Low Flood Threat This Spring…

 

Comparison between 3/1/2011 and 3/1/2015.

Comparison between 3/1/2011 and 3/1/2015.

Although the winter was cold and snowy across the Great Lakes and Northeast, snowfall across the Upper Midwest, the headwaters of the Mississippi River, was well below normal.  Check out the difference between March 1, 2015 and March 1, 2011, regarding snow water equivalent.  This tells us how much water was on the ground if all the snow were melted.  Back in 2011 there was the equivalent of 4″-9″ of water across much of the Upper Midwest.  That water ultimately led to flooding across the Lower Mississippi River Basin and the Atchafalaya River Basin.  Roughly 70% of the water in the Mississippi flows down the main channel south of Simmesport, while the other 30% gets diverted to the Atchafalaya River.  This spring, we’ll see extra water move down the Ohio River and into the Mississippi River, but thanks to lower snowfall across the Upper Midwest, river levels across Louisiana and Mississippi should only crest near the flood stage or below.  The latest forecast for Baton Rouge shows a crest on March 30 of 35.5′ on 3/30; flood stage there is 35.0′.  At New Orleans, the crest forecast is 14.0′ on 3/31; the flood stage there is 17.0′.  On the Atchafalaya, the flood stage at Butte La Rose is 20.0′.  Back in 2011 the river there crested at 23.5′, but this year the crest should be below flood stage in late-March.  Of course, we’ll have to keep an eye on any significant rain systems over the next few weeks, but this year doesn’t look too bad. -David

 

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A Pattern Shift To Spring-like Air…

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Chilly weather continues into the weekend before we see a big warm-up.  Another shot of cold air follows later next week, though.  However, the overall pattern is about to undergo a big change that means temperatures will likely go above normal for mid- to late-March across a good chunk of the country.  We’ll see the long-wave ridge off the West Coast break down, leading to “troughiness”, which in turn allows warmer air to overspread the central and eastern part of the country.  The cold air that’s dominated the Great Lakes and Northeast all winter will retreat to the North Pole, allowing the spring thaw to commence.

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Shift To A Warmer Pattern In Sight…

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As you probably know, the overall pattern is a cold one for the eastern two-thirds of America.  We’ll see the unseasonably cold weather last for the remainder of February and into March, but a pattern change looks to take place by the second week of the month.  The big trough and bitterly cold air that’s dominated the Great Lakes and Northeast much of this winter should retreat northward and be centered around the North Pole.  Meanwhile, the persistent ridge of high pressure off the West Coast looks to break down, with a long-wave trough developing there instead.  The result?  Likely cooler and wetter for the West, with much warmer air overtaking the Central and Eastern US in early- to mid-March.  Winter fans, enjoy the next 10 days before some real spring-like air moves into Acadiana.

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Arctic Blast Impressive Across Acadiana…

A map of low temperatures on January 8, 2015.

A map of low temperatures on January 8, 2015.

Unseasonably cold air moved in early Thursday, dropping our temperature around 20° below normal. The Arctic air resulted in a low of 23° at Lafayette, with upper 10s in the Alexandria area. This may end up being the coldest night of winter, but keep in mind that historically, our coldest air arrives during the first couple weeks of February.

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The Coldest Night So Far This Winter…

Arctic air arrives in Acadiana.

Arctic air arrives in Acadiana.

After a relatively mild December, January is ushering in some unseasonably cold air. Temperatures Wednesday night will fall through the 20s, reaching the lower 20s by daybreak Thursday.  With winds at 10-20 mph, wind chill values will reach the 10s for a period around daybreak.  Make sure to finalize your cold weather preps.

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Christmas Week Severe Threat…

Severe threat December 23, 2014.

Severe threat December 23, 2014.

There’s a Slight Risk of severe weather across parts of Acadiana on Tuesday.  A disturbance moving in from the west will tap moisture from the Gulf of Mexico and produce showers and thunderstorms during the midday and afternoon period across South Louisiana.  Our main severe threat will be from 2 PM to 6 PM with the chance for damaging winds and perhaps an isolated tornado.  The severe threat will shift eastward later in the evening.  Look for some cooler air and dry weather for Christmas Eve and Christmas Day.

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Tracking What May Soon Be Cristobal…

Atmospheric currents.

Atmospheric currents.

The tropical disturbance near Hispaniola Friday evening is offering some forecast challenges.  I’ve marked the steering currents in the atmosphere with the white arrows, with a couple track scenarios in yellow.  There is a potential track to the north between the two big areas of high pressure.  However, if this system isn’t turned northward over the weekend, the energy may slowly drift towards South Florida during the first half of next week.  The Bahamas and Florida should definitely be on alert.  The next named storm will be Cristobal.

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Tracking The Tropics…

Watching a tropical wave in the Atlantic.

Watching a tropical wave in the Atlantic.

The tropical wave in the Atlantic Ocean appears to be gradually organizing.  The upper-level winds are rather favorable, so if the lower-level circulation can organize, we’ll have a tropical system on our hands.  The general motion will be to the west-northwest through the weekend, which will take the disturbance over the mountainous islands of the Caribbean, which will inhibit strengthening.  Next week there is much uncertainty regarding the track.  Some of the main computer models show a tropical system anywhere from South Florida to east of the Bahamas, while another model just shows a weak circulation in the Gulf.  If you see specific landfall model projections from other sources, keep in mind there is no way to pinpoint a track this far out.  Any impact to the Gulf Coast wouldn’t be until later next week, so we have plenty of time to observe this.  Just know there is a tropical wave out there that’s worth watching, so keep checking back.  Late-August usually features an increase in tropical activity and this year looks no different.

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Tropical Wave Worth Watching…

Visible satellite at 2:30 PM on 8/19/14.

Visible satellite at 2:30 PM on 8/19/14.

If you’re a loyal viewer, you know I’ve been tracking the tropical waves coming off the coast of Africa since last week.  This one in particular really bears watching over the next several days.  There appears to be a little organization Tuesday and this may develop into a tropical cyclone over the next couple days.  Given the steering currents in the atmosphere, the disturbance will move to the west-northwest.  Will it curve north and stay in the Atlantic, or move more westward and into the Gulf?  Too early to say, but this is the time of year we really need to watch the Atlantic Basin, so keep checking in for the latest over the days ahead.

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Warm Season Recap…

May 1 - August 11 stats at Lafayette, LA.

May 1 – August 11 stats at Lafayette, LA.

Here are some interesting weather statistics at Lafayette for the period from May 1 through August 11.  The average temperature was-1.4° compared to normal, while total rainfall was +10.09″ compared to normal.  Some changes are on the horizon, though, as the second half of August looks to turn hotter and drier.

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