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Friday, October 30, 2015

More Trick Than Treat For Halloween

Early morning tornadoes did some damage to parts of Texas. There are numerous reports coming out of the towns of Floresville (seen above) and D'Hanis, just outside San Antonio. A vigorous upper-level disturbance moving through the area is packing quite a punch, providing sufficient lift in a moist atmosphere spawning the storms. 

The threat is far from over for the rest of the day across south-central Texas. Shaded in yellow are areas that the Storm Prediction Center believes have the highest risk of seeing potentially more of this kind of weather through the day Friday:

Not only is the upper-low vigorous, but also slow-moving. It won't be until late Saturday night that the threat exits eastward. Here is the current threat risk for Saturday, mainly emphasizing extreme southeast Texas and southern Louisiana:

If things work out correctly, you may be able to salvage the heart of trick-or-treat time in Southeast Texas. However, it will be soggy for most of the day Saturday and there could be some spots dealing with high water. Remember, it was just last weekend that the remnants of former hurricane Patricia soaked some of the same areas. Here is a projection of where rain will fall for Saturday in Texas:

After its all over, some places could pick up anywhere from 2 to 6 inches as indicated by this forecast for rainfall totals:

Stay safe on the roads and especially with so many potentially headed out for holiday activities.

Tuesday, October 27, 2015

Sunshine Returns - But For How Long?

After days of rain, the Lone Star state will get a chance to dry out a bit. Depicted above is the forecast for clouds Wednesday. The white are the clouds and the dark areas, cloud-free, should be mostly sunny. 

The remnants of former hurricane Patricia will move into the eastern third of the U.S. A weak trough of upper-level low pressure behind the surface low Patricia has become will move across the central plains. However, with little moisture to work with, there won't be much in the way of cloud cover. 

The dry spell won't last too long as a new disturbance emerges from west Texas by early Friday. This one moves through fairly quickly, so while there won't be a repeat of the flooding brought on by Patricia, there will be significant rainfall. Here's a depiction of conditions by Friday evening:

Unfortunately, the rain may linger for the trick-or-treaters headed out Saturday.

Friday, October 23, 2015

Major Flood Threat This Weekend

Nearly two-thirds of the state of Texas along with almost the lower half of Louisiana could see some astonishing rainfall this weekend. The green-shaded areas depicted above are under flash flood watches. 

It is possible that over a foot of rain could fall, bringing dangerous conditions to locations that have been very dry for weeks. Remnants of record-setting hurricane Patricia will combine with a cold front progressing across the central Plains, setting the stage for widespread misery.

When I first saw the blaring headlines that the Pacific hurricane named Patricia was the "strongest on record", I thought it was more media hyperbole. However, this time, it's fact. The two main measures of hurricane potency are maximum winds and central pressure. The lower the pressure, the stronger the storm. Here's what it looked like. when it made landfall Friday evening:

This is different than impact, because a storm could strengthen over warm water, far from harming anyone. However, when that danger looms, it certainly gets our attention.

Here's an idea of how strong Patricia is compared to its predecessors:

STORM         YEAR        MAX WINDS  (mph)       CENTRAL PRESSURE (mb)
Patricia        2015               200                              879
Wilma          2005               185                              882
Gilbert        1988                185                              888
Labor Day    1935                185                             892
Rita             2005                180                             895
Allen           1980                190                             899

The storm will weaken with regard to those two parameters as it encounters the mountains of central Mexico, but the moisture from the storm will be drawn into southern and central Texas by Saturday. Here's what computer models show for Saturday afternoon:

By late Sunday, here's the projection for accumulated rainfall. The purple shading indicates amounts that could easily exceed one foot:

Residents in the watch areas should stay alert to rapidly changing conditions as rain will fall repeatedly over the same areas, leading to the flash flood threat. Remember the live-saving adage - turn around, don't drown. The majority of the fatalities from the catastrophic South Carolina flooding earlier this month occurred in cars. People either got trapped in rapidly rising water or they ignored "road closed" signs and drove around barricades.

