Monday, August 22, 2016

Solar Eclipse Weather Pre-Check

Meteorologist Jim Woodmencey
We are one-year away from the Solar Eclipse that will be visible across the United States on August 21st, 2017. I was watching the weather this past week to see where the best locations -- the most cloud-free spots-- would be, IF the eclipse had occurred this August. 

A few days ago, there were clouds in the path over parts of Idaho & Wyoming, most other locations to the east and west (in the western half of the United States) were relatively clear. The day before, some high thin clouds and contrails were present around noontime in western Wyoming.
 
However, on Sunday the 21st of August 2016, skies were generally cloud-free along that entire path of the eclipse, from Oregon to western Nebraska. Although, there was plenty of smoke and haze to be found in parts of Idaho, Wyoming  & Oregon from large forest fires that have been on-going this past month. 
 
If you zoom-in, you can actually see some of the smoke plumes on the visible satellite photo taken in the afternoon on Sunday, August 21, 2016.
 
For next August, it would be ideal to see a repeat of the sky conditions along the path, but without the fires to dim the show.
 
Visible Satellite Photo 21 August 2016

Locations of Large Forest Fires in Western U.S. August 2016
 
 
Posted August 22, 2016 by meteorologist Jim Woodmencey


 
 

Friday, August 5, 2016

Playing it Safe During Thunderstorms


Meteorologist Jim Woodmencey
(Note: the content of this post first appeared in the MountainWeather column in the Jackson Hole News & Guide on July 20, 2016).

Every summer I feel obliged to reiterate a few important points about lightning safety. Maybe this will be your first time hearing this message, or maybe an annual reminder isn’t such a bad thing.

In a previous post, I outlined what to watch for, as far as cumulus clouds developing into a potential thunderstorm. Vigilantly observing the sky throughout the day is the first step towards knowing when it is time to retreat from the mountains, get off the lake, or the local ball fields.

In this post, I will cover what to do when thunderstorms are imminent, and Mother Nature says it’s “game-on” for dangerous lightning.

Lightning Facts

Most people are not killed by a direct hit from a lightning bolt. Although, that certainly would do the job and be “game over”, right there. More commonly, people are injured or killed when lightning strikes nearby, causing an instantaneous surge of electrical current, and intense heat, known as a “side-flash”.

The most common cause of lightning casualties, however, comes from getting shocked by the high voltage current that runs through the ground. Ground current accounts for about 50-percent of all lightning casualties.

Look at it this way; a lightning bolt is like a hand-grenade going off. Standard Army-issue hand grenades have a kill-radius of about 25-feet, and a casualty-radius of about 50-feet. Therefore, getting to a safe, or safer location, where lightning is less likely to hit is your next line of defense.

 Seek Shelter Early

As soon as you can hear the thunder, lightning is close enough to strike, and it is time to seek shelter. Lightning bolts can be seen from about 15 miles away, and thunder can be heard up to about 10 miles away, on a good day. In a canyon, out in the wind, or at a noisy concert, thunder may not be heard until it is much closer.

You can estimate how far away the lightning is by counting the time between when you see the flash of lightning and when you hear the thunder. Count in seconds (one-thousand-one, one-thousand two, etc.). Five seconds equals one mile. If you count to 25, that means the lightning is 5 miles away, which is actually close enough to be able to reach out and touch you.

Don’t wait for it to start raining before you think about seeking shelter, or for the first bolt to hit nearby, as most people tend to do.

Inside a building or a car are the absolute safest places to be. Picnic shelters, a gazebo, a dugout at the ball field, are NOT good shelters from lightning.

If you are out on a hike, don’t run underneath the biggest, loneliest looking tree for shelter, as most people also tend to do, especially once it starts raining. A better option is to get into a group of trees of similar height. Also, make sure you are not standing on top of any tree roots.

If all else fails, get into a low spot in the terrain, that is not a watercourse, and crouch down. Like Army guys do when they dive into a bunker to avoid the grenade’s blast.

If you are in the mountains, do whatever you can, as fast as you can, to get off the higher ridgetops. Waiting it out in a gully or low spot between ridges is better than nothing, but avoid a gully that might become a running watercourse when the downpour starts. And separate yourself from all metal objects, ice axes, climbing hardware, etc.

