Forecasting the Timing of the Cold Front

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By Kevin Arnone on November 12, 2012, 5:30pm Last modified: November 13, 2012, 11:50am

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By looking at a few weather maps and some grid data I can put a good estimate on when I believe the Cold Front will come through our region on Tuesday. 

First map I want to show you is GFS Grid data from 12z on Monday. 

 

 Highlighted in yellow is data from 6z Tuesday until 6z Wednesday.  Which is 1 am Tuesday to 1 am Wednesday.  Highlighted in red is where I believe the main focus is when trying to forecast when the front will pass through.  9z Tuesday or 4 am the temperature at the surface is forecasted to be 58 degrees F, winds are SSW. The winds are very important when forecasting for a front.  A good indication of when a front goes through is wind direction.  As you can see from the data, Tuesday 15z or 10 am the temperature at the surface is forecasted to be 47 degrees F and winds NNW.  An 11-degree drop in 6 hours, now you and I both know for it to be colder at 10 am then 4 am, some weather phenomenon had to occur.

 OK now I want to show you a weather model.  This is the GFS 12Z run, this map is valid for Tuesday 00z which is Monday night 7 pm.  Let me explain what this map is showing.  The green blobs are precipitation. I am not going to get into amounts or which form, just know that green represents precip. The black lines indicate surface pressure. We are located between 1024 and 1028 hpa.  Just to give you an example, during Sandy we were in the low 970’s.  Quite a difference.  The red arrows I drew in indicate surface wind direction.  As you can see from this map, we are forecasted to have S winds.  Now if we compare to the grid data at 00Z on Tuesday we can see that we do have S winds Forecasted (See I’m not lying).  The blue line without the triangles is the temperature at 850 mb or around 5,000 feet high (This height always changes).  That is a great indication of when the cold air from aloft will come into our region. The blue line with the triangles is where I believe the cold front will be located at that time which is 7pm Monday. (I added that, forecasting isn’t that easy.LOL)

OK Now let’s justify an answer.  Below is the GFS 12Z run. However this map is valid for Tuesday 12Z which is Tuesday morning at 7 AM.  Now we already know what this map is showing, we can see that the winds have shifted NNW instead of SSW.  A very good indication that the front has gone through. 

Now we can’t just go off one model right? This picture is the NAM Grid data from 12z Monday. Highlighted in red is where I believe the main focus is when trying to forecast when the front will pass through.  6z Tuesday or 1 am the temperature at the surface is forecasted to be 61.4 degrees F, winds are SSE. The winds are very important when forecasting for a front.  A good indication of when a front goes through is wind direction.  As you can see from the data, Tuesday 18z or 1 PM the temperature at the surface is forecasted to be 45.1 degrees F and winds NNW.  A 16-degree drop in 6 hours.

Both models seem to be fairly consistent. If anything I would suggest the NAM brings the front through just a tad slower.  But I feel as if between the hours of 6AM and 9 AM the Front will passing CT. 

VISIT MY WEBSITE http://ctforecast4u.com/

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Kevin Arnone

Town: Milford, CT  

Reporting for WXedge since February 2012.

Articles: 127

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