Thursday, September 27, 2007

Tropics Remain Active

Tropical Depression 13 rapidly grew into Hurricane Lorenzo over the past 36 hours.

The storm is impacting the western Gulf of Mexico south of Texas.

Meanwhile, Tropical Storm Karen will struggle into the central Atlantic over the next few days. If it survives the wind shear it is moving through, some long-range forecast models show it entering an environment favorable to become a hurricane.

The hurricane season goes through November 30.

Favorite Comment from 9/27 -- Comes from Station MT-VL-5 near Nashua, Montana. They say, "I read my rain gauge at 7 am when I leave for work, but I don't get a chance to report until later (like now).

AWESOME! I too read my gauge in the mornings and sometimes can't find time to report until later that day or even the next. Delayed data entry is just fine -- we appreciate data at anytime.

That is the beauty of CoCoRaHS -- you are building a climate record for your station. Accurate data is more important than punctual data.

However, if you do have a decent rain or snow event, try and file your report as soon as possible because it is very exciting to log in and check the maps to see what happened in your area.

Even A Litle Rain Is Valuable

To see just how important every hundredth of rainfall is, let's quantify it in terms of gallons.

1 inch of rain falling uniformly over 1 acre of land is approximately 27,154 gallons of water.

Here is one more calculation -- there are 640 acres in 1 square mile.

So take Denver for example. There are 153.4 square miles in the city. Multiply that by 640 acres per square mile and you will see that Denver has 98,176 acres.

SO if the city were to receive 1 inch of rain over the entire real estate -- we would multiply 98,176 acres * 27,154 gallons per acre to see that 2,665,871,104 gallons of water fell from the sky. That is over 2 BILLON GALLONS!!

Now there are many other factors obviously to consider. For us here in a dry climate, there is evaporation. For any urban area there is runoff. So not all those gallons necessarily make it into the ground water and surface water, but as you can see, precipitation is the lifeblood of our lives!!

So now you see that even a few hundredths falling over an entire city is extremely important. So the next time you check your raingauge and see just a measily 0.01 or 0.04 -- don't be too let down, go back inside and convert that to gallons.

Then look at your local maps and see the coverage of the rain.

When you think of rain (or melted snow) in terms of gallons, you not only see how important you are as a volunteer weather observer helping us to see what is happening out there in between all the official weather observing points, but you also quickly see that every single drop counts -- LITERALLY!

To convert snowfall -- the standard equivalent is 1 inch of rain to 10 inches of snow -- so for 1 inch of new snowfall, you would run the calculation as stated above and then divide it by 10.

However, that snow to water ratio isn't true for everyone. Here in the Rockies in the dead of winter, we can see snow-water ratios approach 30 inches of snow to 1 inch of water -- thanks to that dry Rocky Mountain powder.

I will be traveling until Monday night so blogging will be tough for me to do -- but if I get a chance, I will.

Have a great weekend everyone!

Wednesday, September 26, 2007

Tale of Two Seasons

The western half of the country is really getting a taste of autumn. We awoke to frost here in the Denver area on Wednesday morning.

Meanwhile, the Great Lakes have been seeing strong to severe thunderstorms and feeling a bit more like late summer.

On Tuesday, severe storms moved through the Chicago area -- producing damage and power outages in Elgin.

Todays favorite comment off the CoCoRaHS comment report comes from the state of Illinois -- observer IL-CK-79. It simply says -- "we needed that!" The observer picked up a nice 0.51 inches of rain from the thunderstorms that moved through the Chicago area.

WOW -- talk about wet in the middle states on Tuesday. 77 CoCoRaHS observers from Oklahoma to Wisconsin picked up 1 inch of rain or more.

4 observers saw more than 2 inches of rain. Three in Missouri and 1 in Oklahoma.

We'd all like to have a day with 1 inch or more of rain so we can measure the precipitation that flows into the overflow can. That is always fun!

But even small amounts of rain, like 0.07 inches or 0.14 inches are extremely valuable. Heck, even 0.01 or 0.02 is helpful. Why?

Look for the answer in tomorrow's blog entry.