Tuesday, October 20, 2015

Much-needed Rain Later This Week

As of this writing, 147 counties in Texas are under a burn ban due to dry conditions. Much-needed rain is in the forecast for later week as low pressure develops in the western Gulf. That, in combination with a strong high pressure cell in the southeast U.S. will allow for extensive periods of rain to move into some of the driest areas in the Lone Star State.

Already, a few spotty showers have developed off the upper Texas coast, a sign that the lower atmosphere is much more saturated than recent days. By Friday, the picture changes dramatically to this:

The low pressure develops by late Sunday and could linger in the Gulf for a while:

Once the rain begins late Thursday, it could deposit over half a foot in the Hill Country, which could lead to flood concerns:

The pattern will be periods of repeated rains over some of the same areas. In situations like this, dry soil actually increases the flood threat because runoff is stifled. 

The best thing to do is to monitor weather conditions and if you know you are in a flood-prone area, you should have a plan to get to higher ground. Continue to monitor this blog for updates heading toward the weekend.


Friday, October 16, 2015

Cool Fall Weekend Ahead!

Believe it or not, a cool front slipped through Southeast Texas late Friday night. The only way you'd know is because of a wind shift as there wasn't any rain and just a few high clouds. You'll definitely feel the difference as drier and cooler air descends down to the coast. Shown above are the forecast low temperatures by Sunday morning.

High pressure filling in behind the front dominates the weather for much of the up-coming week. Gradually, by the end of next week, the high will slide off to the east. Then, a return of southeast winds pushes temperatures higher, increases the humidity and eventually brings rain back to the region.

For the past few days, the long-range GFS model has been hinting that low pressure will develop in the Gulf. Where it ends up and how intense it becomes is still a bit uncertain. However, there is a good chance that widespread, heavy rain will spread from Corpus Christi through Houston and into East Texas. Here's a depiction for the last Sunday of the month:

This will need to be monitored to see exactly where the low forms and more importantly, how much rain falls and where. Until then, enjoy the crisp mornings and warm afternoons!

Thursday, October 1, 2015

Joaquin's Journey

The third hurricane of the 2015 has become the strongest. Today, Joaquin was found to be packing 130 mph winds, making it a dangerous category 4 hurricane. Very warm water and weak upper-level steering conditions are creating the perfect environment for growth. Residents in the southern Bahamas are reporting widespread flooding and wind damage Thursday afternoon. So the question now is, where will Joaquin head next? Here's the latest forecast from the National Hurricane Center:

It still shows the storm remaining just off shore and not making landfall. For the past few days, models that forecast movement have been waffling between sending the storm out to sea and taking aim at some point of the east coast. Not surprisingly, the official track from the National Hurricane Center has been quite wide, nearly paralleling the east coast. This is intended to demonstrate the uncertainty of the forecast.

There are two major complicating factors steering this storm. The first is a stalled cold front, which is draped along the east coast. This has brought some heavy flooding rains from parts of Maine down to South Carolina:

At the same time, there is an upper-level low pressure cell in the southeast that may draw Joaquin northward over the weekend as well as enhance moist conditions from the mid-Atlantic to the southeast:

Computer projections have varied because the location and strength of the upper-low in the Southeast is uncertain. It seems that each day's computer model runs makes a different determination of where the upper-level low will end up.

This afternoon, the so-called spaghetti model plots have a split decision, with roughly half of them trending toward a mid-Atlantic landfall by Sunday and the other half sending the storm toward Bermuda:

There is virtually no chance of Joaquin heading into the Gulf of Mexico, so this will largely be an East Coast concern. It is also interesting to note that in the last 10 years, there have been fourteen Category Four hurricanes, most of them occurring in late September or October. Most have impacted the Caribbean or meandered in the middle of the Atlantic. The last Category Four hurricane to hit the U.S. was Charley in 2004.

Continue to watch for my blog updates on this dangerous storm to see where it ends up. If you know folks along the East Coast, encourage them to remain watchful and to be prepared. Even if the hurricane doesn't make a landfall, the stalled out front could bring more heavy rain that may lead to flooding.