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Isaac in Arkansas (August 30 - September 1, 2012)/Pg1
 
Hurricane Isaac was just off the coast of Louisiana at 425 pm CDT on 08/28/2012.

Hurricane Isaac made landfall along the Louisiana Gulf Coast during the evening of August 28th.

In the picture: Hurricane Isaac was just off the coast of Louisiana at 425 pm CDT on 08/28/2012.

 

A little more than 20 inches of rain fell at New Orleans, Louisiana. Some neighborhoods were inundated by floodwater, and hundreds of people either evacuated or had to be rescued.

Ninety six hour rainfall through 700 am CDT on 09/01/2012.
In the picture: Ninety six hour rainfall through 700 am CDT on 09/01/2012.

 

A couple of days later, the remnants of Isaac were in Arkansas. From a headline standpoint, and given what happened to the south, it was no surprise that the big story locally with this tropical system was flooding. More on this later.

 

 

Discharge along the Mississippi River at Belle Chasse, Louisiana (near New Orleans) was actually negative for a time on 08/28/2012, indicating storm surge from Isaac and an upstream flow.
In the picture: Discharge along the Mississippi River at Belle Chasse, Louisiana (near New Orleans) was actually negative for a time on 08/28/2012, indicating storm surge from Isaac and an upstream flow.

 

A spaghetti plot of potential Isaac tracks as of 700 am CDT on 08/29/2012.
In the picture: A spaghetti plot of potential Isaac tracks as of 700 am CDT on 08/29/2012. The plot was comprised of numerous forecast model guesses. Note that "Model Eastern Edge" and "Model Western Edge" lines do not diverge greatly away from Isaac. This indicated general model agreement with time and more confidence in the track of the system as it moved inland. The "Model Best Fit" line was the most likely track based on the data.

 

A building ridge of high pressure ("H") to the east of Arkansas has been forcing the remnants of Hurricane Isaac ("L") to the west.

Models had difficulty determining where Isaac would go, but they finally came into agreement with a track through western sections of the state. That helped forecasters decide what the impacts would be locally.

In the picture: A building ridge of high pressure ("H") to the east of Arkansas has been forcing the remnants of Hurricane Isaac ("L") to the west.

 

As the system arrived during the afternoon and evening of the 30th, barometric pressure dropped markedly. The lowest pressures measured were at El Dorado (Union County) and Camden (Ouachita County), with 29.46 inches (997.6 millibars) and 29.51 inches (999.3 millibars) respectively. As pressures dropped, east to northeast winds increased and became gusty. Some gusts exceeded 40 mph. Pine Bluff (Jefferson County) had a gust to 46 mph, with 44 mph at Little Rock (Pulaski County) and 43 mph at Hot Springs (Garland County) and Mount Ida (Montgomery County).

Higher gusts downed some trees/tree limbs, and there were power outages reported. The tree damage was partly due to existing drought conditions and a lack of ground water. Many trees were in a weakened state. This made them more susceptible to gusty conditions.

 

Expected storm total precipitation in Arkansas.
In the picture: Forty eight hour rainfall through 700 am CDT on 09/01/2012.
 

Much of the region was east of the center of Isaac. This is typically where the heaviest rain occurs. On the 30th/31st, three to more than six inches fell from northeast into central and southeast Arkansas. White Hall (Jefferson County) received a whopping 10.70 inches of rain, with 8.88 inches at Providence (White County), 8.39 inches at Pine Bluff (Jefferson County), 8.25 inches at Steprock (White County), 8.20 inches at Augusta (Woodruff County) and 8.11 inches at Fordyce (Dallas County).

 

Forty Eight Hour Rainfall (through 700 am CDT on 09/01/2012)
Site Amount (Inches)
White Hall (Jefferson Co) 10.70
Providence (White Co) 8.88
Pine Bluff (Jefferson Co) 8.39
Steprock (White Co) 8.25
Augusta (Woodruff Co) 8.20
Fordyce (Dallas Co) 8.11
Carlisle (Lonoke Co) 7.09
Searcy (White Co) 6.39
Stuttgart (Arkansas Co) 6.11
Georgetown (White Co) 6.06
Star City (Lincoln Co) 5.82
Des Arc (Prairie Co) 5.26
Rohwer (Desha Co) 4.99
Cabot (Lonoke Co) 4.79
Kelso (Desha Co) 4.74
Felsenthal Lock and Dam (Union Co) 4.57

 

Some of the heaviest rain fell during the morning of the 31st. By that time, the system was in northwest sections of the state. The system headed into southwest Missouri during the afternoon and evening.
The WSR-88D (Doppler Weather Radar) showed rain swirling around the remnants of Hurricane Isaac in northwest Arkansas at 808 am CDT on 08/31/2012.
In the picture: The WSR-88D (Doppler Weather Radar) showed rain swirling around the remnants of Hurricane Isaac in northwest Arkansas at 808 am CDT on 08/31/2012.

 

Three hour precipitation since 700 am CDT on 08/31/2012.

Locally more than three inches of precipitation fell along a fairly narrow and nearly stationary rainband across the southern/eastern counties. These tropical rainbands are known for torrential downpours.

In the picture: Three hour precipitation since 700 am CDT on 08/31/2012.

 

The rainband extended through England (Lonoke County), Pine Bluff (Jefferson County) and Fordyce (Dallas County). Extensive flooding was reported in these communities and surrounding areas, with roads barricaded and numerous homes threatened by high water. Sandbagging of homes occurred in some cases. Several water rescues were performed to help stranded motorists. Flash Flood Emergencies were declared in these areas by the National Weather Service.

At Pine Bluff (Jefferson County), at least a couple of cars floated down Highway 63. Around England (Lonoke County), Highway 15 was closed for a time between Highways 70 and 165. Local schools were dismissed early due to hazardous road conditions.

Rainfall records were shattered at Pine Bluff (Jefferson County).  August 24-hour rainfall (7.88 inches on the 30th/31st), daily rainfall (4.61 inches on the 31st) and monthly rainfall (10.70 inches) records were established.

 

As far as isolated tornadoes, they are typically found to the east and northeast of the center of a tropical system in spiraling rainbands. There were some tornadoes on the 30th, but they were southeast of the state over central and southern Mississippi and southwest Alabama. Tornado Warnings were issued southeast Mississippi and southwest Alabama during the morning of 08/30/2012.
In the picture: Tornado Warnings were issued southeast Mississippi and southwest Alabama during the morning of 08/30/2012. The warnings were along rainbands spiraling around Isaac, which was centered in central Louisiana at 815 am CDT. Heavy to excessive rain was also prompting numerous Flash Flood Warnings.

 

More Information
 
There is more concerning Isaac on August 30th through September 1st. To check out the rest of the story, click here.

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