TIM’S WEATHER WORLD

There better be a lot of May flowers...

Our abundant April showers have made this the 20th wettest April to date on record.  O'Hare has seen rain 6 out of the opening 11 days this month totalling 1.91" or .72" above average.  Saturday is the only dry day in our 7 day forecast with the active April pattern continuing next week.

Here are some of the heavier rainfall totals for the month from our WeatherBug network:

• 3.30"   Kenosha
• 3.27"   Western Springs
• 3.04"   Sandwich
• 2.87"   Flossmoor
• 2.86"   Justice

The good news is that recent rain has helped alleviate the dry conditions that existed over northern and northwest Illinois.  For the first time in several months none of Illinois is in drought or even "abnormally dry".  However, most of Minnesota and Iowa are experiencing drought conditions and nearly half of Wisconsin is in at least a moderate drought.

The rain has kept us cooler than average too.  Today will be the 8th day out of 12 this month below average.  Now the longer range forecasts are indicating this trend could also continue towards the end of the month.  Both the 6 to 10 day and 8 to 14 day forecast from the Climate Prediction Center has most of the midwest and Great Lakes outlooked for below average temperatures overall during the period.

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We've come a long way when it comes to predicting and tracking tornadoes.  This week marks the 60th anniversary of the first tornado detected by radar.  On April 9th, 1953 radar technician Don Staggs noticed a "hook echo" on a radar (see image above) at Willard Airport, just south of Champaign.  There was a bit of serendipity involved since the radar was supposed to be off.  Mr. Staggs had actually stayed late that day to do repairs on the radar when he noticed the signature pattern that indicates rain and/or debris being wrapped around the circulation caused by the tornado.  Illinois State Climataologist Jim Angel has an excellent summary of that historic event on his Illinois State Water Survey blog.  Today we have a nationwide network of high resolution doppler radars that can detect circulations inside storms that are frequently the precursors to tornadoes.  The tornado in the photo below is the first caputred by National Severe Storms Labratory doppler radar and chase personnel.  It was taken in Union City, Oklahoma on May 24th, 1973.

More advancement in the forecasting of tornadoes was announced recently by NOAA.  Scientists at NOAA’s National Severe Storms Laboratory and the NOAA Cooperative Institute for Mesoscale Meteorological Studies at the University of Oklahoma say they can now better predict the severity of tornado outbreaks with new experimental high-resolution forecast models.  They have found a correlation between the "updraft helicity" or rotation of the rapidly rising air within simulated storms and the track-length of observed tornadoes seen in actual severe weather events included in their study.

The biggest, most destructive tornado outbreaks are relatively rare, occurring just once every few years.  This study will provide clues that can help more reliably predict the severity of these larger spring tornado outbreaks.

Here is more from NOAA-

"Fortunately, researchers believe that models can reveal important clues about the type of severe weather storms can spawn in localized areas. The problem is similar to using Doppler radar observations to predict whether a storm is producing a tornado or not. Doppler radars don’t have sufficient resolution to detect tornadoes. However, if a "hook echo" feature is present in the radar data along with a strong signal for rotation, forecasters recognize that there is a good chance the storm is producing a tornado.
In a similar way, although the next generation of forecast models will not have sufficient resolution to simulate tornadoes, they can skillfully predict the general characteristics of tornado-producing storms. Thus, when the forecast model predicts structures typically seen with observed tornadoes, this can indicate to forecasters that tornadic storms are likely."

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The latest report for the US Drought Monitor reveals that the drought has deepened slightly in every category (moderate, severe, extreme, exceptional).  51.92% of the country is experiencing at least a moderate drought, up from 51.64% last week.  While most of the Chicagoland area is drought free, this news is especially bleak for the southwest, and in particular Texas.  A large part of the Lone Start State has been in a drought for more than two years and the outlook for this summer calls for the drought to persist or even deepen across the vast majority of the state.  Portions of at least five other states in the west and southwest are expected to see their drought conditions worsen.   Over 63% of the west is in at least a moderate drought.  Every state in the western region is experiencing a drought with the exception of Washington.

It is truly feast or famine when it comes to moisture this spring.  People along the Red River in the northern plains are preparing for what could be historic flooding.  Volunteers in Fargo have a goal of making a million sand bags to help hold the flood waters at bay.  They are employing a "spider" sandbag making machine (see image below) that can produce up to 6000 sandbags in an hour.

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While locally it was a cold March (coldest since 1996) and start to April (coldest in 20 years) the global temperature picture continues to tell a different story.  According to NOAA, February 2013 tied with 2003 as the ninth warmest on record.  Here are more hilights from their report:

• The combined average temperature over global land and ocean surfaces for February was 1.03°F above the 20^th century average of 53.9°F.
• The combined global land and ocean average surface temperature for the December–February period was 0.92°F above the 20^th century average of 53.8°F, making it the 12^th warmest such period on record.
• The combined global land and ocean average surface temperature for the January–February period (year-to-date) was 1.01°F above the 20^th century average of 53.8°F, tying with 2005 as the ninth warmest such period on record.

