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How Much Rain Are We Talking About On Derby Day?

The path our storm system will take late this week and early next week is becoming a lot more clear today. The EURO has all but abandoned it's solution and come on board with the GFS style solution. This solidifies the rain chances I gave you yesterday and we can dig in a bit more.


Differences Between EURO and GFS Computer Models Now


The EURO solution that broke down the blocking pattern too quickly is gone. While I heavily discounted it yesterday, it is nice to see it has throw it out as well. Here are the storm tracks for this storm system through early next week on the GFS and EURO now. Notice how close they are.


AdvanceTrak 3


How Much Rain?


The good news is the track of the storm is more clear, but the bad news it exactly how much falls and when it still tough. It appears very likely that we will see rain on Derby day and it could be heavy at times. With that said, I am not willing to say whether the morning or afternoon is most likely yet. What you notice is quite a difference in how much rain will fall through The Kentucky Derby 139.


NAM Rainfall Through 7 PM Saturday

Notice the NAM is showing about 1" of rain for Louisville on Saturday through the Kentucky Derby.





GFS Rainfall Through 7 PM Saturday

Notice the GFS shows just a bit under 1" for Louisville through 7 pm on Saturday.





EURO Rainfall Through 7 PM Saturday

Notice the EURO is still slower and shows less rain through 7 PM on Saturday and that would obviously have a bit impact on making Derby drier.




The forecasters at WPC ard siding more with GFS style solution. They are pushing out about 1" - 1.25" of rain on Derby Day and that is obviously not what track goers want to see.




Rainfall Totals From This System


Where we are not seeing differences is in the rainfall totals from this system. The GFS and EURO are both pushing out a lot of rain for our area from Friday through Tuesday. Take a look at some of the rainfall totals and keep in mind the timestamp / name of the computer model are located on the top right of each image.






WPC is basically throwing down the gauntlet on this storm system. They show nearly 3" of rain area-wide by Tuesday night.





My Thoughts On This Storm...


The fact is the GFS has been the most reliable computer model when dealing with this blocking pattern. It tends to be a fairly good model with these patterns when they are over land. The EURO dumped it's oddball solution today and now is on-board with the details from the GFS. This increases confidence in this weather pattern.


The problem is this doesn't mean we know the exact timing of the storm yet. This will be a slow and erratic moving storm system. I feel the rain chance needs to be high on Derby day, but the timeline is still foggy. The NAM brings in heavy rain early on Derby day, then goes to showers in the afternoon. The GFS brings in the heavier stuff in the afternoon and could mean a washout for track day. The EURO brings in the rain late Saturday continues to fall through Tuesday. I will be ironing out the details of "when" it will rain in the next 24 hours or so. Regardless I strongly suggest a "poncho" or raincoat in a bag for Derby Day. It is worth while insurance!


One thing seems certain and that is we will get a lot of rain from this system. Most of the data is consistent in producing about 3" of rain from Saturday through Tuesday. Get ready for lots of rain and some cooler temperatures again!





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Marc- do you think we are done with the frosts? I have plants to put out.

Candace, I would say after this storm then you are safer. Frost free is mid May.

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