Weather

Sleet or freezing rain: what’s the difference?

February 22nd, 2015 at 11:02 am by under Weather

With a Winter Weather Advisory in effect for the Hill Country and Austin metro area in the next 36 hours, you may be wondering about the sleet and freezing rain in the forecast. Are the terms not interchangeable? Do the two types of winter precipitation create any difference, once on the surface?

Here’s a scientific breakdown from our friends at the National Weather Service in Amarillo:

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Boiled down, both sleet and freezing rain have droplets that go through a cold-warm-cold pattern when falling through the atmosphere.

Sleet has a large enough cold layer before the surface that it refreezes, and it hits the ground as ice pellets.

Freezing rain remains liquid until it hits a surface. It instantly freezes on the first thing it comes in contact with, be it grass or cars or roadways. That makes freezing rain the greater danger of the two types of precipitation. Even a few hundredths of an inch of ice can make hazardous driving conditions.

A Winter Weather Advisory begins in the Hill Country at midnight on February 23, 2015. That same advisory extends to the Austin metro area, including Travis, Williamson and Hays counties, at 3 AM on February 23, 2015. The advisory expires for everyone at 6 PM on Monday night. Sleet is more likely for the Hill Country with this system, though Monday night/Tuesday morning, everyone through the metro may see a bit of freezing rain. Be safe!

2-22 WWA

 


Latest NWS Update On The Possibility Of Ice Monday & Tuesday

February 21st, 2015 at 4:00 pm by under Weather

.Arctic Airmass Moves In Tomorrow…Freezing Rain Possible Monday Morning Through Tuesday Morning…

 

AREA OF CONCERN
  • Cold Arctic Air - All of South Central Texas.
  • Chances of Freezing Rain Monday -  Mainly along and north of a line from Juno-Kerrville-Burnet on Monday morning. Line could shift to a Laredo-Boerne-San Marcos-Georgetown line if temperatures are a couple of degrees colder than expected.
  • Chances of Freezing Rain Monday Night/Tuesday Morning -The line should shift south and east to a Rocksprings-Boerne-Giddings line by Monday night. Rest of South Central Texas needs to monitor the forecast closely as this forecast impact area could change.                                .
 …IMPACTS
  • Less than 1/10″ of ice accumulation expected. Accumulations only expected on exposed surfaces, bridges and overpasses. Worse accumulations will be in the northern Hill Country where temperatures may dip below 30 degrees. 
  • Travel impacts should be minor as ground temperatures should remain quite warm initially. Exposed surfaces, some bridges and overpasses may see minor icing, and slippery walkways are anticipated. Rainfall is expected to be light so any accumulations should be a gradual process. 
TIMING
  • Arctic air will arrive Sunday and remain in South Central Texas through Tuesday.
  • Chance of freezing precipitation will begin around daybreak Monday morning as temperatures fall to freezing for the northern Hill Country The freezing line will shift southeast Monday evening into Tuesday Night. Temperatures will warm above freezing for all of South-Central Texas by late Tuesday morning ending the threat for winter precipitation.
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 Monday Tuesday

Don’t forget to download our KXAN First Warning Weather App!  It’s now available in your app store, for free!!  What’s included?

-  Video and text forecasts updated multiple times a day

-  Accurate and up to date hourly forecasts, that can be customized for multiple locations.

-  7 day forecast

-  Interactive radar

-  Our “Report It” feature, which lets you take weather pictures and video and send them directly to the First Warning Weather Center.

-  Access to our KXAN Weather Blog

 

 


NWS update for Sunday – Monday – Tuesday

February 21st, 2015 at 10:39 am by under Weather

Thanks to a cold mass of arctic air, at KXAN we’re forecasting small ice accumulations in the Hill Country by Monday morning, with San Saba and Lampasas counties under a Winter Storm Watch starting Sunday night. Ice is most likely on elevated surfaces, like bridges and overpasses: something to keep in mind if you have to be out on the roadways Monday morning!

