Posts Tagged ‘Flooding’

SPC Day 1 Convective Outlook issued at 11:30 AM Sunday

The above graphic is the Day 1 Convective Outlook from the Storm Prediction Center issued at 11:30 AM this morning. Each ‘box’ is labeled for the specific hazard in question, and the graphic can be enlarged by clicking on it. SPC increased the probabilities of severe weather across portions of North Texas with their latest outlook. In order to find your specific risk, look for your area on the graphic above. If you’re in D/FW, you have a 30% chance of seeing severe wind/hail within 25 miles of your location. Outside the 30% area, a larger area of 15% probabilities, meaning you have a 15% chance of seeing severe weather within 25 miles of your location. Severe Weather (excluding tornadoes) is defined as 1 inch or larger hail and winds at or above 58 MPH.

12Z RUC at 7 PM Sunday - 500 MB (18,500 Feet) Winds

As we look at upper level winds, we note that North Texas will be on the southern edge of the stronger 500 MB winds. Most location will be around 30 knots across North Texas. To see sustained, organized severe weather (supercells) we want to see winds at 500 MB above 35-40 knots, so we’re very borderline on that. Low level wind fields remain weak with 850 MB winds at or below 20 knots. Needless to say, this is not a major severe weather event. Today’s severe weather threat will be comprised of marginally severe hail (“coin sizes”) and damaging outflow winds between 60-65 MPH in some cases. The tornado threat is non-zero. Personally, I don’t expect any issues with tornadoes today across North Texas because of the weak wind shear, however there are a few boundaries laying around which could briefly allow storms to develop low level rotation, but that chance is very low. If by chance there was a tornado today, it would be brief and likely very weak. Like I said, I don’t see that happening today. Instability values should be between 1,500 and 2,500 joules. Those moderate instability values will support the possibility of some severe weather this afternoon into early this evening. The severe weather threat should diminish by mid-evening as instability values decrease.

12Z RUC at 7 PM Sunday - 500 MB Wind Barbs, Surface Instability Values, and 1 Hour Precipitation

In terms of timing, much of that will depend on when the atmosphere becomes unstable enough to support thunderstorms along with when an upper level disturbance begins to influence the region. We should see thunderstorms begin developing by mid-afternoon across North Texas, likely around the D/FW metroplex. The above graphic is just one of severe different model solutions. It shows a line of thunderstorms impacting North Texas roughly from Gainesville, down to Fort Worth, southwest to Glen Rose. Today’s situation is quite complex, so please don’t expect the radar to look like that come 6-7 PM tonight. Thunderstorms over the past few days have left numerous boundaries across the region, which then become focus points for possible thunderstorm development. Models are having a hard time depicting all these boundaries which then make it difficult to pin-point where thunderstorms will develop and then move. Most models are in agreement that D/FW should see a heavier batch of showers and thunderstorms later this evening with more storms impacting East Texas.

In summary, we’re not expecting a major severe weather event. Some storms this afternoon will likely be severe with marginally severe hail (coin sizes), damaging winds over 60 MPH, and excessive cloud to ground lightning, in addition to heavy rainfall. It’s a good idea to stay close to a source of weather information later this afternoon and evening so you can stay up to date with weather warnings. We’ll be posting constant updates on our Facebook and Twitter pages this afternoon. We’re also planning to venture out later this afternoon once storms begin approaching the D/FW Metroplex, and we will have our live streaming video available once again. Stay tuned and thanks for stopping by!

- David