LCRA chief meteorologist Bob Rose writes regularly on weather topics. Do you have a weather question for Bob? Send an email to Bob Rose.
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LCRA Meteorologist Bob Rose talks about why our spring temperatures have been below normal and what that could mean mean for summer temperatures and rainfall.
Bob’s Blog on Central Texas weather
Warm and Generally Dry into Next Week Plus NOAA's Hurricane Season Outlook. THURSDAY, MAY 23, 2013 05:35 PM
A fairly typical early-summer weather pattern is expected to be in place across Central and South Texas over the next few days. And while the weather will resemble summer, we are still in the month of May. May’s weather often brings us a few surprises here in Texas as the summer ridge hasn’t settled in just yet and we can still get a few occasional atmospheric disturbances. Because of that, we may yet see a couple more chances for rain locally before the end of the month.
An afternoon visible satellite image looking down across Texas shows several thunderstorms clouds stretching from the Texas Big Bend to northeastern Oklahoma. (This is a somewhat different view of Texas since it is from the GOES West satellite. The GOES East satellite experienced a malfunction early Wednesday).
Today, although a large ridge of high pressure in the upper atmosphere has become established across Texas and the central Plains states, but the ridge has been weak enough to allow some weak waves of low pressure to track north out of Mexico and into Far West Texas. These disturbances caused the development of scattered strong to severe thunderstorms. Ample moisture and warm surface temperatures also aided in the thunderstorm development. Further east, the atmosphere has been quite stable and no thunderstorms are forecast. Interestingly, today’s sky stayed mostly cloudy across most of the region as the low-level moisture was not able to efficiently mix with the middle atmosphere. This evening and tonight, the thunderstorms across West Texas are forecast to remain out to the west and not affect the Hill Country or Central Texas.
The weather for Friday and Saturday will feature morning clouds followed by a partly cloudy sky in the afternoon. High temperatures will generally e in the low 90s. Today’s forecast data indicates additional disturbances will track north out of Mexico into West Texas both days, causing the development of more scattered thunderstorms across West Texas. This activity is forecast to develop a little further to the east, compared to today’s activity; possibly reaching parts of the Hill Country or the western half of Central Texas in the late afternoon or evening hours. Should these thunderstorms indeed develop, they’ll have the potential to become severe, producing large hail and damaging winds. But the chance for precipitation across this area will at best be 20 percent. Most locations will likely stay dry.
On Sunday, the slight chance for afternoon thunderstorms looks to diminish as fewer disturbances track north out of Mexico. Partly cloudy, warm and summer-like weather will be in place. Sunday’s high temperature will generally be in the low 90s. Breezy conditions will begin to develop Sunday as surface low pressure begins to strengthen across the southern Rockies. Expect south winds at 10-20 mph. This partly cloudy, warm and breezy pattern will likely continue through the middle of next week.
Forecast solutions indicate a broad trough of low pressure in the upper atmosphere will move east from the Pacific and reach northern Mexico around next Wednesday. This trough is then forecast to track to the north across western Texas Thursday and Friday. Depending on how far east this trough moves into Texas, it may cause a slight chance for afternoon thunderstorms across the region next Thursday and Friday. Otherwise, partly cloudy and warm weather will likely continue late next week into next weekend.
For what it’s worth, I thought I would mention that some of the long-range forecast solutions are calling for some sort of tropical weather development in the southern Gulf of Mexico or western Caribbean Sea in about 10 days to 2 weeks. It’s way too early to have much confidence in this forecast, but there are a couple of features in the large scale pattern that would promote such development. Stay tuned for more updates.
NOAA Outlook for the 2013 Atlantic Hurricane Season: Earlier today, the National Oceanic and Atmospheric Administration and the National Weather Service issued their outlook for the upcoming hurricane season. NOAA’s outlook is very similar to the one issued by Dr. Gray at Colorado State University back in April. Both outlooks call for this year’s hurricane season to be active to very active with an above normal number of storms. Both outlooks also call for an above normal number of major hurricanes. NOAA does not make a seasonal hurricane landfall outlook.
