Close lightning strike up in West Virginia. fb.me/1FDDVzQKh
Taking a quick look at what might and might not happen with Emily. The system is still trying to get it’s act together and there’s a chance it may never survive it’s crossing of Hispaniola. Still lots of time to watch this storm but here’s what is going on with it right now. If you have plans at the coast this weekend stay tuned.
July is in the books and it ended up being 1.5° above average. Which followed June being 1.9° above average. The summer so far has been the 6th warmest on record in Charlotte. Notice in both cases last July and the summer in 2010 was warmer than this summer.
Got into some heated debates(no pun intended) on Facebook last week about why we talk about the heat so much. By “we” most people mean the TV meteorologist and for that matter the news media as a whole. Even though there is a distinct difference in my opinion. While it certainly is true as broadcasters we have been known to not put things in proper perspective when it comes to the weather coverage. In this case though I think we are just doing what is necessary. Some thought that we were overplaying the heat wave so far this summer, basically hey, “it’s just summer in the Carolinas..blah..blah..blah.” While I agree to some extent, the fatality statistics tell me we should be taking it very serious. Especially when the temperature or heat index get above 98.6°, which is our body temperature. Remember once it gets that hot you need help cooling down, more water, fans or A/C..etc.
The hottest our average high ever gets in Charlotte is 91° over the summer. So if we are 5-10° above that it’s a big deal. Why? Well the hottest we have ever been is 104°(twice in 2007), so that’s only a 13° spread from the “normal” hottest days of summer and the most extreme case in 132 years of records.
In contrast take Winter the lowest our average low ever gets is 32° but our all time low is -5°. That’s a 37° difference from our “normal” coldest winter time temps and our most extreme temperature.
So you can see being 5-10° colder than normal in the winter isn’t as extreme as being 5-10° warmer than normal in the summer.
Then there is this. The past heat wave which was mainly last week and last weekend has already killed 33 people. Take a look at the average annual weather related deaths and notice which causes more deaths.
If you take out Katrina with over 1000 deaths from 2005 Heat still is far and away the #1 weather related cause of death in the U.S.
Seems like we are watching the 90° count again this year after the 87 days of 90° or better last year. Which by the way was the second most on record. We are lucky to have such a long and well established weather record book here in Charlotte. These records go back to 1878 when the observations were taken in Downtown Charlotte. The airport was build in 1935 and in 1939 the weather observations were moved out there.
So far this year as of this blog post we have hit 90° or better 45 times and today we should barely make it 46. I’m forecasting around 92°. Last year we hit it 87 times and even if we hit 90° or better every single day until the end of August that only gives us 83. So we will be high on the list but not as bad as last yea or 1954 when we hit it 88 times. WE HOPE!
The heat has been big news for the past few weeks as much of the country has baked under a large ridge of high pressure. While the temperatures and those records have been impressive.
I have been impressive at the Heat Index or how it feels to you and I and how that has been abnormally high. Remember I blogged about the Heat Index before and what it actually means. In this post I thought I’d look at the climatology of the Heat Index at locations that have been keeping such records since 1972. The following are all graphs of the number of hours the Heat Index value was above 100° or more at selected large cities in the Carolinas. This does include this year up through Sunday 7/24/11.
Asheville, NC (Proving once again the mountains are awesome, )
With another impeding heat wave bearing down on the Carolinas. I thought I’d help explain what the Heat Index really is. In it’s purely mathematical form the calculation is as follows.
Heat Index = 16.923 + ((1.85212 x 10-1) x T)
+ (5.37941 x RH)
- ((1.00254 x 10-1) x T x RH)
+ ((9.41695 x 10-3) x T2)
+ ((7.28898 x 10-3) x RH2)
+ ((3.45372 x 10-4) x T2 x RH)
- ((8.14971 x 10-4) x T x RH2)
+ ((1.02102 x 10-5) x T2 x RH2)
- ((3.8646 x 10-5) x T3)
+ ((2.91583 x 10-5) x RH3)
+ ((1.42721 x 10-6) x T3 x RH)
+ ((1.97483 x 10-7) x T x RH3)
- ((2.18429 x 10-8) x T3 x RH2)
+ ((8.43296 x 10-10) x T2 x RH3)
- ((4.81975 x 10-11) x T3 x RH3)
where T is the dry bulb temperature (°F) and RH is relative humidity (%)
Looks crazy doesn’t it? Well it is when you think about it the Heat Index is really a measure of how the human body reacts to the combination of heat and humidity. More to the point how efficiently or in this case inefficiently it cools itself. So to calculate that you need lots of data besides the temperature and relative humidity. You need to know things like the surface area of an average human, rate of heat loss through skin, evaporative cooling, sweating…etc. So you can see lots of biology is in this as well as meteorology. This calculation is about how your body cools itself and the more humidity the less evaporation of sweat from your skin. This inefficiency makes you feel hotter, thus the Heat Index.
Here’s an easier way to understand it by just using this simple chart.
So lets look at some of the climatology of the Heat Index in Charlotte. Last week South Carolina set a state record for the highest Heat Index in the 20 years of record keeping at 124°. This was in Mount Pleasant, SC.
For Charlotte our worst year of Heat Indices was last summer which actually wasn’t our hottest ever for air temperatures. We’ve never gone above 114°. 2010 was more about the high heat Index values though it was plenty hot out there.
Notice last year we heat a Heat Index of 100°-104° or more for 130 hours.
We hit 105°-109° for 18 hours
We had 1 hour of a Heat Index of 110°-114°
We are way behind last years pace but we still have half the summer to go. Here’s a look at every year since these types of records have been kept. (Via The NC state Climate Office)
Heat Index Climatology: Output
After a large Derecho passed over the south end of Lake Michigan a Lake Shore Flood Warning was issued for a seiche. Here’s a look at what this phenomenon is and a look back at a famous one that occurred on Lake Michigan in 1954.
