Dr. Jeff Masters' WunderBlog

Unprecented floods on the Mississippi, in Colombia, and Canada

Posted by: Dr. Jeff Masters, 14:58 GMT le 16 mai 2011

The great Mississippi River flood of 2011 continues to make history, with Saturday's opening of the flood gates of the Morganza Spillway marking just the second time that flood control structure has been used since its construction in 1956. With the Morganza, Bonnet Carre', and Birds Point-New Madrid Spillways all open, the Army Corps of Engineers has now opened all of its major spillways simultaneously for the first time ever. The Mississippi is rising at Vicksburg, Mississippi, where the water has now reached 56.5', exceeding the previous all-time record of 56.2', set during the great flood of 1927. Natchez, Mississippi, is also at its greatest flood height on record, with the water at 60.6'. The previous record high was 58', set in 1937. However, the opening of the Morganza spillway has reduced the predicted heights of the great flood of 2011 from Natchez to New Orleans by 1 to 1.5'. This will serve to greatly reduce the pressure on the levees and on the Old River Control Structure, which as I discussed in my previous post, is America's Achilles' heel, and must be protected. According the National Weather Service, flood heights along the Lower Mississippi from Natchez to New Orleans will peak this week, and slowly fall next week. Rainfall over the next five days is expected to be minimal over the Lower Mississippi watershed. The next chance for significant rain over the region will come Sunday, May 22.

Figure 1. Saturday's opening of the first gate on the Morganza Spillway, as seen on the live feed from USTREAM.

Devastating flooding continues in Colombia
Devastating flooding has hit South America in Colombia, where exceptionally heavy spring rains have killed at least 425 people so far this year, with 482 others missing. Damages are in the billions, and there are 3 million disaster victims. "Some parts of the country have been set back 15 to 20 years", said Plan’s Country Director in Colombia, Gabriela Bucher. "Over the past 10 months we have registered five or six times more rainfall than usual," said the director of Colombia's weather service, Ricardo Lozano. Up to 800 mm (about 32 inches) of rain has fallen along the Pacific coast of Colombia over the past two weeks (Figure 3). The severe spring flooding follows on the heels of the heaviest fall rains in Colombia's History. Weather records go back 42 year in Colombia. Colombia's president Juan Manuel Santos said, "the tragedy the country is going through has no precedents in our history." The 2010 floods killed 571 people--the second deadliest year for floods in Colombian history, next to 1987. The floods did over $1 billion in damage, and affected 2.8 million people. In many places, the flood waters from this great disaster never fully receded, and are now rising again due to this latest round of intense flooding. More rain is in the forecast--the latest forecast from the GFS model calls for an additional 5 - 10 inches (200 - 400 mm) across much of western and northern Colombia in the coming week.

Figure 2. Satellite-observed rainfall over Colombia during the past two weeks shows a region of up to 800 mm (about 32 inches) has fallen near the Pacific coast. Image credit: Navy Research Lab, Monterey.

Colombia's rainy season usually has two peaks: one the fall in October, then then another in the spring in April - May. The heavy rains are due to the presence of the Intertropical Convergence Zone, the area encircling the earth near the Equator where winds originating in the northern and southern hemispheres come together. When these great wind belts come together (or "converge", thus the name "Convergence Zone"), the converging air is forced upwards, since it has nowhere else to go. The rising air fuels strong thunderstorm updrafts, creating a band of very heavy storms capable of causing heavy flooding rains. In La Niña years, when a large region of colder than average water is off the Pacific coast of Colombia, rainfall tends to increase over Colombia. La Niña was moderate to strong during the fall 2010 rains and floods in Colombia, and was largely to blame for Colombia's deadly rainy season. However, in recent months, La Niña has waned. April sea surface temperatures off the Pacific coast of Colombia (0° - 10°N, 85° - 75°W), warmed to the 13th highest temperatures in the past 100 years, 0.68°C above average. Thus, this month's flooding in Colombia may not be due to La Niña.

See also my December 2010 post, Heaviest rains in Colombia's history trigger deadly landslide; 145 dead or missing

Figure 3. Dramatic video of flooding in Colombia over the weekend. Flood waters swept away cars and buses in a busy street in the city of Barranquilla, and passengers climbed on the roofs of their vehicles in order to escape the flood waters. Video credit: BBC.

