Severe weather in the Northeast U.S.; updates on 90L, 91L, Leslie and Michael

By: Dr. Jeff Masters , 4:07 PM GMT on September 08, 2012

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A significant severe weather outbreak is underway today across much of the Northeastern U.S., including metro New York City and Philadelphia. NOAA's Storm Prediction Center has placed the region in their "Moderate Risk" area for severe weather. A fall-like low pressure system with a very powerful cold front will sweep through the region today, triggering widespread severe thunderstorms that may organize into a "derecho" event with damaging winds covering a large swath of the Northeast. A few tornadoes may accompany the event, and several tornado warnings have already been issued in New York, with a possible tornado touchdown in the Point Breeze section of the Rockaway peninsula in Queens. The same storm system killed four people on Friday in northeast Oklahoma; three of the deaths occurred when strong thunderstorms winds blew a mobile home into a ravine. Record heat was observed in advance of the storm's cold front yesterday; Wichita Falls, TX hit a record high of 109, the hottest temperature ever recorded there so late in the season. When the cold front blew through at 7 pm CDT, the temperature dropped 15 degrees in 16 minutes, falling to 66 degrees by midnight. Wunderground meteorologist Shaun Tanner has more on the severe weather potential for the Northeast in his blog.


Figure 1. Severe weather potential for Saturday, September 8, 2012.

90L in the Gulf not a threat to develop
A partial remnant of Hurricane Isaac off the coast of the Florida Panhandle, Invest 90L, continues to be disrupted by wind shear, and no longer has time to develop before landfall occurs along the Florida Gulf Coast tonight or Sunday. Visible satellite loops show that 90L has a small area of poorly organized heavy thunderstorms, which will bring some areas of heavy rain to Florida today and Sunday.

Leslie still struggling with cool waters
Tropical Storm Leslie continues to feel the impact of the the cool waters it stirred up due to its long pause south of Bermuda, and remains a 65 mph tropical storm. The storm has no eyewall, as seen on satellite loops, but has cleared out a large cloud-free center. As Leslie continues to move north over warmer water, the storm should be able to build an eyewall and become at least a Category 1 hurricane. However, Leslie is expected to pass far enough to the east of Bermuda today and tonight that top winds of 45 mph will be observed on the island. Bermuda radar shows a large area of heavy rain from Leslie is very close to the island.


Figure 2. Morning radar image of Tropical Storm Leslie from the Bermuda radar.

Forecast for Leslie
The strong trough of low pressure pulling Leslie to the north will bring Leslie very close to Newfoundland, Canada by Tuesday night or Wednesday morning. At that time, Leslie should be weakening due to cooler waters and increased wind shear, and is likely to be a tropical storm. Heavy rain will be the main threat to Newfoundland. The latest 11 am EDT NHC wind probability forecast calls for a 24% chance that Leslie will be a Category 1 or stronger hurricane Wednesday morning at 8 am EDT, when the storm will be near Newfoundland. Even if the core of Leslie misses Newfoundland, the island will still likely experience tropical storm-force winds, since 39+ mph winds will probably extend outward from its center 180 miles to its west on Tuesday and Wednesday. Large swells from Leslie continue to pounding the entire Eastern Seaboard, and are creating beach erosion and dangerous rip currents.


Figure 3. Hurricane Michael as seen by NASA's Aqua satellite at 11:50 am EDT Friday September 7, 2012. At the time, Michael was a Category 2 hurricane with 105 mph winds. Image credit: NASA.

Hurricane Michael weakens to Category 2
Hurricane Michael remains a Category 2 storm with 105 mph winds, out over the open mid-Atlantic Ocean. Satellite loops show that Michael is still an impressive storm with a well-developed eye. None of the models show that Michael will threaten any land areas during the coming five days, and Michael will likely die at sea over cold waters northeast of Newfoundland in 5 - 7 days.

91L off the coast of Africa
A tropical wave that emerged off the coast of Africa on Friday has been designated Invest 91L by NHC today. Most of the reliable computer models are predicting that 91L will develop into a tropical depression by Wednesday. None of the reliable computer models foresee that this storm will be a threat to the Lesser Antilles Islands, but it is still early to be assuming that 91L will recurve harmlessly out to sea.

Jeff Masters

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861. aspectre
8:19 PM GMT on September 09, 2012

9Sept.3:05pmGMT: TS.Leslie had passed 133miles(214kilometres)East of Bermuda
The previous mapping of TS.Leslie
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Doesn't look like Leslie will come within Fujiwhara-distance (~900miles or ~1450kilometres) of Michael: Leslie's been moving too fast, and Michael's been moving too slow.
But they aren't so far apart that future interaction is impossible, yet. And because a Fujiwhara would affect both storms' paths...
Derived from the NHC's 9Sept12pmGMT ATCF data for TropicalStormLeslie and for HurricaneMichael
BHB-BarHarbor :: CWRW-FourchuHead :: YYT-St.John's :: YMH-Mary'sHarbour
All times in GMT
8Sept.06pm: TS.Leslie had been 1238miles(1992kilometres)West of H.Michael
9Sept.12am: TS.Leslie had been1222miles(1966kilometres)West of H.Michael
9Sept.06am: TS.Leslie had been 1197miles(1926kilometres)West of H.Michael
9Sept.12pm: TS.Leslie had been 1151miles(1853kilometres)West of H.Michael
9Sept.06pm: TS.Leslie was 1090miles(1754kilometres)West of H.Michael

A closure rate of 148miles(238kilometres) per day isn't sufficient to close the gap before the distance between the two starts increasing again. But if Leslie slows down while Michael speeds up...

