Good morning and happy first day of Meteorological Fall as we get a visit from the remnants of Ida. This will be a significant flooding event for parts of the Northeast which I’ve been hinting about on my past 2 posts. Many areas hit hard from the remnants of Henri and Fred are in the crosshairs again. However, the silver lining will be a cooler and refreshing airmass that follows which I’ll address in a bit. Let’s go over what to expect, the timing, and locations.
Follow the Green Brick Road….
As you can see above the wide swath of green from the Tennessee valley, covering Balt/DC, central/east PA, all of NJ, NYC and LI, Hudson Valley, CT, RI, SE MA and the Cape, are all under a Flash Flood Watch. Ida’s train of rain intersects and rides along a frontal boundary, carrying and dumping a tremendous amount of tropical moisture. It also intersects with a piece of energy to the north which dramatically enhances precipitation. Besides widespread flash flooding, especially in the usual prone flood zones, I can’t rule out power outages due to moderate to damaging wind gusts (especially along coastal sections). Isolated tornado watches are possible (especially near Delmarva, south to central NJ, NYC, LI, SE CT and the Cape), and lastly bonker bolts and boomers with some hail at times. My best advice at this point is if your basement floods on even modest rainstorms, then I strongly advise bringing valuable items upstairs, check your sump pump and drains, and avoid driving though any flooded streets.
Let’s get down to what to expect and when. What has been fascinating to watch is where boundary sets up. Models have been playing the back and forth jog by 50-100 miles, yet have been trending north the past few runs suggesting the northern cutoff line with higher rain totals move into the upper Hudson Valley, N MA and into S VT and the Seacoast. Also there will be some narrow bands across central PA between I76/I78 to I80, Hudson Valley, W CT, and potentially other spots, which have the capability of producing over 6”, and in a short period of time, hence flash flooding. Rain rates will produce 1-3″ per hour. All in, this is a 6 to 8 hour event for the Northeast. These are approximate ranges for rainfall totals along with start and end times:
Balt/DC: Avoids the worst part of storm. Scattered showers later tonight into tomorrow, ending Wednesday night. 1-3”
C/N NJ: I78 on north, 3-6”, with isolated higher amounts. Expect off and on showers in morning with a break in the action in the late afternoon. The main line moves in between 6-8pm and increases in intensity before tapering off around midnight. Wind gusts of 30-40 mph leading to isolated down trees limbs and power outages
SENJ: nil-2”, sharp cutoff for flooding downpours. Higher risk of t-storms and isolated tornado, from later in the evening.
PA: Bullseye potential for highest rainfall totals in a narrow band from C PA on east from I76/I78 north to I80. Possible 5-10” from mid afternoon thru late evening hours.
NYC to LI: 3-6”, off and on showers throughout the day, becoming heavy between 8/10pm before ending well before daybreak.
Lower Hudson Valley: 3-6” (some of those bands I mentioned are possible in this area, producing some 6”+ amounts), between 9pm and 12am, tapering off while your sleeping. Also some solid wind gusts, leading to isolated power outages.
CT: 3-6”Heavy rainfall moves in between 9pm and 12pm along with strong to damaging wind gusts of 40mph (poss higher gusts). While it may not seem like those gusts are that strong, given how saturated the ground is, it doesn’t take much to knock down trees. This will create the potential for high number of power outages. So worst case, be sure to charge phones, and electronics. PLEASE move cars if possible away from any trees!
MA: 2-5”, similar timing as CT, tougher forecast depending on where the sharp gradient falls. The latest runs have been trending north putting MA in the higher total range. Once off shore, there’s a chance winds really pick up for brief period off the tip of LI, the Cape and Seacoast. 40-60mph gust are possible. See above NAM model for possible wind gusts.
S NH towards the Seacoast: The northern trend in the models drive 2-4”. Showers move in during the afternoon, becoming more intense around midnight, ending by daybreak Thursday. Flash Flood Watches were issued for S NH this morning as models trended further north.
Once the remnants of Ida depart for good, temperatures across the Northeast on Thursday afternoon will be in the 70s with an invigorating airmass. Skies clear with a possible stunning sunset on the table. Open the windows over the next few nights as we finally get rid of this lingering triple H’s (hazy hot and humid for those who are new here). Daytime highs will top out in the mid to upper 70s for the entire Labor Day weekend along with mostly sunny skies. Aside from a risk of a shower Sunday afternoon/evening, overall it’s a refreshing dry early Fall type weather. Next chance of rain is not until the middle of next week.
There is action in the Atlantic with a tropical depression off the African coast moving WNW. This will be larger than life Larry which will explode to a Major Hurricane in a short period of time. However, at this point its eventual track recurves North to NE and no threat the US. If you were wondering what happened to the K storm, Kate became a tropical storm Monday only to fizzle back to a depression yesterday and is no threat to land. There’s a hint of a tropical storm in the SW Gulf 10 to 14 days from now but nothing concrete at this time. Look for this half time to end the middle of September as the Atlantic awakens for a potential active second half with the East Coast yet again in the crosshairs.
That’s it for now. Be sure to over prepare for those with flood prone basements. Keep your eyes on the sky tomorrow afternoon and evening in the tornado risk areas. I will be live tracking radar throughout the storm on Twitter. For those who want up to minute warnings, usually ahead of your point and clicks and phone alerts, be sure to turn on your Twitter notifications for my account. IF there are any major changes to my above forecast, I’ll be sure to send out the details. And as always, remember weather never sleeps!
Thanks for the BaltDC forecast!
Of course!
Just a quick note, in the last paragraph I meant to say, keep your eyes on the sky “TODAY”.
Also for CT: I meant to say, heavy rainfall moves in between 9pm and 12AM (not 12pm).