Friday, July 4, 2014

Significant Flood Situation in SE MA Tonight

There have been reports of 3-5" of rain in the New Bedford area already today as Hurricane Arthur races Northeast towards the Canadian Maritime.  An additional 3-6+ inches of rain is likely in Bristol and Plymouth counties which will lead to a significant flooding event in that portion of the state.  
NWS Northeast Regional Radar
That band of yellow and red along the S MA coast has been nearly stationary all afternoon.  Flash Flood Watches are up for most of the state, with warnings in effect for the South Coast
NWS Boston Hazards
Tropical Storm Warnings remain in effect for the Cape and Islands with a Hurricane Warning for the waters offshore.  Here is the latest advisory from the Hurricane Center
NHC 2 PM Hurricane Arthur Advisory
The winds are not going to be a major deal outside of the Cape, but a few gusts over Tropical Storm force are possible across Eastern MA.  Gusts up to 60 are possible in Nantucket/Outer Cape.  The Upper Cape/Vineyard are looking at 45-55 in general.  The major story will be the rain.  The WPC has issued a precipitation discussion for Southeast New England and it is a not a pretty outlook
WPC MPD 
Basically a front is stalled out in Eastern MA.  While this front contributed to keeping Arthur offshore, it is setting the stage for a flood event.  Here is the local surface analysis
WPC 2 PM Surface Analysis
As I type this the NWS has upgraded to Major Flood Emergency in New Bedford.  Flash flooding is likely in other areas as the rainfall rates increase.  Do not drive through a flooded roadway.  The rain ends around midnight west to east.  Rest of the weekend is great.

-Zack Green




Thursday, July 3, 2014

Hurricane Arthur Will Bring Rain to SNE

We officially have our first Hurricane of the 2014 North Atlantic Hurricane Season.  Arthur has been upgraded by the National Hurricane Center as of 5 am.  The storm will still track south and east of the Cape, but some heavy rain is expected tomorrow.  Tropical Storm force winds are likely on the Outer Cape/Islands. 

Overview
The 5 AM advisory/track/warnings

5 am NHC Advisory Hurricane Arthur
A cold front is slowly moving east towards the coast.

WPC 5 am Surface Analysis
The line of thunderstorms died out as it entered Worcester County yesterday.  The same areas that saw some severe weather and flash flooding are expected to again today. 

SPC Day 1 Outlook
Heavy rain, gusty winds, and frequent lightning will be the primary hazards but hail and a brief tornado are not impossible back in NY/VT.  In anticipation of heavy rain there are flash flood watches up for many places in the interior Northeast (in green). 

NWS Eastern Region HQ hazards Page
For today there will be rounds of showers/thunderstorms throughout SNE.  Some places will stay completely dry, others will be hit multiple times.  Keep an eye to the sky.  Boston should be ok for the fireworks tonight.

Friday
Any overnight rain ends early enough that the first half of Friday is dry, albeit muggy.  Around early afternoon the rain from Arthur should arrive.

06z NAM hires Simulated Radar 2 PM Fri (image Weatherbell)
The heaviest winds are from about 5 PM-3 AM for SE MA.  I can't rule out a few stronger gusts in Central MA/E CT/N RI if a strong rain band works north but this is a low probability.  Here is the 3 day rain forecast from the WPC

WPC 3-day rainfall outlook
Worcester and Boston are looking at ~1.75", with  ~2" in Providence, Brockton, ~2.5 in Plymouth, Hyannis.  3"+ likely Outer Cape/Islands.  This is not a major storm for New England, in fact many recent Nor'Easters have had a greater impact.  However it is distruptive.  The good news is after this clears high pressure builds for the rest of the weekend. 