Here is a summary of NOAA’s Outlook:
NOAA’s 2013 Atlantic Hurricane Season Outlook indicates that an above-normal season is most likely, with the possibility that the season could be very active. The outlook calls for a 70% chance of an above-normal season, a 25% chance of a near-normal season, and only a 5% chance of a below-normal season. See NOAA definitions of above-, near-, and below-normal seasons, which have been slightly modified from previous years. The Atlantic hurricane region includes the North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.
The 2013 seasonal hurricane outlook reflects a combination of climate factors that have historically produced above-normal Atlantic hurricane seasons. The three main climate factors for this outlook are:
1) The ongoing set of atmospheric conditions that have been producing increased Atlantic hurricane activity since 1995, which includes
2) An expected continuation of above-average sea surface temperatures (SSTs) across the tropical Atlantic Ocean and Caribbean Sea, and
3) A likely continuation of ENSO-neutral conditions (i.e., no El Niño or La Niña); meaning El Niño is not expected to develop and suppress the hurricane season.
This combination of climate factors historically produces above-normal Atlantic hurricane seasons. The 2013 hurricane season could see activity comparable to some of the very active seasons since 1995.
Based on the current and expected conditions, combined with model forecasts, we estimate a 70% probability for each of the following ranges of activity during 2013:
13-20 Named Storms
7-11 Hurricanes
3-6 Major Hurricanes
Accumulated Cyclone Energy (ACE) range of 120%-205%
The seasonal activity is expected to fall within these ranges in 70% of seasons with similar climate conditions and uncertainties to those expected this year. These ranges do not represent the total possible ranges of activity seen in past similar years.
Note that the expected ranges are centered well above the official NHC 1981-2010 seasonal averages of 12 named storms, 6 hurricanes, and 3 major hurricanes.
Bob
Previous Blog Entries
A Dry, Summer-Like Pattern Will be Settling in for a While. WEDNESDAY, MAY 22, 2013 06:21 PM [+] Click to view this entry
While Tuesday’s severe storms fortunately missed Central and South Texas, we also missed out on another opportunity for rain. When you’re in a severe drought, it seems even harder to get significant rain from occasional storm systems. A strong stable layer in the middle atmosphere over Central Texas kept thunderstorms from developing along the cold front when it pushed to the south. The follow graphic shows the amount and distribution of rain falling between 7 am Tuesday and 7 am Wednesday:
National Weather Service
Note how the rain got as far south as northern Burnet and northern Williamson Counties and reached as far east as north Houston. South of this line, there was little if any rain. So the drought continues…
Tuesday’s cold front pushed south to about the interstate corridor early this morning. Drier and slightly cooler air was felt this morning behind the cold front with low temperatures across the Hill Country in the 40s and 50s. Minimum temperatures across Central Texas were mostly in the upper 50s to low 60s. Meanwhile to the south of Interstate 10, low temperatures were generally in the middle 70s.
Unfortunately, the cooler, drier air is quickly on its way out. Late this afternoon, the cold front is lifting back to the north, bringing warmer, more humid and smoky air north from the Gulf of Mexico. Interestingly, today’s cold front temporarily cleared out the haze and smoke from the sky across the Hill Country and Central Texas that’s flowing north from agricultural fires in Central America. The following visible satellite image from the polar-orbiting Terra satellite clearly shows the clear sky across Central Texas and the widespread haze and smoke near the coast and out over the Gulf:
Courtesy NOAA
Widespread low clouds look to develop across the region late tonight. Low temperatures Thursday morning will be mostly in the upper 60s to low 70s.
