Wednesday, February 1, 2017

Winter? What Winter?

Today marks the start of the last third of winter, climatologically speaking. The winter statistics will be calculated over the months of December through February, even though in many areas winter weather can continue through March and into April. So, where are we at with a month go go in official winter?

One quick way to look at the status of the winter season is to look at a map of the Accumulated Winter Season Severity Index (AWSSI). The AWSSI (pronounced "aww-see") is an index that scores the impact of cold and snow (both snowfall and snow depth) occurring during the winter season. The index was developed by Barbara Mayes-Boustead with the National Weather Service in Omaha, NE, and yours truly. Scores fall into one of five categories ranging from Mild to Extreme. Here is the map as of January 31 showing how winter is progressing across the country.

The categories of the Accumulated Winter Season Severity Index as of January 31, 2017

As you can see from this map, this winter has been particularly severe in the northwestern quarter of the nation from the Pacific Northwest down through the northern Rockies and into the Northern Plains. Over the rest of the country, winter so far has been mild.

Here are the temperature departures for the period from December 1 through January 31. The areas of the country that have experienced warmer than normal temperatures also tend to have below normal snowfall.

Snowfall, as you no doubt have heard, is heavy across the western U.S. More snow is expected over the next several days as another storm slams into the coast.

As of this morning, snow cover is extensive over the western U.S. and across the northern tier of states into New England.

We can look at the progress of the AWSSI though the season by plotting the score for each day through thee season. Individual storms or snowy periods and cold periods can be seen by the sharp changes in the AWSSI plot, The shading on the chart shows the envelope of all AWSSI scores for that location and the five categories for that station. For example, here is the plot for Redmond, OR.

Redmond's normal seasonal snowfall is around 16 inches and annual precipitation is 8.90 inches. Oregon State CoCoRaHS Co-Coordinator Jim Jones, who lives in Redmond, reports that he has measured a total of 47.9 inches of snow since December 1, and 4.39 inches of precipitation, about half the annual total..

In contrast to the extreme winter weather in Redmond, let's take a look at the AWSSI this winter in Utqiaġvik (formerly Barrow), Alaska. The AWSSI is at a record mild level in Utqiaġvik. As of today the score was 1570, and the previous record low on February 1 was 1965. At the rate the winter is going it is not likely to climb out of record mild territory.

You an follow the AWSSI through the rest of the winter and learn more about it at the Midwestern Regional Climate Center's AWSSI page.

Tuesday is Groundhog Day, so Punxsutawney Phil will allegedly tell us how much winter is left (but you get a better forecast just flipping a coin). Four to six weeks more of potential winter weather (i.e. until the beginning or middle of March) is a pretty good bet in almost any year. Sorry, Phil.

Tuesday, January 17, 2017

No Such Thing as a Free Lunch

Monday and Tuesday were rare dry days in California, at least compared to the past month. The recent series of storms with heavy rain and mountain snows wiped out the drought across northern California, but left the southern half of the state relatively untouched. The improvement in the drought situation in the past year is remarkable, though most of this improvement occurred relatively recently. While the storms the occurred the past two weeks were welcome, they also brought too much of a good thing.

The Drought Monitor for California for January 12, 2016 (left), and January 10, 2017 (right).

Even with the drastic improvement in the drought situation, approximately 13 million California residents are still affected by severe to extreme drought. Much of the agricultural Central Valley is still in extreme drought. Over a thousand wells are dry. There may be some improvement in the southern half of the state over the next week as a series of storms slam into the west coast, but drought may not be what residents will have on their mind.

While the rain and snow in the northern half of the state were beneficial in many ways, it also brought its share of misery and damage. The frequent and torrential rains quickly overran the ability of rivers and streams to carry the water within their banks. Flooding and flash flooding was widespread. Runoff rapidly filled reservoirs that were on their last legs to the point that many had to open floodgates to let the excess water out. Heavy rain over southern California the next seven days will likely result some flooding and the threat of landslides. To be sure, central and southern California need the rain, but not all at once. For there to be real relief from the drought impacts the water needs time to seep into the ground to recharge groundwater, a long, slow process. In these heavy rain situations far more water runs off into rivers, stream, and storm drains than soaks into the ground.