Also, DO NOT get under an overhanging rock or in a cave. Electricity will often jump the gap that you are sitting or standing in when lightning strikes nearby.

If you are on a lake or river, get out of the water and off the boat. Water is a great conductor of electricity! Get to shore and find a stand of similar sized trees to wait it out.

The absolute best thing you can do to prevent injuries from lightning striking nearby is: KEEP YOUR FEET TOGETHER.

Standing with both feet together will help prevent dangerous ground currents from running up through one leg and exiting down the other. You may feel a bump under your feet as the ground current passes, if both feet are together, but it is unlikely that you would receive a serious electrical injury.

Secondarily, don’t huddle together in a group. Spread out, at least 25-feet feet apart, if not 50-feet apart, so everyone is not within the same kill/casualty radius. Cows and sheep tend to huddle together during thunderstorms, and often entire herds or flocks are killed because they are all linked together as one big conductor of electricity.

It is best to remain in a safe location for 20 to 30 minutes after the last of the lightning leaves the area; to make sure that the thunderstorm is a safe distance away. It is really hard to convince people to wait a little longer. We usually run right back out to play as soon as the rain stops.

Pay attention to the weather forecast each day, to see what the probability of thunderstorms might be. Be observant of the clouds as they develop during the day. And don’t wait until the lightning is flashing or the rain is pouring to turn around and head for a safer location.



Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for almost 25 years.

Watching the Sky for Thunderstorms



Meteorologist Jim Woodmencey
(Note: The content in this post first appeared in the MountainWeather column in the Jackson Hole News & Guide on July 6th, 2016).

 July begins the heart of the “Thunderstorm Season” in the Rockies. It is also the peak of the tourist season, climbing, backpacking, & baseball seasons, etc. etc. . That means more people will be outdoors enjoying the weather, and potentially getting caught in thunderstorms.

In this post I will describe how thunderstorms work, and what to watch for when you are outside during the day. Those telltale signs that dangerous thunderstorms may be developing. I will follow this post with a subsequent one on lightning safety.

Moist and Unstable Air

Most of us would probably describe a “typical summer day” as: Clear blue skies in the morning, followed by some puffy cumulus clouds in the afternoon, and maybe a chance of some afternoon thunderstorms.

How big or ominous those cumulus clouds become will depend on two things:
1) How much moisture is in the air. 2) How unstable the air is.

That clear blue sky that you see in the morning actually contains some moisture, in the form of invisible water vapor. As the day goes on, and the ground heats up, the air begins to rise. As the warmer air rises higher into the atmosphere it encounters colder temperatures, and the invisible water vapor condenses into visible water droplets.

If the air keeps rising, cooling, and condensing, then water droplets start to gather together, and clouds appear.

Relative humidity (RH) is one way to measure how moist the atmosphere is. For thunderstorm development, it can still be very dry in the lower levels of the atmosphere, with low RH. But at the same time, high RH may exist in the upper levels of the atmosphere, which is enough to perk up thunderstorms once there is enough instability.

How unstable the atmosphere is will depend on the difference in temperature between the ground and the upper levels, like up around 20 to 25,000-feet. The bigger the difference in temperature, the more unstable the air is, that is, it must be warmer down low and colder up high to be unstable. Think, “hot air rises”, that’s instability.

If the air isn’t rising, or if temperatures aren’t very cold aloft, or the atmosphere is staying bone dry up through 25,000-feet, then all we see is clear blue skies, all day.

Be Observant

There are a few things to keep an eye on to determine if those little white puffy clouds are going to develop into full-blown thunderstorms on any given day. Watch the sky for these signs of impending thunderstorms:

1) The first puffs of cumulus appear before noontime.
2) The individual cumulus clouds start gathering together and growing vertically.
3) The base of the cloud gets darker, indicating the clouds are growing taller.
4) Taller clouds, darker bases and more of the sky covered by those clouds, the greater the potential for heavy rainfall, hail, and/or strong gusty downdraft winds. And of course, lightning.

