Daily Archives
September 18, 2014

TK Special Briefing….

by troyk | on Sep 18, 2014 | Comments Off

Austin and South Central Texas Weather Statement
Issued by UT Incident Meteorologist Troy Kimmel
555pm CT – Thursday / 18 September 2014

… The Flash Flood Watch, as issued by the NWS Austin-San Antonio, Remains in Effect until 7am Friday …
… Flash Flood Warning for Northern Burnet and Western/Central Williamson County Continues Until 745pm …
… New Flash Flood Warning Just Issued for Parts of Williamson, Travis, Burnet, Llano and Blanco Counties Until 830pm …
… Possible Dangerous Flash Flood Event Developing Again Tonight Depending on Where Heaviest Rains Occur …

Just before 6pm, rain showers and heavier thunderstorms, accompanied by gusty winds and frequent deadly
lightning, are moving southward through Williamson and Burnet Counties into northern Travis County.
Thunderstorms over Burnet County are shown to have produced over 1000 lightning strikes the past 60 minutes
while the thunderstorms over Williamson County have produced lesser amounts (still dangerous though).

As we head toward sunset, as this rain and thunderstorm activity settles southward into the Austin metro area,
the potential exists for another dangerous flash flood event to develop especially if the precipitation moves over
or develops over the areas of Travis and Hays Counties that received over 4 inches up to over 6 inches last night.
If rains develop in these areas.. especially bounded by IH35 on the east and Lake Travis on the west over the western
parts of the Austin metro area, flash flooding will develop very rapidly. On the other hand, if the heaviest rains occur
over areas where rainfall was less last night, the problems would unfold more slowly. The long and short (and frustrating)
part of this story is that we really won’t know until the rain sets in or develops over over any given area.

Forecast rainfall amounts between now and daybreak tomorrow morning.. based on NWS Austin San Antonio produced
guidance… is, on average, in the 1 to 3 inch range with isolated totals of 3 to 5 inches possible.

As a result, I cannot state strongly enough that all interests MUST remain weather aware tonight into the morning
hours on Friday throughout our Austin metro and IH35 corridor area.  We must remain situationally weather aware and
avoid  all flood prone areas including low water crossings and areas were  water traditionally  accumulates.. even if it’s
not raining in your immediate area. As weather deteriorates into the night, I would recommend you not being out into
the night unless absolutely necessary.

Weather tools:
City of Austin / Low Water Crossing Flooding…. www.atxfloods.com
LCRA Hydromet…. http://hydromet.lcra.org/full.aspx

Continuing to monitor.. tk

TK’s Audio Weather Webcast….

by troyk | on Sep 18, 2014 | Comments Off

Updated 935am CT – Thursday / 18 September 2014

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TK’s Austin and South Central Texas Weather Forecast….

by troyk | on Sep 18, 2014 | Comments Off

Updated 845am CT.. Thursday / 18 September 2014

TODAY…. Mostly cloudy with scattered to numerous rain showers and thunderstorms. Rainfall, where it occurs given a 60% chance of rain at any given location, will average 1/2 to 3/4 inch. High 86. South southeasterly wind 5 to 12 mph.

TONIGHT…. Mostly cloudy with scattered rain showers and thunderstorms. Rainfall, where it occurs given a 50% chance of rain at any given location, will average 1/4 to 1/2 inch. Low 71. Southeasterly wind 5 to 10 mph.

FRIDAY…. Some morning low clouds.. otherwise partly to mostly cloudy with scattered rain showers and thunderstorms. Rainfall, where it occurs given a 40% chance of rain at any given location, will average 1/4 inch. High 89. South southeasterly wind 5 to 12 mph.

FRIDAY NIGHT…. Partly cloudy with widely scattered rain showers and thunderstorms. Rainfall, where it occurs given a 20% chance of rain at any given location, will average 1/4 inch. Low 70. Southeasterly wind 5 to 10 mph.

SATURDAY…. Some morning low clouds.. otherwise partly cloudy with widely scattered rain showers and thunderstorms. Rainfall, where it occurs given a 20% chance of rain at any given location, will average 1/4 inch. High 90. South southeasterly wind 5 to 12 mph.

SATURDAY NIGHT…. Partly cloudy with widely scattered rain showers and thunderstorms. Rainfall, where it occurs given a 20% chance of rain at any given location, will average 1/4 inch. Low 70. Southeasterly wind 5 to 10 mph.

SUNDAY…. Some morning low clouds.. otherwise partly cloudy with widely scattered rain showers and thunderstorms. Rainfall, where it occurs given a 20% chance of rain at any given location, will average 1/4 inch. High 90. South southeasterly wind 5 to 12 mph.

