4/19/13 - A Temperature Roller Coaster Ride

Article By:  Lester Rhoads
Ohio Weather Blog Long Range Forecaster

We've been on a temperature roller coaster for the last several weeks and that looks to continue as we go through the rest of April and into May.  We were in the low 80s in Cincinnati yesterday and the low 40s today with even a few sleet and rain showers this evening!  What a change...  Well what are a few of the factors driving this pattern and why is it lasting so long?

First of all we are still in a pattern that favors blocking.  In the below graphs, note the AO and NAO and how they take another dive as we hit May.

As you can see, this means more strong cold fronts with 2-3 day warm up's ahead of each system and 2-3 days of a cool down behind each system.  Wash, rinse, and repeat.   The latest computer models indicate another trough coming in for next week around mid week with an associated cold front due in on Wed.  We then, will see another system next weekend and there is more beyond that taking us into the first week of May. 

The pattern also looks to remain active.  Take a look at the 11-15 day 500 MB height anomaly map for the 11-15 day period.

As you can see, a ridge builds into the Rockies with a trough along the East Coast and over SE Canada.  There is a weakness in the atmosphere that places the Great Lakes and Ohio Valley regions right in the cross hairs for continues storm system with warm up's and cool down's continuing for the next few weeks. 

For comparison, here is the 6-10 day from the ECMWF model.

The Euro produces a much colder pattern with a positive PNA type of pattern with the ridge centered further west and the trough is centered right over the Ohio Valley.  This is a much colder outcome here with a strong North Atlantic ridge.  This is not a negative NAO by the way.  So there you have it! 

Thanks for reading and I appreciate your feedback!

Active Weather Times Ahead

Good afternoon folks!  The cold and dry weather pattern that we had last week is gone.  It has been replaced by a warmer and more active pattern more typical of Spring.  In addition to the storms this week across the Ohio Valley and Great Lakes regions, after we cool down a bit on Friday and this weekend, warm air will make a return for next week.  Both the GFS and ECMWF computer models indicate more storms will be in our future.  The GFS model tries to bring in the next cold front on Monday while the ECMWF does so by Tuesday.  Both models indicate an active second half of next week!

Do we have any cold spells for the second half of April?  We just might see one!  Check out the AO Forecast.



As you can see, it takes a dip and we get cooler (Friday and this weekend).  Then it rises for next week and takes another dip just after mid month.  I am watching that period, after mid month, to see if we get another cool down similar to the one coming later this week.  This is a classic spring time battle between the warm and cold so severe weather events will become more common for the rest of April and into May as well.

Check out the GFS Ensemble Mean for the 11-15 day period.  It also agrees with a cooler pattern developing after mid month.



Basically, what we can expect going forward is bouts of warmth and cold with an active weather pattern in between.  Severe weather will also become more of a threat as well.  Enjoy the nice weather if you're reading this from Cincinnati and enjoy the storm potential later on today if you live off to the North.

March 2013 Wrap Up from NWS Office in Wilmington

Hello everyone!  While on my lunch break at work today, I stumbled upon some cool information that might interest you.  We know March was an above avg snowfall month for the Ohio Valley and the month also features well below avg, temps. 

I found some cool graphics that the NWS Office in Wilmington posted on their facebook page.  The below graphics will show you snowfall departures for March as well as precip. and temps.

In addition, after we get through this week, the models are trying to show a wetter pattern developing for next week along with a warm up to above avg temps which we will be seeing this weekend across the Ohio Valley.  By mid month, there are signs of well above avg temps developing.  For information specific to Cleveland and Cincinnati, please visit the forecast page which Bryan and I are updating on a daily basis.



Easter Climatology From The NWS Office in Wilmington

I found this link on Facebook about Easter Climatology for Cincinnati, Columbus, and Dayton.  The article talks about temps and precip on past Easter Sundays. 

http://www.erh.noaa.gov/iln/climo/summaries/Easter/CVG.php

Info and article by The National Weather Service Office in Wilmington, Ohio

Have a great Easter Sunday from Bryan and I here at Ohio Weather Blog!