However, don’t be lulled into thinking that clouds and thunderstorms can only develop during the afternoon hours. There are many days that don’t fit this “typical” summertime thunderstorm scenario.

Thundertorm Enhancers

Storm systems, otherwise known as low-pressure systems, will periodically roll across the Rockies in the summer, and these will add additional moisture & instability to the atmosphere.

Often associated with a low-pressure system, is a “cold front”. Cold fronts produce more lift and give a boost to the instability. Some of the more potent and violent thunderstorms we see are directly related to the passage of a cold front.

The last thing to be aware of is, the “summer monsoon”. In brief, the Desert Southwest Monsoon is a seasonal wind flow pattern that brings very moist and unstable air up from central Mexico, across the Four-Corners Region, and sometimes that monsoon moisture gets circulated as far north as Northwest Wyoming.

Thunderstorms associated with the monsoon are some of the most random that we will see in the summer, and can occur any time of the day or night.

Whenever you experience a thunderstorm in the middle of the night or just after sunrise – when the afternoon heating is not really a factor– it is very likely that a storm system, a cold front, or the monsoon is triggering the thunderstorm activity.

Keeping an eye on thunderstorm development is of paramount importance to anyone who is spending the day outside. If the clouds develop into lightning-producing thunderstorms, then you are at risk of being injured or killed by a lightning strike; whether you are climbing the Grand, playing a around of golf, fishing the river, or out on the lake or ball field.


Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for almost 25 years.

Understanding Your Weather Prognosis


Meteorologist Jim Woodmencey

(Note: Content in this post first appeared in the MountainWeather column in the Jackson Hole News & Guide June 8, 2016)

Sometimes, the forecast can be confusing or misleading, especially when it comes to understanding the “probability of precipitation. In this week’s column I will explain what those percentages really mean, by way of analogy.

Weather Doctor

Being a meteorologist is a lot like being a doctor, except that my patient is the atmosphere. That patient shows up in my office everyday with a different set of symptoms and ailments. My task is to analyze what is wrong with my patient.

I begin my assessment by looking at satellite and radar images, along with a host of weather maps and observations to get some baseline information. Kind of like the nurse taking your vitals and patient history.

Next, I try and diagnose the problem (or problems) the atmosphere might be presenting to me. I look for the obvious signs and symptoms first. Some days they may be so obvious that the diagnosis is relatively simple. For instance, if it is already pouring rain and thunder-storming outside, then the forecast will be easy, “rain and thunderstorms today”.

That would be kind of like a real patient walking into the doctor’s office with an open fracture of the lower leg. The diagnosis is easy, “your leg is broken”.

Most days though, my patient’s condition requires further diagnosis and testing, as I’m sure it is with many doctor’s patients. Whenever the complaints and symptoms are quite subtle or perhaps very complicated, then an accurate diagnosis becomes more difficult. The same is true with the weather.

Initially, I might say, “I think it might rain today”. The doctor might say, “I think you might have a tumor”.

That’s when the doctor sends you for the blood tests, the x-rays, the MRI’s, the colonoscopies (ugh!), or whatever other tests are necessary to help make a better diagnosis of your problem and how to treat it. That is when I head to the computer models, to help guide me towards making a decision about what the weather is going to do.

Sometimes, the final prognosis, meteorologically or medically, is more of a guess. An educated guess, based on your training, experience and how often you have seen these same conditions.

Probability

The doctor might tell me that after surgery, that I might have a 50/50 chance of surviving.  Like the doctor’s prognosis, weather forecasts are also an expression of uncertainty. Probability of precipitation may be the most looked-at part of any weather forecast, but I imagine it is also the least understood.

Probability in a forecast is usually expressed in percent, 30-percent chance of showers, a 60-percent chance of thunderstorms, etc. etc. But what does that really mean?

Probability of precipitation is an expression of two factors: Confidence and Area.
How confident is the forecaster, or the computer model, that precipitation could actually occur, and over how much of the forecast area will it occur, if it does.

Case1: The forecaster is very confident, 100-percent, that measurable precipitation will occur, but it may not occur everywhere within the forecast area, such as Teton County, as an example. That might generate a 50% probability of precipitation (PoP).

