LCRA chief meteorologist Bob Rose writes regularly on weather topics. Do you have a weather question for Bob? Send an email to Bob Rose.
Bob's Video Blog: Yahoo! Rain!
May brought the rain back to Central Texas and not a minute too soon. Lake Travis is expected to rise a couple feet, but don’t think that we’re out of the drought just yet. There’s still a lot of catching up to do.
Bob’s Blog on Central Texas weather
Rain Ending; A Drier and Warmer Weather Pattern Setting In. TUESDAY, MAY 15, 2012 06:12 PM
A trough of low pressure moving southeast out Far West Texas caused the development of widespread rain and scattered Monday night into Tuesday. Although Monday’s forecast data indicated the heaviest rain would fall across the Rio Grande Plains, the heaviest rain actually developed across the Hill Country and Central regions. Surface reports and weather radar estimates showed widespread rainfall totals of 1 to 2 inches across much of the region. An isolated totals of just over 3 inches was noted west of La Grange, in Fayette County. Unfortunately, very little of this rain fell across the coastal plains region, generally to the south of Interstate 10.
The following National Weather Service graphic shows the amount of rain falling between 2 pm Monday afternoon and 2 pm Tuesday afternoon:
The area of low pressure responsible for today’s rain was located late this afternoon over the middle Texas coast. Most of the rain associated with this feature was located over East Texas and slowly moving to the east. The counterclockwise circulation around the upper low may still cause a few isolated rain showers across the region this evening but most all of the activity should diminish after sunset with the loss of daytime heating. Clouds will clear and the sky will become partly cloudy overnight. Expect lows Tuesday morning generally in the upper 50s to low 60s.
A ridge of high pressure in the upper atmosphere currently located over northern Mexico is forecast to move east across Texas on Wednesday. The ridge will cause the development of a drier and more stable atmosphere across the state. Wednesday’s weather will feature a mostly sunny sky and warm temperatures. Highs will generally be in the mid 80s. The ridge of high pressure is forecast to remain over Texas late week and through the weekend, causing more sunny, dry and warm weather. High temperatures will be in the upper 80 Thursday and Friday, warming to near 88-90 degrees over the weekend. Lows will be mostly in the mid and upper 60s. Breezy south and southwesterly winds of 10-15 mph look to develop Friday through Sunday as surface low pressure strengthens across the southern Plains states.
Today’s medium-range forecasts call for only minor changes in the pattern next week. A trough of low pressure tracking northeast out of the southwestern US early next week will help push a weak cold front towards Texas. Today’s data indicates the front will likely stall somewhere around the Red River Valley. The front may just be strong enough to cause a few scattered showers and isolated thunderstorms Monday afternoon and again on Tuesday. However, I don’t expect much activity to develop this far south. Weather conditions Monday through Tuesday will be partly cloudy with high temperatures mostly in the upper 80s. Generally dry and warm weather looks to follow next Wednesday through Friday with high temperatures in the upper 80s to near 90 degrees.
Eastern Pacific Tropical Storm Aletta: The first tropical storm of the 2012 eastern Pacific tropical weather season developed earlier today. The storm is named Aletta. Late Tuesday afternoon, Aletta was centered about 810 miles south of the southern tip of Baja, California and was moving to the west near 8 mph. Maximum sustained winds were near 45 mph. Aletta is moving into the open Pacific and poses no threat to land. The tropical storm is forecast to maintain its current intensity into Wednesday then begin to fall apart late Wednesday into Thursday as it moves over cooler waters and encounters increasing wind shear.
Coincidentally, today, April 15 marks the official start to the eastern Pacific tropical weather season. It’s somewhat unusual to get a named storm this early into the season. Going back to 1949, there have only been 2 other named storms that have developed by May 15th.
Bob
Previous Blog Entries
A Chance for Rain through Tuesday. Dry and Warm Late Week and this Weekend. MONDAY, MAY 14, 2012 06:37 PM [+] Click to view this entry
Scattered showers and thunderstorms are back in the forecast for tonight and Tuesday as a wave of low pressure in the upper atmosphere tracks southeast out of Far West Texas. This small area of low pressure is forecast to stay far enough to our west to keep the heaviest rain and strongest storms mainly across the Concho Valley and Rio Grande Plains region. Parts of the western Hill Country could also see some significant rain overnight into Tuesday.
