East Coast Slammed

What will go down as the most intense coastal storm of the hurricane season in the U-S so far is still raging from eastern NC to New England.  It's far from over.  Much of eastern NC has already been washed out by up to 22" of rainfall this week.  It's pouring there again now, with several more hours of torrential rains likely before the remnants of Nicole clear the area.  The complex combination of an old front, Nicole, and other areas of low pressure have led to a nearly-uniterrupted band of rainfall that reaches 1200 miles in length.  Yesterday, the National Hurricane Center, which has done a terrific job during this year's busy season, determined that Tropical Storm Nicole no longer had "tropical" characteristics, having been absorbed by the frontal system.  There is a growing body of evidence suggesting that was premature.  Winds are already gusting to more than 50 mph ahead of Nicole's circulation at places like Emerald Isle and Hatteras, NC. There is also a lack of any "cold" air filtering into Nicole's circulation, a sign she is still barotropic... or warm cored.  Such systems do not have fronts. They are fueled by vertical energy transfer rather than horizontal, like we see at our latitude.  The fact the NHC called this system off means they stopped sending recon flights to measure its strength.  That lack of data may prove costly.  On the other hand, local weather offices on the East Coast are monitoring this situation and providing timely alerts. It's not as if all of this wind and rain will come as a surprise to anyone living out there.  Of course, preparing for 45-mph winds versus 70-mph winds is a major difference.  Perhaps continued recon of the storm could have provided a better look at the potential for a greater disaster than what is currently progressing. 

Mike

September closes out with a winner

This past month will go into the books with a temperature surplus and a rainfall deficit.  The average temperature will finish around 65 degrees, or a little more than a degree above normal.  Precipitation-wise, we'll end up with 2.78" officially at O'Hare, which is 1/2" below normal. The majority of that total (1.72" of it) came on the 1st and 2nd, which means the past four weeks have been very dry.  That dry trend may be broken this weekend, starting tomorrow night.  First, a cold front will whisk through here tomorrow night.  Some computer models suggest we could get mroe than 1/4" of rain from that alone.  I am doubtful as the models have consistently been over-estimating the atmospheric moisture available for weeks.  Yesterday was a perfect example of that, as some forecasts alluded to the shower threat.  As I pointed out however,  the models on which they were based were plainly out to lunch with regards to the humidity profiles.  If we don't get any rain with the actual front, the other possibility will be lake-effect rain showers.  The set up looks good on Saturday, but again will be largely dependent on whether there's enough H2O in the air to work with.  Thermally, this will be our coldest air since mid May.  If we dip into the 30s, it'll be the first such occurrence since May 9th.  That raises the prospect for frost.  I remain confident the city and areas close to the lake will avoid frost as the urban heat island and lake influence should hold temps up.  Farther inland, and especially on Sunday night/Monday morning, I think few low-lying areas will see a crunchy coating around sunrise. Cloud cover (or lack thereof) will be crucial.

Mike

Update on Nicole

Tropical Storm Nicole has dissipated over Cuba this afternoon. However, there is a tremendous amount of moisture associated with her remnants.  That will interact with the frontal boundary draped over the East Coast to bring more heavy rains from Florida into the Mid-Atlantic.  Parts of southeastern North Carolina have picked up more than a foot of rain already from what's known as a predecessor rain event.

Mike

Quiet here with minor wrinkles

Another mostly sunny day is on tap courtesy of high pressure to over the upper Ohio Valley.  A weak cold front is advancing toward the area but won't arrive until tonight.  That means temperatures today will be free to climb well into the 70s.  As for precipitation with the front... I'm not impressed.  The atmosphere is very dry and while there will be a little lift associated with the front, I think increasing cloud cover will be the most likely result of the frontal passage.  Behind the front, readings will be a few degrees cooler tomorrow, but the REAL cooldown is set for the weekend.  A much stronger surge of Canadian air will dive in Friday night, setting the stage for one of the coolest weekends we've seen in a long time.  Highs both days will be in the 50s, and as that cooler air aloft blows over the warmer lake waters, a few lake-effect showers could pop up.  Like Monday, the showers would be spotty and light. And that brings us to the other key question mark for the weekend... will it be cold enough for some frost in the outlying areas?  Right now I'm leaning toward "no" and here's why.  I'm banking on enough cloud cover to hang around both nights to prevent full radiational cooling.  Those clouds act like a blanket, and redirect the longwave radiation being sent toward the upper atmosphere back to earth. 

The other development this morning is the classification of the season's 14th named tropical storm. Nicole is still a fairly ragged system spinning over Cuba and her future will be brief.  Nicole is likely to be disrupted by a frontal boundary over the southeast coast and an extra-tropical low which will be the main player over the next few days.  However, moisture from Nicole will feed into the frontal zone, and flooding rains are possible over the southeast as a result.  Heavy rain might not be completely unwelcome.  Much of Georgia through the Mid-Atlantic are experiencing drought conditions. 

Mike

Lake Effect... not just for Winter anymore!

