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Thursday, July 2, 2015

Heating Up and Drying Out

Summer's heat and humidity makes a comeback to southeast Texas. A ridge of high pressure depicted above should block a series of storms emerging out of the central plains. The predominant northwest flow in east Texas sends rainy weather into the Southeast U.S. A few rouge rumbles might make it through, but most should stay dry.

The high pressure ridge sends temperatures back into the low to mid 90s and the added humidity will make it feel like its over 100 degrees so, take it easy out there. This graph shows the "apparent" temperature (taking into account the effect of the added moisture in the air):

Right now, it looks like the pattern could break down in time guessed it, the July 4th celebration. Currently, the day doesn't look like a washout, but its a bit too early to time the arrival of storms that day. best advice is to check back to this blog a little closer to Saturday for updates.

Thursday, June 18, 2015

Bye-Bye Bill

Tropical Storm Bill captured by a NASA satellite as it makes landfall near Matagorda, TX June 16, 2015

As tropical systems go, Bill wasn't the worst Southeast Texas has seen, but it did leave a mark. If you've lived in the region for any length of time, you know the difference between a hurricane and a tropical storm. I describe it this way: a hurricane is like a traveling evangelist, it blows in - blows up and then blows out. A tropical storm is like the neighbor who comes over to ask for a cup of sugar but ends up an unwelcome dinner guest. As advertised, Bill was a rainmaker and as is the case with fickle tropical systems - some received more than others.

Here is a look at the rainfall totals estimated by radar from Bill:

The bullseyes of red and purple occurred far west of Houston in Wharton and Colorado counties where over 5" of rain fell. Similarly high amounts fell in Liberty, San Jacinto, Trinity and Polk counties. While not that much fell in Houston proper, there was enough to temporarily close some streets.

As the storm pinwheeled up into north Texas and Oklahoma, dumping flooding rains there as well. Even though the storm is exiting the state, the threat for more flooding isn't over. Runoff into the Brazos, Trinity and Colorado rivers could cause flooding later in the weekend. Additionally, there is a flood threat across the Ohio River Valley as Bill's remnants head there Friday and Saturday.

The second named storm of the season was also the second to make landfall. That hasn't happened since 2006. Hopefully, the forecast of El Nino disrupting the rest of the season will hold and residents of Texas will get a break.

Sunday, June 14, 2015

Bracing For Bill

All eyes focus on the Gulf of Mexico as an area of low pressure is getting more and more organized. It is very possible that this will become the second named storm of this season. Bill will likely remain a tropical storm, but residents along the Texas coast should remain on high alert. After the wettest May on record in many places, Bill threatens to renew the flood threat. The rain could begin falling as early as Monday afternoon and might last through early Wednesday.

The air force reconnaissance planes, so-called "Hurricane Hunters" will investigate the system today and Monday morning looking for crucial information gained only by flying into tropical turmoil. They may indeed find a developing surface low pressure system aided by very weak upper-level winds. A weak high pressure ridge in the Gulf will tend to nudge Bill westward toward the Texas coast. A conglomeration of models has this opinion, although there is a wide spread as to the likely landfall location:

Most of the heavier rainfall in a tropical system falls east of the center. Therefore, the further west Bill heads, the worse it will be for Houston, Galveston and Lake Charles. If Bill heads closer to the Texas-Louisiana border, the greater the chance the flood threat ends up in central and southern Louisiana.

Here is the current thinking about the expected rainfall through mid-day Tuesday:

Anywhere from 3" to 6" are likely. Depending on the track of the storm, these rain bands could easily come in off the Gulf and repeatedly drench the same areas. This "training" effect could lead to flash flooding over an area hard hit by Memorial Day flooding. Residents should be alert and have a plan for getting to higher ground and avoiding low-lying areas that have a history of flooding.

Tuesday, June 9, 2015

Rain On The Horizon

The #NormanNumber™ in Houston for Tuesday June 9 is 8. Partly cloudy, hot and muggy. Little more than a stray shower likely. High: 93°.