A late afternoon water vapor image across Texas and northern Mexico showed that area of low pressure was located across Far West Texas, between Guadalupe Pass and Wink. The system is steadily moving to the southeast:
The bright white areas of moisture noted across much of West Texas are where precipitation has been developing throughout the afternoon. Today’s analysis indicates the atmosphere is quite moist across West and Central Texas. Throughout the day, the atmosphere has become increasingly unstable across the Hill Country, Central Texas and coastal regions. Scattered rain showers and thunderstorms look to develop and persist across the area overnight and into Tuesday. But as I pointed out early on, the focus for the heaviest rain and strongest storms will occur mainly across the Concho Valley and Rio Grande Plains regions. Elsewhere, most of the thunderstorms should stay below severe criteria.
This rain and thunderstorm activity is forecast to continue overnight and into Tuesday as the upper low tracks to the southeast. Today’s forecast solutions call for the low to reach a position over south central Texas about midday on Tuesday. This system is forecast to move southeast and move into the Gulf of Mexico Tuesday evening. Rain showers and thunderstorms will track across much of the region throughout the day. In the afternoon, the activity does looks to decrease from northwest to southeast as the upper low begins to exit the region. Most all of the activity is forecast to diminish by Tuesday evening. High temperatures Tuesday will generally be in the upper 70s.
Rain amounts between Monday evening and Tuesday evening are forecast to average around an inch across the western Hill Country. Across the eastern Hill Country and most of Central Texas, rain amounts will generally average around a half inch. Less than a half inch totals are forecast across the coastal plains region. The following rainfall forecast graphic is courtesy of the National Weather Service:
Dry weather will return Tuesday night as the upper low exits the region. On Wednesday, a ridge of high pressure in the upper atmosphere is forecast to spread across Texas out of the southwest. This ridge will cause a dry, sunny and warm weather pattern late week and through the weekend. High temperatures will be in the upper 80s Wednesday and Thursday but do look to warm close to 90 degrees Friday and through the weekend. South and southwesterly breezes are forecast to increase at that time. Low temperatures will generally be in the middle and upper 60s.
Medium-range forecast solutions indicate a cold front will push southeast out of the Rockies early next week. The front is forecast to push into Texas on Monday, moving across Central Texas late Monday night into Tuesday morning and pushing off the coast Tuesday afternoon. Today’s data indicates there will be some rain showers and thunderstorms along the cold front but significant totals don’t appear likely. Dry and just slightly cooler weather is expected behind the cold front during the middle part of next week.
Eastern Tropical Pacific Tropical Weather Season Begins Early: The first tropical depression of the 2012 Eastern Pacific Hurricane Season developed earlier today. This development comes one day before the official start to the season on May 15th. At late afternoon, the center of Tropical Depression One-E was centered about 655 miles south-southwest of Manzanillo, Mexico. The depression is moving to the west near 6 mph and maximum sustained winds are near 35 mph. National Hurricane Center forecasters indicate the depression is becoming better organized and should strengthen into a Tropical Storm tonight or Tuesday. But the tropical storm is then forecast to weaken beginning late Wednesday or Thursday. The system should continue moving to the west, and poses little threat to land.
In this late afternoon satellite image from the National Weather Service, the tropical depression is the blob of clouds located on the left side below Mexico. Another area of disturbed weather can be seen just off the coast of Central America.
Hurricane season in the Atlantic basin is just a little over 2 weeks. Today’s tropical depression development in the eastern Pacific is a sign sea surface temperatures have warmed up early across the eastern Pacific. With the expected trend toward El Nino this summer, an above normal number of tropical storms and hurricanes are forecast in the eastern Pacific basin while activity across the Atlantic basin is forecast to be near or slightly below normal.
Bob
Quiet Weather this Weekend with Slight Chance for Rain Developing Early Next Week. FRIDAY, MAY 11, 2012 06:27 PM [+] Click to view this entry
Thursday’s storm system brought widespread, soaking rain to most of the region. Hail, and high winds accompanied many of the storms and a tornado did quite a bit of damage in the town of Weimar, in western Colorado County. All in all, it was a very spring-like pattern typical of the month of May.
The following National Weather Service rainfall graphic shows the amount of rain falling between 7 am Thursday and 7 am Friday.
