JUNE 22nd - 28th 2008

This week is lightning safety week and because I live in Florida, I thought I would talk a little bit about it.

For those that are new to Florida and for the those that do not live here, Florida is known as one of the top lightning capitals of the world.

The number one weather killer in the U.S. is floods, with lightning right behind it standing in the No. 2 spot. In Florida though, lightning is the No. 1 killer. Lightning kills more people each year, on average, than do tornadoes and hurricanes… combined.

REMEMBER - ALL thunderstorms produce lightning.

Before we go further though, let’s understand some basics.

We will start with what thunder is and then move on to the rest:

Thunder

From the bone-jarring clap to the distant rumbling roar, we have all heard thunder. But what is it? Simply put, thunder is the audio part of a bolt of lightning. When a bolt of lightning passes through air it rapidly heats and expands and it is this rapid expansion that creates a sonic wave or sonic boom. This is because this heated air expands faster than the speed of sound.

• If you hear a drawn-out rumbling, the lightning strike is further away. But if you hear a loud CRACK, then it is close by.

What is lightning?

If you have ever walked across a carpeted floor and touched someone or your pet and received a shock, then you had an electrostatic discharge that was caused by friction. Multiply that many, many, many times and you get lightning, which is a very large electrostatic discharge.

What causes lightning

This answer is a little more complicated, because it is not fully known yet. There are many theories, but no exacts. However, bits and pieces of the conditions are known. Let’s go back to the walking on carpet example. We know that friction caused our shock. Well, inside a thunderstorm cloud there is a lot of friction happening between a positively charged top and a negatively charged base.

This positive and negative comes about from strong updrafts and downdrafts, where the updrafts are carrying small water droplets from the lower areas to the upper areas, anywhere between 35,000 to 70,000 feet. And the downdrafts are carrying hail and ice from the upper frozen areas to below.

When particles from the within these drafts collide the water droplets freeze and as is freezes it releases its heat. This heat in turn slightly warms the surface of the hail and ice, keeping it warmer than the surrounding areas, allowing soft hail to form. As this soft hail collides with even more water droplets and ice, our storm cloud with a positive top and negative base forms because negative charged electrons are shaved off the rising particles and attach to the falling particles.

When the positive and negative areas grow larger within the cloud an electric field is created between the top and the base. (Note - negative and positive charges attract each other.) Now, we know that our atmosphere is a great insulator, and from that we can surmise that the electric charge between the positive top and negative base has to build up enough to overcome our natural atmospheric insulation. When this happens the discharge is seen as lightning.

To further complicate matters though, positive charges beneath the ground start to build and basically follow the storms. If this charge beneath the ground is stronger than the charge in the storm then instead of Cloud-to-Cloud or Intra-Cloud lightning, the negative charge comes down meeting with the positive charge that is rising up from below the ground. This is what we see as Cloud-to-Ground lightning.

• CC - Cloud-to-Cloud
• IC - Intra-Cloud
• CG - Cloud-to-Ground

Lightning is the first to arrive and the last to leave, so always follow the 30/30 rule.

30 seconds / 30 minutes

If the time between a thunder clap and lightning flash is 30-seconds or less, seek proper shelter immediately and remain there until at least 30-minutes after the final clap. (See definition of proper/substantial shelter below.) Lightning can strike more than 10 miles from the storm and has been known to strike over 50 miles if all conditions are right. Do not wait until the last minute to seek shelter. Most people are struck before and after a storm has peaked, and this is when most lightning deaths occur.

Think about it - the visible part of the sun that we can see is between 10,000° F - 11,000° F (depending on your source) a mere pittance compared to up to 50,000° F from a single lightning bolt. If it is hot enough to melt sand, turning it into a naturally formed glass, do you really want to test it out on you, or your loved ones?

Substantial shelter is defined as: A building or large enclosed area with a roof, walls, plumbing and electrical wiring. The reason for all of these things is because lightning will always take the path of least resistance. The plumbing and wiring act as a conductor or conduit, guiding the discharge.

Sheds, pavillions, tents, porches, are not considered safe.

If you have no safe shelter to get to, then an enclosed vehicle will work. Here is the catch though: it has to be a metal vehicle, meaning, metal roof and metal sides. The reasoning is the same as a building/shelter, the metal acts as a conductor. Those rubber tires are no match for lightning.

What this means is: plastic & fiberglass vehicles offer no protection. An open-cabbed tractor offers no protection. And neither does a convertible, even with the top up.

