the Associated Press) from tornadoes in Virginia since 2011’s Superoutbreak.

via The Weather Channel
via The Weather Channel

Additional tornadoes are expected later Thursday. Emergencies have been declared in several Southern states including, Louisiana, Mississippi, Alabama and Florida.

Although Austin is currently expecting cooler, more winter-like temperatures, we can expect to be back in the 70s come this weekend. Check out today’s Austin weather forecast here.

Cold, frosty start to mild, sunny Thursday; ditch sweaters for shorts this weekend

National Weather Service
National Weather Service

Thursday forecast for Austin: Now this is what winter in the metro area is supposed to be — cold, frosty mornings that turn into brisk days with light winds and daily temperatures mostly in the 50s before peaking no higher than the mid-60s by the late afternoon. But this return to normal winter temperatures won’t last beyond the work week.

Thursday’s outlook calls for a high near 67 with west-southwest winds of 5 to 10 mph that will become north-northeast breezes in the afternoon, the National Weather Service says. At night, clear skies and dry air translate into evening low temperatures around 39.

Friday’s forecast is nearly identical to Thursday, with a high near 65 and shifting winds — this time north-northeast breezes become south-southeast winds in the afternoon, the weather service says. Another night of clear skies is expected but the low is closer to 44.

Spring-like warmth returns this weekend as temperatures rise to near 72 on Saturday and as high as 76 on Sunday, according to the weather service. Increasing cloudiness, starting on Saturday night, will trap radiant heat and keep nighttime lows balmy in the mid- to upper 50s.

By Monday, rain chances also return to the forecast as light sprinkles are expected from 7 a.m. to 7 p.m., the weather service says. The above-normal warmth continues with temperatures peaking near 75.

We could see major rainfall in Austin once again this year as Tuesday’s outlook calls for a 40 to 50 percent chance of storms under mostly cloudy skies. Strong rain chances continue Wednesday.


 

Statesman Weather app keeps Central Texans forewarned

The all-new American-Statesman weather app is available for iPhone and Android devices. Statesman Weather features include radar, a 7-day forecast, real-time severe weather alerts, as well as the latest weather news and social sharing. Download for free in the Apple iTunes and Google Play stores by searching for “Statesman Weather.”

Comet flyby to be closest in centuries

The image on the left is a combination of five 300-s exposures tracking the 'asteroid,' while the image on the right is a smoothed version to help enhance the tail (indicated by the arrow), proving that it is in fact a comet. (M. Kelley/S. Protopapa/UMD)
The image on the left is a combination of five 300-s exposures tracking the ‘asteroid,’ while the image on the right is a smoothed version to help enhance the tail (indicated by the arrow), proving that it is in fact a comet. (M. Kelley/S. Protopapa/UMD)

If you’re outside come March 22 and happen to feel a sudden rush of wind…

No, not really. But you (and everyone else on Earth) will come as close to a comet as anyone has since 1770, when comet P/2016 BA14 becomes the third closest comet flyby of Earth of all time, the Weather Channel reports. How close are we talking? Still about 9 times the distance to the moon. The Lexell comet in 1770 passed about six lunar distances away. “Asteroids frequently flyby at such close distances, but comet encounters are rare,” says astronomer Michael Kelley.

Although the comet’s close range is enough to pique our interest, astronomers are more interested in the possibility that the comet is a sister comet to 252P/LINEAR 12. 252P/LINEAR 12 will pass by on March 21. There is a chance that P/2016 BA14 actually broke off of 252P/LINEAR 12.

“If we can understand if and why these small comets broke apart years ago, we may be able to better determine the general impact threat comets present to the Earth,” Kelley says.

If you want to catch a glimpse of P/2016 BA14, make sure you have your binoculars or a telescope ready come early morning March 22. Tonight, party cloudy and windy, is not the best night for comet watching, but you can check back for your up-to-date Austin weather forecasts here.

Live chat about winter weather with LCRA meteorologist Bob Rose

In an hourlong live chat with the Statesman starting at noon Wednesday, Lower Colorado River Authority meteorologist Bob Rose offers his thoughts about Austin’s winter weather and his expertise as we look ahead at Central Texas climate this year.

Sunshine, mild temperatures Wednesday through rest of the work week

National Weather Service
National Weather Service

Wednesday forecast for Austin: After weeks of warm, spring-like days, punctuated Tuesday by a bout of heavy rain and wildly gusty winds, Austin weather is finally settling into its normal pattern for winter: crisp days with temperatures peaking in the 60s and nighttime lows 20 to 25 degrees cooler.