300-year flood in Canada; wildfires destroy large portions of Slave Lake, Alberta
In Manitoba, Canada, heavy spring snow melt in combination with heavy rains have combined to create record flooding on the Assiniboine River. Authorities intentionally breached a levee over the weekend to save hundreds of homes, but inundated huge areas of farmland as a result. The flood is being called a 300-year flood, and damages are already in excess of $1 billion. In Alberta, Canada, reverse extreme is causing havoc: severe drought and strong spring winds have made ideal conditions for wildfires, which swept into the community of Slave Lake (population 6,700) yesterday. The fires destroyed hundreds of buildings, burning down the town hall and at least 30% of the town, according to preliminary media reports.

Figure 4. Video of the May 15, 2011 Slave Lake fire.

First tropical wave of the year over the Atlantic
The first tropical wave of 2011 is now over the tropical Atlantic near 6°N 46°W, according to the latest Atlantic Tropical Weather Discussion. The wave will bring heavy rain to the northeast coast of South America over the next two days, but is too far south to be a threat to develop into a tropical depression. The Atlantic hurricane season is just two weeks away, and the Eastern Pacific hurricane season began yesterday. So far, the models are not predicting any tropical storm development in the East Pacific or Atlantic over the next six days.

Jeff Masters

The Great Flood of 2011 (jperilloux)

KCS train crossing the trestle through the Bonnet Carre Spillway at Norco, LA. Flood water diverted from Miss. River

Categories: Flood

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1. TropicalAnalystwx13 15:08 GMT le 16 mai 2011
Thanks Doc. Member Since: 6 juillet 2010 Posts: 89 Comments: 25290

3. Tazmanian 15:10 GMT le 16 mai 2011
So far, the models are not predicting any tropical storm development in the East Pacific or Atlantic over the next six days yawn the season a bust Member Since: 21 mai 2006 Posts: 5088 Comments: 111346

5. Neapolitan 15:19 GMT le 16 mai 2011
Quoting USAprimeCreditPeggy: 300-year flood in Canada I do not understand this phraseology. Does it mean a flood will happen every three hundred years? It means that, statistically-speaking, such an event is calculated to happen every 300 years on average. Far more than 300 years may pass between such events, of course--or one could happen every year. It seems we've seen a lot of 100-year and 300-year and 500-year weather events lately, so the actuaries are going to be really busy revising those exceedance probabilities. Member Since: 8 novembre 2009 Posts: 4 Comments: 11153

6. NICycloneChaser 15:19 GMT le 16 mai 2011
Quoting Tazmanian: So far, the models are not predicting any tropical storm development in the East Pacific or Atlantic over the next six days yawn the season a bust Lol, no storm in mid-May clearly indicates a below-average season... :P Member Since: 10 août 2010 Posts: 2 Comments: 1957

10. tkeith 15:25 GMT le 16 mai 2011
Quoting Tazmanian: So far, the models are not predicting any tropical storm development in the East Pacific or Atlantic over the next six days yawn the season a bust LMAO! Member Since: 1 novembre 2004 Posts: 25 Comments: 8839

11. TropicalAnalystwx13 15:26 GMT le 16 mai 2011
I believe that this year will closely follow the season of 2008 for the Atlantic...That, and 1996 (number of impacts only). Member Since: 6 juillet 2010 Posts: 89 Comments: 25290

15. beell 15:43 GMT le 16 mai 2011
Quoting Neapolitan: It means that, statistically-speaking, such an event is calculated to happen every 300 years on average. Far more than 300 years may pass between such events, of course--or one could happen every year. It seems we've seen a lot of 100-year and 300-year and 500-year weather events lately, so the actuaries are going to be really busy revising those exceedance probabilities. And just to be clear, the formulae for recurrence probabilities will not change. To what particular geographic area they are applied-may. Member Since: 11 septembre 2007 Posts: 124 Comments: 12875

16. Jax82 15:43 GMT le 16 mai 2011
plenty of moisture in the E Carib. Member Since: 2 septembre 2008 Posts: 1 Comments: 1261

17. kimoskee 15:44 GMT le 16 mai 2011
Small tremor felt in Jamaica. Link Member Since: 17 août 2008 Posts: 0 Comments: 670

18. aquak9 15:45 GMT le 16 mai 2011
oh dear...We need a qualified person to post TheChart, please. Member Since: 13 août 2005 Posts: 163 Comments: 25007

19. muddertracker 15:48 GMT le 16 mai 2011
:) Member Since: 16 août 2007 Posts: 1 Comments: 2126

20. RitaEvac 15:49 GMT le 16 mai 2011
No storms, see yall next year. Member Since: 14 juillet 2008 Posts: 1 Comments: 8899

