Today in Severe Weather History for August 3

On this date in 1970, Hurricane Celia struck the Texas coast, making landfall near Corpus Christi as a strong category 3 storm.  

The storm packed winds of up to 180 mph at Aransas Pass, where boats were thrown around like tinker toys in the bays and waterways.

The deadly storm killed 15 and caused over $450 million in damage (roughly equal to $2.6 billion today).  Nearly 9,000 single family homes were destroyed and over 60,000 damaged in the Corpus Christi/Aransas Pass areas.  

Damage was so widespread and severe, many insurance companies refused to write or even renew policies in this area following Celia.  This caused the state of Texas to establish the Texas Catastrophe Property Insurance Association (today referred to as the Texas Wind Pool).  

Due to the severity of the damage produced by Celia, the name was retired and never used again.  It was replaced by the name "Carmen" the following year - and funny enough, that name was also retired after first use in 1971.

Weather Resource: The Saffir-Simpson Scale of Hurricane Intensity

The Saffir-Simpson Scale was developed in 1971 by civil engineer Herbert Saffir and meteorologist Bob Simpson, who at the time was Director of the National Hurricane Center.  The purpose of the scale is to divide Hurricanes into classes based on the intensity of the sustained winds within the storm.

Saffir–Simpson Hurricane Scale
Category	Wind speed	Storm surge
	mph (km/h)	ft (m)
Five	≥156 (≥250)	>18 (>5.5)
Four	131–155 (210–249)	13–18 (4.0–5.5)
Three	111–130 (178–209)	9–12 (2.7–3.7)
Two	96–110 (154–177)	6–8 (1.8–2.4)
One	74–95 (119–153)	4–5 (1.2–1.5)
Additional classifications
Tropical storm	39–73 (63–117)	0–3 (0–0.9)
Tropical depression	0–38 (0–62)	0 (0)

By correlating the wind speed, one can also get a fairly good idea as to the amount of storm surge that is likely to be associated with the hurricane, as noted on the chart above.  (Chart was adopted from a related article on Wikipedia found here).




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Today in Severe Weather History for August 2

On this date in 1954, severe thunderstorms produced hail up to golfball size for nearly 30 minutes straight in northcentral Kansas and southcentral Nebraska.  One hail drift in northcentral Kansas measured 200 feet long, 70 feet wide and over 3 feet deep!

"Invest 91" Becoming More than An "Invest"

***7/30/11:  Please note, this post concerns Invest 91 from last year - 2010.  If you're looking for this year's (2011)  Invest 91, which is about to become "Emily", please go to this post instead.

------------------------------------Original post follows:

The above is a recent visible satellite image showing a couple of interesting features off the coast of Africa.  First and foremost, in the red circled area, is "Tropical Invest 91".  "Invest" is a term that the National Hurricane Center (NHC) uses to describe an area of interest (or investigation) that has not yet become a Tropical Depression, Storm or Hurricane.

The convection (thunderstorm activity) has become more dominant and well defined around what appears to be a developing circulation center associated with the system this afternoon.  If Invest 91 isn't already a Tropical Depression, it will be very soon if this trend continues...

You can see more of the convective development I was talking about in the close-up visible image below:

Back to the first image at the top of the post, the white circled area notes more dust that is floating West off of Africa (note the milky-white coloration within the encircled area).  So far, Invest 91 is developing South of the most widespread dust cloud, which will enhance development as it has full access to the beaming tropical sunlight.

The midday computer forecast models didn't stray too far from the early morning versions (except for a gradual northward turn toward the end of the forecast period) as far as the potential track of this system is concerned:

The brighter red track on the above map shows what the GFS Model thinks will happen to the system.  It is obviously very early on in the developing stages of this system, but here is an even closer view of how the GFS model depicts this system, which would by then be Hurricane Colin, about 1 week from today (click image to enlarge):

As I said, it's very, very early in the game, but this gives you an idea of some of the tools that meteorologists have to work with.  Lets see how the situation unfolds over the coming week.  It will be interesting to look next Sunday at what the actual position of the storm is relative to the computer forecast model snapshot above.

Tropics Coming Alive Again?

A nearly stationary area of low pressure in the Tropical Atlantic (about 850 miles West/Southwest of the Cape Verde Islands) has slowly become better organized over the last 24 hours.  It is expected to drift toward the West at 5-10 mph over the next 24-48 hours, with some further development likely.

The system has been dubbed "Tropical Invest 91" by the National Hurricane Center, which is currently forecasting a "60 percent chance" that the system will become at least a Tropical Depression over the next 2 days.

Here is a view of what the latest computer forecast models pose as the potential track of this system over the coming week:

The development of 91L comes on the heels of what has been a relatively quiet week to 10 days in the tropics.  This can at least be partly attributed to continued above average dust storm activity in Africa.  As you can see in the recent high resolution satellite image below, dust swirls continue to move off the coast of Africa into the far east Tropical Atlantic.  This at least partially retards the potential for tropical development by blocking part of the much needed solar energy that these storms feed off of.

There have been signs that the dust clouds have begun to wane over the past few days, which may lead to an increase in tropical activity in the Atlantic as we move further into August.

In the meantime, interests in the Carribean and the Southeast U.S. should closely monitor the development and progression of 91L for the next week to 10 days.

Record Setting Hailstorm in South Dakota

It's official.  One of the hailstones captured by a farmer in Vivian, SD on July 23rd was the world's largest!

The "prize winning" hailstone measured 8.0 inches in diameter and 18.625 inches in circumference.  It weighed in at nearly 2 pounds (1.9375 lbs. to be exact).

It is estimated that the updraft (upward wind motion) within the thunderstorm that produced the hail was traveling at speeds of 160-180 mph.  With that in mind, and considering the fact that the hailstone weighed nearly 2 pounds, it likely fell to earth at a speed of nearly 150 mph!

Below is a picture of the divot left in the ground by the record producing stone:

Needless to say, damage around the Vivian area was extreme.  Take a look at the photos below:

Yes, you're seeing the last photo correctly...it was taken on the inside of a home near Vivian, where a hailstone crashed right through the roof and ceiling, landing in the living room!

Below is a 4-panel image of the Aberdeen, SD NEXRAD radar as the storm approached Vivian.  From upper left to lower right, the images show reflectivity (precipitation echoes such as rain and, of course, hail) at elevations of 0.5 degrees (approximately 16,000 feet above ground level), 0.9 degrees (21,000 ft. AGL), 1.3 degrees (27,500 ft. AGL) and 1.8 degrees (33,000 ft. AGL):

Storm chaser Chad Cowan captured some amazing photos of the structure of this storm.  Go to his website here to take a look.

The previous record-holding hailstone by diameter was captured near Aurora, NE on June 22, 2003 at 7 inches in diameter.  The previous record holding stone by weight was captured in Coffeyville, KS on September 3, 1970, weighing in at 1.67 pounds.

It should be noted that considerable melting took place on the Vivian stone before NWS employees were able to measure and weigh it.  That means the actual record setting values were probably quite a bit higher!

Today in Severe Weather History for August 1

Hurricane Chantal made landfall near High Island, TX on this date in 1989.  The storm was responsible for the deaths of 13 people, mainly due to flash flooding.  Chantal produced 82 mph wind gusts at Galveston Island, and dumped 7 to 12 inches of rain across central and eastern portions of Texas. Widespread heavy rain continued for several days as the system lifted North into Oklahoma.

Because the storm did not produce extensive damage, the name was not retired and was re-used again in 1995, 2001 and 2007.  It will be used next in the 2013 tropical season.