Speaking of global warming....

Here are a couple of related stories of interest-

1. A new report says climate change is making extreme weather events in Australia worse.
2. A former chief economist for the World Bank warns that "both emissions of greenhouse gas and the effects of climate change were taking place faster than he forecast seven years ago."
3. A new study published in Nature Geoscience says paradoxically global warming is creating more sea ice around Antarctica.

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More like Bear weather today than baseball weather.  Bring your winter jackets to the Sox home opener today.

After back to back 59° highs at O'Hare Saturday and Sunday we will see a dramatic drop in temperatures today.  Highs will only reach into the upper 30s so it will feel more like February than the start of April.  Hang in there.  Both the 6-10 day outlook and the 8-14 day outlook (below image) offer the hope for a big warm up as we approach the middle of the month.  Most of the eastern half of the US is outlooked for above average temperatures for the period.

Thank goodness we can say goodbye to March.  25 of 31 days were below average.  The average temperature was 32.6°, more than 5° below average and more than 20° colder than last March!

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It was a near miss with Sunday's record breaking snowstorm that pounded downstate Illinois with nearly a foot and a half of snow in some spots.  Residual effects from the storm might churn up a few flurries or light snow showers here but we should make it through Monday relatively unscathed.  St. Louis saw over a foot of snow yesterday and Springfield reported 17", both records for the date.  Champaign will end up with nearly a foot of snow.

What a difference a year makes for snowfall!  48.7% of the contiguous US has snow cover compared to just 7.7% on this date last year.  We have seen 30" of snow at O'Hare so far this winter compared with 19.8" last year.

Today will be the 14th straight day with below average temperatures here.  While we do see a warm up by the weekend back to about average (lower 50s), the long range outlook through the first week of April calls for spring to stay on hold.   The 8-14 day forecast from the Climate Prediction Center has us outlooked for below average temperatures (top image below) and above average precipitation for the period.

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As we begin the 11th straight day with below average temperatures it might give us hope to know the long range forecast is calling for a warmer than average spring.  However, it is also calling for a wetter than average spring.  The updated April, May and June forecast from the Climate Prediction Center was just released and it has most of the US outlooked for above average temperatures (top image below) during the period.  It also outlooks most of the Midwest and Great Lakes with above average precipitation.

Melting snow combined with spring rain could cause some flooding problems.

According to NOAA's spring flood risk assessment:

The melting of late-season snow may cause minor to moderate flooding in the upper Mississippi River basin, including southern Wisconsin, northern Illinois and northern Missouri. The tributaries in the plains of the upper Missouri River basin, specifically along the Milk River in eastern Montana, the Big Sioux River in South Dakota and the Little Sioux River in Iowa may also see minor to moderate flooding. With significant frozen groundcover in these areas, spring flood risk is highly dependent on rainfall and the speed of the snowmelt.

Areas along the middle Mississippi, lower Missouri and Ohio River basins have already experienced minor flooding this year and the threat of minor flooding will continue through the spring. These basins include portions of Kansas, Missouri, Illinois, eastern Iowa, Indiana, Ohio, Kentucky and Tennessee. Minor flooding also is possible for the lower Mississippi River basin and in the Southeast, including portions of Arkansas, Alabama, Louisiana, Mississippi and Georgia.

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A year ago it felt like summer on this date.  We hit 81° and ended a five day streak with a high of 80° or more.  No such taste of summer this year.  Today will be the 7th day in a row with temperatures below average.  It now looks likely the next seven days in row (at least) will be below average.  14 out 17 days so far have been below average this month.

While light snow will fall at times today we have already seen our share of snow this month with just over 10" so far.  That is a little more than a third of the entire season's snowfall to this point.

So it looks like spring, which officially begins Wednesday at 6:02 AM, will be put on hold for now.  The 8 to 14 day forecast that takes us through the end of the month confirms this with our area outlooked for below average temperatures and above average precipitation.

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This March stands in cold contrast to the record warmth of March 2012.  9 out of the first 12 days of this month have been below average while last March 9 out of the first 12 days were above average.  The last 21 days of March 2012 were all above average.

Here are some highlights from March 2012:

• 9 record highs were tied or broken
• O'Hare broke or tied record highs for nine consecutive days (14th through 22nd)
• Highs hit 80° or above 8 times
• Highs hit 60° or above 21 times
• the average high of 53.5° for the month shattered the old record by 4.9°
• the 15.6° departure from normal for the month was the 3rd largest departure from the 1981-2000 normal for any month in Chicago
• the average temperature for the month would tie for the 14th coolest May in Chicago

The outlook for the remainder of this month is not nearly as toasty.  The 8 to 14 day outlook suggests we will be below average for the period (see below).

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