22. aquak9 15:51 GMT le 16 mai 2011
Quoting USAprimeCreditPeggy: I need an avatar. modified- I LOVE the screen name. Member Since: 13 août 2005 Posts: 163 Comments: 25007

24. RitaEvac 15:56 GMT le 16 mai 2011
It's uncle Sam's wife Member Since: 14 juillet 2008 Posts: 1 Comments: 8899

25. Bitmap7 15:58 GMT le 16 mai 2011
Quoting kimoskee: Small tremor felt in Jamaica. Link Those tremors aren't visible on the usgs or iris only two quakes have been posted since yesterday it seems. I did hear a rumbling around that time though. Member Since: 4 mai 2011 Posts: 0 Comments: 429

27. Bitmap7 16:02 GMT le 16 mai 2011
Magnitude M 4.8 Region JAMAICA REGION Date time 2011-05-16 15:07:07.5 UTC Location 17.94 N ; 77.86 W Depth 20 km Distances 96 km W Spanish town (pop 145,018 ; local time 10:07:07.5 2011-05-16) 26 km S Savanna la mar (pop 18,616 ; local time 10:07:07.5 2011-05-16) 10 km S Black river (pop 4,229 ; local time 10:07:07.5 2011-05-16) Member Since: 4 mai 2011 Posts: 0 Comments: 429

28. aquak9 16:02 GMT le 16 mai 2011
Here we go again. Ya'll know what to do. Member Since: 13 août 2005 Posts: 163 Comments: 25007

29. twhcracker 16:02 GMT le 16 mai 2011
on tv it said the nashville flood was a 1000 year flood event. Member Since: 30 juillet 2007 Posts: 6 Comments: 1448

30. tkeith 16:08 GMT le 16 mai 2011
Quoting aquak9: Here we go again. Ya'll know what to do. schools out already? Member Since: 1 novembre 2004 Posts: 25 Comments: 8839

32. earthlydragonfly 16:10 GMT le 16 mai 2011
Quoting tkeith: schools out already? LOL Member Since: 1 juillet 2005 Posts: 10 Comments: 1649

34. PrivateIdaho 16:15 GMT le 16 mai 2011
We had a 0.364-year storm here yesterday. Member Since: 29 août 2010 Posts: 0 Comments: 5211

36. NICycloneChaser 16:18 GMT le 16 mai 2011
Quoting PrivateIdaho: We had a 0.364-year storm here yesterday. :O You get almost 3 of those a year?! Member Since: 10 août 2010 Posts: 2 Comments: 1957

37. kimoskee 16:21 GMT le 16 mai 2011
Link Member Since: 17 août 2008 Posts: 0 Comments: 670

40. PrivateIdaho 16:28 GMT le 16 mai 2011
Quoting NICycloneChaser: :O You get almost 3 of those a year?! ...but we got 4 last year! Member Since: 29 août 2010 Posts: 0 Comments: 5211

42. overwash12 16:36 GMT le 16 mai 2011
Quoting USAprimeCreditPeggy: Earthquakes, floods, what is next? Hurricanes! Member Since: 24 juin 2007 Posts: 0 Comments: 1049

43. TampaSpin 16:38 GMT le 16 mai 2011
Quoting RingOfDestruction: GOOD, se largo la analfabeta esa, Anyway, do y'all think that South Florida is in danger this summer? Isn't it every year!!!! It only takes one for some to say it was a horrible season. Member Since: 2 septembre 2007 Posts: 175 Comments: 19747

45. DookiePBC 16:41 GMT le 16 mai 2011
Quoting USAprimeCreditPeggy: Earthquakes, floods, what is next? Plagues of high schoolers unleashed upon this board! On the good news front...some of that clear liquid fell from the skies over Palm Beach County this weekend!! Member Since: 1 septembre 2009 Posts: 0 Comments: 433

46. Skyepony (Mod) 16:41 GMT le 16 mai 2011
I made it to the shuttle Launch this morning..took some pics for ya'll. Will get the rest up in a bit. Member Since: 10 août 2005 Posts: 144 Comments: 29312

47. overwash12 16:44 GMT le 16 mai 2011
Nice # 46,Good for you! Member Since: 24 juin 2007 Posts: 0 Comments: 1049

48. PrivateIdaho 16:45 GMT le 16 mai 2011
Best ride ever! Member Since: 29 août 2010 Posts: 0 Comments: 5211

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