The city of Austin wants us to remind you that Stage 2 water restrictions remain in place, despite the recent rain.

Austin—Stage 2 Water Restrictions are still in effect for Austin Water customers because the combined levels of Lakes Buchannan and Travis are less than half-full.  Austin entered Stage 2 Water Restrictions on September 6, 2011, when the Lower Colorado River Authority requested mandatory water restrictions of its wholesale customers.

Even though the recent rains have lessened the effects of the drought and added more water to the lakes, Lake Travis is 31 feet below its normal for April and Lake Buchanan is 16 feet below normal for this time of year. (more…)

Rain and thunderstorms are expected to increase across the area Thursday night into Friday morning.  A few severe thunderstorms are also possible. The latest projections from computer models and the National Weather Service  have decreased slightly the forecast rainfall totals to 2-3″, with isolated 4-6 inch amounts.

The upper level storm system bringing the rainfall is now tracking across northern Mexico, and won’t move away from our area until Saturday, so some lingering showers could continue into the weekend, though the heaviest rain should end by Friday night.

A strong upper level disturbance will begin to impact the area on Thursday and continue through Friday…with the potential for severe thunderstorms and flooding rains. The main severe weather threat will be Thursday afternoon and evening along and south of a line from Karnes City to San Antonio to Del Rio. The main threats will be large hail and damaging winds. The other threat will be flash flooding. Widespread rainfall is expected. Rainfall amounts will average 2 to 4 inches, with isolated amounts over 4 inches possible. A flash flood watch is in effect for the Hill Country and South Central Texas, from 6 PM Thursday to Noon Friday.

FLOOD WATCH
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
THU MAY 10 2012

...A FLASH FLOOD WATCH REMAINS IN EFFECT FOR ALL OF SOUTH CENTRAL
TEXAS FROM 6 PM THIS EVENING UNTIL NOON FRIDAY...

.AN UPPER LEVEL LOW PRESSURE SYSTEM ACROSS NORTHERN MEXICO WILL
MOVE EASTWARD ACROSS TEXAS THROUGH FRIDAY. NUMEROUS SHOWERS AND
THUNDERSTORMS ARE EXPECTED THROUGH THIS AFTERNOON AND INTO THE
EARLY MORNING HOURS FRIDAY. RAIN CHANCES ARE EXPECTED TO DECREASE
FROM WEST TO EAST DURING THE DAY FRIDAY.

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Rainfall totals over the last two days have been significant over some areas, not so much in others. But, if you haven’t been one of the lucky ones yet, there is still hope.

Light rain was tapering off Tuesday evening, and only scattered showers or a thunderstorm are expected Wednesday. Rain and storms are expected to increase across the area again Thursday through Friday.

We are tracking a slow moving upper level low pressure system over the Baha Peninsula, which will track  to Texas between now and Friday. This storm could bring another 1-3 inches of rain to our area, with some isolated totals of 4-5 inches or more.

This graphic shows how much rain is expected to fall between Tuesday night and the weekend:

Intense afternoon heat helped initiate  a cluster of severe thunderstorms over the northwest Hill Country Saturday evening.

Some storm development will be possible again during the peak heating hours Sunday, but a more significant storm system is expected to bring much needed rainfall to  our area next week.

Computer models indicate a low pressure system aloft is developing now over southern California, and will cut off from the main belt of the westerlies, resulting in a slow, but steady eastward progression toward Texas next week. In fact, the storm should move so slowly that it doesn’t even move into Texas until late Thursday or early Friday, which will result in several days of rain possibilities for our area.

Based on current model data, the heaviest rainfall totals may occur from the southern Hill Country, across the Edwards Plateau to the Rio Grande (see map below).

The Austin metro area could receive 1-2 inches or more, as you can see in this map:

   Late Update:  A fairly thick deck of clouds at 25, 000 ft. may obscure tonight’s full moon for many.  Clouds spreading southeast from Hill Country storms aren’t helping either.

The full Moon has a reputation for trouble. It raises high tides, it makes dogs howl, it wakes you up in the middle of the night with beams of moonlight stealing through drapes. If a moonbeam wakes you up on the night of May 5th, 2012, you might want to get out of bed and take a look.  This May’s full Moon is a “super Moon,” as much as 14% bigger and 30% brighter than other full Moons of 2012.

The scientific term for the phenomenon is “perigee moon.” Full Moons vary in size because of the oval shape of the Moon’s orbit. The Moon follows an elliptical path around Earth with one side (“perigee”) about 50,000 km closer than the other (“apogee”).  Full Moons that occur on the perigee side of the Moon’s orbit seem extra big and bright.