Just remember though, whether in a building, house, car, truck or bus - do not touch any of the metal or anything electrical, including the radio, CB, and more - because then you will become part of the channel through which lightning will seek a route through.

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Edited:

Yeah! Back to normal now, forecast and discussion has been updated. :) We are no longer under a SEE TEXT, but a SLGT risk now.

…FL…
SIMILAR SETUP ACROSS FL PENINSULA TO WED WITH STEEPER THAN USUAL LAPSE RATES ALONG WITH DRIER AIR IN MID LEVELS. AFTERNOON THUNDERSTORMS WILL INITIATE VICINITY E COAST SEA BREEZE BOUNDARY IN THE N AND OUTFLOW BOUNDARIES IN THE S WHERE THERE IS ONGOING ELEVATED CONVECTION. PRIMARY THREAT WILL BE MARGINALLY SEVERE HAIL
AND WET MICRO BURSTS.

---

Think we have a slight problem here…Here is the Day 1 Outlook Graph:

 

Here is the Forecast Discussion that went with it:

SPC AC 190601

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0101 AM CDT THU JUN 19 2008

VALID 191200Z - 201200Z

…THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL AND SRN PLAINS…

…SYNOPSIS…
A PERSISTENT AND SEASONABLY COLD UPR LOW OVER SERN CANADA WILL SHIFT SLOWLY NE TODAY…WHILE THE SUBTROPICAL RIDGE OVER MEXICO BUILDS N. IN BETWEEN THESE SYSTEMS…A MODESTLY FAST FLOW REGIME WILL EXIST… CARRYING NUMEROUS MID-LEVEL SHORTWAVE TROUGHS FROM THE E PAC BASIN/ WRN U.S. TO THE PLAINS.

…CENTRAL/SRN PLAINS…
WATER VAPOR IMAGERY INDICATED A SHORT WAVE TROUGH MOVING EWD AT THIS TIME ACROSS THE GREAT BASIN. THERE ARE EXPECTED TO BE ONGOING CLUSTERS OF TSTMS OVER MUCH OF NEB…WITH EXTENSIVE CLOUD DEBRIS LIKELY INHIBITING THE ONSET OF SURFACE HEATING ACROSS PARTS OF THE CENTRAL PLAINS THIS MORNING. THE TRAILING PORTION OF A SURFACE
TROUGH MOVING EWD THROUGH THE UPPER MS VALLEY TODAY SHOULD EXTEND WWD ALONG THE SD/NEB BORDER THIS AFTERNOON.

SURFACE HEATING WITHIN A MOIST AIR MASS /SURFACE DEWPOINTS IN THE 60S/ COMBINED WITH 7-7.5 C/KM MID LEVEL LAPSE RATES SHOULD RESULT IN MODERATE INSTABILITY ACROSS MUCH OF THE CENTRAL/SRN PLAINS BY PEAK HEATING.

ASCENT SPREADING EWD WITH THE GREAT BASIN SHORT WAVE TROUGH IS EXPECTED TO REACH THE CENTRAL PLAINS THIS AFTERNOON…AIDING WITH NEW TSTM DEVELOPMENT AND RE-INTENSIFICATION OF ANY MORNING TSTM ACTIVITY THAT REMAINS ACROSS THIS REGION INTO THE AFTERNOON. GIVEN UNCERTAINTY OF PLACEMENT OF ONGOING MORNING TSTM CLUSTERS/ATTENDANT CLOUDINESS AT 12Z…AND THEIR AFFECTS ON NEW TSTM DEVELOPMENT LATER TODAY…THIS OUTLOOK WILL NOT INCLUDE SEVERE PROBABILITIES GREATER THAN 15%. MODERATE INSTABILITY AND EFFECTIVE BULK SHEAR OF 35-50 KT FROM NEB SWD SUGGESTS THAT SUPERCELLS WILL BE POSSIBLE WITH HAIL AND DAMAGING WINDS. VERY LARGE HAIL MAY OCCUR FROM WRN NEB SWD TO THE OK/TX PANHANDLES WHERE THE COMBINATION OF STRONGEST DEEP LAYER SHEAR/INSTABILITY SHOULD COINCIDE. MODELS SUGGEST LOW LEVEL SHEAR MAY BE SUPPORTIVE FOR A FEW TORNADOES FROM SRN NEB SWD THROUGH WRN
KS/ERN CO TO THE TX PANHANDLE/FAR WRN OK.

