Tuesday, May 28, 2013

FLASH FLOOD WATCH

Good Afternoon everybody! As of 4 p.m. we are currently sitting at 90°F here in Austin under a partly cloudy sky. The National Weather Service has just issued a FLASH FLOOD WATCH for much of central Texas, including, but not limited to: Burnet, Blanco, Williamson, Travis, Hays, Comal, Bexar, Bastrop, Caldwell, Lee, and Fayette counties. The FLASH FLOOD WATCH will go into effect at 7 a.m. Wednesday morning and continue through 7 p.m. Wednesday evening. All the counties shaded in dark green are under the FLASH FLOOD WATCH on Wednesday. This is not a sure thing right now, however, IF storms are able to develop they could dump anywhere from 1-3 inches of rain across central Texas on Wednesday.




Here's the Set-Up:

A trough of low pressure (a dip in the jet stream/elongated area of lower atmospheric pressure) will be approaching Texas and much of the central plains from the west...as this trough of low pressure approaches air is forced to rise ahead of it. As warm, humid air rises into cooler air aloft it will condense and in turn precipitate. The jet (river of fast moving air) flowing around trough carries disturbances (areas of lift) within it...those areas of lift help to further enhance shower and thunderstorm activity.




The National Weather Service posted this along with the FLASH FLOOD WATCH: An upper level disturbance is expected to force thunderstorms developing over the mountains of northern Mexico and west Texas right now east towards far western portions of central Texas this evening. That complex of storms will continue to march east into the Texas Hill Country and finally into the I-35 corridor during the day on Wednesday. The complex of storms that is forecast to develop is known as an MCS (Mesoscale Convective System). Once this MCS develops it will have plenty of deep Gulf moisture to allow for it to continue to move east into central Texas. While the risk of large hail and destructive winds looks to be low for Wednesday, the biggest threat from the storms will be torrential downpours that could lead to flooding. Already saturated ground will result in rapid runoff. We picked up between 3-4 inches of rain here in Austin last Friday and Saturday with the San Antonio Metro Area picking up over 12 inches of rain last Friday and Saturday. In fact, San Antonio recorded their second wettest day EVER on Saturday with 9.87 inches of rainfall! Most models are not forecasting a major rainfall event, however, it is possible! The models did not forecast last week's rains either!




Highs across the area should be held down in the 80s thanks to the added cloud cover and the chance for storms. However, the humidity levels will be quite high making it feel rather sticky. Lows tonight will only fall into the lower 70s.

This same trough of low pressure that MAY bring us storms here in central Texas will be wreaking havoc across the central Plains where they will be under a MODERATE RISK for severe weather: large hail, large tornadoes, and destructive winds all likely in the areas shaded in red! Much of western Oklahoma and central Kansas is under the MODERATE RISK.


Monday, May 20, 2013

Severe Weather Threat Increasing Tomorrow

Good Afternoon everybody! As of 2 p.m. we are up to 92°F here in Austin with plenty of haze and humidity in the air as well. Breezy, moist southerly winds off of the Gulf of Mexico will be fueling large tornadic thunderstorms across Oklahoma, extreme north Texas, northwestern Arkansas, and southern Missouri later this afternoon. Taking a look a the latest visible satellite imagery, storms are already beginning to fire along a stationary frontal boundary across Oklahoma and extreme north Texas. In fact, the Storm Prediction Center is currently monitoring areas from the Red River south into extreme northern portions of central Texas for the issuance of a possible SEVERE STORM WATCH or TORNADO WATCH within the coming hours. 

Intense heat and moisture combined with a slow moving southward moving frontal boundary will increase our chances for severe storms here in Central Texas for Tuesday. The main threats from the storms that develop Tuesday afternoon will be very large hail, damaging winds, and isolated tornadoes. The greatest tornado threat on Tuesday looks to be across northeastern portions of Texas, however, a tornado can never be ruled out when severe thunderstorms are in the forecast. The chance for storms tomorrow is at 50-60% for central Texas. Highs will climb well into the 90s Tuesday afternoon and that intense heat combined with lift produced from the boundary will work together to allow for explosive thunderstorm development. The Storm Prediction Center says there is at least a 30% chance for every storm that develops to produce some sort of severe weather. Hail up to the size of baseballs is not out of the question!

Storm Prediction Center's Outlook for Tuesday:



Storm Prediction Center's Probabilistic Outlook for Tuesday:



Future Simulated Radar for Texas tomorrow evening...strong/severe storms will be stretching from northeast Texas all the way back down into central Texas:



The atmosphere will be extremely unstable across much of Texas tomorrow as evidenced by EXTREMELY HIGH cape values...cape is a measure of how quickly the air is rising...the higher the cape the worse the storm...CAPE VALUES will be anywhere from 3000 to 5000 joules/kilogram across the state tomorrow:



By the way, if you are wondering why it has been so hazy lately it is due to the large agricultural fires burning across Mexico...farmers burn sugar cane this time of year in southern Mexico and strong southerly winds carry that smoke into Texas. 