Case 2: The forecaster’s confidence that measurable rain will occur is not that high, say 50-percent confidence, but if it does rain, it would rain over the entire forecast area. That would also generate a 50-percent PoP.

The problem is, you don’t know which case was used for the forecast. Which doesn’t really make this any less confusing or misleading, does it?

Given that, I would say that the best way to interpret these examples is to say: “There is a 50-percent chance that precipitation could occur at any point within the forecast area, during the forecast time period”.  

A “50-percent chance of rain” does not mean that it will rain over half of the time period, or over half the forecast area. Which is a common misinterpretation of PoP.

The table compares the percentages to the uncertain terms and the alternate descriptors used in most forecasts, to give you a reference to work from when making decisions about what that forecast really means.

Remember, the forecast is just guidance, like your doctors advice. In some cases, it may or may not rain, and you may or may not die.

Note: My apologies to any doctors reading this, I did not mean to imply that weather forecasting was as easy as brain surgery.

  
Probability of Precipitation
Probability
“Uncertain” Term
Alternate Description
10 to 20 %
Slight Chance
Isolated
30 % to 50 %
Chance
Scattered
60 % to 70 %
Likely or Possible
Widespread or Numerous
80 % to 100 %
No terms used, forecast just reads: “Rain”, “Snow”, “Thunderstorms”, etc.


Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for nearly 25 years.


Monday, September 14, 2015

The Early Winter Outlook



Meteorologist Jim Woodmencey
It seems like weather predictions for the coming winter are beginning earlier and earlier every year. They used to come out in early October, then it was September, now they are appearing in mid-August.

The early release of the Old Farmer’s Almanac hit the major media a couple weeks ago. You can buy it in stores beginning this week. Or, if you have to write a column about it, like me, you could buy the pre-release digital copy.

It seems odd to me to be previewing the winter, when I haven’t even had the chance to review the summer. After all, fall doesn’t officially begin for another three weeks. But, here we go!


Outlooks Galore

The various Farmer’s Almanacs are just one way to get a leg-up on what the winter might be like. The Climate Prediction Center, a division of NOAA and the National Weather Service is another source.

El Nino has dominated the weather limelight this summer, and certainly the current and predicted state of the El Nino weighs heavily in the long-range outlooks for this winter. You can get updated on what I wrote recently about El Nino by searching the archives on the JH News and Guide website, or on my mountainweather blog page.

The short story is, it looks like the current El Nino will continue through the winter and early spring. NOAA expects it to become stronger and peak in November or December.  Previous strong El Nino events have brought above average snowfall to the Sierras and the Southwest United States.


NOAA-CPC

I analyzed all of the long-range outlooks from the Climate Prediction Center (CPC) for the winter months, broken down into three overlapping three-month categories, namely: November-December-January, December-January-February, and January-February-March. I also compared what is known as their “Three-Class” version and their new experimental, and as yet “unofficial”, “Two-Class” version of these outlooks. I like the new 2-class version, because it is simpler and less ambiguous than the 3-class version.

Basically, the 2-class version establishes what is “normal”, or average, by using historic weather data from 1981-2010. They pick out the coldest and the driest 15 years, and the warmest and the wettest 15 years.  From there, forecasters then estimate which regions of the country they believe will be well above or below these averages and assign probabilities.

For instance, a 60-percent probability that it will be warmer than normal, means there is a 40-percent probability temperatures could be below normal. If they are unsure, then it is a coin-flip, 50/50 chances of being above or below, or what they call EC “Equal Chances”.

Suffice it to say; no matter how you slice it, all versions of the CPC outlooks are bleak for the Northern Rockies. The overall picture they are painting for our area is for warmer than normal temperatures and below normal precipitation from November through March. However, the probabilities of that happening are generally around 60-percent. Doesn’t that give us a 40-percent chance of it going the other way, colder and snowier? Think positive!

Farmer’s

When I opened up my digital version of the Old Farmer’s Almanac, the familiar yellow-jacketed almanac you’ll see in Stone Drug or in your favorite grocery store this week, I found that it doesn’t do us any favors either. Their big color map of the U.S. has all of Idaho, Utah, western Montana, western Wyoming and western Colorado categorized as, “Mild and Dry”.

