Wednesday, September 30, 2009

Let The Change Begin, Restarting State Climate Series

I am blogging to the sound of wind whistling past my back door and watching a huge bank of clouds billow up over the Continental Divide.

Living on the southeast side of Denver with a full western exposure offers some wonderful views!

It's all part of a huge weather change sweeping across the region today. After topping out in the upper 80s on Tuesday, residents of Salt Lake City are waking up to foggy conditions with rain and temperatures holding in the lower to mid 40s.

A few severe storms are possible today across northeast Colorado, western Kansas and western Nebraska. Right now the thinking is that storms will be isolated, but the ones that do form could be potent.

Back in May I attempted to start a climate series where we'd talk about all the states in detail over a series of days in the blog.

Tennessee was first, followed by Washington, Missouri and Vermont. In late July I got so busy with work and summer that I just couldn't put the time into researching more states.

Well thanks to Ben Black, CoCoRaHS observer and volunteer recruiter for Hawaii, I am happy to announce the climate series is back and will start with information courtesy of Ben!

Hawaii Climate Intro

Hawai`i has joined the lower 48 states in contributing rainfall data to CoCoRaHS! They are actively building a network of volunteers across the settled islands of the 50th state.

Yes, Hawai`i is an island state, but it’s really also a mountain state. The great volcanic peaks that formed the island chain rise from the ocean floor over 20,000 feet just to break the surface of the water, then as much as another 13,796 feet to face off against the oncoming weather born here by the westerly flow of the trade winds.

The trade winds carry weather generally from offshore of Mexico and Baja to Hawai`i on their way toward Asia. This prevailing weather pattern is the delivery service for much of the precipitation that keeps this outpost in the Pacific green and inviting to residents and visitors.

Click here to read more about the global circulation of wind patterns and the trade winds.

Another source to learn more about trade winds.

Tuesday, September 29, 2009

Low Pressure Developing Over Western US

A large area of low pressure will form and intensify over the western US today and tonight. It will kick up the winds across a broad area, as seen in the US watch/warning/advisory map below -- with all the fire weather watches in place from Arizona to Montana.

As that low pressure begins to move east on Thursday, it will have the potential to kick up quite a fairly large severe weather outbreak in the middle of the country.

Meanwhile it is chilly around the Great Lakes as an area of low pressure pulls cold air south out of Canada.

Sunday, September 27, 2009

Active Days Ahead As Omega Block Sets Up

Well the first big taste of fall will sweep into the northern tier of the United States this week as a large area of low pressure moves out of Ontario, Canada and into the Great Lakes vicinity.

That low pressure will bring cool, unsettled and very windy weather to that region. In fact, waves on the open waters of Lake Superior could reach as high as 20-25 feet.

A second area of low pressure will move into the Pacific Northwest and bring fall weather to the inter-mountain region as well as some below normal temperatures.

In the middle, we will find a small ridge of high pressure.

There is a special type of weather pattern created when you have low, high, low as you look from west to east. It is visually represented below in a picture from the GFS forecast model that was ran on Sunday night at 6 pm.

The picture is a forecast of what the jet stream is predicted to look like at 500 millibars, or approximately 20,000 feet, on Tuesday night at 6 pm.

Look at the pattern of low pressure, high pressure, low pressure -- going from west to east...does it look like anything you might know...think Greek letters.

This type of pattern in the upper atmosphere is called an Omega Block because it looks like the greek letter Omega.

It is important for a meteorologist to notice this type of pattern in the upper atmosphere because it can create weather patterns that persist for several days.

Below is a picture from the same model run where I took the snapshot above...but this picture is for 180 hours out into the future -- which would be Sunday night at 6 pm. We are still looking at 500 mb, which is the jet stream level at approximately 20,000 feet.

It still shows an Omega Block -- only the ridge in the middle has flattened out just a bit. This could be a sign that the flow above wants to open up and the low pressures that have been sitting in place may move out.

So what does this mean exactly?

In the short term, areas under the troughs, or low pressure, will be cool and unsettled. The area under the high pressure, which is the ridge in the middle of the first picture, will be mostly on the quiet and mild side.

And if you are on the edges of the low pressure, it will be windy due to the pressure difference, or gradient, between the low pressures over the east and west and the high pressure in the middle.

So if this forecast verifies, it will be turning cooler, unsettled and windy for places like Salt Lake City, Denver, Chicago, Minneapolis, Detroit and New York this week.

