Atlantic Sat Image

Atlantic Sat Image
Clouds over Atlantic

Thursday, April 28, 2011

Why so much devastation?

As of this writing, 190 tornadoes have been reported since April 27th through the 28th. Most of the activity was focused across the Nation's mid-section and the Deep South. Sadly, almost 300 people were killed by these terrible twisters, most of them in Alabama.

So what happened?
Despite watches posted hours in advance and warnings up almost 30 minutes before the tornadoes ripped through neighborhoods, many people were caught unprepared, not because of anything they did wrong, but from the voracity and destructive power of the twisters.

An expert from the National Weather Service's severe weather lab out of Norman Oklahoma, Greg Carbin , said "These were the most intense super-cell thunderstorms that I think anybody who was out there forecasting has ever seen," He added, "If you experienced a direct hit from one of these, you'd have to be in a reinforced room, storm shelter or underground" to survive."

There is still much to learn
The huge thunderstorms that caused these tornadoes were just too wide, too powerful and too locked onto populated areas to avoid a horrifying body count.

As meteorologists, our knowledge of what makes tornadoes tick is still lacking. We have huge gaps in our understanding of their formation, development, and structure. For example we know that these monsters are born from super-cell thunderstorms , yet, not all super-cell storms cause tornadoes.

Historical Data
Once it's all said and done, this 2 day event may top the worst outbreak on record. Between April 3rd and 4th 1974, one hundred forty eight twisters were reported, once NWS reviews all the reports to make sure none are duplicates, we may end up with the worst month ever. We stand at 190.

So far this month over 450 reports of tornadoes have been received by the weather service. The most ever is May 2003 with 543.

But why?
Is Mother Nature telling us anything? I wish I could say there is some devious underlying plan, but there is none. This is a seasonal cycle that unfortunately had plenty of fuel to grow into the killer it became.

Most of the severe weather on earth is caused by a clash between hot and cold air.
If you take a look at a map of the USA, you will notice 2 North-South mountain chains, the Appalachians and the Rockies. These act as a roadway funneling cold air south. Once that cold air runs into warm moist air from the Gulf, they crash into each other spawning strong storms. This usually happens during Spring between Texas and Illinois. This is known as tornado alley. (( Interesting note: If we had a mountain chain running West to East from Washington State to New York, our tornado chances would be almost zero as all the cold air would be blocked from entering the country.))

Bottom line
This "hot vs cold" scenario developed with the addition of two very volatile ingredients.
1)Very strong jet stream in the upper levels of the atmosphere. This helped add even more instability and energy for super-cell storms to sprout.
2)High pressure parked over us injected even more heat and humidity into the Nation's mid section. This acted like jet-fuel instead of regular unleaded gasoline.

The result of this clash has been horrific and it helps to reinforce the notion of how violent Mother Earth can be. Sometimes it doesn't matter how many warnings are posted, or how prepared a community may be... sometimes you just can't stop this kind of disaster from happening.

As we are about to go into hurricane season, I sincerely hope you stay tuned for the latest advisories , and be as prepared as you can possibly be. DON'T TAKE MOTHER NATURE LIGHTLY.

Friday, April 22, 2011

Hurricane Conference 2011

The week-long hurricane conference held in Atlanta this year has come to an end. It was nice to run into some old friends and fellow meteorologists like Brian Norcross, now at the Weather Channel, Dr. Richard Knabb, formerly of NHC and now also with the Weather Channel, and former NBC6 and PLG 10 meteorologist John Gerard, now working in San Antonio. Hurricane guru Bill Gray was there as was former NHC director Max Mayfield. It was great to be surrounded by great minds and I made the best of it soaking up all the wisdom they offered.

Many things were discussed during the conference, from improving hurricane forecasting, to better communication of important information. Here is a summary of the conference:

Behind the scenes :
A clearer "Storm Status" identification will be issued for each advisory. In the past, even if a hurricane had downgraded to a tropical storm, the advisory would still say "Hurricane Name" and then in the following text it would say,"has been downgraded." Starting in May, all advisories will give the exact status of the system. Not a biggie, but very important when one is tracking multiple storms.

New this year, all The Tropical Cyclone Discussions will include both km/ and mph conversions. This is normally not a big issue until you've been on the air for 19 hours straight.

NHC is now offering a pronunciation guide for Storm Names. Remember Noel? Or was it No-el? Well NHC has eliminated the confusion by providing a list of the correct pronunciations. Here is this year's list.

2011
Arlene ar-LEEN
Bret bret
Cindy SIN-dee
Don dahn
Emily EH-mih-lee
Franklin FRANK-lin
Gert gert
Harvey HAR-vee
Irene eye-REEN
Jose ho-ZAY
Katia ka-TEE-ah
Lee lee
Maria muh-REE-uh
Nate nait
Ophelia o-FEEL-ya
Philippe fee-LEEP
Rina REE-nuh
Sean shawn
Tammy TAM-ee
Vince vinss
Whitney WHIT-nee

Important information:
Nothing causes more damage in hurricanes than the storm surge. In the past, storm surge height was tied into the Saffir Simpson wind scale but this had a huge inherited problem... no coastline is identical. A cat 3 storm surge will be different in Miami as compared to New Orleans. Over the past few years NHC has been working on how to present the risk of storm surge to your coastal community.