Rainfall totals for the past 30 days have been impressive, with totals in the northern half of the state ranging from 12 to 31 inches, with most of that coming in the past two weeks. Snow in the Sierras was equally if not more impressive. The CoCoRaHS observer at CA-PC-1, Soda Springs measured a total of 202 inches of snow since December 18 (that's 16.8 feet)!

Daily snowfall for the CoCoRaHS station CA-PC-1, Soda Springs, CA for the last 30 days.

The snow was so heavy and intense that a number of ski resorts had to close because of road closures and the sheer amount of snow. Heavy, wet snow brought down trees and powerlines.  With many northern reservoirs now full, snow is more important. The Sierra snowpack supplies about one third of California's water supply. It's the snow piling up in the winter and then slowly melting through the spring and summer that keeps water flowing.

Snow water equivalent in the Sierra range is 164 percent of average as of January 13, ranging from 132 percent of average in the Northern Sierra, 162 percent of average in the Central Sierra, and 197 percent of average in the Southern Sierra. An important statistic is the percent of the April 1 snow water equivalent average. The snow that remains as of April 1 is the snow that melts during the warm season to supply water to California. As of January 13 the percent of April 1 average was near to above the record.

The precipitation outlook for the next seven days is both good and ominous for California. A series of storms now strung out over the Pacific will make landfall in the next week, The outlook is good in that much needed rainfall should reach central and southern California this time around. In northern California, more heavy rain over swollen rivers, full reservoirs, and saturated ground will likely cause another difficult period for northern California residents.

Even with the rain so far and more expected, it will not necessarily mean the end of drought worries in California. There is still the rest of the winter and spring to get through, and the challenge will be managing the water that has fallen so far, and that yet to come.

Thursday, January 5, 2017

The Nine Habits of Highly Effective CoCoRaHS Observers

Resolutions for self-improvement usually accompany the start of the New Year. I'm not typically one for resolutions but I'm going to give it a try this time around. It's been about 3 months since my last blog post and I won't bore you with the reasons/excuses of why it's been so long. It's a new year and I am going to try and get back on track. So, if there are topics you would like to me write about or revisit again let me know - ideas are always welcome.

Now to the topic for this blog post. A few months ago I was thinking about what characteristics make an effective CoCoRaHS rainfall observer and jotted down a list. I recalled seeing the book "The 7 Habits of Highly Effective People" published in 1989 by Stephen Covey, and that inspired the title of this post.

So, here's what I've come up with for the nine habits of highly effective CoCoRaHS observers.

Report every day

One of the attributes of a good climate record is consistent, regular observations. Consistent observations over a period of time help identify patterns and trends. Precipitation varies a lot in time and space, so regular observations are needed to capture these variations. Effective observers realize this and make an effort to have a report for each day. It usually is a daily report, but sometimes is an amount that spans two or more days (a multi-day report).  The bottom line is that at the end of the month or end of the year, each day is accounted for by an observation.

Report zeros

This goes hand-in-hand with #1. Effective observers know that zero is a number and a measurement. Zero is NOT equivalent to no measurement. A missing measurement does not mean "it did not rain". It's just missing. Effective observers also report zero for snowfall and snow depth when there is no snow or no snow on the ground, even when it's too warm for snow.

Make sure to have the correct observation time

Effective observers make sure to enter the correct observation time if it is different from the default time on the entry form. Sometimes life gets in the way and we can't always make our observation when we need to. The correct observation time helps those using the precipitation data to interpret it correctly.

Check submissions AFTER hitting the Submit button

Effective observers almost always remember to check their observation after they have submitted it on the CoCoRaHS web site. They easily do that by scrolling down the page past the Message of the Day to view their observation. They quickly catch the typos (for example, entering 10.00 instead of 0.10) and make what they entered is what they intended.

Keep a local record of observations

Even the most conscientious observer can get sidetracked and forget to enter the observation on any given day. Effective observers keep a separate written record of their observations for a period of time as a backup "just in case". They also realize that they may be contacted by their local coordinator or the CoCoRaHS staff about a past observation if an error is suspected or an observation needs to be verified. A written record can help answer those questions.