While it should be fairly quiet and seasonal in places like Wichita, Kansas City, Dallas, Oklahoma City and Little Rock this week -- with the exception of Thursday when we will see the chance for a severe weather outbreak in the middle of the nation as the low pressure intensifies over the Rockies.

Stay tuned to the forecast over the next several days to see how this Omega block pattern plays out. Sometimes it resolves quickly and sometimes it can keep the flow in the upper atmosphere stagnant for several days.

Thursday, September 24, 2009

Jet Stream Turning Active?

Well taking a look at a few weather models, it looks like the jet stream, which has been parked over southern Canada for several days now, will start to dip south as we head into the month of October.

The first signs of this will come early next week as an area of low pressure develops over the Great Lakes.

It should bring some very windy conditions to the western Great Lakes by early next week.

Behind that low pressure will be an even bigger area of disturbed weather, or a trough, moving onshore in the Pacific Northwest by the 1st of October.

This should bring some cooler and unsettled weather into the Rockies for the first few days of October.

It looks like the southwest and western US will stay hot and dry under a ridge of high pressure. This isn't good for the fire conditions, especially across California.

Wednesday, September 23, 2009

CoCoRaHS On Facebook

If you are a member of Facebook, please join the CoCoRaHS group page. We have nearly 400 members.

On the page you can chat, start or respond to weather discussions, and even post your weather pictures!

It is also a chance for you to make new friends who just happen to also be fellow weather geeks like myself!

The snow storm in the Front Range of Colorado was a no go as the upper level, cut-off low pressure drifted off course.

It went just a little bit too far east and switched our winds to a northwesternly direction.

That is a downslope wind for most of Colorado's Front Range and thus dries out the atmosphere.

Oh well -- that is just how it goes sometime. Plenty of more opportunities for snow here.

Tuesday, September 22, 2009

Welcome To Fall; Kudos To Georgia Observers

Fall is here, and for a large chunck of real estate, we fell it.

Such as here in Denver where temps tumbled below 50 degrees along the Front Range of Colorado Sunday night have will stay there much of the week.

The higher elevation of southern metro Denver, including my house, are under a winter storm watch for 6-12 inches of snow possibly falling overnight tonight! Absolutely amazing!

Meanwhile out west, it is a different story with high fire danger and plenty of heat stretching from Seattle all the way to Los Angeles.

Heavy rain fell from Missouri to Texas on Monday along with some hail and high wind reports thanks to a squall line of severe thunderstorms.

Much needed rain is falling across central Texas today.

The flooding continues across 17 counties of Georgia. I saw an interview with the Georgia State Climatologist on television yesterday and he highlighted only CoCoRaHS precipitation reports during his interview.

One was in Douglas County -- checking in with over 11 inches of rain at the time, and the other was on the opposite side of metro Atlanta with 9.60 inches of rain.

That is excellent publicity and validation for what we do -- so congratulations to the Georgia observers who have been able to help document the footprint of this historic weather event.

I am sure it will be studies in great detail over the days and week to come.

On this date in 1989, Hurricane Hugo was over the Carolinas and losing strength. Meanwhile, strong northwesterly winds ushered unseasonably cold air into the north central U.S., just in time for the official start of autumn. Squalls produced light snow in northern Wisconsin. Winds in Wisconsin gusted to 52 mph at Rhinelander.

In 1988 in this date, an early morning thunderstorm produced baseball size hail at Plainview, in Hale County TX. Late in the evening more thunderstorms in the Southern High Plains Region produced wind gusts to 75 mph at Plainview TX and Crosby TX.

And in 1983, forty-one cities reported record cold temperatures during the morning. Houston, TX, hit 50 degrees, and Williston ND plunged to 19 degrees.

Monday, September 21, 2009

Fall Arrives Tomorrow, Wet & Cold For Some

Happy Monday!

Wow what a busy weather map can clearly see signs of the pending fall arrival this week by looking at the western US. A slew of frost, freeze and even a few winter weather advisories color the map.

As I type, it is 44 degrees in Denver with a chilly rain falling. Drive up the road less than 100 miles and it gets even colder with 37 degrees and light rain in Cheyenne, Wyoming!

I absolutely love this time of the year. And am going to patiently sit by the window tonight to see if a flake or two of snow tries to mix in with the rain as we see our first overnight lows in the mid to upper 30s since last spring in the Mile High City. might be thinking of building a boat if you live in the southeast, especially across the northern half of Georgia, Mississippi and Alabama.

Click here to read a summary out of the Atlanta area, where over 4 inches of rain has been recorded in just 2 days.