SUNDAY NIGHT…. Partly cloudy with widely scattered rain showers and thunderstorms. Rainfall, where it occurs given a 20% chance of rain at any given location, will average 1/4 inch. Low 70. Southeasterly wind 5 to 10 mph.

MONDAY…. Some morning low clouds.. otherwise partly cloudy with scattered rain showers and thunderstorms as a cold front moves through the area. Rainfall, where it occurs given a 30% chance of rain at any given location, will average 1/4 inch. High 89. South southeasterly wind 5 to 12 mph shifting north northeasterly as the cold front passes.

MONDAY NIGHT…. Partly cloudy. Low 68. North northeasterly wind 5 to 10 mph.

TUESDAY…. Partly cloudy. High 88. Northeasterly wind 5 to 12 mph.

TUESDAY NIGHT…. Partly cloudy. Low 68. North northeasterly wind 5 to 10 mph.

WEDNESDAY…. Partly cloudy. High 88. Northeasterly wind 5 to 12 mph.

NATIONAL WEATHER SERVICE / 8 TO 14 DAY OUTLOOK
Valid Thursday / 25 September 2014 through Wednesday / 01 October 2014…
Temperature… Near to Slightly Below Average
Precipitation… Below Average

AUSTIN SUNSET/SUNRISE TIMES…..
Sunrise this morning (18 September)…………………………………………. 7:17 am
Sunset this evening (18 September)………………………………………….. 7:32 pm
Sunrise Friday (19 September)…………………………………………………. 7:18 am
Sunset Friday (19 September)…………………………………………………. 7:31 pm

TK’s Weather Discussion….

by troyk | on Sep 18, 2014 | Comments Off

Updated 800am CT – Thursday / 18 September 2014

…. Flash Flood Watch Remains in Effect ….
…. Abundant Moisture and Passing Upper Air Low Pressure Disturbances ….
…. Rain Chances Decrease by Friday Night into the Weekend ….

On this Thursday morning…. a weakening stationary front extends from south central Mississippi northwestward into southwestern Arkansas and eastern Oklahoma and then into Kansas. A surface low pressure trough extends south southwestward from western Kansas into far west Texas and eastern New Mexico. As a result of this surface weather pattern, our local surface winds are southeasterly.

In the upper levels of the atmosphere… a broad trough.. or line.. of upper level low pressure is moving eastward through the eastern third of the USA with another trough of low pressure moving ashore onto the west coast. The upper air reflection of Pacific tropical cyclone Odile.. with abundant high and mid level Pacific moisture.. is located over southwestern New Mexico west of El Paso. Weakened upper level high pressure.. acting like a lid on the atmosphere.. as been shoved southward into northeastern Mexico and deep south Texas. As a result of this pattern, the upper level winds over south central Texas and the Austin metro area, about 18,000 feet above the ground, are west northwesterly at 20 to 25 mph.

After overnight flooding in the Austin metro area.. with rainfall amounts of up to 6 inches and continuous lightning (in the 2 to 3 o’clock hour this morning – in an hours’ time – I actually saw, through our lightning data recording equipment, almost 5000 distinctive strokes of lightning in west Austin!!), things have now become a bit more quiet.

However, with the upper level trough to our northeast and the advancement eastward of the remnants of Odile, the upper level high pressure area, or the “lid” on the atmosphere, has been pushed southward in Mexico. At the same time.. abundant low level moisture continues, along with an increasingly unstable air mass, continues over the area. As the upper air disturbances.. from the west.. traverse the area and creates atmospheric lift, we’ll continue to see much better rain and thunderstorm chances through tomorrow. The latest computer and NWS manual guidance suggests that we could see another 1 to 3 inches of rain with isolated heavier amounts. While the rainfall will certainly be beneficial in nature overall, where rainfall occurs in areas that were flooded earlier today, we could see rapid onset of flooding. At the least, localized urban and small stream/low water crossing flooding is possible. In addition, with cloud cover and precipitation chances over the next few days, afternoon high temperatures remaining slightly below seasonal averages.

By late Friday into the weekend, the upper level high pressure ridge (the “lid” on the atmosphere) will strengthen a bit with rain chances coming down and clouds thinning out a bit.

Guidance suggests that another cold front will move southeastward across the area by late Sunday into early Monday with a renewed chance of rain showers and thunderstorms.

Regarding my forecast, my local forecast confidence: My forecast confidence over the next two days is high to very high (still concerned with the exact rain timing and amounts). My confidence is very high Friday night through much of the upcoming weekend. My forecast confidence falls back to medium to high for late Sunday night into Monday in reference to precipitation and cold frontal timing.

Have a good Thursday….
Meteorologist Troy Kimmel

Contact me:
tkimmel@austin.utexas.edu

http://www.facebook.com/troykimmel