Today’s computer-forecast solutions indicate a broad ridge of high pressure in the upper atmosphere will develop across Texas and the south central US Thursday, with the ridge remaining over the area through the middle of next week. The ridge will cause stable, generally dry and warm summer-like weather through the upcoming period. Daily high temperatures will be in the low and middle 90s with low temperatures around 70 degrees. A slight chance for thunderstorms may develop Friday afternoon and again Saturday afternoon across the western Hill Country as a weak wave of low pressure tracks north out of Mexico and across West Texas. With the ridge in place, and limited moisture to work with, little if any rain is expected.
Looking out to next week, the ridge of high pressure is forecast to shift east of Texas next Thursday and Friday as a trough of low pressure develops over the central and southern Rockies. The trough may cause a few thunderstorms to develop along the West Texas Dry Line which could possibly affect parts of the Hill Country. Otherwise, a partly cloudy, dry and warm pattern looks to continue late next week into next weekend.
THE SKY SHOW BEGINS: The long-awaited sunset sky show of May 2013 is beginning. In only a few days, Venus, Jupiter and Mercury will form a tight triangle in the western sky, visible to the unaided eye around the world. Last night, Fred Espenak of Portal, Arizona, photographed the trio in the early stages of convergence:
"The three planets were easily visible to the naked eye in spite of the bright twilight glow," says Espanel. "Mercury should be even easier to spot in the coming days as it climbs higher into the sky. "
In the nights ahead, the line of planets will collapse to form a triangle. At closest approach on May 26th, they will fit within a circle less than 3 degrees wide. Start watching tonight--it's a great way to end the day. For more information, check out http://www.spaceweather.com
Bob
Strong to Severe Thunderstorms Possible This Afternoon and Evening. TUESDAY, MAY 21, 2013 11:20 AM [+] Click to view this entry
…Strong to severe thunderstorms are forecast to develop across the eastern Hill Country and most of Central Texas beginning around mid afternoon, continuing into tonight. Large hail, damaging winds and isolated tornadoes will be possible with these storms...
A strong disturbance in the upper atmosphere tracking southeast out of southern New Mexico is forecast to track across North Texas this afternoon and tonight. This disturbance will help push a cold front southeast out of North Texas. As of mid-morning, the cold front stretched from Wichita Falls to Sweetwater to near Midland. The front is forecast to reach the northern Hill Country in the mid to late afternoon and the Austin/I-35 corridor area this evening. The front will serve as a focus for thunderstorm development. Forecasters will also be monitoring the eastward progress off the Dry Line out of West Texas. The Dry Line will serve as another focus for thunderstorm development. This morning’s atmospheric analysis indicates the atmosphere over the eastern Hill Country and Central Texas is potentially very unstable. A cap, or stable layer in the middle atmosphere is currently in place, limiting the development of thunderstorms. However, as the temperature warms this afternoon, the cap is forecast to weaken, allowing thunderstorms to develop primarily along the 2 boundaries, with the storms moving generally to the east and southeast.
The Storm Prediction Center has placed much of the Hill Country and all of Central Texas under a Slight Risk for severe thunderstorms this afternoon and tonight (yellow shaded area). Note; a moderate risk for severe thunderstorms (red shading) covers the area from just north of Austin across northeast Texas into southern Arkansas.
Thunderstorms are forecast to develop across the Hill Country along the two boundaries around mid afternoon with the storms tracking east into Central Texas late this afternoon and evening. Very large hail, damaging downburst winds and dangerous lightning will be the primary severe weather threats. However, isolated tornadoes will be possible. The most favorable area for tornado development is expected to be in the moderate risk area, across parts of North and Northeast Texas. The thunderstorms are forecast to continue into tonight then weaken by midnight as they sink to the east and southeast. Totals from today’s storms are forecast to average around a half inch with isolated totals of 1-2 inches possible.
On Wednesday, the focus for rain and thunderstorms will shift to the coastal plains region as today’s cold front pulls up stationary near Interstate 10. Today’s forecast data indicates the storms on Wednesday’s will generally stay below the severe threshold. Totals to near a half inch are forecast. Across the Hill Country and Central Texas, sunny and dry weather is forecast, with high temperatures near 90 degrees. Dry and sunny weather looks to continue through the Memorial Day weekend.