Here’s what the National Weather Service office has to say on the chilly intrusion:

HEADLINE…Arctic Airmass moves in Sunday…Winter Precipitation possible Monday Morning through Tuesday Morning…

AREA OF CONCERN
  • Cold Arctic Air - All of South Central Texas.
  • Chances of Frozen Precipitation Monday/Tuesday -  Mainly along and north of a line from Rocksprings-Kerrville-Burnet on Monday. The line could shift south along a Del Rio-Uvalde-New Braunfels-Giddings line by Monday night. Rest of South Central Texas needs to monitor the forecast closely as this forecast impact area could change.                                     .
 …IMPACTS
  • Cold Arctic Air - Temperatures will be well below normal with high temperatures only in the 30s and 40s on Monday.  Lows Tuesday Morning will be in the 20s and 30s.
  • Frozen Precipitation - Light icing on elevated surfaces.  Travel may be impacted especially out in the Hill Country and northern areas where temperatures will likely be coldest.
TIMING
  • Arctic air will arrive Sunday and remain in South Central Texas through Tuesday.
  • Chance of precipitation will begin shortly after the front moves through the area. Temperatures could drop below freezing for the northern Hill Country as early as Monday Morning. The freezing line will shift southeast Monday evening into Tuesday Night. Precipitation should shut off from west to east by Tuesday Morning.
CONFIDENCE… Arctic Air (High)…Frozen Precipitation amounts and area (Low)
DISCUSSION
A strong upper level ridge of high pressure is strengthening off the coast of the Western US. A strong low will develop to the east and this pattern will send a strong arctic front into South Central Texas by Sunday morning. This front will bring much colder temperatures with 30s/40s across the area Monday Morning continuing into the day Monday. At the same time, strong winds aloft will allow for lift to aid in the development of light precipitation beginning Sunday and lasting into Tuesday. The main focus will then shift to the temperature forecast. As of today, locations north of a Rocksprings to Kerrville to Burnet line will have the best chances to see freezing rain or perhaps sleet Monday morning and then again Monday night. There should be a warmup into the middle 30s for these locations in the afternoon hours. However, even colder temperatures are expected by Monday evening and Tuesday morning and locations north of a Del Rio to Uvalde to New Braunfels to Giddings line could see freezing precipitation.
We are still a few days out from this possible winter event so trying to nail down the specific times and area of greatest impact is very difficult. If temperatures are warmer or colder by even two degrees, a significant shift in the forecast will be needed. All residents need to monitor the forecast closely this weekend for possible winter weather advisories/watches/warnings.  There may be travel impacts, especially in the northern Hill Country on Monday – Tuesday.
The NWS has provided this image to go along with the discussion:
Untitled
Though Austin is in the “low probability” area for ice, it’s still something our weather team is watching. Here is our current prediction for frozen precipitation through Tuesday:
2-21 2
The metro area is right on the cusp of the line between cold rain and ice. With temperatures that will hover in the 30s all day Monday, we’re monitoring the potential for slick roads.
Ideally, the air will dry out before the coldest push of air comes through Monday night. This system still has time to shift and change, though, so keep checking back with us and the current forecast at KXAN.com.

Public invited to free SKYWARN training Saturday

February 20th, 2015 at 10:24 pm by under Weather

 

skywarn

24th Annual
  Lou Withrow SKYWARN
  Austin / South Central Texas
  Severe Weather Spotter Training Session

   ACC Eastview Campus, Building 8000, Room 8500
   3400 Webberville Road, Austin, TX 78702
Saturday / 21 February 2015

   8:15 am to 4:15 pm /  BASIC & ADVANCED TRAINING

  Sponsored by:        
         Austin Community College (ACC)
National Weather Service / Austin – San Antonio
Midland Electronics
         L C R A
         3M Austin Amateur Radio Club
         American Red Cross – Centex Chapter
City of Austin Watershed Protection

 
    Session Chairperson:          Session Asst Chairperson:        Technical Chairperson:
    Troy Kimmel (Email)            Bob Rose                                     Mark Murray

    Session Hosts:
    Larry and Barbara Gensch
    ASSOCIATED PUBLICATIONS:
    South Central Texas SkyWarn Spotter Manual (pdf)
   

     REGISTRATION:
             No advance registration required. This session is FREE of charge (other than lunch on your own).
             Plenty of Free Parking.
             Sign in / Registration starts at 8:15am the day of the training (please do not arrive before 8:15am).
             A certificate of completion will be presented to those participants, at the end of the day, for those
completing the entire training session.

