Moon and Mars appear close tonight

November 25th, 2014 at 4:12 pm by under Weather
2014-nov-25-mars-moon-night-sky-chart

Tonight – November 25, 2014 – the waxing crescent moon and the red planet Mars appear in the southwest sky at nightfall. Be sure to check out these worlds at early evening because they’ll follow the sun beneath the horizon by mid-evening.

While our Earth has one large ball-shaped moon, Mars has two tiny potato-shaped moons. Our moon lies at a mean distance of 384,400 kilometers (238,855 miles), but Mars’ two moons reside very close to the surface of the red planet. Deimos, the smaller of Mars’ two moons, is 23,460 kilometers (14,577 miles) from Mars.

This illustration compares the relative sizes of Mars' moons, as seen from the surface of Mars, with the size of our moon, as seen from the Earth's surface. Image credit: NASA/JPL-Caltech/Malin Space Science Systems/Texas A&M Univ.

This illustration compares the relative sizes of Mars’ moons as seen from the surface of Mars, with the size of our moon as seen from Earth. Image via NASA/JPL-Caltech/Malin Space Science Systems/Texas A&M Univ.

Phobos, the larger, lies only 9,270 kilometers (5,670 miles) away. These distances are from the center of Mars. These moons lodge closer yet to Mars’ surface.

The closer a moon’s orbit, the faster the moon goes in its orbit around its parent planet. Deimos’ orbital period is 30 hours and 12 minutes. But the orbital period of Phobos, the closer moon, is only 7 hours and 39 minutes. Phobos is one of the very few moons in the solar system to orbit a planet in less time than its parent planet’s rotational period. Mars rotates full circle in 24 hours and 39 minutes, so one day on Mars is only slightly longer than one Earth day.

The synchronous orbit of two artificial satellites, whereby we're looking downward at the Earth's north pole, and the satellites are orbiting above the Earth's equator. At a distance of 35,786 kilometers above the Earth's surface (42,164 kilometers from the Earth's center), the satellites' orbital periods equal Earth's rotational period. Image credit: Wikipedia

The synchronous orbit of two artificial satellites. In this image, we’re looking downward at the Earth’s north pole, and the satellites are orbiting above the Earth’s equator. At a distance of 35,786 kilometers above the Earth’s surface (42,164 kilometers from the Earth’s center), the satellites’ orbital periods equal Earth’s rotational period. Image via Wikipedia

The distance at which a moon’s (or an artificial satellite’s) orbital period equals the planet’s rotational period is called the synchronous orbit radius. On Mars, this distance is 17,031 kilometers (10,583 miles) above Mars’ surface, or 20,427 kilometers (12,693 miles) from the center of Mars. Farther away than the synchronous orbit, the moon’s orbital period is longer than the planet’s rotational period. Below the synchronous orbit, the moon’s orbital period is shorter than the planet’s rotation.

Because Phobos circles Mars below the synchronous orbit distance, the orbit of this moon is decaying, with Phobos moving closer to Mars at the rate of about 1.8 meters (6 feet) per century. Astronomers believe Phobos is doomed to crash into Mars or to break up into a ring of rubble in about 50 million years.

At a distance of 60 Earth-radii (384,400 kilometers), our moon resides at roughly 9 times the Earth’s synchronous orbit radius of 6.6 Earth-radii (42,000 kilometers from the Earth’s center). At present, the moon is retreating from Earth at the rate of about 3.8 meters (12.5 feet) per century.

What do Phobos and Deimos look like from Mars?

Bottom line: On the evening of November 25, 2014, as darkness falls, watch for the picturesque pairing of the waxing crescent moon with the red planet Mars.

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Earth records warmest October on record

November 25th, 2014 at 11:27 am by under Weather
toasty blog
(Japan Meteorological Agency)

Capital Weather Gang/Washington Post — Multiple datasets have confirmed it was the warmest October on record for the globe, keeping the planet on a course towards its toastiest year.

The Japan Meteorological Agency, NASA, and the University of Alabama’s temperature records all showed October temperatures at the top of charts.

  • The Japan dataset reveals the October temperature was 0.61 F above the 1981-2010 average, well (0.18F) above the next warmest year, 2003 (in records dating back to 1891).
  • NASA’s temperature record indicates this October tied with October 2005 as the warmest (in records dating back to 1880), 1.37 F above the 1951-1980 average (its base period).
  • The University of Alabama (which dates back to 1979) showed October 2014 tied October 2012 as warmest in its record, 0.67 F above the 30-year average for October.

Read the rest of this entry »


Understanding lightning

November 24th, 2014 at 4:33 pm by under Weather

By John S. Jensenius, Jr., NWS Lightning Safety Specialist

Lightning is one of the top three storm-related killers in the United States. It is also one of the least understood weather phenomena. The Overview Section gives a brief introduction to lightning science and safety. Want to learn more? In the Understanding Lightning Section, you can find a more detailed look at the science behind one of nature’s most underrated killers.

understanding lightning, described in text


Hundreds of area rainfall totals

November 23rd, 2014 at 3:49 pm by under Weather


Here is a map of estimated rainfall across South Central Texas from the previous 48 hours ending at midnight. Many locations across the eastern half of the area received over 2 inches of rain with a swath of 4+ inches from New Braunfels to San Marcos to Austin.