Review observations at the end of the month

Effective observers check their observations at the end of the month to be sure that all days are accounted for and there are no obvious errors. This is where that written record can save the day.

Periodically review the training materials

Everyone can use a refresher from time to time. It helps to review certain topics, like snow measurement and reporting prior to the winter season. Effective observers review the training animations and other training information on the web site from time to time as needed.

Follow correct procedures

Effective CoCoRaHS observers use the 4-inch standard rain gauge, make their observation at about the same time each day, and submit their observations using the correct form (Daily Report for daily observations, Multi-Day Report for multi-day accumulations). They know when and how to submit a Significant Weather Report or Hail Report.

Enjoy what they do

CoCoRaHS observers are typically highly motivated and enjoy what they do. They realize that many users count on the observations they make and report every day. They are dedicated and enthusiastic. Many recruit family and friends to join and/or help, and strive to never miss an observation.

Happy New year, everyone!

Wednesday, October 5, 2016

Hurricane Matthew Heads Toward the U.S.

Hurricane Matthew as it was
making landfall in Haiti on October 4, 2016
In my last post I mentioned Tropical Storm Matthew which at that time was in the southern Caribbean and moving west. Now, a week later, Matthew is a major hurricane (Category 3 or higher) that has already caused widespread destruction in Haiti and eastern Cuba, and is now taking aim on the Bahamas, Florida and the southeastern U.S. The last time a major hurricane made landfall in the U.S. was in 2005 when Wilma made landfall in southwestern Florida. Wilma was the fourth major hurricane to make landfall that season, along with Dennis, Katrina, and Rita. The nearly ten years since Wilma is a new record for time between major hurricane landfalls in the U.S. The average is about two major hurricanes making landfall every three years. It has been almost nine years since any hurricane has made landfall in Florida. Matthew is likely to end that streak and Florida will become intimately familiar with a hurricane again. Nine years between hurricanes is a very long time in Florida. hen you think about it, many people now living in Florida haven't yet gone through a hurricane, preparing for it, making plans for evacuation, or cleaning up in the aftermath.

The forecast of Matthew's track has been challenging to say the least. Matthew re-intensified after losing some strength crossing over Haiti and Cuba, and as of 11:00 p.m. EDT tonight was a Category 3 storm with maximum sustained winds of 115 mph. The current thinking is that Matthew will travel parallel to the coast from Florida, possibly briefly making landfall, to South Carolina and then turn east into the Atlantic - temporarily. Models are indicating that beyond that time the hurricane could loop around west and make landfall in Florida for possible a second time. It's one of several possibilities but one that certainly could happen.

Landfall or not, Matthew is going to be a handful to deal with. Flooding from storm surge and heavy rain will be likely along the coast.

72-hour rainfall expected from Hurricane Matthew. A small change in the path of the storm could result in significant changes to expected rainfall.

The impacts from high winds will partly depend on Matthew's track. If the storm center stays offshore so will the worst of the winds. Should the eye of the storm make landfall, winds and damage will be much worse. Here is one graphic from the NWS Jacksonville, FL office showing maximum winds gusts possible through Saturday.

At the Exuma International Airport in the Bahamas tonight winds were already gusting over 140 mph.

Hurricane Matthew approaching the Bahamas at 9:45 p.m. EDT October 5.

Fortunately, community officials and governments are taking this situation seriously. Evacuations were announced yesterday and are in progress from South Carolina south through Georgia and Florida.

By the time many of you read this conditions and the forecast for Matthew will have likely changed. This storm will be affecting the southeastern U.S. for perhaps the next seven days or more. Please check the latest information at the National Hurricane Center, and if you are in the southeastern U.S. be sure to also check with your local National Weather Service Office.

This storm will affect many of our CoCoRaHS observers from the Bahamas to the Carolinas. Remember that your safety is priority - don't risk your safety for a rainfall observation. Remember, too, that you can also send Significant Weather Reports at any time.

Wednesday, September 28, 2016

A Wet Setup for the Eastern U.S.

Much of the northeastern U.S. has been dealing with abnormally dry to extreme drought conditions this past summer and early fall. Some relief came in the past two weeks in the southern part of the region, but that last U.S. Drought Monitor still depicted large areas of severe to extreme drought in the Northeast, with dry conditions generally extending southwest long the Appalachians into northern Georgia and Alabama.

