•One more dry and mild day tomorrow
•Showers move in by overnight tomorrow
•Watching the mid week period for potential for some unsettled weather, probability for anything more than some nuisance snow or rain is low but if your interested in the “what if” read the blog below
•Colder weather returns by Thursday and lasts into next week
Details/Some Thinking Out Loud/Lesson-
This week will only perpetuate the roller coaster weather we have been experiencing , this week will start out dry and sunny tomorrow with above average temps in the upper forties. Tomorrow night showers move in late and linger into Tuesday, by Wednesday we watch for an area of low pressure that may try to develop off the coast. As of now, most of the models are not seeing the potential, but the pattern does support the possibility, so the Wednesday into Thursday time frame will be monitored.
One thing that has been a constant is the return of colder temperatures in the wake of this system, by Friday into next week temps will return to more seasonable levels and eventually back to below average for next week. As stated earlier, we will go from 40’s and showers to temps back into the 20’s by the end of the week.
Questions remain as to what our weather pattern will bring for the remainder of the month, at the moment it appears we will return to a colder pattern, although not as cold as the beginning of the month, the storm track will depend on other features in the atmosphere. One of the key factors we look at is the North Atlantic Oscillation (NAO) which in a negative phase, creates blocking in the atmosphere and causes the jet stream to buckle and storm to travel up the coast, in a positive phase the pattern becomes more progressive and storms tend to travel west to east across the country without supporting big east coast storms.
While not impossible to get a storm on the East coast with a positive NAO, it certainly lessens the available ingredients needed to foster a major storm. We are currently in a negative NAO pattern which looks to linger till about the 20th before turning into a more positive phase, it is because of this negative phase that the mid week storm tracking off shore seems like a bit of a funky scenario. If a storm does in fact form next week, it will likely be somewhere along the coast, its strength is something that is also uncertain, although it looks like a minimal storm at the moment . The Global Forecast System (GFS) has nothing more than a weak wave of energy that passes harmlessly to our southeast, the Canadian Model has a weak storm, close the coast with temps to warm for all snow.
This is where the forecasting comes into play, all three models show some sort of energy along the coast at around the same time, but each model is handling how it comes together a bit differently. Below is the latest North Atlantic Oscillation (NAO) forecast, remember that a negative phase means that there is blocking (High Pressure) in the North Atlantic .
Solid blue line is observed NAO and the circles are the forecasted NAO phase, above the zero line is a positive NAO and below is Negative, so as you can see we are in a negative phase that promotes blocking and drives any storms that develop up the coast.
Next question is how do we know if blocking is in place? We can look at another model to determine that. Below is the European Model showing high and low pressure, basically the higher the positive number equates to higher the pressure, see that area of red,white, and purple in the North Atlantic? That is the blocking high pressure, meaning any storm that forms along the coast is forced to track closer to the coast and away from the high pressure. Now your probably wondering, what is the area of green near the Carolinas? Glad you asked, that’s our area of interest and in the next image you will see that the European model forms an area of low pressure in this region, something that not all of the models support, and not necessarily what will occur.
Okay so you learned about the NAO, and thanks to these great graphics you can clearly see the high pressure set up to our NE, picture that area of blocking as a force field that will deflect any area of low pressure, causing it to travel the path of least resistance, to avoid. Now lets look at the storm on the Euro model, we have highlighted its forecasted track with a black arrow, keep in mind this forecasted track goes against what this storm should do with the current setup, the yellow line is the track that you would expect a storm to follow with such strong blocking to the NE.
Well there you have it, just some of the things a weather nerd looks at on the weekend, at this point the probability of a storm is very low, but its important not to ignore certain indicators and this is also an example of why when forecasting you should not take these models verbatim. The joy in forecasting is that by tomorrow morning there may not even be a low pressure off the coast of the Carolinas at all, and each one of these key strokes would have been about something that never really existed or had a shot of coming to fruition.Never the less, I will be doing it again tomorrow, and the next day, and the next day, because it’s the science of it all, the chase that inspires me. If at the very least, whoever took the time to read this entire post has learned a bit about the NAO and about forecasting, then that’s rewarding in itself.