Wednesday, June 14, 2017

Remembering Agnes

45 years ago this June, a Gulf of Mexico storm evolved into a nasty tropical weather system that wreaked havoc all up and down the east coast of the US.  I was 9 years old at the time and I remember very well that weather during the early portion of our summer vacation.  Horses being led out of barns threatened by the rising creek that drained Silver Lake; the lake upon which our house was located.  (Ironically, we got very little water in our basement during Agnes!)  My parents' 1967 Chevy Impala flooded when parked down near Lewisberry.  Helping in Harrisburg removing mud from basements by wheel-barrowing debris up planks laid atop of the steps...Just so many memories of the impacts of Hurricane Agnes...and the Euro is hinting at a possible tropical development in the Gulf early next week...First a look back at Agnes in terms of the tropical rains...
The system essentially had a tremendous amount of overrunning precip here in PA and NY as cool dry air was attacked by this slug of tropical moisture.  A tremendous amount of rain fell over the Susquehanna watershed and that water had to flow past Harrisburg!  Take a gander...

The Walnut Street bridge used to be a one way auto bridge out of the city to the West Shore.  After Agnes, it became a footbridge only!
Now the track is was very different than where the Euro is hinting at a possible land-falling system...

Note where the Euro has a 40% probability of development next week...
And the total precip that the model is suggesting...follow the path of heavy rain from the Gulf into east TX...but from there...?

Also note in the graphic above the lack of precip here in south central PA.  But there will be a chance of us getting hit with a thunderstorm Sunday evening as a cold front will progress through the state in the early morning hours of Monday...A warm weekend followed by some pleasant O Canada air once again!
OK...gotta run.  But of course I'll leave you with a tune that might? be appropriate for our Gulf coast states at the very least sometime next week...

Smitty

AA:  Looking at possibly a tropical system forming in the gulf later next week.  As for here, just a chance of some heavier rains Sunday night into Monday as a cold front pushes across the state.  Definitely drying out from the last few days and the next several days...

Sunday, June 11, 2017

Oscillations and our Weather

As I sit here striking the keys with a slightly waning gibbous moon shining down upon me, I of course was thinking of the upcoming week of weather.  Again, if you want the cliff notes version, drop to the bottom of this post and peruse the AA I compose for my good buddy Timmy.  Otherwise, check out my reasoning for my beliefs...

Today, I want to focus on what I believe is the primary driver of the atmospheric engine...the Pacific Ocean.  Since water has greater density than air, water has a much greater influence in terms of distribution of heat energy across the planet.  And the greatest movement occurs in the equatorial Pacific.  Most, if not all of you reading this have heard of El Nino/La Nina...the warming and cooling of the Pacific Ocean.  Think of the Pacific basin as a big bathtub and the slow global sloshing of the water back and forth not too different than when you were a kid playing in your own little bathtub!  Here is the forecast of the ENSO (El Nino Southern Oscillation) from various models...


Most are predicting a slightly warmer (El Nino) Pacific in the upcoming months...here is the current Sea Surface Temps and from the recent past...note that since April, a slight cooling has occurred off the west coast of South America...this is normal.
But now, I want to share with y'all another lesser known oscillation which I believe also has a major impact on our wx here in the states.  The Madden Julian Oscillation or the MJO.  The MJO is essentially a rainfall pattern in the Indian and Pacific basins.  Monitoring the movement of these precip patterns, there seems to be a correlation to global wx events (SE Asia monsoons, flooding rains in the western states, arctic outbreaks...you get the picture...). Over the recent years, computers have correlated a "phase" of the MJO and the subsequent weather here in the US both in terms of temps and precip.  It is my belief that the temperature response is actually quite reliable.  With that said, here is the MJO forecast...note it is clearly moving into Phase 1 & 2!  Start at the green and follow with the dark gray shading...

So Smitty...what the heck does all of that mean?  Here is Phase 2 temps for the states focusing on May, June, July months...
Phase 2 shows a slight cool bias east of the Mississippi...and the modeling seems to agree that a cooling trend will occur after a brief stint of heat...normals for Harrisburg at this time of year are highs in the low-mid 80s and lows in low to mid 60s...
So it appears the atmospheric response once again to the MJO will correlate nicely here in the eastern US...time will tell,,,here is the surface map as of early Sunday morning...with a low to the north and the Bermuda High flexing its muscle, a warm to hot west to SW flow will result advecting heat to the east from the desert SW states...humidity will only slowly increase through the week...
But by Thursday, a big Canadian High will work its way across O Canada and push a cooler NE flow into our region here east of the Appalachians...take a look...
So why did I go over all of that?  I just wanted y'all to know that there is so much that goes into the weather prediction game that often goes completely unnoticed by the general public...and I love this stuff!  By the way, with a positive PNA, that too often causes a net cooling here in the east...Huh?  Take a look...
I just find all of this fascinating...and for those of you who made it this far...I'm sure you do too!  And good for you...and THANKS for reading!

Now for those of you who just like the song...here is a nice "Back and Forth" oscillation of two outstanding vocalists...enjoy!

And enjoy this brief heat wave; rest assured a cooling trend will occur shortly afterwards...(I think?!?)  Ha!

Smitty

AA:  Hot and dry through Wednesday with increasing humidity.  A good time to catch up with your mowing accounts!  Then moving into a cooler and somewhat damper time, but not too wet...here is the total precip for here in PA over the next 10 days...