Showers and thunderstorms, some severe, are already rolling through western and central Virginia and central North Carolina. This precipitation is associated with a somewhat complex surface system over the upper Ohio Valley and western North Carolina.

Surface map for 7:00 p.m. CDT Wednesday, September 28, 2016.

The surface system in turn is associated with a large closed upper low centered over central Indiana. That low has brought very cool weather to the Great Lakes and central Midwest along with the wet weather. Typically close or cutoff lows like this move very slowly, since they are separated from the overall jet stream flow. This upper low is expected to move very little over the next 48 to 72 hours, drifting south to northern Kentucky, then back north to northern Indiana.

500 millibar map for 7:00 p.m. CDT Wednesday, September 28, 2016

This kind of setup means a prolonged period of wet weather for the central Appalachians northward into New England. The heaviest rainfall is expected to be northeast of the low center. Over the next seven days the highest amounts are expected from the eastern Great Lakes across southern Pennsylvania into northern Virginia as well as southern New England.

Quantitative Precipitation Forecast for the 7-day period ending 7:00 p..m. CDT Wednesday, October 5, 2016.

The fly in the ointment at this point is Tropical Storm Matthew. It is currently located just east of the Windward Islands and is moving west. The latest forecasts take Matthew into the eastern and central Caribbean Sea by the weekend. Beyond that the forecast track for Matthew, which should by then be a hurricane, is uncertain and there is low confidence in the projected path.

Wednesday, August 24, 2016

Fire and Rain

A lot of attention is being paid to the tropical Atlantic where Fiona is now history, Gaston is strengthening, and a third disturbance, which could end up being Hermine, is being watched closely. Although there were five previous systems, including two hurricanes (Alex and Earl), only two, Bonnie in late May and Colin in early June, directly affected any part of the U.S., mostly with heavy rain.

In the meantime, resident of south-central Louisiana are still trying to clean up after a no-name tropical-like system dumped two feet of rain on them just 10 days ago.

7-day precipitation for Louisiana ending August 16. However, most of this fell in just two days (August 12-13).

The public and the news media don't get quite as excited about things when they aren't being talked about days in advanced (hyped, if you wish), and don't seem as interested in the aftermath when there is no "name" (e.g. Katrina, Sandy, Andrew) to blame it on. With or without a name, the destruction is the same.

Flooding in Baton Rouge.
Credit: U.S. Department of Agriculture -

In Louisiana an estimated 60,000+ homes are damaged, to say nothing of businesses, schools, and other buildings. The US Coast Guard, National Guard, local emergency responders, and citizens helped rescue more than 30,000 residents and 1,400 animals. Thirteen people lost their lives in the flooding. At least 7,000 people are in shelters, and more than 100,000 people in the state have registered for federal emergency aid. Twenty parishes (counties) have been declared federal disaster areas.

Two photos showing flooding in a Baton Rouge neighborhood on August 14 (top) and five days later on August 19.
Credit:Twitter @JesseWeather

In the western U.S. wildfires have been in the news. Much of the west, but California in particular, is tinder dry, and wildfires are everywhere.

Almost all of the western states are dealing with fires at the present time.  Large fire activity picked up with seven new large fires reported Monday. Currently, 32 large fires have burned more than a half million acres. Some of these fires have been burning for well over a month. The fires have destroyed numerous homes, disrupted truck and rail transportation, and caused air quality issues throughout the west.

Although fire activity is high, the number of fires and the acres involved are less than last year. According the the National Interagency Fire Center, the states currently reporting large fires and their number are: California (6), Colorado (1), Idaho (7), Montana (2), Nevada (1), Oklahoma (1), Oregon (5), Utah (6), Washington (6), and  Wyoming (6).

In Alaska 52 wildfires are currently being monitored. Alaska wildfires have burned more than 384,000 acres, substantially less than last year.

Active Alaskan wildfires as of 8/24/2016.
Credit: University of Alaska Fairbanks Arctic Region Supercomputing Center as part of the UAF SMOKE forecast project.
The outlook for the next month or so is for continued above normal fire risk in California and a return to normal fire risk in the intermountain west.