Tuesday, May 14, 2013

More storms on the way!

Hello everybody! I hope you all had a wonderful weekend and got a chance to enjoy the beautiful weather. As for today (Tuesday) skies will remain mostly sunny to partly cloudy and temps will be quite warm in the middle to upper 80s across the area. Southerly winds have returned to the area and have allowed for low-level Gulf of Mexico moisture to return to the area; as evidenced by dew points climbing into the 50s and 60s today as compared to numbers in the 40s yesterday. 


 The Storm Prediction Center out of Norman, Oklahoma has placed southern portions of west Texas (from San Angelo to Del Rio) under the SLIGHT RISK CATEGORY for severe weather. This slight risk area does include the extreme western Hill Country as well. Latest high resolution forecast models show a strong disturbance moving out of northern Mexico later this afternoon/evening will produce enough lift to generate strong/severe storms across southwestern Texas...those storms will be capable of producing very large hail and damaging winds in excess of 60 mph. An isolated tornado can never be ruled out during a severe thunderstorm event.


 So, why should we care what's going on in west Texas? Well, those storms that develop across northern Mexico and Del Rio, Texas later this afternoon will organize into a line of storms and push east towards central Texas late tonight and into the early morning hours of Wednesday. If the storms are able to hold together, they will have the potential to bring strong gusty winds, heavy rainfall, small hail, and plenty of lightning to the area overnight.  The chance for storms tonight is 60% across the Hill Country, 50% along the I-35 corridor, and 40% for areas east of I-35.

One high resolution model I look at brings a solid line of storms into central Texas between midnight and 2 a.m.


 Another high resolution model I look at brings a line of storms into central Texas early Wednesday morning between 4-8 a.m.


 Once the possible storms blow through early Wednesday, skies will clear and temps will soar back into the 80s (the atmosphere will recharge itself)...the warmer we get, the more unstable conditions will become. The high resolution NAM model is forecasting very high CAPE values to return to central Texas Wednesday afternoon/evening (especially across the Hill Country). CAPE values may exceed 4000 joules per kilogram over the Hill Country which means storms that develop will quickly become severe with large hail and damaging winds. The higher the CAPE the more unstable the atmosphere (meaning that air will be rising very quickly and forcefully into the atmosphere aloft)...remember, you need lots of rising air to get storms.


 As that disturbance moves from northern Mexico into north central Texas tomorrow a line of storms should develop west of the DFW Metroplex across the Interstate 20 corridor...upper level winds will push those storms towards central Texas late Wednesday afternoon/evening. Individual storms that are able to develop tomorrow afternoon across central Texas will have to be monitored closely for the possibility of very large hail and damaging winds. The chance for rain Wednesday is at least 50%.


 Models are indicating a widespread 0.50 inches of rainfall could fall between tonight and Wednesday night across the area...of course, some areas may receive as much as 1.50 inches of rainfall if caught under a heavy downpour.

  

Wednesday, May 8, 2013

Severe Weather on the Way!

Hello everybody! I hope you are all doing well. I know it has been a while since I last posted. Well, moisture levels have really come up across the area from just 24 hours ago thanks to a southerly surface wind flow off of the Gulf of Mexico...those breezy southerly winds will persist through Friday ahead of our next strong storm system and frontal boundary that will work together to bring us a very good chance for thunderstorms on Friday. 

The Storm Prediction Center in Norman, Oklahoma has placed central Texas under the SLIGHT RISK CATEGORY for severe thunderstorms capable of producing large hail, damaging winds, and isolated tornadoes on Thursday and Friday. Honestly, I think areas north and west of Austin will have the greatest risk for severe weather on Thursday, however, severe storms will still be a possibility in Austin. The greater risk for severe weather comes on Friday as a Pacific Frontal Boundary attached to a low pressure system clashes with the warm, humid air over central Texas.

Forecast Radar for Friday Evening: Storms develop in Hill Country and push east towards Austin!



Thursday's Severe Weather Risk Area: 



Friday's Severe Weather Risk Area:



Besides the threats for large hail, damaging winds, and isolated tornadoes, latest computer models continue to indicate a good soaking for much of central Texas with the storms that are expected to arrive late Thursday and persist through Saturday. Of course the storms will come in waves, it is not going to be storming for 48 hours straight. Highs will continue in the 80s through the next seven days with lows in the 60s!

GFS Forecast Rainfall Accumulation: 0.50-1.50 inches



NAM Forecast Rainfall Accumulation: 1-2 inches



Weather Prediction Center's Forecast Rainfall Accumulation: 1-2 inches



Mother's Day Forecast: As of now, Mother's Day looks to be partly sunny and warm with highs in the lower 80s. Rain will have moved well east of central Texas by then. Overall, looks to be a nice day.