Localized flash flooding possible tonight

September 6th, 2014 at 7:23 pm by under Weather

9-6 omni

 

As a slow-moving cold front interacts with deep, tropical moisture overnight tonight — the stage could be set for localized heavy rainfall and flash flooding.

Our exclusive in-house high-resolution model, pictured above, is forecasting the possibility of several hours of heavy, slow-moving thunderstorms in parts of Central Texas (including Metro Austin) from around 12:30am until 4am Sunday morning.

If this situation does play out, we could face problems with overnight flash flooding.

Find more details on your First Warning Forecast here, and in the below discussions courtesy of the NOAA Hydrometeorological Prediction Center and the National Weather Service:

NWS:

LATER TONIGHT...A COLD FRONT OVER NORTH TEXAS IS EXPECTED TO
MOVE INTO THE HILL COUNTRY AND BRING AN ADDITIONAL FOCUS FOR RAIN
LATE THIS EVENING INTO THE OVERNIGHT HOURS. THE COLD FRONT...AS
WELL AS ASSOCIATED OUTFLOW BOUNDARIES FROM CONVECTION...IS EXPECTED
TO PRODUCE HEAVY RAIN AND POSSIBLE LOCALIZED FLOODING. THESE AREAS
ARE GENERALLY NORTH OF A LINE FROM DEL RIO TO SEGUIN TO LEXINGTON.
THE REASONING OF POSSIBLE LOCALIZED FLOODING IS DUE TO SLOW MOVING
STORM MOTION/STEERING FLOW WHICH COULD RESULT IN RAINFALL AMOUNTS
OF 1 TO 3 INCHES WITH UP TO 5 INCHES POSSIBLE. THE TIMING IS FROM
ABOUT 7 PM TO 4 AM SUNDAY MORNING. BY SUNDAY MORNING...THE COLD
FRONT SHOULD BE EXITING OUR SOUTHERN COUNTIES WITH ISOLATED
SHOWERS AND THUNDERSTORMS LINGERING IN THE WAKE OF THE FRONT
MAINLY ALONG INTERSTATE 35 AND EASTERN COUNTIES.

NOAA HPC (technical):

...CENTRAL TEXAS...

THE BULK OF THE PCPN CURRENTLY ACROSS THE SRN PLAINS IS
ANAFRONTAL...HOWEVER...PER THE MOST RECENT STLT/RADAR TRENDS AHEAD
OF THE SFC COLD FRONT...SUPPORTED BY THE LATEST MESOSCALE
GUIDANCE...EXPECT A SWATH OF SLOW-MOVING CONVECTION TO ORGANIZE
ALONG AND AHEAD OF THE COLD FRONT ACROSS CENTRAL TEXAS WHERE THE
THERMODYNAMIC PROFILE IS MUCH MORE SUPPORTIVE OF A HEAVY RAINFALL
THREAT. THIS AS PRECIPITABLE WATER VALUES POOL NEAR 2.00 INCHES
ALONG THE FRONT...COUPLED WITH THE AVAILABLE DEEP-LAYER INSTBY
WITH MUCAPES BETWEEN 1500-2500 J/KG. WEAK OVERALL FLOW...INCLUDING
THE LLVL INFLOW...WITH 0-6 KM BULK SHEAR VALUES GENERALLY 15 KTS
OR LESS WILL LIMIT THE ORGANIZATION/DURATION OF DEVELOPING
CONVECTION...HOWEVER AS PER THE HIGH RES GUIDANCE HOURLY/3- HOURLY
RAINFALL RATES OF 2.5/3-5 INCHES RESPECTIVELY COULD CERTAINLY
TRIGGER ISOLATED RUNOFF ISSUES DESPITE THE CURRENT HIGH FLASH
FLOOD GUIDANCE.

Western drought drops Lake Mead to lowest level since it was built

September 5th, 2014 at 1:30 pm by under Weather

On July 11, the day these photos were taken, the Lake Mead reservoir reached its lowest water level since the lake was first filled during the construction of the Hoover Dam in the 1930s, according to the Bureau of Reclamation. The lake’s elevation was 1,081.77 feet—147.23 feet below capacity and 133.99 feet below its last peak in 1998. Similar to how the rings in the cross-section of a tree trunk can tell a story about that tree’s past, the high points and low points of Lake Mead’s water history can be glimpsed from observing recent photos taken at the Hoover Dam.