      WHO SHOULD ATTEND:
             This training is open to the general public.
             Those involved in public safety and severe weather safety / recognition, such as amateur radio operators,
             first responders (police officers, firefighters and EMS officials), emergency management officials and
             media representatives (reporters, photojournalists) are encouraged to attend this important session.

     PRELIMINARY SCHEDULE:

PROGRAM HIGHLIGHTS:
             …. Basic and Advanced Spotter Training ….
           

      8:15 – 9:00 am…. Session Registration

      9:00 – 9:15 am….  Session Welcome by Troy Kimmel and Bob Rose
                                        Facility Guidelines and Reminder – Larry and Barbara Gensch

      9:15 – 9:35 am…. National Weather Service Welcome
                                            Joe Arellano, Meteorologist in Charge, NWS / Austin-San Antonio

      9:35 – 9:40 am…. South Central Texas SkyWarn Spotter Guide Update – Troy Kimmel
                                            (found at: http://www.utexas.edu/depts/grg/kimmel/skywarnbook.pdf )

      9:40 – 10:15 am….  TBA 

      10:15 – 12:00 noon…. Basic SkyWarn Training Session
                                                   Paul Yura, Warning Coordination Meteorologist, NWS/Austin-San Antonio

     12:00 noon – 1:15 pm…. LUNCH – On Your Own

     1:15 – 2:15 pm….  KEYNOTE SPEAKER – TBA

2:15 – 3:45 pm…. Advanced SkyWarn Training Session
                                           Paul Yura, Warning Coordination Meteorologist, NWS/Austin-San Antonio

3:45 – 4:15 pm…. SkyWarn Exercise and Session Close


Upcoming Pet Events In Austin

February 20th, 2015 at 3:04 pm by under Weather

In honor of it being National Love Your Pets Day, and our obvious love for animals around the First Warning Weather Center, we figured ‘let’s take a brief break from the “weather” blog, and pass along some fun pet events happening in town this weekend!’  So… who better to do the honors than our very own lovable, stylish weather dog, Kaxan!

kaxan

 

 

Woof! That’s ‘Hello!’ in dog speak!  Kaxan here.  First thing is first… Happy Love Your Pet Day!  One of the best days of the year if I do say so myself.  Don’t forget to give your pet a good belly rub, new toy, or my favorite, treat today!  

Alright, let’s get down to business.  My friends in the KXAN First Warning Weather Center have asked me to bring to you the most tail waggin events for pets in and around the Capitol City.  So, get your cats, lizards, piglets, rabbits, and of course dogs ready for some fun!  Here we go:

 

THIS WEEKEND 

APA

Austin Pets Alive! 4th Annual No-Kill Anniversary Party

When:  Sunday February 22, 2015

Where:  Palm Door On Sixth

Info:  Celebrate four years of no-kill in Austin on February 22nd at Palm Door on Sixth! Enjoy great food, music by Dale Watson, a photo booth provided by On the Flipside and the beautiful reminder that you live in a city that is capable of such an incredible thing.

Ticket Info:  No-Kill is a journey, not a destination, and we must continue to work as a community to save our four-legged friends. One hundred percent of ticket sales and donations go to Austin Pets Alive!  Tickets are $45, which includes some cool stuff and a great day!  Click here to order tickets!