Tuesday, September 25, 2007

Wacky Fall Weather

If you were in Fort Wayne, Indiana on Monday -- you experienced a record high. In fact, the temperature shot up a full 34 degrees in just 6 hours.

The city climbed from a morning low of 56 degrees at 7:46 am to 90 degrees by 1:25 pm.

The top temperature was 92 degrees set at 3:34 pm.

South Bend also set a new record high of 91 degrees. The previous record readings in both cities were in the upper 80s and had stood since 1941.

Indianapolis also set a new record high on Monday of 92 degrees. It was only the 4th time on record that a temperature hit 92 degrees or higher this late in the season. Temperature records date back to 1871.

In Nebraska on Monday there were a few tornado touchdowns in the south-central part of the state. Hail fell and damaging winds blew from Nebraksa to Minnesota.

Today the severe weather threat will shift into the Great Lakes states.

Meanwhile here in Colorado, as I sit and write this blog from SE Denver, it is 43 degrees with drizzle at 1:09 am.

Ahhh, it must be fall!

Be sure to look at some maps and the comment reports before leaving the CoCoRaHS site today. There should be some interesting observations.

To see comments, click on View Data in the top menu and then Daily Comment Reports. To see all states, choose "select state" in the menu and then click "search".

Here in Colorado, we should see several reports of snow or a mix at least from the mountain observers.

Monday, September 24, 2007

Varied Precipitation Reports

Some residents along the Front Range of Colorado awoke to small hail and heavy rain Monday morning. Where I live in the SE Denver metro area, it was overcast with peaks of sunshine while others were getting rain.

That is the beauty of CoCoRaHS.

In the Denver metro area, there are only 4 official automated points of weather data. But CoCoRaHS allows us to see precipitation details in between those 4 stations. A morning thundershower or thunderstorm is quite special in a dry climate like Colorado because usually we need daytime heating to cause enough instability for a storm.

I can recall growing up in Arkansas running to the bus stop on many mornings, dodging the lightning and rain and sometimes hail.

For those not in Colorado, we are known for our rapidly changing weather conditions, especially in the mountains.

This morning, rain rapidly changed to snow along with driving winds between Idaho Springs, Aspen and Vail -- closing portions of Interstate 70 over the Continental Divide and causing some accidents outside of the Eisenhower Tunnel.

For both residents and visitors, it is time to dig out the winter survival kits to keep in the trunk of your car because you just never know what you may run into over the higher passes. Other colder climates will need to do this in the coming weeks too. (like Wisconsin, Wyoming, South Dakota and Montana for example)

The wettest location in the CoCoRaHS network on Sunday was Bennett County, South Dakota. Two different stations each had nearly 2.00 inches of rain. Check it out on the maps by clicking here. Then select South Dakota in the state pull-down menu and Bennett County in the Cities/Counties list.

Observer WY-NT-22 says it is feeling like fall in his or her Monday comment.
AMEN to that!!

Sunday, September 23, 2007

Fall 2007 Arrives

Regardless of how the weather outside feels today where you live, it is now fall.

For some the signs are already here, especially in the Rockies where the annual fall color show has begun.

One CoCoRaHS observer in Cook County, Illinois has noticed some golden leaves on the Locust trees.

As the sun angle in the sky gradually lowers in the days ahead, and the days become shorter, cold air will build across the Arctic and occasionally move south in the form of strong cold fronts.

These fronts will bring anything from snow and cold to severe weather across the lower 48 states.

The average first date for measurable snowfall in Denver is October 19. But for many cities in colder climates of the US, that date doesn't come until mid-November, including Chicago and Indianapolis.

A measurable snowfall is defined as being 0.1 inches or more.

Now is a great time to get out the snowboard and snowstick for those in the snowy climates, and to brush up on your snow measurement skills.

Any questions? Feel free to ask. In the days ahead we'll do some reviewing in the blog, as well as in Nolan's email updates.

The other day I suggested if you have time -- you should read some of the daily comment reports from CoCoRaHS observers in your state and around the nation.

To do this, go up to the menu across the top of the page and click on "View Data" -- then click on "Daily Comment Reports" when the page loads.

To see all states, change your pull-down menu to say "Select State" -- otherwise select the specific state you are interested in.