I urge everyone to keep up with weather developments this afternoon and evening. Listen to NOAA All-Hazards radio or your local news media outlet for the latest watches and warnings. I plan to send out another update around mid afternoon.
Bob
A Chance for Strong to Severe Storms Tuesday. Dry and Warm Late Week. MONDAY, MAY 20, 2013 06:43 PM [+] Click to view this entry
A very active pattern of weather continues across the southern Plains states. Over the past 3 days, nearly 50 tornadoes have occurred across this region and more severe storms and tornadoes are expected on Tuesday. Today’s analysis of the upper atmosphere shows a very interesting weather setup:
A large area of low pressure is in place across the northern and central Plains states. Circulation around the low is bringing cooler, drier air south out of Canada. Meanwhile, a broad ridge of high pressure is in place over the southeastern US and the Gulf of Mexico. Circulation around the ridge is pulling warm and very moist air north from the Gulf of Mexico. The circulation from both of these systems is converging from northern Texas to the Corn Belt. A strong Jet Stream can be seen in the wind barbs, stretching from southern New Mexico to the western Great Lakes. This strong Jet has enhanced thunderstorm development by providing a very efficient exhaust to thunderstorm updrafts. The clash of air masses, very warm and moist conditions at the surface and a strong Jet Stream are all contributing to this very active pattern. Unfortunately, these same conditions are forecast to be in place again on Tuesday but the activity may develop further south into the Hill Country and Central Texas regions as a weak cold front sinks south out of northwest Texas.
This evening, there will be a slight chance for thunderstorm development across the Hill Country. Thunderstorms may develop along the Dry Line across the western Hill Country and track to the east. However, a stout stable layer in the middle atmosphere is present across most of the Hill Country and Central Texas, so the chance for thunderstorm will be slight. Should a thunderstorm happen to develop, it would likely become severe, producing very large hail and damaging winds. The threat for thunderstorm development will decrease in the late evening as temperatures cool. Across the rest of the region, the weather should be quiet overnight. Low temperatures Tuesday morning will be in the low 70s.
A more widespread threat for rain showers and thunderstorms is forecast across the region Tuesday afternoon into Tuesday night when a trough of low pressure in the upper atmosphere tracks southeast out of southern New Mexico and moves east across North Texas. With a stationary cold front in place across North Central Texas and a Dry Line stretching to the south across the Concho Valley, atmospheric conditions will be favorable thunderstorms to develop along these two boundaries in the afternoon, moving to the east-southeast. The atmosphere over the Hill Country and Central Texas is forecast to grow increasingly unstable in the mid to late afternoon hours so developing thunderstorms will have a strong potential to become severe. The Storm Prediction Center has placed all of the Hill Country and all of Central Texas under a Slight Risk for severe thunderstorms Tuesday afternoon into Tuesday night:
Severe weather outlook for Tuesday and Tuesday night:
Yellow area notes the Slight risk area for severe thunderstorms while the green area notes the area of general, non-severe thunderstorms.
The primary severe weather threats will be very large hail and damaging downburst winds but isolated tornadoes cannot be ruled out. The area of thunderstorms is forecast to track southeast Tuesday evening into Tuesday night; slowly weakening after dark. Most of this activity is forecast to diminish before it reaches the middle Texas coast. Rain amounts from Tuesday’s storms are forecast to average around a half inch with isolated totals of 1-1.5 inches possible.
Today’s forecast data indicates there will be a very slight chance for thunderstorms across the coastal plains region Wednesday afternoon. Across the rest of the area, partly cloudy and dry weather is expected. Wednesday’s high temperature will generally be around 90-92 degrees. A building ridge of high pressure in the upper atmosphere over Texas and the south central US late week and into the upcoming weekend will cause a mostly sunny, dry and warm weather pattern. Daily high temperatures look to be in the low 90s with low temperatures around 70 degrees. Today’s long-range forecast data indicates this dry and warm pattern will continue on Memorial Day and through the first half of next week. High temperatures will be in the low and middle 90s.