Storm Surge Exceedance products will become operational this year. The exceedance graphics show the storm surge height, in feet above normal tide level, which has a specific probability of being exceeded in the next 3 days. The available probability thresholds range from 10 to 90 percent, at 10 percent intervals.

The cone is shrinking!
Due to the great work the forecasters have accomplished over the years... the forecast swath will be smaller. Forecasters tell me that since 1990 track errors have decreased by 60%. With this impressive stat, they are now reducing the dreaded cone.

At 12 hours out there is no change from before, but at 24 hours, the cone will be reduced by 59 nm, at 36 hours by 79 nm, at 48 hours by 98 nm , at 72 hours by 144 nm, at 96 hours narrowed by 190 nm, at 120 hours down to 239 nm. Keep this in mind, even though this is an enormous leap forward there is still risk.

Experts tell me that no forecast is ever perfect. Even today, track errors may be as large as 40-50 miles per day and with huge gaps in data out in the Atlantic it is a bit more difficult to gain full understanding of any system. As a matter of fact forecasters expect storms to go out of their forecast path a third of the time.

The intensity of a storm is another matter all together. While progress has been made since 1990 on track forecasting, no progress has been made on how strong a storm will be. Experts tell me that 48 hours into a forecast the intensity of a hurricane could be off by as much as one category.


The problems forecasters face are 1) The evolution of large scale environments 2) Oceanic environment 3) Structure of cyclone's inner core 4) Physical processes within the storm - ie warming of the hurricane. Experts say they need to understand more the ocean's impact on the storm to better forecast it's intensity. They are working on this and will hopefully have more tools and better forecasts in the next few years.

2011 season forecast: The official outlook will be released in May from NHC. You can expect another above average season as has been typical over the last few years, what we will never know is where any one of them will make landfall.

Please stay tuned to WSVN, on air, on the web, or on your smart phone for the very latest. We will try our hardest to keep you up to the minute when any system threatens.

Monday, April 11, 2011

Will we ever get rain?

I have been receiving about 10-13 e-mails everyday regarding our dry conditions. They ask more or less the same things, why is it so dry? When will we see the rain return to South Florida.

Let's take the questions one at a time. Why is it so dry? We are in our dry season, which typically runs between November and May. No surprise here, but we aren't even receiving the small amounts we usually get. Miami is running about 9.5 inches below normal values, while Ft. Lauderdale is in the dry side almost 15 inches. (( NWS provided these numbers and they are from October 2010 through present. )) You can blame a host of things for this but primarily its been due to high pressure sitting over us for much of 2011.

High pressure is a huge mass of heavy dense air which tends to keep our atmosphere stable. Without any mixing, we don't get rain. So blame it on that.

Another factor contributing to the drought ,specially farther north ,is the low level of Lake Okeechobee. The depth right now is under 12 feet, what is average is around 14 feet. It is of concern, but the Lake is NOT our primary water source. We get our water from the Biscayne aquifer which sits directly below us. The Lake is low in part to Mother Nature and in part to it being drained by the Army Corp of Engineers. They have a list of reasons why, but that's for another post.

So now the last question...When will we see the rain return to South Florida? Typically the rainy season kicks off in the middle of May. The wind patterns change bringing in more heat and humidity leading to our run of the mill afternoon thunderstorms. This will help to bring our water levels back up. We will also get plenty of rain from the occasional tropical wave, and or, tropical system swinging though South Florida. Hopefully if we can get through the next 6-8 weeks, the rains should return.

Friday, April 8, 2011

Busy in the Weather Office

The next few months will be rather busy at the 7 Weather office as we approach the start of hurricane season 2011. We need to clean out our computers from all of last year's data, create new graphics for the upcoming season, and upgrade all the software.

So far, we have worked on a few folders and it feels like this is an insurmountable task, but WSVN has a great team of meteorologists who love what they do and always put in great effort to bring you the best hurricane coverage possible. So we'll be just fine.

One of the things we are working on, is adjusting the "Cone of concern" graphic. This will be the second year in a row that the National Hurricane Center narrows the dreaded swath. Every year the hurricane center improves on it's forecast accuracy and thus we adjust accordingly. It's not that difficult a process but time consuming, as we need to use some of last year's data to set the new parameters. (( Hope we haven't deleted it yet!!))

Other graphics we are preparing include, historical information, potential impacts to our area, storm names, storm surge threats and many more.

Already the team from CSU headed by Dr. Gray has released their projections for the season and NOAA will make public their forecast soon as well. No matter what the numbers say, just prepare as if we will get hit and you will survive whatever mother nature throws our way. These outlooks are just that, an outlook. We could end up with 17 storms in the Atlantic and if none make landfall we are all happy. Or it could be like Andrew... just one.... and it hit us.

Hurricane season runs from the first of June through the end of November and I encourage you to check here for my thoughts, worries, and concerns regarding storms in the tropics.

Hoping we don't see any again this year!