Click here to read flash flooding reports out of central Alabama.

These weren't the only states that saw a lot of rain, with the rain gauges across Oconee County, South Carolina also getting a workout. One CoCoRaHS observer there checked in with 8.92 inches of rain. Absolutely amazing!

This is that same area of disturbed weather that dropped so much rain over Texas, Arkansas and vicinity last week.

Rainfrog left a comment of the blog last week wondering about the shift in seasons we are seeing and how it relates to the normal. I know we've talked in recent blogs about early signs of the seasonal change in both animal behavior (esp. bears) and vegetation.

That is such a broad question and could be looked at from so many different angles I don't really know where to start looking in terms of data.

I think it really might be more of a question that is relative to local area -- and could be answered quickly by going to the climate data month-to-date on your local National Weather Service office's web site.

Now once the season change is complete, it will be easier to crunch data and compare the time period to past years for the entire nation.

It has been a while since we talked severe weather, but there is a chance for strong to severe storms today across eastern and central Oklahoma, southeast Kansas, southwest Missouri and western Arkansas.

Taking a look at the extended forecast through the rest of September, the jet stream is expected to stay over southern Canada during much of the period, which will keep the weather in the lower 48 fairly seasonal and quiet -- quiet meaning no huge, or major organized storm system. That doesn't mean total sunshine and tranquil weather however.

There will still be a few pockets of disturbed weather, such as the current scenario over the central Rockies and across the southeast states.

Toward the last few days of the month it looks like the jet stream will start to dip south, and could spawn some active weather as we head into October, especially across the Great Lakes and northeast states. That is a long way out and may completely change between now and then, however.

The tropics remain quiet, and our very blessed quiet season continues. We are just about past the peak of activity, historically speaking, so keep your fingers crossed for a continued quiet season.

Here is a little weather history for September 21.

  • A great hurricane smashed into Long Island and bisected New England causing a massive forest blowdown and widespread flooding. Click here to read more.

  • On this date in 1989, Hurricane Hugo made landfall along the South Carolina coast. Can you believe my mom let me stay home from school to watch the wall to wall television coverage? It was so amazing to me. Click here to read more.
  • Tuesday, September 15, 2009

    I'm Still Here, Checking In

    Hey blog readers!! I am so sorry it's been quiet of late. I am just so overwhelmed with my jobs and in currently in Baltimore, MD for a conference.

    Things will get better for me as we head into October, but I will try and get back to more frequent entries.

    So what is up with the water across Texas and now Arkansas -- eventually spreading into the Tennessee River Valley and Mid-Atlantic?

    It is a large cut-off low pressure. So what is that? It is simply an area of low-pressure in the atmosphere that is "cut-off" from the jet stream flow aloft.

    Right now the jet stream is across southern Canada and so the low pressure responsible for all the rain in the mid-south is just slowly spinning along, and will continue to do so until the weather pattern changes. (meaning the jet stream moves south and pushes the low pressure along, or some other weather feature comes along and moves it out, like a front)

    We are expecting that rain here in the Baltimore area starting Wednesday and lasting off and on into the weekend.

    Along with the large area of clouds and rain comes cool temps. Oddly enough, it was hotter in the Dakotas today than many southern cities.

    There is also an area of "cut-off" low pressure over the central Rockies. It has been bringing unsettled weather to much of Utah and western Colorado.

    Real quick before I close, I just saw a weather story about the cool and wet summer much of the nation has just experienced and how it has impacted pumpkins.

    Apparently the national pumpkin crop needs hot weather to flourish and since the year has been so cool and wet, we may have to pay more this year for pumpkins to decorate our yards!

    Saturday, September 12, 2009

    Fall-Like Weekend For Many

    Cool weather can be found in several places this weekend, including here in the Rockies.

    Denver's high is only forecast at 60 degrees today with showers. It will snow tonight above the timberline in the high country.

    An area of low pressure aloft is parked over central Texas and it will bring cool weather and rain to the southern plains today. Several flash flood watches are in effect from central Texas to central Kansas.

    There is a large area of disturbed weather over the Gulf of Mexico this weekend. Currently it is not expected to become tropical. But, it will have an influence on the weather along the coast over the next few days. Keep abreast of your local forecast for more info.

    Monday, September 7, 2009

    More Signs Of Autumn, El Nino Chit Chat

    Well I hope you all had a relaxing Labor Day holiday weekend. I planted some new ornamental grasses and a pine tree in my yard -- and went to the Colorado State Fair.