GREATER CONFIDENCE EXISTS WITH THE DEVELOPMENT OF ONE OR MORE MCSS THIS EVENING THROUGH TONIGHT AS A SLY LLJ STRENGTHENS OVER THE SRN PLAINS AND KS ACTIVITY EVOLVES/GROWS UPSCALE WITH AN MCS MOVING SSEWD ACROSS TX PANHANDLE/MUCH OF OK INTO N TX BY 12Z FRIDAY. A SECOND MCS MAY TRACK ESEWD ACROSS ERN KS INTO WRN MO.

FARTHER S…A MID LEVEL IMPULSE…EMANATING FROM NRN MEXICO…IS EXPECTED TO MOVE EWD TODAY REACHING SERN NM/SW TX THIS AFTERNOON. ASCENT WITH THIS FEATURE SHOULD SUPPORT TSTM DEVELOPMENT ACROSS THIS REGION. MODERATE INSTABILITY AND SUFFICIENT EFFECTIVE SHEAR WILL SUPPORT ORGANIZED STORMS PRODUCING MAINLY HAIL AND DAMAGING WINDS.

…NRN HIGH PLAINS /WY-MT/…
AS THE UPR LVL RIDGE BEGINS TO BUILD NWD ON THURSDAY…TSTM POTENTIAL WILL LIKELY DECREASE…BUT NOT BE ENTIRELY OUT OF THE FORECAST. A WEAK FRONT IS EXPECTED TO HANG UP ALONG THE HIGHER TERRAIN. ALTHOUGH COMPARATIVELY DRIER THAN PREVIOUS DAYS…A NARROW TONGUE OF MID 40S TO NEAR 50 DEG F SURFACE DEWPOINTS SHOULD RESIDE INVOF THE FRONT. DIURNAL UPSLOPE WINDS AND DIFFERENTIAL HEATING WILL BE THE IMPETUS FOR ISOLATED HIGH BASED TSTMS THIS AFTERNOON/EVENING OVER SRN MT/ERN WY. STRONGER VERTICAL SHEAR IS PROGGED TO BE OVER WY WHERE SUPERCELL STRUCTURES WITH LARGE HAIL MAY OCCUR. OTHERWISE…FARTHER N…ACTIVITY WILL PROBABLY BE LESS ORGANIZED WITH ISOLATED HAIL/GUSTY WINDS.

…DAKOTAS TO UPPER MS VALLEY…
MODELS SUGGEST THE POTENTIAL FOR TSTMS TO DEVELOP ALONG A SURFACE TROUGH MOVING EWD ACROSS ERN SD AND THE UPPER MS VALLEY. WEAK FORCING ALOFT MAY TEND TO LIMIT THE OVERALL DEVELOPMENT OF STRONGER TSTMS. HOWEVER…30-35 KT OF DEEP LAYER SHEAR AND MLCAPE UP TO 1000 J/KG SUGGESTS THAT A FEW STORMS WILL BE SEVERE WITH ISOLATED
HAIL/STRONG WIND GUSTS THE PRIMARY THREATS.

…ERN MA TO NRN NEW ENGLAND…
A MID LEVEL IMPULSE MOVING NEWD ACROSS NRN NEW ENGLAND TODAY WITH COLD MID LEVEL TEMPERATURES /-20 TO -22C/ AND SURFACE HEATING WILL RESULT IN STEEP LAPSE RATES. TSTMS ARE EXPECTED TO DEVELOP BY LATE MORNING/EARLY AFTERNOON AS THIS TROUGH MOVES ACROSS THE REGION…WITH ISOLATED HAIL BEING THE PRIMARY THREAT.

..PETERS/HURLBUT.. 06/19/2008

CLICK TO GET WUUS01 PTSDY1 PRODUCT

NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z

CURRENT UTC TIME: 0920Z (5:20AM), RELOAD THIS PAGE TO UPDATE THE TIME. If you notice in the graph, Florida has a SEE TEXT box, but you won’t find the corresponding text in the discussion.

I think this is an oops. ;-)

2 Comments

Just thought I would share this great (to me!) resource that I found and have been thrilled with.

It is the NWS Jetstream Online School for Weather.

Just a few of the things that I like about it are:

• I can learn on my time schedule, even in the middle of the night!
• I can print out certain parts or all the lessons, whichever way I need to at that time.
• I can stay in one section for as long as I need to, to understand something. No rushing!
• There is a quiz for each section. I take it twice, once, before I start learning about the section to see what I know and what I don’t know, and then again, after. You really get to see how much you’ve progressed!
• I can learn at my own pace. Hmmm, think I mentioned that already. ;)

- Click on image for larger version of matrix -

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