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Wednesday, February 26, 2014

Monday's Potential Storm

For forecast details about the next 4 days, check my previous post.  

Great summary from NWS Boston
There is a lot of chatter about a big winter storm.  5 days ago a coastal storm was possible today (Wednesday) but the ingredients didn't come together.  So a lot can change when looking out to Monday’s potential storm.  I know it’s not fun to hear a meteorologist say…'we don’t know yet'.  But at least I can give you the reason why.

The storm in question is located over the Pacific Ocean.  Computer models work by taking a combination of weather observations and satellite data to get a picture of what’s going on in the atmosphere. But observations from buoys are more sparse than weather stations on land.  While computer models will attempt to fill in the gaps, it’s not always perfect.  We call this poor sampling.  And my teacher in Meteo 201 used to say “garbage in, garbage out”.  If the data used to feed computer models is wrong (or unavailable) the resulting forecast will be wrong. Errors amplify with time. This is one of the reasons why we send airplanes into hurricanes to gather data.   Until this storm moves over land (and that will not happen until Friday) the forecast remains highly uncertain. 

This storm will go on to produce much needed heavy rain Friday – Saturday for areas on the west coast that are in extreme to exceptional drought. The Plains and Midwest will be up next with severe weather and heavy snow Sunday.  On Monday, it’s the east coast’s turn.  But as usual, the exact track and strength of the storm will determine the impact. The GFS is colder with significant, plowable snow for New England.
The GFS (one of the major american computer models) for
Monday afternoon. This model is colder and shows all snow
Monday with snow showers lingering into Tuesday & Wednesday

The European model is warmer with snow changing over to a mix, then back to snow.  Neither model is going to be exactly right at this time (remember: garbage in, garbage out) but for what it’s worth the GFS has a better track record this year.

The ECMWF or "European" computer model for Monday afternoon.
This model is warmer and shows snow changing to a mix then back to snow.
For now, some impact from this storm is increasingly likely.  But snow totals, precipitation type and intensity are to be determined. 

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