Click here for more rainfall totals.

NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
 ...48 HOUR RAINFALL REPORTS ENDING 10 AM CST SUNDAY...
 LOCATION                       AMOUNT    TIME/DATE       LAT/LON
 ...TEXAS...
 ...BASTROP...
TOM MILLER DAM                 4.39 IN   1000 AM 11/23   30.17N/97.47W
SMITHVILLE 0.9 E               3.73 IN   0853 AM 11/23   30.01N/97.14W
PAIGE 4.6 SW                   3.55 IN   0824 AM 11/23   30.16N/97.16W
SMITHVILLE                     3.51 IN   1010 AM 11/23   30.01N/97.16W
SMITHVILLE                     3.12 IN   0800 AM 11/23   30.02N/97.15W
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Onion creek levels falling rapidly after overnight flooding

November 23rd, 2014 at 9:14 am by under Weather

onion

 

Rain has now moved out of the area and creek flows are diminishing. This is good news for folks along Onion Creek, who were under a brief flood warning late last night.

After cresting a couple of feet above flood stage early Sunday morning, the flow and levels of Onion Creek are rapidly diminishing.

Continue to use caution on area low-water crossings. Check the latest status of closures here.


Noon update on severe, flooding potential

November 22nd, 2014 at 12:22 pm by under Weather

From NWS Austin-San Antonio:

  • Portions of Central Texas removed from severe storm potential today (although a few strong storms still possible).
  • Increased Heavy Rainfall potential and flash flooding, through midnight now along and east of I-35.
AREA OF CONCERN
Severe Storms:
  • Afternoon: Main area of concern for severe storms along and west of a Fredericksburg to San Antonio to Campbellton line.
  • Evening: Main area of concern for severe storms along and South of a San Antonio to Hallettsville line.
  • A few stronger storms can’t be ruled out through the day north of these areas.
Heavy Rainfall:
  • Main area of concern for heavy rainfall will be across the Hill Country as well as along and east of I-35, including Austin, San Antonio, San Marcos & New Braunfels

Read the rest of this entry »


Dangerous flash flooding, isolated tornadoes possible today

November 22nd, 2014 at 9:56 am by under Weather

nws

 

Showers and heavy thunderstorms are still forecast to increase through the afternoon as a potent low pressure system approaches, drawing deep moisture over our area.

Training of heavy rain (moving over the same areas repeatedly) could lead to flash-flood inducing rainfall totals of up to 9″ in some areas. Our hi-res model is consistently painting the heaviest rain today from the eastern Hill Country towards the I-35 corridor.

In addition to the threat of heavy rain, severe thunderstorms could produce large hail, damaging wind gusts and even isolated tornadoes.

Read the rest of this entry »


Severe storm risk and heavy rain expected Saturday

November 21st, 2014 at 2:51 pm by under Weather

Here is a breakdown of the potential severe weather threats for this Saturday, November 22nd. The greatest severe threat will be large hail, but damaging straight line winds and a few tornadoes are also possible. Some storm training is possible with locally heavy rainfall amounts of 1 to 2 inches possible. The severe threat will be primarily along and east of a Rocksprings to Carrizo Springs line and between the hours of Noon and 9 PM CST.

Rainfall totals through Saturday night are expected to range from light amounts across the western counties to near 1-2 inches across the northeastern counties. There could be isolated 4 inch rain totals for locations near Austin, Burnet and La Grange.
——————
From National Weather Service:
Click here to see the NWS morning briefing regarding Saturday’s storm.
HEADLINE
 
…Strong to Severe Thunderstorms Possible across South-Central Texas Saturday Afternoon and evening….Locally Heavy Rain Possible…
 
AREA OF CONCERN
All of South-Central Texas
IMPACTS
  • Strong to severe thunderstorms with large hail, damaging winds and heavy rainfall.
  • Isolated Tornadoes with a few Supercells possible.
  • Rainfall totals 1-2 inches, isolated 4 inches possible. Rain Rates of 1 to 2 inches per hour in heavier storms.
  • Mainly minor urban flooding possible. Higher totals may cause isolated flash flooding concerns.
TIMING
Showers along with a few thunderstorms will likely be ongoing across most of South Central Texas Saturday morning. Thunderstorms will become more widespread through the morning hours across the Hill Country, and during the afternoon hours along the Interstate 35 corridor and areas east of I-35. Main impact time of this system will be from Noon to 9 PM Saturday as strong to severe storms move east across the area. Threat will end along the I-35 corridor by 6 PM Saturday…while the threat will linger through the evening for the far eastern areas of South Central Texas.
CONFIDENCE
Moderate to High.
DISCUSSION
An approaching upper level storm system will interact with increasing moisture from the Gulf of Mexico to produce widespread showers and thunderstorms across South Central Texas on Saturday. Rain showers and even isolated thunderstorms are possible later tonight ahead of this system. The chance for rainfall and strong to severe storms will be greatest during Saturday afternoon and evening as forcing from an upper level disturbance moves across the region. Severe storms, some of which may be supercells, may produce large damaging hail, damaging wind gusts, and isolated tornadoes. All of South Central Texas is under a Slight risk of severe weather. Weather watches and warnings may be issued on Saturday. Be Prepared.
While it is rare to have severe weather in November, South Central Texas has seen its share of late Fall severe weather outbreaks. How significant this event becomes will be partly determined by how much sunshine we get on Saturday. If it stays cloudy and cooler, the threat for severe weather will go down. If temperatures warm due to a good amount of early sunshine, storms will be bigger and stronger, also leading to higher rain totals.
Additional updates will occur Saturday Morning.

