Will Winter Go Out With A Bang?

Do not hold your breath if you are looking for 50 & 60-degree spring days. While the last week has been pleasant and has given us a taste of spring, it seems that was just an early April Fools joke from Mother Nature as winter looks to make a comeback later this week. 

Negative OLR anomalies, or wetter than normal conditions, are currently seen from the Dateline to Hawaii. These bursts of convection near the Dateline that propagate east is what is causing our MJO to enter enhanced phases. 

The green contours, again centered near the Dateline to Hawaii, show where precipitation is favorable to develop. In this case, we're seeing some strong cyclones in the Tropical Pacific along with some enhanced convection along the Equator. 

The current observations explained above is the reason why we are seeing the MJO amplify into phases 7, 8, and possibly 1. What does this mean for the rest of March into April? We should continue seeing persistent riding over the EPO and PNA regions. In turn, this should keep our area either at normal or below normal from a temperature standpoint. 

MJO phase 8 composite's for the month of March show a large Aleutian trough helping to promote a -EPO/+PNA. Also, there is a signal for a -NAO/-AO couplet. 

The GFS by the end of this week shows a split-flow over the west with the aforementioned signals in place. However, the core of the negative height anomalies look to remain to our north. The northern stream energies are disorganized which is keeping the trough stretched out and heights along the east coast flat. In this type of set-up, you will not see any east coast storms trying to come up the coast. 

Fast forward to the 22nd of March and this set-up is starting to look a little more organized. There is clear amplification in the trough but it needs more separation with the upper low south of Greenland. If the models can retrograde the western ridge a bit and help position the trough axis a bit west of where it's currently shown, that could go a long way in getting a coastal storm to pop off our coast.

At the surface, the 12z EURO is trying to show a storm in the 21st-22nd time period. With favorable looking teleconnections, namely the NAO and MJO, there is a high likelihood of a storm developing at that time. 

The 00z GFS is also trying to hint at something in this time frame. 

It's important to keep in mind that by late March the average temp. for Central Park is between 46-49 degrees F. So even temp. departures 10 degrees below normal will still keep the area above freezing. Whatever storm comes our way, we will need an impressive cold air source to accompany it and for the system itself to be as potent as possible to manufacture some of its own cold air and force dynamic cooling. Given that we are still in the 7-10 day time frame, I would not even look at the surface right now rather pay closer attention to how the upper levels trend. 

WHAT TO WATCH:

1. 21st-26th time frame for 1-2 storms. Both of these systems have the potential to bring wintry weather to the area, however, it will be extremely difficult to do given the time of year. A lot needs to go our way. 
• Can the -NAO help slow down the flow and keep the ridge axis positioned favorably in the west, while also helping to develop a coastal storm? 
• Will there be enough cold air for the storm to work with? We need to see better trough amplification on the models moving forward. 
• Will we see a wave eject out of the STJ? We need to give the northern branch something to work with out of the south or else whatever storm comes our way will remain weak (likely too warm). 
2. The general 18th-31st time period should see mainly normal to below normal temps. due to the blocking developing in the Atlantic & Pacific. Remember, below normal this time of year is probably temps. in the upper 30's to low 40's. I am not confident in anything colder than that during the day, just yet. 

CONFIDENCE:

Personally, I thought the upper air pattern looked better a few days ago than it does right now. The trough being advertised does not impress me and the lack of STJ interaction is a little concerning if you're looking for a winter weather event. Therefore, I am at low confidence for a winter storm in the 21st-26th time frame but high confidence for a coastal to develop. Those N&W of I-95 are in a much better spot to see wintry weather the end of this month. 

We'll see what happens...still quite some time to go. Will be monitoring the H5 pattern closely in the meantime. 

Have a great St. Patty's Day...if that's your thing. 

-Francesco Paparatto 

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