Showers Possible This PM, Tropical Storm Bill Forms

While we would like to sun the today, leftover clouds from yesterday will help to limit the potential for thunderstorms this afternoon.  The big weather story is in Texas where Tropical Storm Bill formed last night and will bring heavy rain and gusty winds to the Central/Northern Texas coast.  By Sunday the remnants of Bill may bring periods of rain to Southern New England.  Until then we see mostly seasonable weather, with a chance of storms Thursday night.

Here is the 5 am surface analysis from the Weather Prediction Center (WPC)
WPC surface analysis 5 am
The front south of New England has yet to lift north through the region.  It will as the trailing cold front moves east.  Here are the temperatures as of 7 am
7 am 2 m RTMA temperatures (image weatherbell)
By 8 PM tonight the trailing front will have swept offshore.
WPC Surface forecast 8 PM Tuesday
Before this front clears the region high temperatures should rise to around 80.
11z HRRR 2 m temps valid 2 PM (image weatherbell)
Some showers or weak thunderstorms are possible as the cold front moves through.  Lightning is always dangerous but I am not expecting hail or severe wind. 
11z HRRR Simulated Radar snapshot 6 PM (image weatherbell)
The SPC threat is much less than 2 days ago. 
Day 1 SPC severe weather outlook
Here is Bill on the IR rainbow satellite
GOES_East Rainbow IR 745 am (NOAA)
The projected track curves the storm north into Oklahoma and then to the northeast into the Ohio Valley.  Interestingly enough the storm may hold itself together for awhile as it dumps a swath of heavy rain from Texas to Ohio.
NHC official track for Bill
Why the storm will hold together is ultimately unclear but there are several theories.  The truth is probably a blend of all three.  A lot of rain has already fallen in Texas and Oklahoma this spring so the soil is very moist.  A weak storm like Bill will be able to draw energy from this.  See this piece from Dr. Marshall Shepherd.  At the same time Bill is getting better organized as it makes it way to the coast so its core is stronger.  Also the storm will have favorable upper atmosphere dynamics to work with.  Ridges of high pressure will be present on either side of the system.
06z NAM 500 mb vorticity Wed 8 am (image NCEP)
Social media has turned meteorology into high school with grown ups arguing over whose theory is correct.  Few choose to step back and say "maybe we both are correct."  The bottom line is that while its scientifically interesting that the storm will be able to hold some strength well inland, the impacts are the same- RAIN.  Here are the 7 day totals
WPC 7 day rainfall estimates
I'm still working out how this will impact New England.  My guess is that it will interact with a cold front and we end up with more precipitation on Sunday/Monday than the WPC anticipates at the moment. 

Maybe some storms Thursday night but the rest of the week looks good, as do Friday/Saturday.  Saturday partly cloudy high around 80.

Thanks for reading
-Zack Green


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