The highest rust-colored ring on the concrete dam structure shown in the top photo marks the height of the water when the lake is near capacity (it’s never allowed to literally fill to the tip-top).  The top of the dark ring around the water intake towers at image left in the foreground indicates the height of the water level on December 21, 2012—the highest the lake has been this decade. At the time, water levels were down 95.4 feet from 1998 levels. The white “bathtub ring” seen on the rocky sides of the reservoir in the bottom photo shows the historical high water level in the reservoir. The ring is a coating of minerals, deposited on the rocks while they were covered by water.

The Lake Mead reservoir—the largest in the United States—stores Colorado River water for delivery to farms, homes, and businesses in southern Nevada, Arizona, southern California, and northern Mexico. According to the National Park Service website, about 96 percent of the water in Lake Mead is from melted snow that fell in Colorado, Utah, New Mexico, and Wyoming. Each year, these “Upper Basin” states are required to allow a minimum flow of Colorado River water to reach Lake Mead.

This year’s new low was hardly unexpected. Runoff in the Upper Colorado River Basin was 94 percent of average in 2014, but that flow wasn’t enough to make up for the previous two years’ shortfalls: runoff was only 47 percent of normal in 2013 and 45 percent in 2012, according to the Bureau of Reclamation.

The past two years are a continuation of a15-year dry spell in the U.S. Southwest that has led to more water going out of Lake Mead than coming in. The lake reached an all-time high of 1,215.76 feet in November 1998, but it has not approached that level since. The Bureau’s Boulder Canyon Operations Office projects the lake’s elevation to continue to drop through the fall, falling to approximately 1,080 feet in November of this year.

Fluctuations in regional climate and the resulting water level in Lake Mead are an expected part of its operation, but many scientists are concerned that the recent prolonged drought could be a sign that the region will confront significant water supply challenges as greenhouse gas concentrations continue to rise.

Projections of precipitation changes in the Colorado watershed are less certain than those for temperature changes in the Southwest, but rising temperature along with declining snowpack and streamflows may threaten the reliability of surface water supply across the Southwest, according to the 2014 National Climate Assessment.

The report also warns that the current drought could be just beginning. Southwest paleoclimate records show that severe mega-droughts at least 50 years long have occurred in the past several thousand years. Unlike those ancient droughts, however, similarly dry periods in the future are projected to be substantially hotter, and for major river basins such as the Colorado River Basin, drought is projected to become more frequent, intense, and longer lasting than in the historical record.


Drought severe to exceptional across much of Central Texas

September 4th, 2014 at 3:55 pm by under Weather
Drought Monitor
DROUGHT INFORMATION STATEMENT
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
1245 PM CDT THU SEP 4 2014

...DROUGHT CONDITIONS REMAIN THE SAME OVER THE PAST WEEK...
SYNOPSIS...
AFTER AN AUGUST THAT FEATURED SPORADIC RAINFALL...SEPTEMBER HAS SEEN
SPOTTY RAINFALL WITH THE MAJORITY OF RAIN FALLING ACROSS THE
SOUTHERN AND SOUTHEASTERN PORTIONS OF THE REGION. MOST
RIVERS...CREEKS AND STREAMS CONTINUED TO SHOW DECREASING FLOWS
ESPECIALLY IN LOCATIONS THAT HAVE MISSED THE RECENT RAINFALL. THE
MAJORITY OF SOUTH CENTRAL TEXAS WAS REPORTING BELOW AVERAGE STREAM
FLOWS WHILE THE EASTERN HALF REPORTED BELOW TO MUCH BELOW AVERAGE
FLOWS.  Read the rest of this entry »

Texas Water Development Board Meeting Open To Public

September 3rd, 2014 at 7:56 am by under Weather
TWDB_splashLogo_verysmall
FROM:
Texas Water Development Board (TWDB)
WHAT:
The public and interested stakeholders are invited to attend a TWDB Board  meeting.
WHEN:
Thursday, September 4, 2014, at 9:30 a.m.
 