LAKESHORE HAZARD MESSAGE NATIONAL WEATHER SERVICE CHICAGO IL 931 AM CDT MON JUL 11 2011 ...SEICHE WARNING FOR THE ILLINOIS SHORE OF LAKE MICHIGAN UNTIL 100 PM CDT... .A STRONG LINE OF STORMS MOVING ACROSS THE LAKE THIS MORNING LIKELY WILL CAUSE WATER TO PILE UP ALONG THE MICHIGAN AND INDIANA SHORES AND BE REFLECTED BACK TOWARD THE ILLINOIS SHORELINE. THIS PHENOMENA IS KNOWN AS A SEICHE. ILZ006-014-111800- /O.NEW.KLOT.LS.W.0002.110711T1431Z-110711T1800Z/ LAKE IL-COOK- 931 AM CDT MON JUL 11 2011 ...LAKESHORE FLOOD WARNING IN EFFECT UNTIL 1 PM CDT THIS AFTERNOON... THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A LAKESHORE FLOOD WARNING...WHICH IS IN EFFECT UNTIL 1 PM CDT THIS AFTERNOON...IN ANTICIPATION OF A POSSIBLE SEICHE. * LAKE SHORE FLOODING...ALONG THE ILLINOIS SHORELINE OF LAKE MICHIGAN. * TIMING...THROUGH THE MORNING INTO THE EARLY AFTERNOON. * IMPACTS...WATER LEVELS ARE EXPECTED TO RISE AND FALL...PERHAPS BY 2 OR MORE FEET...DURING THE PERIOD OF THE WARNING. PRECAUTIONARY/PREPAREDNESS ACTIONS... RESIDENTS ON OR NEAR THE SHORE IN THE WARNED AREA SHOULD BE ALERT FOR RISING WATER...AND TAKE APPROPRIATE ACTION TO PROTECT LIFE AND PROPERTY...ESPECIALLY ALONG THE BEACHES AND IN THE HARBORS. DO NOT VENTURE INTO THE LAKE AS THE WATER RECEDES
Wondering what they are here’s the description of a powerful 1954 seiche on Lake Michigan from The University of Illinois.
Seiches: Sudden, Large Waves a Lake Michigan Danger
While a tsunami will never strike Illinois, the Lake Michigan coast, including Chicago, is subject to the danger presented by a seiche, a sudden, large type of wave that can cause loss of life and property damage.
Unlike a tsunami, which is caused by submarine earthquakes shifting the ocean floor, coastal landslides, or a meteor striking the ocean, a seiche (pronounced saysh) is caused by air pressure and wind. When storm fronts move rapidly from across a large body of water such as Lake Michigan, air pressure changes and strong downbursts of wind can form one large wave or a series of large waves. The wave or waves will travel across the lake until the seiche reaches shore, where it can be reflected and travel to the opposite shore. The height of the waves depends on the strength of the wind and air pressure contrasts that form the seiche. The largest seiche on record to strike the Illinois coast of Lake Michigan reached a maximum height of 10 feet, caused lakeshore damage, and drowned eight people. The illustration explains the 1954 seiche (view a larger image).
During spring and summer, small seiches with a height of a few inches to 1 foot regularly strike the Illinois shore of Lake Michigan. The National Oceanic and Atmospheric Association issues warnings to Lake Michigan mariners and lakeshore residents when weather conditions favor seiche development.
There was no warning for the record-high seiche that struck the Chicago lakeshore at 9:30 a.m. Saturday, June 26, 1954. The seiche approached from the southeast and struck the entire Illinois coast with a wave about 2–4 feet high. Swelling as it approached the North Avenue groin, also called the North Avenue pier, the wave reached a maximum height of 10 feet. Fishermen on the North Avenue pier and piers to the north at the entrance to Montrose Harbor were swept into the lake. Many were rescued, but eight drowned. The photograph at bottom right, taken in 2000, shows the groin at North Avenue beach (view a larger image). The arrow indicates the direction from which the seiche approached.
The seiche was caused by a severe squall line that crossed southern Lake Michigan a few hours earlier, passing from northwest to southeast. The storm generated wind speeds of up to 60 miles per hour and sent a seiche toward Michigan City, Indiana. A 5.5- to 6-foot wave reached shore there at 8:10 a.m. and was reflected back across southern Lake Michigan, heading northwest toward Chicago. Unlike a tsunami, which can travel across the open ocean at hundreds of miles per hour, a seiche moves much more slowly. It took 80 minutes for the seiche to travel 40 miles from Michigan City to the Chicago lakeshore at North Avenue. That translates into a speed of roughly 30 mph.
Every time we have strong to severe storms I get a handful of reports of funnel clouds or tornadoes. Most of the time this is due to misidentifying low clouds that look very ominous but are non-rotating clouds. This is especially easy to do with strong outflow from storms during really hot and humid days. When strong thunderstorms form on days when the temperatures are in the 90s and there’s lots of humidity. The updrafts take that warm & humid air high into the atmosphere where it cools rapidly. That cool air then becomes very dense and wants to rush back to the surface where it then interacts with the hot and humid surface air. This clash near the surface creates “arcus” or shelf clouds that look pretty awesome. These clouds can have all kinds of movement to them but it’s not often a horizontal rotation you’d see in a funnel cloud or wall cloud.
Here are some shelf clouds I saw last weekend at the Beach. Scary looking and they can lead to straight line wind damage from the outflow.
Roger Hill has put together the Non-Tornado Home page. Which has many examples of clouds that looks like tornadoes but aren’t. The best way to determine if a tornado or funnel cloud is present is to see video and radar data in combination. Check out the page…..there are some great examples in there click on the link below.