While Louisiana residents continue to recover from the rain and flooding almost two weeks ago, they are also keeping a watchful eye on the developments in the Atlantic. The tropical disturbance now labeled #99L is showing signs of organization and there is a 50 to 80 percent likelihood it will develop into a tropical cyclone in the next 3 to 5 days. It is way to early to determine a confident track for this potential cyclone, so those with interest from the Gulf Coast to the Florida east coast should be staying abreast of the latest information and advisories from the National Hurricane Center.

Friday, August 12, 2016

Louisiana Deluge

A flooding disaster of major proportions is underway in Louisiana and is likely to get worse over the next few days.

As of early Friday morning up to 15 inches of rain had accumulated during  the preceding 24 hrs. A westward moving low pressure system that is tropical in nature had been producing torrential rains from western Mississippi through eastern and  south-central Louisiana.

24-hour precipitation valid at 7:00 a.m. CDT 8/12/2016

Amounts reported by CoCoRaHS observers topped 11 inches this morning, and a late report at 7:00 p.m. tonight reported 14.65 inches (this is likely a 36 hour total).

CoCoRaHS reports >7.00 inches for Louisiana and Mississippi 8/12/2016

The U.S. Cooperative observer in Livingston, LA reported 10.55 inches of rain this morning, and then  another 6.54 inches as of 3:00 p.m. this afternoon. The observer reported rainfall rates of 3 inches  per hour for an extended period this morning. Rainfall totals exceeding 20 inches will be common by Saturday morning across Louisiana.

The low pressure system responsible for this rain has been hanging along the Gulf coast the past several days and become somewhat more organized as it drifted east. It was located over western Mississippi this morning, and slowly drifted westward during the day today.

Surface map at 1:00 p.m. CDT 8/12/2016 showing low pressure center over western Mississippi.

Visible satellite image for Louisiana at 4:15 p.m. CDT 8/12/2016. The bulging clouds over north-central Louisiana are indicative of strong convection.
 The low is expected to eventually begin drifting to the east and northeast this weekend. The potential for additional heavy rain remains high through the weekend.

Excessive rainfall outlook for the period from 7:00 a.m. CDT Saturday 8/13 to 7:00 a.m. CDT Sunday 8/14/2016.

The 3-day Quantitative Precipitation Forecast for the period from 7:00 p.m. CDT Friday, 8/12 to 7:00 p.m. CDT Monday, 8/15/2016.

Flooding is extensive. Rivers and streams rose rapidly with the high rainfall rates. Numerous rivers in southeast Louisiana and southern Mississippi were overflowing their banks and threatening widespread flooding and most rivers are expected to reach major flooding levels.

River levels and forecasts for southwest Mississippi and southwest Louisiana.
There have been two fatalities reported as a result of the flooding, and another person was reported missing at the time of this writing. Louisiana Gov. John Bel Edwards declared a state of emergency today because of the severe flooding and additional heavy rain expected.

Update Saturday, August 13  10:30 a.m.

Here are two-day rainfall totals for Louisiana. Radar rainfall estimate of 27.47" near Brownfields, LA corresponds well with observed rainfall.

48 hour rainfall totals for stations reporting >10" in Louisiana for period ending 7:00 a.m. CDT August 13.

Wednesday, July 13, 2016

A Different Spin on Vorticity

"Vorticity" is the name of the latest video from Phoenix-based photographer Mike Olbinski. I've featured Mike's work in a past blog post on the southwestern monsoon.

This film  is a time-lapse summary of many of the features Olbinski photographed this spring while chasing weather for 18 days and 20,000 miles over a period of two months. He records many "spinning" features in the atmosphere: rotating mesocyclones, roll clouds, tornadoes, downpours, dust, and churning skies. The film is dramatic and awe-inspiring, and the music by Kerry Muzzey gives the film an epic feel.

                                       Vorticity (4K) from Mike Olbinski on Vimeo.

If you have a good Internet connection be sure to view this in full screen HD. I've viewed this several times already and each time I see something new I didn't notice before.