This almanac’s forecast has the Cascades of Washington, Oregon, and northern California under, “Cold and Snowy”. Should I pack my bags for Mt Baker or Mt. Hood? Not so fast.

In the 2016 edition of the Farmer’s Almanac, the orange and green-jacketed almanac, they are calling for, “Very Snowy and Typical Winter Cold” for Montana, Wyoming, and Colorado. Bingo! Let’s run with that forecast, it sounds so much better than the doom and gloom of all the others.

Caveat Emptor

Buyer beware! These are long-range outlooks, which I would liken to reading a fairy tale. Good or bad, it does not necessarily mean the predictions will come true.

Computer models generate much of what goes into these forecasts. I work with computer models everyday, and I can tell you that there are plenty of days that the models can’t get it right, for just 24-hours into the future. Naturally, I am a little skeptical of any model that predicts weather conditions 3 to 6 months into the future.

Take a deep breath, don’t worry, be happy, it will get cold this winter and it will snow. Some winters are better than others, and I would never write this one off before the first snowflake has even had a chance to fall.


NOAA Climate Prediction Center Three-Month Outlooks
Three-Month Period
Temperature
Precipitation
NOV-DEC-JAN
55% above
55% below
DEC-JAN-FEB
60% above
65% below
JAN-FEB-MAR
50% above
60% below
Probabilities from the new Experimental “Unofficial” Two-class Climate Outlooks


Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for almost 25 years.

Monday, August 31, 2015

Hyper-El Nino may be Over-hyped

Meteorologist Jim Woodmencey


(Note: The article in this post was originally published in the Jackson Hole News and Guide on August 19, 2015).
The comments and questions are starting to come more often now, about the current El Nino and how it will affect our winter. I blame the bigger media outlets for creating this hype, by attaching monikers to their headlines like: “Super El Nino”, “Strongest El Nino Ever”, and my personal favorite, “The Great Godzilla of an El Nino”.

It makes me want to throw-up when I read these headlines, especially since nothing extraordinary is actually happening yet.

To help squelch some of the hype, by way of plain-old scientific explanation, in this week’s column I am going to tell you what El Nino is, what the current and forecasted state of the El Nino is, and what affects this El Nino might have on weather patterns this winter. In particular, what it might mean for snowfall in Jackson Hole.

El Nino Defined

El Nino is not a monster storm, nor is it a series of monster storms that guarantee copious amounts of snow. I will guarantee you though, that every single major weather event that happens between now and next spring will be blamed on El Nino.

El Nino is part of a larger phenomenon that has to do with the Sea Surface Temperature (SST) in the equatorial Pacific, collectively known as “ENSO”, or the El Nino Southern Oscillation.

ENSO comes in three different flavors: 1) El Nino, when SSTs are warmer than average. 2) La Nina, when SSTs are cooler than average. 3) Neutral (No-Nino), when SSTs are near average.

The strength of an ENSO event is measured by how much warmer or cooler those SST’s are getting, and how far across the Equatorial Pacific they are spreading. This in turn creates differences in pressure across the Equatorial Pacific. Sometimes, in the case of an El Nino, a complete reversal of the normal wind flow pattern may occur.

Ocean temperatures down near the equator are relatively warm to start with, but during an El Nino they may get 1 or 2 degrees warmer. This creates more thunderstorm activity over the ocean, and the effects of that extend up into the upper atmospheric circulation, as well.  And voila, we have a disruption of the “normal” atmospheric circulation, which translates to a change in the weather patterns both north and south of the Equator.

El Nino 2015

I don’t know if you remember back to May of 2014, but NOAA scientists then were predicting that a “Super El Nino” would develop for the fall and winter of 2014-15. That never materialized. El Nino conditions (warmer SSTs) never showed up until March of 2015, too late to disrupt winter weather patterns in the northern Pacific.

May-June-July 2015 average SSTs warmed up to 1-degree (Celsius) above the average in some portions of the ocean. Winds were not reversing yet, but they were slowing down, and more convection was noted; that is, more thunderstorms were showing up on the satellite photos.