WHERE:
Stephen F. Austin Building   
1700 North Congress Avenue
Room 170
Austin, TX 78701
WHY:
The Board will consider financial assistance for communities looking to address water and wastewater needs within their regions. Communities requesting financial assistance include the cities of Early, Hutto, McAllen, and Los Fresnos, as well as the Beaver Creek Water Control and Improvement District No. 1 and the Lower Colorado River Authority. The Board will also hear an overview of the Texas Natural Resources Information System. 
WHO:
TWDB staff will be on hand to answer questions and accept public comment.

 

HERE IS THE LATEST AREA DROUGHT STATUS MAP COURTESY OF THE US DROUGHT MONITOR:

Drought

Since the last map was issued the “Exceptional” (highest level”  drought status in Gillespie County has expanded a bit.  The “Extreme” drought has spread into Blanco and Llano counties this time around.  Finally, Metro and Eastern conditions have worsenend too.  A few weeks ago, the lowest level of drought, “Abnormally Dry” spread from Travis County through many of our Eastern Areas.  Now, “Moderate” to “Severe” drought statuses have overcome those same spots.

 

TWDB Homepage Link:     http://www.twdb.texas.gov/

 


NASA rainfall observing satellite out of fuel, but continues to provide data

September 1st, 2014 at 7:58 pm by under Weather

Rani Gran, NASA’s Goddard Space Flight Center

Pressure readings from the Tropical Rainfall Measuring Mission‘s (TRMM) fuel tank on July 8 indicated that the satellite was nearly at the end of its fuel supply. As a result, NASA has ceased maneuvers to keep the satellite at its operating altitude of 402 kilometers (~250 miles). With its speed decreasing, TRMM has begun to drift downward. A small amount of fuel remains to conduct debris avoidance maneuvers to ensure the satellite remains safe.

TRMM’s slow descent will continue over the next 2 to 3 years. It will continue to collect useful data as its orbit descends to about 350 (217.5 miles) over the next 18 months. Once TRMM reaches an altitude of 150 to 120 kilometers (93 to 75 miles), it will re-enter the atmosphere.

The TRMM satellite, a joint mission between NASA and the Japan Aerospace Exploration Agency (JAXA), was launched in 1997 to measure precipitation over the tropics, carrying the first precipitation radar into space.

“TRMM has met and exceeded its original goal of advancing our understanding of the distribution of tropical rainfall and its relation to the global water and energy cycles,” said Scott Braun, the mission’s project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Its planned three-year mission has already lasted 17 years and provided researchers with an unprecedented data set that combined more traditional radiometer measurements with 3-dimensional radar scans across the tropical ocean and into the lower mid-latitudes from 35N to 35S latitude. Also unique to TRMM is its inclined orbit that allows it to cut across the paths of polar orbiting satellites and revisit locations at different times of day, which is important for understanding how rainfall evolves with the day/night cycle. TRMM provided the first measurements of this type over the tropical ocean.

Read the rest of this entry »


Developing tropical system may bring rain next week

August 31st, 2014 at 8:35 pm by under Weather

nhc image

Sunday night, the National Hurricane Center is keeping a close eye on an “invest” crossing the Yucatan Peninsula set to emerge over the southwestern Gulf of Mexico waters on Labor Day.

NHC’s prescribed odds of development have been steadily increasing over the past 48 hours, as forecast tracks are shifting slowly northward.

inv99

As of Sunday night, most computer forecasts still steer the storm west-northwestward into the Mexican coast mid week. But compared to previous model runs, some of the computer’s tracks are shifting northward.

If this developing storm takes one of the more northerly options, coming onshore near the TX/Mexico border, Central Texas could see increased rain chances Tuesday and Wednesday.

Stay tuned to KXAN and KXAN.com for the latest as this situation develops.


Dangerous heat in some areas Labor Day weekend

August 31st, 2014 at 3:26 pm by under Weather

heat index

 

With heat index values as high as 109 degrees Sunday and Monday afternoons in some areas, be sure to exercise extreme caution while spending time outdoors.