Bob
Summer Weather Has Arrived Early and Looks to Stick Around For Quite a While. FRIDAY, MAY 17, 2013 06:15 PM [+] Click to view this entry
It would appear that over the past couple of days our weather pattern has quickly transitioned to summer. Thursday and again today, the temperature soared into the low and middle 90s across much of Central Texas while triple-digit temperatures were observed across the western Hill Country. Temperatures early this morning only dipped to the low and middle 70s. The combination of very warm temperatures and high relative humidity levels are certainly making it feel like the middle of summer. Unfortunately, this warm and sticky pattern looks like it’s going to be with us for some time now as the positions of the position of the Jet Stream is no longer allowing cool Canadian air to reach south into Texas. In fact, long-range forecast data indicates summer-like temperatures will likely continue across the region through the end of the month.
By the way, you may have noticed quite a bit of haze across the sky today. This haze is actually smoke from agricultural fires in Central America that is being pulled north into Texas by gusty south winds. Today’s polar orbiting satellite image covering the eastern half of Texas and the western Gulf of Mexico from the Aqua satellite showed this “haze” quite well:
Today’s analysis of the upper atmosphere across North America showed a broad ridge of high pressure covering the southern Gulf of Mexico and southern Mexico, extending north to the southern Plains states. This feature, combined with a bubble of hot air spreading into Texas out of Mexico is responsible for the recent spell of unseasonably hot temperatures:
Note how the Jet Stream is generally flowing from California to southern Canada and south into the northeastern US. With this type of configuration, the cooler air is now well to the north of Texas.
Late this afternoon, a cluster of thunderstorms developed across the northern Hill Country between Junction and San Saba. These storms developed along the Dry Line, in a small zone where a mid-level stable layer weakened enough to allow thunderstorms to develop. 100-degree temperatures across West Texas also aided in making the atmosphere more e unstable. This area of storms will continue into the evening hours and diminish after sunset. Across the rest of the region, a broad layer of warm air in the middle atmosphere will limit thunderstorm development. The sky will become cloudy overnight and low temperatures Saturday morning will again be mostly in the low 70s. A south wind of 10-15 mph will continue overnight.
A very similar weather setup is forecast Saturday. Overall, weather conditions will be mostly sunny, breezy and warm. High temperatures will range from the upper 90s across the western Hill Country to near 90 degrees towards the coast. Expect a south winds at 10-20 mph. There will again be a slight chance for some late afternoon thunderstorms across the northern and western Hill Country as the Dry Line pushes east out of West Texas. Should storms develop, they’ll have a strong potential to become severe. The chance for rain will be at 20 percent. These potential storms could possibly move as far east as the Interstate 35 corridor before diminishing in the late evening.
That small chance for thunderstorms is forecast to decrease on Sunday with the Dry Line holding across Far West Texas. Expect another sunny and breezy day with high temperatures ranging from the upper 90s out west to near 90 degrees towards the coast. Very similar weather and temperatures should continue into Monday.
Some slight changes in the pattern look to occur Tuesday afternoon into Wednesday when a weak cold front sags south out of North Texas and pulls up stationary somewhere over Central Texas. There will be a slight chance for scattered rain showers and thunderstorms between Tuesday afternoon and Wednesday evening across the entire region. Wednesday’s sky will likely stay mostly cloudy on Wednesday. High temperatures both days will be near 88-90 degrees. Rain amounts between late Tuesday and late Wednesday are not expected to be very heavy with most totals averaging between a quarter and a third of an inch.
Late next week into next weekend, high pressure in the upper atmosphere is forecast to re-strengthen across Texas. Dry and hot weather is forecast with high temperatures in the 90s and lows in the 70s. Unfortunately, today’s forecast data doesn’t call for any significant rain across Central Texas through the end of the month.