 

THIS MONTH

rvm

4th Annual Capitol City Rockers vs. Mods

When:  Sat, February 28, 1pm – 6pm

Where:  Lone Star BMW/Triumph, North Lamar Boulevard, Austin, TX

Info:   Alright, alright, alright! The 4th annual Capital Rockers vs Mod Feb 27th –March 1st 2015 is in full effect. Gear heads come together with both custom and vintage motorcycles and scooters represented as we rave on in the city of Austin. It’s a nice little Spring Social and Ride for those with a penchant for petrol and an overdeveloped throttle hand.So change that oil and pull that dent out of your tank; it’ll be here before you know it.

Ticket Info:  Click here for tickets or go to the main page.

 

MARCH

horses

TEXAS STAR TRAIL RIDE ‘ Horse Riding In The Hill Country’

When:  Mar 6-14, 2015

Where:  All over the Hill Country!

Info:  A 107 mile horse ride that the Original Texas Star Trail took through Fredericksburg, Luckenbach, Stonewall, Johnson City, Blanco, Fischer, Wimberley and Driftwood.  Each year, about 300 people take part in the 112 mile ride. It’s the experience of a lifetime, and one you will not forget. We cross 40 cattle guards through more than 20 hill country ranches, including the LBJ Ranch.

Click Here For More Info

 

 

REGIONAL CHAMPIONSHIP DOG AGILITY SHOW

When:  Friday, Mar 13 – Sunday, Mar 15  8:00 am – 5:00 pm

Where:  Kerr County Hill Country Youth Event Center

Info:  A regional competition with competitors from all over the country.  Watch dogs run and jump as handlers direct them through an obstacle course.

For more information click here!

 

FANCY FEATHERS 4-H CLUB APA/ABA SANCTIONED OPEN CHICKEN SHOW

4h

When:  Mar 21, 2015

Where:  Dripping Springs; 1042 Ranch Park

Info:  Annual event where breeders, from near and far, bring their fancy chickens to be judged according to the APA or ABA Standards of Perfection established for each breed and variety. Even if you don’t enter chickens, you are still welcome to attend.

For more information cluck here!

 

IF THERE ARE ANY OTHER EVENTS YOU WOULD LIKE TO POST, JUST LEAVE A COMMENT AT THE BOTTOM.


Study: Projected droughts could be worst in 1,000+ years

February 19th, 2015 at 9:30 am by under Weather

(Science Advances) — In the Southwest and Central Plains of Western North America, climate change is expected to increase drought severity in the coming decades.

These regions nevertheless experienced extended Medieval-era droughts that were more persistent than any historical event, providing crucial targets in the paleoclimate record for benchmarking the severity of future drought risks.

We use an empirical drought reconstruction and three soil moisture metrics from 17 state-of-the-art general circulation models to show that these models project significantly drier conditions in the later half of the 21st century compared to the 20th century and earlier paleoclimatic intervals.

This desiccation is consistent across most of the models and moisture balance variables, indicating a coherent and robust drying response to warming despite the diversity of models and metrics analyzed. Notably, future drought risk will likely exceed even the driest centuries of the Medieval Climate Anomaly (1100–1300 CE) in both moderate (RCP 4.5) and high (RCP 8.5) future emissions scenarios, leading to unprecedented drought conditions during the last millennium.

(more…)


LCRA declares current Highland Lakes drought worst ever

February 18th, 2015 at 3:16 pm by under Weather

See the recent First Warning Weather in-depth report on the possibility of the current drought lasting decades.

AUSTIN, Texas – Preliminary 2014 data shows the drought gripping the Highland Lakes is now the most severe drought the region has experienced since construction of the lakes began in the 1930s.

As a direct result of the prolonged record-dry conditions and record-low inflows from the streams and tributaries feeding the Highland Lakes, the “firm yield,” or inventory of water LCRA can provide reliably every year, has been decreased by about 100,000 acre-feet, to 500,000 acre-feet per year. (An acre-foot of water is 325,851 gallons.) Further reductions in firm yield are possible as the drought continues.

LCRA staff provided its revised firm yield estimates in an update to the LCRA Board of Directors during a Water Operations Committee meeting on Feb. 18.

In the presentation, staff reported preliminary data shows the Highland Lakes are now in a new “critical period” marking the driest conditions on record, eclipsing the 1947-57 drought that until now was the worst on record for this region.