Note the large area of 1 to 3 inch totals across the eastern Hill Country and across most of Central and South Central Texas. There were a few isolated totals in the range of 4 to 5 inches. The rain wasn’t quite as heavy south of Interstate 10 where totals were generally between 0.5 and 1 inch.
Thursday’s rain, combined with rain from earlier in the month has produced a fairly wet May across much of the region. Monthly totals to date are well above average at most locations as can be seen in the following graphic. This is the rainfall departure from normal since May 1st:
Note some locations are close to 4 inches above normal. In Austin, rainfall at Camp Mabry through May 11th totals 4.21 inches which is close to the normal monthly total of 4.36 inches. Austin-Bergstrom’s May rainfall through May 11 has been 4.09 inches.
The area of low pressure responsible for Thursday’s rain was centered this afternoon just north of Abilene. Circulation around the low was pulling moisture across North Texas and south into Central Texas. Scattered showers and some isolated thunderstorms have developed in this moist and unstable circulation as seen in this afternoon visible satellite image:
Scattered showers will continue across parts of North and Central Texas through this evening but most of the activity should diminish after sunset. A few spotty light rain showers will again be possible across the coastal plains region Saturday morning but most other locations look to stay dry. The area low pressure is forecast to track northeast to Oklahoma on Saturday, loosening its grip on most of Texas.
Late this afternoon, a weak Canadian cold front was pushing south out of the southern Rockies and the southern Plains states. This front is forecast to quietly track across the Hill Country and Central Texas regions on Saturday and into the Gulf of Mexico Saturday night. The front will mainly just shift the wind out of the north and reinforce the mild air already in place. The sky will start off cloudy but will become partly cloudy by afternoon. High temperatures will range from the upper 70s north to the low 80s near the coast. Lows Sunday morning will include the mid and upper 50s across the Hill Country, near 60-62 degrees across Central Texas and in the low 60s towards the coast. Sunday’s weather will be mostly sunny and pleasant with high temperatures near 80-82 degrees.
A trough of low pressure in the upper atmosphere currently located across the northwestern US is forecast to track southeast out of the southern Rockies Monday then move across west and southwest Texas on Tuesday. This low isn’t expected to be nearly as strong or dynamic as the current one located over Texas. As a result, I don’t expect as much rain or severe weather.
The approaching trough of low pressure is forecast to pull clouds north from the Gulf of Mexico Monday, resulting in a partly to mostly cloudy sky.
A few showers and isolated thunderstorms look to develop acrossthe region beginning Monday night, continuing through Wednesday morning. Rain amounts are not forecast to be very high with this next system, with most totals staying under a half inch. High temperatures Monday and Tuesday will generally be around 80 degrees.
As this area of low pressure exits to the southeast, a weak ridge of high pressure is forecast to develop across Texas next Wednesday through Friday. The ridge will produce a dry and warm weather pattern. Highs will be in the low and middle 80s with lows generally in the low 60s. There are some indications another cold front will push across the area sometime next weekend, possibly causing a few rain showers. Looking out over the next 2 weeks, today’s forecast data doesn’t show any significant rain across Central and South Texas. However, keep in mind we’re now approaching the point of the year where we typically see the highest probability for rain of the entire year. Stay tuned for more details.
Bob
Thursday Update on Heavy Rain/Severe Weather Potenitial THURSDAY, MAY 10, 2012 11:07 AM [+] Click to view this entry
A large area of low pressure pushing east out of northern Mexico will cause a threat for heavy rain beginning this afternoon, continuing through into Friday. Overnight, the low pressure system shifted east a little faster than previously forecast. As a result, rain showers and thunderstorms are already beginning to spread across much of the Hill Country and parts of Central Texas. Another noteworthy item that changed overnight is the increased threat for severe weather now for most all of the region. Today’s forecast data indicates that with the approach of the low pressure system, the atmosphere is forecast to become quite unstable and will support the development of strong to severe thunderstorms. The Storm Prediction Center has placed all of Central Texas, the Texas Hill Country and the middle Texas coast under a Slight Risk for severe thunderstorms through Friday morning. Severe weather threats will include large hail, damaging winds and even some isolated tornadoes. A Severe Thunderstorm Watch is currently in currently effect until 1 pm for the area stretching from the Concho Valley to Deep South Texas. The watch extends as far east as Mason, Gillespie and Kendall Counties. Severe thunderstorms producing large hail are currently occurring southwest of San Antonio near Pearsall and Cotulla, moving northeast around 25 mph. SPC forecasters indicate the watch area may be shifted east into Central Texas, including the Austin area, later this afternoon. And note; the watch may be changed to a tornado watch. Severe weather will be possible over night and into Friday morning as the center of the low pressure system moves directly across the Hill Country and Central Texas.