The Big Block Will Ease.... But More Cold Still?

Good evening everyone!  The massive -AO and blocking pattern that we have been seeing looks to weaken some as we head towards the end of March and into the start of April.   You can see that occurring by the graph below.

Does this mean that we will see a big time warm up?  The answer is simple.  No.  Why you may ask?  As the block eases we are going to see a massive ridge of high pressure, or block over Alaska.  This is known as a negative phase of the EPO.  A -EPO can sometimes allow for cooler then avg. temps over the Eastern US.  This feature looks to develop next week and continue for the next couple of weeks.  While we may see a few warm days every now and again over the next couple of weeks, the threat for significant and long lasting warmth, will most likely not occur.

You can see the big ridge below on the 500 MB anomaly map from this afternoon's 12Z GFS Ensemble model run.  This is valid for the 11-15 day period.

The 12Z ECMWF Ensembles also agree for the 6-10 day period.  You can see the ridge over by Alaska.

The bottom line is, if you're looking for sustained above avg. temperatures, or some fun tracking a lot of severe weather in the Ohio Valley, chances are you won't be a happy camper until we get deep into April or once we get into May.

Lester Rhoads
Long Range Forecaster
Ohio Weather Blog

The Calendar Says Spring...

Good evening everyone!  The calendar says Spring, and in fact the new season got underway this morning.  However, this post will attempt to explain why we are not seeing spring like weather as winter still has a firm grip on a large part of the country. 

The main cause for the winter like weather is due to the AO and the NAO both being severely negative.  The AO is the most negative that we have seen in a long time and for late March, it is the most negative that we have seen since record keeping began!  The index value from yesterday came in at a whopping -5 and it could bottom out at -6!  The AO when in a negative phase causes the polar vortex to be displaced to the south, along cold, arctic air to invade the Lower 48.  With the NAO also being very negative, the cold pattern has been able to stick around for a while.

Here is the forecast for the AO for the next two weeks as predicted by the GFS Ensemble Model from this afternoon's 12Z run.  *Image courtesy of Allan Huffman*

As you can see, the model shows the AO finally rising to positive values by the time we get into April so we could see a bit of relaxation in the cold weather by then.  Next, let's take a look at the NAO.  It has also been very negative but the various computer models do show a tendency for it to rise as well from this afternoons 12Z run.

*Image courtesy of Allan Huffman*

Based on these two teleconnection indices, we should see a little warmer weather ahead.  I do think, however, that we won't see significant changes until we get into April a little bit as far as above normal temperatures go.  But once we do see some warmer air move in, severe weather will become a concern and I will have more information down the road for you on that, once we get closer.

The 12Z GFS Ensemble Mean shows the cold pattern nicely through the end of March as you can see in the image below.

As you saw earlier in this post, that when the AO and NAO rise I mentioned that the pattern should turn a little bit warmer.  Well, let's take a look at the GFS Ensemble Mean for the 11-15 day period.

The pattern does not look at cold as it has been.  You can see the blocking as weakened and the large, cold trough has lifted out of Ohio.  This will be a slow warming trend once we get into April and the GFS Ensemble Mean clearly shows this. 

In conclusion, look for the winter like pattern to continue through the end of March with a slow moderating trend as we get into April.  Severe weather season is coming and I will alert you to that threat as conditions warrant.

Lester Rhoads
Ohio Weather Blog
Long Range Forecaster

Intersting weather

Well as you guys know it winter is not done yet....

We have a winter weather advisory for the eastern sites. We can ecpect some ice and light snow amounts there. Below 1in maybe 2 in select spots. Behind this system we will see some snow showers( lake effect) and this could add up to some extant. Here is what the name is saying. It looks pretty good on snowfall amounts in the snowbelt but this will have to be watched.

More to come.

Bryan Polivka
Cleveland Ohio
Ohio Weather Blog Forecaster