Wednesday, August 24, 2016

End of the Work Week Forecast

Its Wednesday and one of the last weekends of summer is rapidly approaching.  Here is the latest for the next several days.  After the general forecast I will discuss the Atlantic tropics.  

General Overview
High pressure remained in control today for more warm and beautiful weather.  Tomorrow the high is offshore and winds will increase out of the southwest ahead of a cold front.
WPC Surface forecast Thursday 2 PM 
Monday dew points were around 50.  Tuesday they crept up to 55 and today they are around 60. Tomorrow we inch a few more degrees higher into the mid 60's,
18z NAM hires 2 m dew points Thursday 5 PM (image Tropical Tidbits)
The good news is we stay dry during the daylight and evening hours Thursday.  Max temps are 85-90 across Southern New England.
NWS Max temps Thursday (Image Weatherbell)
Heading to the beach?  Surf will be a bit higher tomorrow thanks to an increasing southwest wind.  Moderate rip currents are likely for the beaches north of Boston.
NWS Boston Surf Zone forecast 
These surf conditions will expand to the south for Friday.  Overnight Thursday into Friday the cold front sweeps through the region.  Isolated showers and thunderstorms will break out ahead of the front after midnight Thursday through Friday 3 PM.
WPC Surface Forecast Friday 8 AM
Its a good thing the front does clear by late afternoon as dew points will crank into the low 70's.
18z NAM hires 2 m dew points Friday 2 PM (Image Tropical Tidbits)
Any showers will keep temps down a bit from Thursday but when the sun is shining temps will max out in the mid to upper 80s.  The dew points will make it feel like the low 90s
NWS Max temps Friday (image Weatherbell)
I'm not expecting much in the way of rainfall from any of the storms.  Tomorrow I will post my thoughts on timing.  By the weekend dew points drop as well as temperatures.  Expect low 80's with dew points in the upper 50's on Saturday with sunny skies.  Repeat for sunny although a few stray clouds may pop up.  

Tropical Discussion
Tropical Storm Gaston is experiencing some wind shear so it has yet to become a Hurricane.  I thought it would have by now but it looks like it will have to wait a few days.  First here is the Atlantic surface map.
OPC Tropical Atlantic Surface Analysis
Now here is an infrared satellite image with the current major players.
NOAA GOES-East infrared satellite 615 PM 
Now the same image with the water vapor satellite.  Notice the counter clockwise flow around the upper low heading right into Gaston's path.  This is wind shear.  The upper level winds are strong enough to displace the thunderstorms around Gaston to the east of the center.  In order for a hurricane to be strong the thunderstorms need to be over the top of the center.  Never the less the only impact from Gaston will be strong waves if it can get its act together in a few days because he will track out to sea.
NOAA GOES East Water Vapor Satellite 
Part of that shear looks to be impacting the disturbance near Puerto Rico called 99 L which just means it is a wave or tropical low to be watched.  This is the low that will have a chance to develop into a tropical storm once it clears Hispaniola.  Of course the wave has to survive the trek near the mountainous island (home of Haiti and the Dominican Republic).   Given that a low level center has not formed yet I think it will.  So the 120 hour forecast shows a cone like this.
NHC 120 hour cyclone forecast
By Saturday at 2 PM I expect a storm to be gaining strength in the Bahama's sort of like the recent North American Model run shows.
18z NAM radar and precip 2 PM Saturday (image Tropical Tidbits)
That's about all the actual surface forecasts I will commit to at this point.  But now I think the storm does go into South Florida as a strong Tropical Storm or a weak Hurricane.  I'm hesitant to post what I'm about to say so I will toss about a disclaimer.  I am NOT FORECASTING HURRICANE KATRINA.  However it does remind me of Katrina's first landfall in South Florida as a Category 1 Hurricane.  People forget that Katrina hit near Miami first before it became the monster it did in the Gulf of Mexico.  The track and intensity looks similar to the first part of Katrina, not the second.  Now for the next part of the storm I think it is shifted into the Gulf of Mexico.  High pressure will be in control near the Mid Atlantic coast which will force the storm west.
12z EPS 500 mb height anomaly (image Tropical Tidbits)
After that a trough will move through the Central US leaving a piece behind to capture whatever tropical system is there.  It will be pulled north into the US Gulf Coast.  I can't speculate on strength yet so I won't.  Then by the end of next week the moisture from the system may end up in the Northeast but that's a ways away.  

South Central Florida begins to feel the burnt of the storm Sunday afternoon through Monday.  The Central Gulf Coast will be feel impacts Tuesday and Wednesday if it is able to emerge into the Gulf and not stay over land in Florida.  This is all assuming it forms and doesn't get ripped apart in the Caribbean.  

I'll post another update tomorrow.

-Zack Green

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