The other big concern over the next 36 hours will be the threat for moderate to heavy rain. Widespread rain showers and thunderstorms will spread across the entire region this afternoon and this activity looks to continue overnight and into much of Friday. Moderate to heavy rain is forecast tonight through Friday morning as the low pressure system moves by. With the ground wet from recent rains, significant runoff is forecast. This may cause rapid rises on area creeks and streams along with some street flooding. The National Weather Service has posted a Flash Flood Watch for all of the region except for the coastal plains until noon on Friday.
The latest precipitation forecasts continue to call for widespread rain totals of 2 to 4 inches between now and Friday evening. Isolated totals of 4 to 6 inches will be possible. This morning’s forecast data indicates a trend for some of the heaviest rain to now occur along the middle and upper Texas coast.
One item to take note of is the possibility we could see even higher rain totals than what is currently forecast. Some of today’s forecast solutions indicate a large complex of strong thunderstorms and heavy rain will organize across the western Hill Country late this afternoon, with the complex of storms slowly moving to the east. Should such a scenario occur, heavy rain would fall over the same area for a prolonged period of time and this could produce some high totals of rain.
The threat for heavy rain will decrease Friday afternoon as the area of low pressure begins moving toward East Texas. Light rain will be possible Friday night into Saturday morning behind the upper low. Partly cloudy and dry weather looks to develop Saturday night into Sunday.
I’ll plan to have another update on this developing weather situation around mid afternoon.
Pasted below is the latest National Weather Service rainfall forecast for the period from Thursday morning through Saturday morning:
Bob
Afternoon Update on the Threat for Heavy Rain/Severe Weather THURSDAY, MAY 10, 2012 05:13 PM [+] Click to view this entry
A quick update on weather conditions expected overnight and into Friday.
A large area of low pressure continues to track east out of northern Mexico. This afternoon’s forecast data indicates there will be a threat for strong to severe thunderstorms across the entire region through tonight. A severe thunderstorm watch is currently in place for most of the Hill Country and Central Texas until 8 pm and a tornado watch covers most of South Texas through 7 pm. So far today, the majority of the severe weather has occurred to the south and southeast of San Antonio, between Cotulla and Karnes City. But additional strong to severe thunderstorms are still a possibility across the entire region this afternoon and overnight. Severe weather threats will include large hail, damaging winds. There will also be a threat for isolated tornadoes, mainly for areas generally to the south of Interstate 10.
This afternoon’s forecast data still calls for widespread moderate to heavy rain across the region overnight and into Friday morning. However, the highest totals of rain now look to occur generally to the east of Interstate 35 and closer to the coast. The earlier forecast for a large, slow-moving complex of thunderstorms moving out of the Hill Country doesn’t appear as likely a scenario as was thought earlier today. It now appears a large complex of storms may develop across south central Texas overnight, with this system moving to the northeast.
Widespread rain showers and thunderstorms will likely continue across all of the region this evening and overnight as the large area of low pressure tracks east. The heaviest rain is forecast to move east of the Hill Country by Friday morning. The heavy rain should move out of the Central Texas region by midday and the coastal plains region sometime in the late afternoon. Light rain is forecast Friday afternoon into Friday night, with the rain ending from west to east Saturday morning.
Forecast data still shows the potential for significant totals of rain between now and Saturday evening. Widespread totals of 2 to 4 inches are forecast. Some totals of 4 to 6 inches will be possible, mainly across the coastal plains region.
Tonight’s heavy rains pose the potential for deadly flash flooding across the entire region. A Flash Flood Watch has been posted for all locations through midday Friday. This is a very dangerous situation, especially since the peak period for heavy rain and flooding will be overnight, after dark. It’s easy to underestimate how much water is covering the road and how fast the water is flowing in the dark. I urge everyone to Turn Around, Don’t Drown.
Dry weather is still forecast Saturday night through Sunday night. There is some thought at least a slight chance for rain may return on Monday.