“We’re in a historic drought like we’ve never seen in our lifetimes,’’ said Phil Wilson, general manager of the Lower Colorado River Authority. “Based on our preliminary analysis of 2014 data, we are now in a new critical period. As a result, our reliable inventory has been reduced by 100,000 acre-feet a year, to 500,000 acre-feet per year. Even in these conditions, however, lakes Travis and Buchanan remain significantly above their all-time lows, thanks to smart water management decisions and excellent water saving efforts by our customers throughout the lower Colorado River basin.”

The most water used by firm customers in a single year was about 250,000 acre-feet in 2011, far below the estimated 500,000 acre-feet per year firm yield.

(more…)


Become a registered storm spotter this weekend

February 18th, 2015 at 7:18 am by under Weather

Saturday / 21 February 2015 – 815am to 330pm
24th Annual Lou Withrow SkyWarn Training Session (Basic and Advanced Training)
ACC Eastview Campus, Building 8500
3400 Webberville Road, Austin, TX 78702

— PLEASE PARK IN LOTS B, C, D or F ONLY —
— DO NOT PARK IN FACULTY/STAFF LOTS —

SkyWarn trainer:  Paul Yura, NWS/Austin-San Antonio Warning Coordination Meteorologist

Keynote speaker:  Dr. Kevin Kloesel from the University of Oklahoma

SkyWarn web info page (including parking lot map)

Updated South Central Texas SkyWarn Spotters Guide (pdf)

This day of training is free and open to the public and recommended for…
. storm spotters
. amateur radio operators
. law enforcement and first responders (PDs, FDs, EMS, etc)
. news media (reporters, photographers)
. governmental agencies (EMs, etc)
. anyone with an interest in learning more about severe and inclement weather


Do recent global precipitation anomalies resemble those of El Niño?

February 17th, 2015 at 8:15 pm by under Weather
(Climate.gov)

Since October 2014, sea surface temperatures (SST) across the tropical Pacific have exceeded the thresholds of weak El Niño (1), but the atmosphere has failed to really participate. Otherwise, we’d have seen above-average convection (thunderstorm activity) in the central tropical Pacific Ocean, a weakening of the surface trade winds, and a lowering of the Southern Oscillation Index and the Equatorial Southern Oscillation Index (2)—none of which showed up consistently.

However, how much does the atmosphere matter? Can the warm SSTs alone have global climate impacts? While the answer may vary depending on location and type of impact (3), here we ask whether the most recent season (the November 2014-January 2015 average) showed global precipitation responses that resemble those expected during El Niño.

What was the global precipitation pattern during November 2014 to January 2015?

Figure 1 shows the pattern of the deviations from average (or “anomalies”) of precipitation across much of the globe for the November to January average. The brown color shows regions receiving below average rain and/or snow, and green shows above average.

Figure 1. Observed precipitation from November 2014–January 2015, compared to the long-term average (in mm). Below-average rainfall is shown in brown; above-average rainfall is green. Data from CAMS_OPI, produced at NOAA/Climate Prediction Center.

Over the United States, much of the Ohio and Mississippi valleys were somewhat drier than average, while southern Texas and part of Florida were wetter than average. In South America, most of Brazil had below average rainfall. How do these patterns, and the many other features shown in Fig. 1, compare with the historically expected patterns during El Niño?

What should it have looked like?

Figure 2 shows the expected pattern of El Niño precipitation anomalies for November-January, based on an analysis of the historical data from 1981 to the present (4). At first glance, the historical El Niño pattern does not look much like what happened this year. For example, in the United States during El Niño, above average rainfall would be expected across a wider range of the southern United States. The area of below average precipitation in the Ohio and Mississippi valleys in the recent observations is broader than seen in the historical El Niño pattern (See footnote 5 for more detail for the United States).