Here is a great comment from an observer near Chadwick, Illinois on Sunday morning.

"Have no idea where the .02 moisture came from - maybe the big fat bublebee dead in the top funnel. Temp 53, sunny, clear and no wind."

Here is a data entry tip for those who are busy with work and other projects. A zero entry for precipitation may not seem like a big deal, but to a climatologist, it is just as important as that 6.01 inch rainfall.

You never know how a zero report could come in handy. One example would be if an observer did get that huge 6.01 inch rain. Seeing who got rain and who got zero precipitation is extremely helpful for a climatologist or meteorologist reconstructing the storm.

If you are extremely busy like myself (working 2 jobs plus keeping up with life in general and hobbies like CoCoRaHS) you may find it helpful to keep a written log of precipitation during the week, then sit down on Saturday or Sunday and do the "catch-up" data entry.

In a month like September when there are ALOT of zero reports, it is ok to do this.

Just try your best not to FORGET to do that "catch-up" data entry.

In the event you do get a nice dose of rain or snow, it is awesome to file that report as fast as possible because now that CoCoRaHS is so big, there are literally thousnads of people logging in to check those maps each morning to see who got big rain and who did not -- users include fellow volunteers, the media, and the National Weather Service.

Saturday, September 22, 2007

Last Day Of Summer Is Tale Of Two Seasons

Depending on where you are located this weekend, the last day of summer is bringing everything from snow to tornadoes.

A large area of low pressure spinning near southern California will keep the west cool and damp this weekend.

What is a cut-off area of low pressure? It is a low pressure that is not in the main flow of jet stream winds in the upper atmosphere. Cut-off low pressure areas will sit and spin until they either dissipate or eventually drift close enough to the jet stream flow that they get picked up and moved off.

Sometimes a cut-off low pressure can be bad, such as earlier in the summer when a cut-off low pressure kept Texas and Oklahoma very wet for several weeks.

In this case it is GREAT news for the Los Angeles area, which saw the first rainfall in 6 months and the heaveist September rain in 2 decades!

The rain caused some flash flooding across the large burn scars from summer fires in the vicinity.

Meanwhile the eastern states will end summer on a very warm note, so get out and enjoy because it is the time of year when things could change quickly.

And tropical depression #10 moved onshore near Ft. Walton Beach, Florida Friday. It wasn't the wind and rain maker many feared, but there were several tornadoes reported with the storm system.

One twister caused significant damage outside of Orlando.

And did you by chance see a radar of the upper midwest on Friday? A long line of severe thunderstorms (also known as a squall line) stretched from Iowa to the upper peninsula of Michigan at one point. The storms brought rain, wind and hail to the area. Much of Wisconsin was under a tornado watch at one point on Friday.

Friday, September 21, 2007

September Weather

20 CoCoRaHS stations have checked in with an inch or more of rain as of 10 am Mountain Time on Friday morning. The reports came from Wisconsin, New Mexcio, North Carolina and South Dakota.

One of those reports came from observer NM-ED-3, who lives on the northwest side of Carlsbad, New Mexico.

A thnuderstorm moved over that region just after 10 pm on Thursday night, and dropped 1.10 inches of rain in 15 minutes. The observer described the flooding as severe with over a foot of water rushing down the streets.

That much rain in 15 minutes is a lot for any location, but especially in a dry and arid climate like New Mexico.

Although our network isn't up and running yet across Florida, there have been some drenching rains there this week too. The city of Jacksonville has recorded over 10 inches!

Those soaking rains will spread west along the central Gulf Coast with the current tropical disturbance in that part of the world.

If you are heading to New Orleans this weekend, bring the rain gear!

Thursday, September 20, 2007

Eyes On The Tropics

Forecasters will be watching the tropics over the next few days as an area of disturbed weather off the west coast of Florida could develop into either a tropical or sub-tropical storm.

You can follow the latest on the National Hurricane Center's website by clicking here.

Although we'd hate to see a tropical system threaten our friends along the Gulf Coast, the rain that could spread into the southeast would be awesome -- since they have been in a widespread drought this summer. Stay tuned to see how this plays out!

