Thursday, September 22, 2016

Pumkin Spice Cold Front

Friday morning update... No surprise, the GFS is now looking like the Euro at 500mb.   The super cool air, I warned about forecasting, looks less likely.  With that said, IT WILL TURN SIGNIFICANTLY COOLER.  However, the temperatures forecast by the GFS will likely turn out to be wrong.  Look at the two models and their latest versions.

The GFS midday Monday shows the trough moving into the Great Lakes.  This helps drive a cold front through the state.  But look how different it looks in the southwest U.S.  A piece is left behind which is different than previous runs.

The Euro at the same time looks very close to the GFS now.  It's worth noting the Euro has been fairly consistent which is another reason why I have liked this model.  It's not run 4 times a day and comes up with 4 different solutions.

The GFS numbers now have temperature highs in the upper 70s Monday and Tuesday compared to previous runs which had it in the 50s and 60s.  The Euro is also a bit slower pushing the front through the state.  This brings in big differences in the forecast for Monday.  The Euro says we go into the 90s Monday which the GFS has 70s.  However, by Tuesday, both show a better feeling air mass across much of the state.

So there are still challenges in the forecast, but I would continue to hedge my bets on the slower Euro, BUT continue to hope the GFS can beat it only because I want cooler weather faster. LOL.

Also, I don't expect the cooler air to last by a few days.  It will warm up again, maybe not into the 90s, but the cooler air will modify.

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FINALLY,  a change in the weather!  We're getting a turn to fall, but there are two questions that can't be answered yet.  How cool and how long will it last?  The two main models (GFS and Euro) continue to show differences, but both models do cool us down significantly. As I always say in the long range, I would hang my hat more on the Euro than the GFS in most situations and this is no different.

Some of the maps are courtesy of Weatherbell.com and EuroWx.com 

At 500mb, about 20K feet up, we see significant difference between the models. You can clearly see the Euro cuts off a low over the southwestern United States and leaves it behind with the main trough (all the red) moving through the Great Lakes.  That will help drive the front into the state.  This would lead to cooler temperatures, but not as cool as the GFS which brings the whole trough through.

The GFS brings the whole thing though Monday into Tuesday.  See that big area of red north of Arkansas?  Nothing is left behind. This solution would send a surge of VERY cool air into the state.   However, at this time, I think it would be best to consider this a bit too strong.

Just for fun, the GFS temperatures behind the front Tuesday at 1PM are only in the 50s.  This is due to the colder push of air behind the front, but more importantly, because of cloud cover.
The GFS Tuesday at 1PM, shows extensive cloud cover keeping temperatures quite cool.  Again, at this time, I would hedge my bets against this at this time.

The Euro shows highs in the 60s north, 70s central, and 80s south Tuesday.  This looks more realistic.

In summary, it will cool down!  The question is, does the Euro or GFS have the right idea?  Many times, it's something in between, but I would bet it will be closer to the Euro.

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