Weatherwise, there's no question, Lake Michigan can be our friend or foe.  Today, it is the enemy of those hoping to see sunshine in the city. We often think of lake effect as only having to do with generating those bursts of white-out snows in the winter.  Truth is, if the temperature difference between the lake water and the air moving above it is great enough, and wind conditions are just right, you can have lake effect at other times of the year as well.  That's what we see taking place today.  A plume of cloud cover stretches from the north shore through the city all the way into Central Ilinois early this afternoon. The 35-mile-wide band of clouds is quite spectacular in satellite imagery! There was even enough moisture to crank out some rain showers this morning. Those of you in the western suburbs have no idea what I'm referring to as the sun has been out all day long.  The rest of the week looks quiet with no storm systems crossing the area.  The warmest day of the week will be Wednesday when 70s return.  I see a possible return of very mild air here next week. Not a lock yet, but the pattern favors it.

Mike

A LOT MORE LIKE FALL

The high this past Saturday only made it up to 60° which is the coolest day since last May. While this is 10° below average what made it feel even chillier is the warm weather we saw on Thursday when the high hit 89° and Friday when the high early in the day touched 80°. The quick switch to the fall chill makes it a little difficult to get acclimated. Quiet weather is expected for this upcoming week with highs in the 60s to lower 70s. A storm system travelling out of the Southeast will bring a lot of rain to our east espcially on Tuesday. The moisture from this system will move as far to the west as about South Bend and possibly clip areas east of Portage but for the most part this system will miss us.

 The extended models show an impressive push of Canadian air heading south by next weekend but the brunt of this chilly air mass will pass to our east. So while highs next weekend in our area will be in the 60s parts of New England will see their first snow of the season with higher elevations seeing some accumulation.

    Phil

Open the windows!?

After a week with temperatures in the upper 80s to low 90s across the region, mother nature will provide the free air conditioning for the first weekend of autumn.  With highs in the 60s this weekend, open the windows for some fresh air!  We recieved a taste of the cooler air yesterday as the cold front swept through, and it appears the "cooler" will be the case for the 7 day outlook as autumn kicks in to full swing.  Saturday starts off mostly sunny but as a weak disturbance enters from the west, it could trigger a passing shower late afternoon into the evening--highs in the low to mid 60s.  After a slight chance of rain Sunday morning, look for partly cloudy skies with highs back into the low 60s.  A gradual warming trend occurs the rest of the week with highs in the low 70s Tuesday through Friday.  For the Bears game Monday night, temps are expected to fall into the 50s throughout the game.  GO Bears!  Have a wonderful weekend!  MARK BISHOP

Not exactly a carbon copy... but close

If you remember back to Tuesday, then you have a pretty good idea of what kind of weather to expect today.  The cold front which sparked the strong storms Tuesday evening ushered in a one-day shot of cooler air yesterday.  Now, that frontal boundary has been pushed to our north again, allowing the same toasty air mass we enjoyed Tuesday to return.  Officially we hit 88 at O'Hare on Tuesday and I see no reason why we won't be within a degree or so of that mark today.  However, unlike the turbulent transition to cooler weather we endured Tuesday with damaging winds and hail, this time some of the factors are not coming together for severe weather.  I can't rule out a shower or thunderstorm this evening, but the prime time for flash and crash will be well after midnight.  In fact, our in-house MicroCast weather model brings a line of t'showers through between 2 and 6 a.m.  At that time of day, storms are usually in a weakening mode, so large hail and/or damaging winds would appear unlikely.  After the showers exit, cooler air will filter in for the rest of Friday and the weekend.  Highs will be pinned in the 60s both Saturday and Sunday.  I am currently evaluating the prospects for a few light showers this weekend and will happily share my thoughts at 4pm.  Enjoy this first full day of Autumn!

Mike

Birthday weather

OK... young Ms. Butler let the cat out of bag.  The Fire Department will be on call in case my conflagration of candles gets out of hand tonight!  As has happened many times in my short life (yeah right) my birthday coincides with the changing of the seasons. Tonight at 10:09 CDT, the sun passes directly over the equator, marking the Autmnal Equinox.  While we in the weathe biz adhere to a slightly different meteorological calendar for record-keeping clarity, astronomical fall begins tonight.  Some people have asked me on Facebook why some websites and calendars say the date of this year's equinox is September 22nd, and others say it's on the 23rd.  Simple.  They're both right.  The equinox happens at a precise moment.  That moment this year is 10:09 CDT.  But that moment also happens occur after midnight in Europe, where it will already be the morning of the 23rd.  Same moment, but different times, and in this case, different dates.

Weather-wise, clouds will dominate the sky with some episodes of sunshine.  While a passing shower can't be ruled out, the day will be largely dry.  Highs will be in the 70s, still mild, but not as toasty as yesterday. Then we break into the heat again tomorrow, only to be ousted by a stronger surge of cooler air Friday.  With that next front another round of thunderstorms will be likely, though I doubt they will have the gusto of Tuesday's action.

Mike

SEPTEMBER 22, 2010

Greetings to all!

Did you know what a special day this is?  Well for you autumn lovers, the new season rolls in this evening at 10:09 Central Time.  But tomorrow, the first full day of fall, will feel a LOT more like summer.  However, today we celebrate the birthday of my colleague, Mike Caplan.  I often refer to him as being like my OLDER brother! 

HAPPY BIRTHDAY PAL.

Tracy