If you are traveling to the western coast of Mexico or the Baja of California over the next few days -- prepare to deal with Hurricane Ivo. It may weaken into a tropical storm before landfall, but will still bring plenty of wind and rain to the region.

Favorite observer comment from Wednesday: Finally a smidge to report! This comes from 6.8 miles south of Arlee, Montana.

Wednesday, September 19, 2007

Hail Falls From Kansas To Wisconsin

The CoCoRaHS maps today will be interesting to look at -- especially in states like Iowa, Kansas, Wisconsin and Nebraska.

Strong to severe thunderstorms rolled across the plains on Tuesday.

There was one intense rain report filed 2.6 miles north of Independence, Missouri on Tuesday. The CoCoRaHS observer there saw 0.40 inches of rain in 30 minutes.

Hail fell across southeast Nebraska, eastern Iowa and southwest Wisconsin. The thunderstorms also produced strong winds that caused damage.

Sustained winds at 46 mph with gusts to 79 mph were reported 1 mile north of Vinton, Iowa. Not too far away in Keystone (Benton County) a 55,000 bushel grain bin was blown over.

Click here for a complete listing of storm reports sent to the National Weather Service.

Do you ever take time to read through the daily comment reports here on CoCoRaHS? There are literally hundreds -- but it could be fun to read for your state.

One of my favorites from Tuesday came from the observer 3.0 miles ENE of Perrin, Texas (Station TX-JC-2).

He is a 185 pound man that was knocked to the ground by a wind gust from the outflow boundary of a nearby thunderstorm around 8 pm Monday evening. Now that is some powerful wind!

Meteorologists keep close tabs on outflow boundaries because they can do a few different things. Sometimes they create new thunderstorms, essentially acting like a small-scale cold front. They can also linger and be the focal point for new thunderstorm growth with daytime heating on the following day.

Tuesday, September 18, 2007

The Transition Between Seasons

Summer 2007 is rapidly drawing to a close -- and Mother Nature is busy showing us hints of the days ahead.

Many have experienced a pre-autumn chill over the past few days. Snow was even reported in northern Minnesota over the weekend as lows dipped into the 20s and 30s.

Here in Colorado, snow fell in the mountains above 11,000 feet Sunday night, closing Trail Ridge Road in Rocky Mountain National Park for a few hours Monday morning.

And from northern Colorado to Wyoming and Montana, the annual fall color show is underway.

Another sign of the transition from summer to fall is severe weather -- yes I said severe weather! Not so much for us in the Rockies, but CoCoRaHS states like Iowa, Missouri, Indiana, Illinois and points south can see short but potent outbreaks of severe weather this time of year. Some southern states actually see a second peak in severe weather during the autumn months as cold air from Canada collides with warm moist air hovering along the Gulf of Mexico.

Something that we will see less and less of in the days to come are Intense Precipitation Reports for heavy rain on CoCoRaHS as the cold weather season takes over. But if you happen to experience intense precipitation in the days ahead and can file a report, we'd love to document this information.

One observer in La Plata County, Colorado experienced 0.42 inches of rain in 6 minutes on Monday afternoon. And in Santa Fe County, New Mexico -- a CoCoRaHS observer saw almost 2.50 inches of rain in 4 hours from a series of slow-moving thunderstorms.

You can check out both of these reports filed on 9/17/2007 by Clicking Here. It will default to Colorado, but if you choose "Select State" in the pull-down menu it will pull any reports from all CoCoRaHS observers.

Tuesday, September 4, 2007

Welcome To The CoCoRaHS Blog!

Hello -- I am Chris Spears, a CoCoRaHS volunteer since 2002. I worked with Nolan Doesken as a CoCoRaHS student intern while finishing my meteorology degree at Metropolitan State College of Denver.

I am very passionate about both people and the weather. So I approached Nolan and Henry at CoCoRaHS headquarters about hosting a weather blog on the CoCoRaHS website.

This will not be an opinionated blog and will not cover topics of conflict, such as climate change. The purpose is to talk about the current weather and the data you all collect and archive every single day.

I am truly a climatologist at heart, so I will also attempt to throw in as many neat and interesting weather facts as possible.

I hope you enjoy the blog --