The heat beat goes on for most of this week. Expect typical early June weather in Southeast Texas. By week's end, however, a change begins to develop as more widespread and heavy rainfall return to the region. 

High pressure will strengthen across the Florida panhandle which will nudge a surge of Gulf moisture back toward the upper Texas coast. That should allow for showers and thunderstorms to develop. Here is what Saturday's map looks like:

At the same time, low pressure will begin to emerge from west Texas, setting up a kind of atmospheric "squeeze play". This could result in slow-moving storms, renewing the flood threat that plagued the state at the end of last month.

Tuesday, June 2, 2015

Finally Drying Out!

After a water-logged month of May, temperatures are set to head into familiar territory for June in Houston. The above shows the temperature trend for the rest of this week. Highs in the low 90s should be common; its only happened twice so far this year.

May rainfall tallied 14.17" inches in the gauge at Houston's official reporting location, making it the fifth highest ever. In all, there were only ten days when it didn't rain last month. A series of upper-level disturbances paraded through the Lone Star State spawning tornadoes and turning streets into rivers, but now the pattern is changing.

A high pressure ridge will settle in over at least the next ten days. That will help the mercury climb over 90 degrees and keep the rainfall threat very low. At best, a few isolated showers developing along the sea breeze may form, but these should be short-lived.

Friday, May 29, 2015

Just Can't Get A Break

The Norman Number in Houston for Friday, May 29 is 6. Morning downpours head into the Gulf. A few more spotty showers may develop in the muggy air, otherwise partly cloudy and warm. High: 85.

Still reeling and recovering from the extensive flooding earlier in the week, Southeast Texas braces for yet more rain. Thanks to swollen rivers and bayous, additional rains will cause new rises and new flood fears.

A steady-moving line of storms emerged from North Texas late Thursday night, prompting a renewed Flash Flood Watch. Fortunately, that threat diminished around daybreak as the storms weakened considerably despite ominous skies.

That short-lived respite from another threat of heavy downpours won't last, however. A muggy airmass over the region will allow for a few isolated showers, mainly along the coast Friday. 

By Saturday, a cold front will begin moving southward from the Red River valley. It has the potential for widespread rain. Here's a model depiction for Saturday afternoon:

Not out of the question - more training storms that could lead to flash flooding. Rainfall amounts could fall in the 1" to 2" range. 

There is a glimmer of hope toward the beginning of next week. as a weak ridge of high pressure forms in the Northern Gulf. This could potentially suppress heavy rainfall, but even a few spotty showers could linger.

Looks like this month will go down as one of the wettest Mays ever in Houston. As of today, the 13.59" is the fifth highest total. With two days left in the month, only 2.28" would have to fall to best the 15.87"mark set in 1907. Given how things have been going, that wouldn't be too surprising.

Tuesday, May 26, 2015

Historic Flooding!

                                           (I-45 at North Main - courtesy +AlexGreen713

Overnight deluges turned interstates into waterways, stranding thousands. Bayous and rivers overflowed their banks and continue to rise. The map above shows the astonishing totals across Harris county. If you didn't know better, you might think a tropical system came through as the totals climb to nearly a foot. Much of that fell in five hours.

Hardest hit, parts of southwest Houston. Alief picked up over 9", Sugar Land over 10". Both official airport locations set daily records with Bush at 4.34" and Hobby at 3.95". For the month, this May is the 10th wettest. Even as residents struggle to recover, more wet weather is on the way later this week.

A vigorous upper-air disturbance collided with a steadily-moving bow echo last night. But there was an extra ingredient that came into play. An odd westward-moving boundary from Louisiana created extra lift. All of those systems have since moved east and potentially, rain-weary Houstonians could get a break Tuesday and Wednesday. However, a new disturbance is slated to move across Texas by Thursday and Friday that could cause more rain. 

Check back here Friday for an update on that and the chances May 2015 could move up in the record books.