Severe storms possible Saturday

November 20th, 2014 at 4:19 pm by under Weather

If you missed our KXAN First Warning Weather in-depth report on the new winter outlook, watch it by clicking here.


Here is a look at the system that is going to bring us widespread rain and the chance for severe weather. Currently, the potent upper low is over the northern Pacific Ocean off the coast of California. By Friday morning, the upper low will be over Southern California and by Saturday morning the low will be over West Texas.

Here is the Storm Prediction Center’s convective outlook for Saturday. There is an enhanced risk for severe thunderstorms across the eastern half of South Central Texas. The main threat will be damaging wind gusts with a chance for tornadoes and large hail.
From the National Weather Service:
…Strong to Severe Thunderstorms Possible across South-Central Texas Saturday Afternoon through early Saturday evening…
 
AREA OF CONCERN
All of South-Central Texas, especially along and east of Highway 281.
IMPACTS
  • Strong to severe thunderstorms with large hail, damaging winds and heavy rainfall.
  • Isolated Tornadoes with a few Supercells possible.
  • Rainfall totals of 1/2 to 1 inch. Isolated totals to 2 inches. Rain Rates of 1 to 2 inches per hour in heavier storms.
  • Mainly minor urban, nuisance type flooding for the San Antonio and Austin metro areas expected at this time. However, we will need to watch areas along and east of I-35 carefully for heavier rainfall amounts.
TIMING
Showers along with a few thunderstorms will likely be ongoing across most of South Central Texas Saturday morning. Thunderstorms will become more widespread through the morning hours across the Hill Country, and during the afternoon hours along the Interstate 35 corridor. Main impact time of this system will be from Noon to 6 PM Saturday as strong to severe storms move east across the area.
CONFIDENCE
Moderate to High.
DISCUSSION
An approaching upper level storm system will interact with increasing moisture from the Gulf of Mexico to produce widespread showers and thunderstorms across South Central Texas on Saturday. Light showers are already forming this afternoon over areas generally along and east of Highway 281…this will continue into Friday with a few isolated thunderstorms also forming. The chance for rainfall and strong to severe storms will be greatest during Saturday afternoon as forcing from an upper level disturbance moves across the region. Severe storms, some of which may be supercells, may produce large damaging hail, damaging wind gusts, and isolated tornadoes.
Additional updates will occur on Friday and Saturday as the timing of the upper level system are fine tuned.
You can see the latest forecasts and watches/warnings/advisories by going to the Austin-San Antonio National Weather Service website at www.weather.gov/austin

Is the jet stream getting weird?

November 20th, 2014 at 1:15 pm by under Weather

The following is an excerpt from a Dr. Jeff Masters blog post on Weather Underground:

This week’s intense cold blast is being triggered by an unusually extreme jet stream pattern, featuring a sharp ridge of high pressure along the U.S. West Coast and a deep trough of low pressure diving to the south over the Central United States. This configuration allows cold air to spill out of the Arctic behind the trough into the Central U.S., and be replaced by anomalously warm air flowing northwards along the West Coast of the U.S. deep into the Arctic. This extreme jet stream pattern is due, in part, to the influence of Super Typhoon Nuri, which caused a ripple effect on the jet stream after the typhoon became one of the most powerful extratropical storms ever recorded in the waters to the west of Alaska eleven days ago. However, we’ve seen an unusual number of extreme jet stream patterns like this in the past fifteen years, which happens to coincide with the period of time we’ve been observing record loss of summertime Arctic sea ice and record retreat of springtime snow cover in the Arctic. Could it be that these changes in the Arctic are causing the wacky jet stream behavior of recent years? That’s the theory being advanced by a number of prominent climate scientists. I’ve written extensively about the topic, and my most recent post on the subject was in April, California Drought/Polar Vortex Jet Stream Pattern Linked to Global Warming. A updated story that I wrote for the just-published December issue of Scientific American discusses the theory and its detractors, and you can read it on-line for $6 (or buy a copy at the news stand.) My conclusion in the article: If Arctic changes are truly to blame for wacky jet stream behavior, losing the remaining 50 percent of the Arctic sea-ice coverage between now and 2030 will bring even greater antics. If the Arctic is not involved, that is worrisome as well—because that means jet stream changes are due to an unknown mechanism, leaving us with no idea how the jet stream will respond as climate change progresses. Thus, my forecast for the next 15 years: expect the unprecedented.