    Overall I didn't do enough work inside the house, but that is ok...I relaxed and had fun.

    I noticed some frost and freeze advisories in central Oregon today, and recently we had a few in the Great Lakes region.

    The days are growing shorter and it will not be long before we see more and more of these issued around the USA.

    As we head into the first full week of September, the active weather headlines include Tropical Storm Fred -- which will not even come close to posing a threat to the US coast. The storm will move north in the far eastern Atlantic.

    There is an area of disturbed weather off the outerbanks of North Carolina and the National Hurricane Center is watching it for signs of tropical development.

    At this time, anticipate unsettled weather along the coasts of North and South Carolina over the next 48 hours.

    Elsewhere things are fairly quiet around the lower 48 states with the exception of a cold front sweeping across the northern plains. This weather feature will keep unsettled skies in the forecast from the central Rockies to the Dakotas.

    Some lingering monsoonal moisture will keep a chance of showers in the forecast for portions of Arizona and New Mexico -- but given how disappointing this monsoonal season has been, I wouldn't get too excited.

    However, some nice rains did fall Monday night across west-central New Mexico with slow moving thunderstorms.

    It has been a fairly dry monsoon this season, which began July 1 and ends September 30. The National Weather Service office in Flagstaff wrote a nice report on just how dry it has been across their forecast area. Click here to read.

    And recently the topic of El Nino came up on the blog -- and like myself, I am sure you are wondering what the current outlook for the winter season looks like?

    Well El Nino is currently in progress, but is weak -- some might call us in a neutral phase right now, meaning neither El Nino or La Nina.

    Looking ahead, it really isn't clear if El Nino will crank up again or if we will stay in a neutral phase.

    So it is hard to say what the future holds.

    If we enter a definite "neutral" phase, I think you can expect a winter that will keep us on our toes. Equal chances for anything is what we can except.

    Perhaps a little exciting weather for everyone? That would be fun.

    Friday, September 4, 2009

    Labor Day Weather

    All in all the upcoming holiday weekend looks really nice for much of the lower 48 states.

    In past years we've dealt with everything from record heat and severe storms to hurricanes over Labor Day.

    This year it looks pretty quiet with the exception of unsettled weather in the Pacific Northwest as a large area of low pressure spins off the coast.

    Some monsoonal moisture will spark afternoon showers and thunderstorms over the southern and central Rockies.

    A few storms are also possible with daytime heating in the southeast and across the southern plains.

    I hope you all get a chance to get out and enjoy the "unofficial end" to summer! The technical end of summer is still a few weeks away.

    I will leave you with some really great pictures of hail fog courtesy of Storm Chaser Tony Laubach. Click here to read his blog and see some neat shots.

    Wednesday, September 2, 2009

    Fire Weather Meteorologists

    I ran across an article today that I thought you might find interesting about meteorologists who focus on fire weather.

    Click here to read more.

    All eyes are on Tropial Storm Erika as it moves west-northwest. Interests in the Bahamas and the southeast US should keep an eye on this system.

    Hurricane Jimena is losing some strength but the damage has been done in some communities of the Baja of California. Huge surf, high wind and heavy rains have toppled trees and powerlines.

    The storm will further weaken and significantly slow down, lingering well into the weekend over the desert southwest and northern Mexico as a remnant area of low pressure.

    The climate prediction center is predicting the chance for heavy rain over Arizona and New Mexico this Labor Day weekend -- so for all our desert observers -- have your gauge ready to go!

    And if you will be out of town, make sure it is empty before you leave and then be ready to report a multi-day accumulation when you return!

    Tuesday, September 1, 2009

    Autumn Signs Are Here

    Over the weekend I had some friends from Arizona in town and took them on a mountain venture.

    About 35 miles west of Denver is the highest paved auto road in North America, the road to Mount Evans.

    On the way up we saw several patches of fall color, which is a few weeks too early.

    We also stopped at the visitors center at the base of Mount Evans and they told us a bear tried breaking into the store the night before.

    At the top of the mountain we were in several snow squalls, which isn't too unusual for August at 14.260 is just a sign of things to come.

    Hurricane Jimena is a monster and will do a lot of serious damage to the Baja California over the next 24 hours.

    Some of that moisture will travel into the southern US and maybe as far north as Colorado.

    It is hazy here in Colorado today due to the huge fires in southern California.

    And we may have the next tropical system on our hands in the Atlantic basin before too long as disturbed weather continues to organize near the Leeward Islands of the Caribbean.