Such is the case on May 5th at 10:34 pm when the Moon reaches perigee.  Only one minute later, the Moon will line up with Earth and the sun to become brilliantly full.  The timing is almost perfect.

Okay, the Moon is 14% bigger than usual, but can you really tell the difference? It’s tricky. There are no rulers floating in the sky to measure lunar diameters. Hanging high overhead with no reference points to provide a sense of scale, one full Moon can seem much like any other.

The best time to look is when the Moon is near the horizon.  For reasons not fully understood by astronomers or psychologists, low-hanging Moons look unnaturally large when they beam through trees, buildings and other foreground objects. On May 5^th, this Moon illusion will amplify a full Moon that’s extra-big to begin with.  The swollen orb rising in the east at sunset should seem super indeed.

Folklore holds that all kinds of wacky things happen under the light of a full Moon.  Supposedly, hospital admissions increase, the crime rate ticks upward, and people behave strangely. The idea that the full Moon causes mental disorders was widespread in the Middle Ages. Even the word “lunacy,” meaning “insanity,” comes from the Latin word for “Moon.”

The majority of modern studies, however, show no correlation between the phase of the Moon and the incidence of crime, sickness, or human behavior.  The truth is, the Moon is less influential than folklore would have us believe.  (CLICK HERE for a University of Washington compilation of related studies–some which do show a relationship)

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See related story here on KXAN News Page

Synopsis: La Niña has transitioned to ENSO-neutral conditions, which are expected to continue through northern summer 2012.

La Niña dissipated during April 2012, as below-average SSTs weakened across most of the equatorial Pacific Ocean and above-average SSTs persisted in the east (Fig. 1). The Niño 4 and Niño 3.4 indices were warmer than -0.5^oC throughout the month, and the Niño 3 and Niño 1+2 indices remained positive (Fig. 2). The oceanic heat content (average temperature in the upper 300m of the ocean) anomalies also became positive in April (Fig. 3), as below-average sub-surface temperatures largely disappeared and above-average sub-surface temperatures expanded in both the central and eastern Pacific (Fig. 4). Consistent with the demise of La Niña, enhanced trade winds and reduced convection over the central equatorial Pacific were much weakened during April, and the area of enhanced convection that had previously dominated the western Pacific and Indonesia became disorganized (Fig. 5). Collectively, these oceanic and atmospheric patterns indicate a transition from La Niña to ENSO-neutral conditions. (more…)

(NOAA)  Starting today, NOAA is using a sophisticated new weather forecast computer model to improve predictions of quickly developing severe weather events including thunderstorms, winter storms and aviation hazards such as clear air turbulence.

The Rapid Refresh now provides NOAA’s most rapidly updated weather forecast, replacing an older model that served a similar function. The Rapid Refresh, developed by NOAA’s Earth System Research Laboratory in Boulder, Colo. and NOAA’s National Centers for Environmental Prediction (NCEP) in Camp Springs, Md., updates every hour with a new forecast extending out 18 hours for North America. Such forecasts are especially important in aviation, where fast-developing weather conditions can affect safety and efficiency, but they are equally important for severe weather and energy-related forecasting. (more…)

  Smoke from agricultural burning in Mexico and Central America is expected to increase across Texas this weekend.  While the concentration will be light, it may be enough to decrease our air quality from the “good” to “moderate” category.  Notice in the graphic below, smoke (in blue) is expected to spread across much of the state by Saturday evening.

Projected Smoke Coverage (in blue) at 7 p.m. Saturday

Here’s the Air Quality Forecast from the Texas Commission on Environmental Quality:

Friday 04/27/12
Winds should be strong enough to generate blowing dust in parts of the Panhandle and could possibly raise the daily PM10 AQI into the “Moderate” range in the Lubbock area, with highest concentrations from late morning into the early evening. Satellite imagery indicates light amounts of smoke from agricultural burning in Mexico and Central America moving into the Texas coast this morning but surface concentrations do not appear to be enough to raise the daily PM2.5 AQI beyond the “Good” range. Elsewhere in the state, moderate to strong winds and low incoming background levels should help to keep air quality in the “Good” range.

Saturday 04/28/12
Smoke from agricultural burning in Mexico and Central America should increase in South Texas where the daily PM2.5 AQI could possibly reach “Moderate” levels and the smoke will likely spread rapidly northward and northwestward into Central and Southwest Texas in the afternoon and evening. Elsewhere in the state, moderate winds and lower incoming background levels should help to keep air quality in the “Good” range.  (more…)