-Zack Green


Wednesday, July 2, 2014

Tropical Storm Arthur Update (UPDATE 206 PM)

A severe thunderstorm watch has been posted for much of Southern New England
STSW 386 (SPC)
Most of the thunderstorm activity will be north and west of Hartford-Worcester-Portsmouth.  Here is the short range high resolution computer simulation for 4 PM

16z HRRR simulated radar valid 4 PM (image weatherbell)
The action should wane this evening before firing back up tomorrow.  Our buddy Arthur is looking better this afternoon

NOAA  GOES_Tropical Floater visible satellite 145 PM
He may be a Hurricane by the end of the day.  The latest EURO computer model just arrived and is showing significant rainfall in Eastern New England.  More tonight/tomorrow morning.
________________________________________________________________________________
Good Morning.  As expected Tropical Depression 1 was named Tropical Storm Arthur yesterday at 11 am.  Since that time the pressure has fallen and winds have increased.  The storm is still fighting dry air
GOES_floater Water Vapor Loop (NOAA)
Notice the dark colors north of the system.  That is dry air that is killing some of the thunderstorm growth in the center of the storm.  We do see thunderstorms making a comeback in more recent images.

NWS Southeast Regional Radar
The National Hurricane Center has been consistent with the track.  It should pass either right over or just to the east of the Outer Banks before racing south and east of the Cape

NHC Forecast track/intensity, watches & warnings
Most guidance shifted slightly west overnight.  It still appears rounds of tropical downpours are likely tonight through Friday with a chance for stronger bands later Friday night as Arthur passes.  As of now I recommend keeping plans North and West of the Pike.  I would be prepared to deal with Tropical Storm conditions in SE MA/RI.  A clear picture will emerge today as to where any potential heavy rain sets up. 

Here is the WPC 5-day outlook

WPC 5 day precip outlook
It does appear the heaviest rains will be in the Mid-Atlantic and up through Albany as well as the Cape/Islands.

WPC Surface Forecast Thursday 8 PM
Again tropical systems are difficult for the models to handle.  There is a 10-20% chance much of Southern New England sees tropical storm force winds which could bring down some trees/power lines.  That's a 80-90% chance it won't happen, but something to keep an eye on. 

Have a good day
-Zack

Tuesday, July 1, 2014

1st Tropical System to Impact July 4th Plans

A tropical depression has formed off the Florida coast and is forecast to strengthen into a Tropical Storm/Hurricane by the end of the week.  It will impact the 4th of July holiday up and down the East Coast.
NOAA GOES-East IR rainbow satellite loop
Currently winds are 35 mph but the storm is expected to be named Arthur later today
NHC 5 am advisory/5 day track
By Friday Night/Saturday morning a hurricane may be passing south and east of the Cape.  Right now the storm is not moving much.  It will begin to move in response to a cold front pushing east out of the Midwest

5 am Surface Analysis (WPC)
This cold front/tropical interaction will create interesting weather for the next several days.  First of all, severe weather is likely in parts of the Northeast tomorrow, though not for Southeastern New England

SPC Day 2 Severe Weather Outlook
Overnight Wednesday into Thursday is when Southern New England may get into the severe action.  Of greater concern is the potential interaction between the tropical system and this front.  The NAM low res has precipitable water amounts of 2"

06z NAM op precipitable water Thurs 11 am (image weatherbell)
As of now it appears at least an inch of rain will fall across much of the area in the next 5 days.  There will be jackpot areas of much more rain but its tough to tell where these will be right now.

WPC 5 day precip forecast
Guidance will help today as the storm gets a bit stronger and starts to move slowly northward.   It is important to remember that sea surface temperatures are above normal along the east coast.  This system is small so strengthening is likely.  While unlikely, a more westerly track would have big time implications for coastal Southern New England.  Even with a track south and east high waves and rip currents will effect beaches this weekend.

OSPO SSTA 6.30.14
With a weak El Nino likely to develop this summer, most of the tropical action will be in close to the United States.  One can see the Eastern Gulf and SW-Central Atlantic as prime areas for development this season.  More to come. 

Rain Ending As Snow For The Blackstone Valley Tuesday

Tomorrow is Tuesday and surprise, surprise...precipitation is in the forecast.  WBZ went back and found that there has been measurable preci...