You can see some more of Mike's work (including Monsoon II) at

As for the title of the film, vorticity is a clockwise or counterclockwise spin in the troposphere. We typically look at vorticity at the 500 millibar level, which is about 20,000 feet. If you have followed this blog you have seen vorticity depicted on some of the 500 millibar maps I've included, like this one. The orange and yellow shading depict areas of vorticity, spinning that produces upward motion, and thus usually clouds and precipitation.

500 millibar showing areas of vorticity

Wednesday, July 6, 2016

Waters Have Receded, but the Mess in West Virginia Remains

The I-79 Clendenin exit in Kanawha County, WV, on June 24, 2016.
Credit: Facebook/West Virginia Department of Transportation
Two weeks ago Friday residents of West Virginia woke up to a disaster in the making. Heavy thunderstorms trained over the mountainous terrain of southeastern West Virginia dumping almost ten inches of rain in less than 12 hours over parts of two counties.

The flooding washed out many roads, caused landslides, destroyed numerous bridges, and left behind a thick layer of mud and debris in many communities. The death toll from this flood stands at 26, making it the third most deadliest flood in the state's history. In the days following the flood at least 32,000 homes and businesses were without power and more than 60 secondary roads in the state were closed.

The Elk River soared to a record crest of 33.37 feet on the morning of June 24, rising about 27 feet above the level it was on June 23.

Heavy rain occurs frequently during this time of the year in many parts of the country, but why was this particular event the disaster it was?

Geography plays a big part. The topography of West Virginia is mountainous, and the steep hills and long narrow valleys are conducive to flooding in very heavy rain events, particularly in the southeastern part of the state. In this particular situation, the heavy rain fell in a relatively short period of time (hours, not days) rushed down the hillsides and was funneled down the valleys. Rivers rose quickly and in some cases cut off escape routes.

The second major factor were training thunderstorms - thunderstorms that repeatedly move over the same area. There were actually two rounds of rain that moved across the state, but the second round that occurred beginning on the afternoon June 23 was the straw that broke the camel's back.

The surface weather map at 8:00 a.m. on June 23 showed a cold front extending from a low over Indiana through the Midwest, and a warm front extending east from the low through Ohio and Pennsylvania.

8:00 a.m. EDT June 23, 2016

By 8:00 p.m. on June 23 the front extended from Missouri east into southern Ohio. It stalled out there as a series of low pressure waves rippled along the boundary. These ripples along with warm, humid air south of the front was the ingredients needed for the heavy rain.

8:00 p.m. EDT June 23, 2016

As of 12:30 a.m. on June 23 there were only a few thunderstorms developing in western West Virginia, with most of the activity further north along the front.

However, during the pre-dawn hours thunderstorms rapidly developed and were producing some heavy rain. Showers and thunderstorms continued during the morning hours.

By late afternoon and evening thunderstorms were numerous and oriented west to east across central and southern West Virginia. There was only a slow southward advancement so the thunderstorms essentially trained across the same area.

By 10:30 p.m. EDT the line of storms finally pushed south, leaving widespread flash flooding in their wake.

Counties outlined in green are under flood warnings.

Nicholas and western Greenbrier Counties in West Virginia received the most rain, though heavy rain also occurred in western Virginia and flood warnings were issued for several counties there. Radar estimated up to 10 inches in Greenbrier County, with up to seven inches falling in only three hours.

24-hour rainfall ending at 8:00 a.m. EDT on June 24
36-hour rainfall amounts end the morning of June 24, 2016
Measured amounts included 8.29 inches in White Sulphur Springs and 8.00 inches in Lewisburg, both in Greenbrier County. The CoCoRaHS observer at Runa 0.1 W in Nicholas County measured 7.20 inches of rain. 24-hour amounts this high have one a 1 in 1000 probability of occurring (0.1 percent).

Credit: NWS Blacksburg, VA

Fifteen of the fatalities occurred in Greenbrier County. Damage was extensive. The Greenbrier GolfClassic scheduled to start July 7 was canceled. The President declared central and southeast West Virginia major disaster areas.

Below are two links that contain slideshows of the flooding and damage in West Virginia and Virginia.

The Weather Channel

While the floodwaters have receded, residents affected by the flooding will be dealing with the aftermath for some time to come.