Follow the tips below, courtesy of NOAA:

  • Slow down. Reduce, eliminate or reschedule strenuous activities until the coolest time of the day. Children, seniors and anyone with health problems should stay in the coolest available place, not necessarily indoors.
  • Dress for summer. Wear lightweight, light-colored clothing to reflect heat and sunlight.
  • Put less fuel on your inner fires. Foods, like meat and other proteins that increase metabolic heat production also increase water loss.
  • Drink plenty of water, non-alcoholic and decaffeinated fluids. Your body needs water to keep cool. Drink plenty of fluids even if you don’t feel thirsty. Persons who have epilepsy or heart, kidney or liver disease, are on fluid restrictive diets or have a problem with fluid retention should consult a physician before increasing their consumption of fluids. Do not drink alcoholic beverages and limit caffeinated beverages.
  • During excessive heat periods, spend more time in air-conditioned places. Air conditioning in homes and other buildings markedly reduces danger from the heat. If you cannot afford an air conditioner, go to a library, store or other location with air conditioning for part of the day.
  • Don’t get too much sun. Sunburn reduces your body’s ability to dissipate heat.
  • Do not take salt tablets unless specified by a physician.

Isolated flash flood impacts Gillespie County

August 30th, 2014 at 9:51 pm by under Weather

gillespiee

Between approximately 6:30 – 9 PM Saturday evening, a large thunderstorm sat nearly stationary over western Gillespie County in the Hill Country.

The local Sheriff’s office reported that RR 783 between Doss and Harper was flooded — with 1.5 feet of water over the roadway.

Radar-indicated rainfall estimates were over 4″ in one isolated rural location nearby, but unfortunately we do not have any rain gauges in that spot.

Here are some actual rainfall totals from the LCRA Hydromet network of rain gauges, which you can always find on KXAN.com under the Weather tab.

8-30 RAIN

 


Texas Longhorns season opener forecast

August 30th, 2014 at 7:06 am by under Weather

8-30 game day

 

An area of low pressure is still spinning off the South Texas coast Saturday–close enough to provide a few showers and thunderstorms locally Saturday afternoon and evening.

Most of us are forecast to remain dry for tailgating and game time Saturday, but if these isolated storms do impact the area, they may contain brief heavy rain and dangerous lightning.

Remember, “When Thunder Roars, Go Indoors!” and of course, Hook ‘Em!


Southwest may face ‘megadrought’ this century

August 28th, 2014 at 5:41 pm by under Weather

Megadrought risk

Due to global warming, scientists say, the chances of the southwestern United States experiencing a decade long drought is at least 50 percent, and the chances of a “megadrought” – one that lasts over 30 years – ranges from 20 to 50 percent over the next century.

The study by Cornell University, University of Arizona and U.S. Geological Survey researchers will be published in a forthcoming issue of the American Meteorological Society’s Journal of Climate.

“For the southwestern U.S., I’m not optimistic about avoiding real megadroughts,” said Toby Ault, Cornell assistant professor of earth and atmospheric sciences and lead author of the paper. “As we add greenhouse gases into the atmosphere – and we haven’t put the brakes on stopping this – we are weighting the dice for megadrought conditions.”

As of mid-August, most of California sits in a D4 “exceptional drought,” which is in the most severe category. Oregon, Arizona, New Mexico, Oklahoma and Texas also loiter between moderate and exceptional drought. Ault says climatologists don’t know whether the severe western and southwestern drought will continue, but he said, “With ongoing climate change, this is a glimpse of things to come. It’s a preview of our future.”

Ault said that the West and Southwest must look for mitigation strategies to cope with looming long-drought scenarios. “This will be worse than anything seen during the last 2,000 years and would pose unprecedented challenges to water resources in the region,” he said.

In computer models, while California, Arizona and New Mexico will likely face drought, the researchers show the chances for drought in parts of Washington, Montana and Idaho may decrease.

Beyond the United States, southern Africa, Australia and the Amazon basin are also vulnerable to the possibility of a megadrought. With increases in temperatures, drought severity will likely worsen, “implying that our results should be viewed as conservative,” the study reports.

“These results help us take the long view of future drought risk in the Southwest – and the picture is not pretty. We hope this opens up new discussions about how to best use and conserve the precious water that we have,” said Julia Cole, UA professor of geosciences and of atmospheric sciences.

The study, “Assessing the Risk of Persistent Drought Using Climate Model Simulations and Paleoclimate Data,” was also co-authored by Julia E. Cole, David M. Meko and Jonathan T. Overpeck of University of Arizona; and Gregory T. Pederson of the U.S. Geological Survey.

The National Science Foundation, National Center for Atmospheric Research, the U.S. Geological Survey and the National Oceanic and Atmospheric Administration funded the research.