All of that has led NOAA forecasters to predict: “This El Nino will peak in the late fall/Early winter with 3-month average SSTs near or exceeding 2-degrees C above normal. IF this forecast comes true, it will place the 2015 event among the strongest El Ninos in the historical record (1950-2015).”

The strongest El Nino winters on record were 1997-98, which peaked at 2.3 –degrees above normal, and 1982-83, which peaked at 2.1 degrees above normal, for their three month average SSTs in November-December-January.

What’s Expected?

If this does develop into an El Nino of those proportions, then what should we expect to happen? Usually during El Nino winters the jet stream, or storm track, tends to dip further south in the Northern Pacific, moving over California and the Southwestern United States, then cruising across the Southeastern U.S., keeping those locations wetter than normal in winter.

In both 1997-98 and 1982-83 the Sierra Nevada Mountains in California had huge winter snowfalls, both were attributed to the strong El Nino.

The Pacific Northwest and northern Rockies are a bit too far north of the storm track during strong El Nino’s to reap the same benefits. The opposite though is true during strong La Nina winters, when the storm track usually does favor the Pacific Northwest and Jackson Hole, and leaves California and the Southwest dry.

In Jackson, during the strongest El Nino Winter of 1997-98 we had average snowfall in town and just above average snowfall in the mountains. In the El Nino Winter of 1982-83, we had below average snowfall, both in town and in the mountains.

When I take into account all the El Nino years, weak & strong, it’s a 50/50 proposition for Jackson Hole. Half the El Ninos ended up with above normal snowfall around here, half had below normal snowfall.

Given all that info, I wouldn’t get too hyped-up about this “Giangundous El Nino 2015” just yet for Jackson Hole, it might make for a bigger snowfall winter here or it might not. Unless you live in Tahoe, then it’s going to be HUGE, for sure, dude!



Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Range for almost 25 years.

Tuesday, July 28, 2015

Snow in July in theTetons

Meteorologist Jim Woodmencey
An unusually cold Low pressure system for late July moved across the Northern Rockies on Monday, July 27th, 2015 , bringing with it  a dramatic drop in temperatures, and snow to the higher elevations of the Teton Range in western Wyoming, as well as some strong, gusty winds.

SNOW
Snow was observed at the top of Teton Pass Monday evening, at an elevation of just over 8400-ft. Snow was on the ground down to around the 9500-ft. elevation on Tuesday morning in the Tetons. It is not especially unusual in the higher Tetons to have snow in July, however, to see it on the mountains to such a low elevation this time of year it is. Last summer it snowed down to about the same elevations in late August. So, we are a month earlier this year!

WIND
There were some strong gusty winds with that front, hitting 70 mph at the Lower Saddle (11,610-ft.), 54 mph on top of the JH Tram (10, 318-ft.), and 49 mph over on Lava Mountain near Togwotee Pass (10, 430-ft.).
The Jackson Hole Airport experienced wind gusts of 30 to 40+ mph between noontime and  3:00 pm. They maxed out with a 43 mph gust.

TEMPS
Temperatures dropped over 20 degrees in the valley as the front passed in the afternoon, going from a highs in the mid to upper 60's around noontime to the mid to upper 40's by 3:00 pm.

The low temp at the JH Airport Tuesday got down to 30-degrees. In town it was mid 30's and not really threatening the record low of 31 degrees for July 28th, set back in 1940. The record low for July 29th is 27 degrees, and I have foretasted a low near 30 for Wednesday morning.

In the mountains temps went from a high near 70 degrees at 10,000-ft. on Sunday afternoon to highs in the upper 50's at noontime Monday, then the temperature plummeted to near 30 degrees by 3:00 pm Monday afternoon. A 40-degree drop in about 24-hours!

At one point Monday evening at the Lower Saddle of the Grand Teton, the temperature was 25 degrees and the wind was blowing steady at almost 40 mph, causing the windchill factor to make it feel like 7 degrees. Yes, seven!



Summary of Weather Events around Jackson Hole & the Teton Mountains for July 27th, 2015.

   


Post by Meteorologist Jim Woodmencey

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