But that’s really only for Wednesday and the rest of the work week. Then winter is suspended again, and we’re back to balmy highs in the upper 70s this weekend.

So let’s talk about Wednesday: The forecast calls for sunshine and a high near 64. Blustery winds continue to blow out of the northwest at 15 to 20 mph, with gusts as high as 30 mph, the National Weather Service says. At night, skies will remain clear, but without the humidity we saw in the past few days, the air will get a lot chillier as temperatures dip to 39 or closer to freezing. The Hill Country and western parts of the Austin metro area could see a light freeze, so protect your plants and bring your animals inside at night.

Thursday looks even nicer, with sunny skies and a high close to 70. With similar conditions as Wednesday, Thursday’s nighttime low with drop to the upper 30s in the metro area and possibly colder in the Hill Country.

Friday’s weather will feel like a clone of the previous two days with sunshine and a high temperature near 66. Clouds start to gather under mostly clear skies at night, with an evening low around 43. Winds will shift, becoming southerly breezes that bring warmer air, the weather service says.

Saturday opens with sunny skies and warm southerly winds will push temperatures to a high near 74, forecasters say. But at night, increasing cloud cover and the accompanying humidity will likely keep low temperatures to around 54.

The clouds linger on Sunday, but the day should see high temperatures near 76. South winds of 10 to 15 mph kick up, with gusts as high as 20 mph, the weather service says. With mostly cloudy skies at night, Sunday’s evening low will be around 57, forecasters say.


Statesman Weather app keeps Central Texans forewarned

The all-new American-Statesman weather app is available for iPhone and Android devices. Statesman Weather features include radar, a 7-day forecast, real-time severe weather alerts, as well as the latest weather news and social sharing. Download for free in the Apple iTunes and Google Play stores by searching for “Statesman Weather.”

High winds, gusts to batter Austin area Tuesday with a little more rain

National Weather Service
National Weather Service

Tuesday forecast for Austin: The overnight rains that soaked the Austin metro area early this morning delivered the biggest rainfall of 2016, at least at Camp Mabry in Central Austin, which saw 1.33 inches, according to the National Weather Service.

Rain gauges monitored by the Lower Colorado River Authority reported rainfall across Central Texas from 1.26 inches at Onion Creek in southeast Travis County to almost 2 inches in Cedar Park.

Morning commuters that use northbound MoPac Boulevard are girding for the worst, as traffic will bottleneck once again from three lanes to two just north of Lady Bird Lake because of construction. A portion of MoPac was briefly closed in Northwest Austin when standing rain water flooded the onramp from U.S. 183. But the rain has ceased for now and all roadways are clear and open.

Tuesday morning on Congress Avenue. (Ralph Barrera / American-Statesman)
Tuesday morning on Congress Avenue. (Ralph Barrera / American-Statesman)

The biggest weather threat Tuesday comes from high winds and gusts. The weather service has issued a wind advisory for the Austin metro area — including Travis, Hays, Williamson and Bastrop counties — from noon to midnight. Winds are expected to kick up to 25 to 35 mph with gusts as high as 45 mph.

A wind advisory is issued when sustained winds of 26 to 39 mph are expected, the weather service said. Winds this strong can make steering difficult for drivers on open highways and tall vehicles, including 18-wheelers and larger SUVs. The weather service also recommends that residents in the affected areas secure loose items in their yards.

A chance of thunderstorms remains in the forecast for Tuesday until 1 p.m., then only showers are likely, the weather service says. Temperatures should peak around 64. At night, rain chances diminish to 40 percent before 7 p.m. but the blustery winds will continue through midnight. The nighttime low drops to around 44.

Sunshine returns in the outlook for Wednesday. Temperatures will top out near 64 as north-northwest wind of 15 to 20 mph include gusts as high as 25 mph. The humidity from all that cloud cover earlier in the week disappears, which will make Wednesday night particularly chilly, with a low around 39.


Statesman Weather app keeps Central Texans forewarned

The all-new American-Statesman weather app is available for iPhone and Android devices. Statesman Weather features include radar, a 7-day forecast, real-time severe weather alerts, as well as the latest weather news and social sharing. Download for free in the Apple iTunes and Google Play stores by searching for “Statesman Weather.”