Figure 2. Geographic pattern of deviation from average precipitation expected for November-January during El Niño, based on a statistical analysis of data from 1981 to present. The “classic” El Niño rainfall signal in this season is above-average rainfall (green) in the east-central tropical Pacific, the southern United States and Mexico, and the Horn of Africa, with below-average rainfall (brown) around Indonesia, over the Caribbean and northern South America, and across southern Africa. Units are relative, not physical. Map based on analysis by Dr. Brad Lyon at IRI, Columbia University.

Outside of the United States, the most obvious disagreement between the typical El Niño pattern and what occurred this year is in the central and east-central tropical Pacific Ocean itself, where the observed rainfall was below average while during El Niño it would nearly always be above average. El Niño normally is associated with below average rainfall over Indonesia and northern Australia, which was generally not observed this year. The same can also be said about southern Africa. In South America, on the other hand, there is moderate (but far from perfect) agreement with the expected El Niño anomalies. So, overall, how did the observations stack up?

And now the math…

(more…)


Did Austin Marathon, Half Marathon runners go faster because of the weather?

February 15th, 2015 at 11:49 am by under Weather

The question isn’t a new one, but it arose this morning when discussing the feats of the Austin Marathon and Half Marathon runners. The forecast was a muggy one, with AM patchy fog in the area:

2-15 Marathon

Fog itself is not a sort of precipitation, as most people think: it’s actually a type of atmospheric suspension, which is created by water vapor condensing into tiny water droplets that are light enough to remain in the air. Fog is most likely when there are fewer than 4 degrees that separate the air temperature and the dew point temperature. Note the places where fog exists when air and dew point temperatures are compared (as an example from this morning):

002 0021 0023

Where the dew points are generally within 4 degrees of the air temperature, you can see that visibility is reduced, due to fog formation. This example demonstrates that fog, made from water vapor, was present this morning. Water vapor is the real item we’re after.

A good blog on all things weather comes to us from Meteorologist Jeff Haby, who produces TheWeatherPrediction.com. Here is an interesting read on the ways that an object traveling on the Earth can be affected by the weather. Haby notes air pressure, air temperature, wind direction/speed and humidity, using the example of a baseball that has been hit and is traveling away from home plate.

Kacy Clemens

 

(“Texas’ Kacy Clemens hits an RBI single against Houston in the fourth inning of an NCAA college baseball tournament super regional game in Austin, Texas, Friday, June 6, 2014. (AP Photo/Michael Thomas)”)

The chemical composition of a molecule of air allows for anywhere between 0.01% – 4.24% of breathable air be made up of water vapor. Check that out here. Below is a table of what air molecules are made from, but the gist is that Oxygen (O2) and Nitrogen (N2) are “heavy” at a molecular level, while water vapor is “light.”

Untitled

 

(This image is from Wikipedia, which certainly doesn’t know everything, but usually gets its tables right!)

Combined, O2 and N2 make up about 99% of an air molecule. If there’s more water vapor in the air, it forces a displacement of N2 and O2 from the area (of equal pressure, temperature and volume) around it. Thanks to Avogadro’s number (it’s nerdy: check out the definition here), the number of molecules has to be the same. So lighter ones (water vapor) push the heavier ones (dry O2 and N2 molecules) out.

That means that, regardless of the way moist air FEELS sticky and sluggish, it is actually LIGHTER than dry air. If the air is lighter, there is less friction to force an object to slow down, like baseballs … or, in the case of today, humans.

The Austin Marathon and Half Marathon were also helped by a relatively mild air mass. Warmer air = lower air density. Higher temperatures force a parcel of air to expand, which increases volume and lowers density. We like to think about it like this: if you heat up plastic, sealed package of, say, broccoli (gross!) in the microwave, that package will expand ( = increased volume). If you were then to take that puffy package and measure how many pieces of broccoli were in each cubic inch of space, you’d find that they were fewer broccoli bits than when the package was cold and small. The density of air molecules works the same way!

BOTTOM LINE: with all other things being equal, a mild, moist air mass over Austin today may have helped propel the Austin Marathon and Half Marathon runners just a little bit faster. (Congratulations to all the finishers and winners of the race!)