Copy&paste bda, bhb, cwrw, yyt, 51.535n55.445w, ymh, 32.8n42.1w-29.0n62.5w, 33.3n42.3w-29.7n62.6w, 33.6n42.5w-30.5n62.6w, 33.7n42.9w-31.5n62.5w, 33.7n43.5w-32.7n62.3w into the GreatCircleMapper
The previous mapping of H.Michael
Member Since: August 21, 2007 Posts: 0 Comments: 4860
860. StormDrain
4:56 PM GMT on September 09, 2012
Quoting HurricaneHunterJoe:
I haven't seen this model and location before.You may already have it.

http://www.met.sjsu.edu/weather/models/wrf_wf.htm l

For some reason I am unable to post pics or links.
Backtracked and got this page: San Jose State University Department of Meteorology and Climate Science, Weather Center.
From there, click model graphics and then click WRF 12 and 3 km TC genesis, west Africa.
This is the 850 mb temp, height, wind WRF 00z, 12k forecast for 0700 cdt today.


Pretty neat. Didn't even know San Jose State had a Dept of Meteorology. Thanks!
Member Since: October 9, 2005 Posts: 13 Comments: 495
859. midgulfmom
4:47 PM GMT on September 09, 2012
MAweatherboy1, the12z GFS maps you posted on the last blog were for what storm please? Guessing 91L, is that correct? TIA
Member Since: July 9, 2005 Posts: 2 Comments: 1164
858. midgulfmom
4:41 PM GMT on September 09, 2012
Quoting MAweatherboy1:
Two of the 6z GFS ensemble members...



Hi...sorry just checking in. What system are these for please, 91L? TIA
Member Since: July 9, 2005 Posts: 2 Comments: 1164
857. WunderAlertBot (Admin)
4:40 PM GMT on September 09, 2012
JeffMasters has created a new entry.
856. lobdelse81
4:40 PM GMT on September 09, 2012
Quoting GeorgiaStormz:


not really:



maybe in canada...

We arent going to go so far away from climatology to september snows this year..this isnt 1942 again.... i dont think..

Come on, I don't think this September will feature the opposite extreme as what this past March brought to much of the Great Lakes, plains, and on eastward when we were transitioning into spring and we got June-like weather. December-like weather in September, that just is impossible and i don't buy it.
Member Since: September 9, 2011 Posts: 0 Comments: 439
855. unknowncomic
4:38 PM GMT on September 09, 2012
Quoting SFLWeatherman:
Not to burst a bubble, but someone thinks this is a better MJO forecast because it is dynamic. I would like to see an expert clariffy which one is better.

Member Since: August 2, 2011 Posts: 0 Comments: 2108
854. wxchaser97
4:32 PM GMT on September 09, 2012
Quoting LargoFl:

That is obviously a very big hurricane wind field.
Member Since: March 16, 2012 Posts: 127 Comments: 7959
853. Methurricanes
4:31 PM GMT on September 09, 2012
does anyone else see a WSW movement with Micheal?
Member Since: August 1, 2011 Posts: 0 Comments: 701
852. TropicalAnalystwx13
4:29 PM GMT on September 09, 2012
The 11am EDT advisory packages bring Lesile's ACE up to 12.7 units, Michael's ACE up to 13.0 units, and the season total up to 67.9 units.
Member Since: July 6, 2010 Posts: 113 Comments: 32530
851. HurricaneHunterJoe
4:29 PM GMT on September 09, 2012
I haven't seen this model and location before.You may already have it.

http://www.met.sjsu.edu/weather/models/wrf_wf.htm l

For some reason I am unable to post pics or links.
Member Since: September 18, 2010 Posts: 0 Comments: 5237
850. LargoFl
4:28 PM GMT on September 09, 2012
FLOOD STATEMENT
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
1025 AM EDT SUN SEP 9 2012

...A RIVER FLOOD WARNING REMAINS IN EFFECT FOR THE WITHLACOOCHEE
RIVER AT TRILBY AND THE CYPRESS CREEK AT WORTHINGTON GARDENS...

.MINOR FLOODING WILL CONTINUE ON THE WITHLACOOCHEE AT TRILBY AND
THE CYPRESS CREEK AT WORTHINGTON GARDENS. WITH WET CONDITIONS
EXPECTED THROUGH THE WEEKEND...PROLONGED MINOR FLOODING IS
POSSIBLE.
Member Since: August 6, 2011 Posts: 4 Comments: 41000
849. LargoFl
4:26 PM GMT on September 09, 2012
Member Since: August 6, 2011 Posts: 4 Comments: 41000
848. TropicalAnalystwx13
4:25 PM GMT on September 09, 2012
Quoting washingtonian115:
Trade winds have been strong in the caribbean and instability has been below average...So I really have my doubts.

Even so, trade winds are not a problem in the West and northwest Caribbean where most tropical cyclogenesis occurs in October. True, instability is way below average, but it was just the same last year and we got Major Hurricane Rina.
Member Since: July 6, 2010 Posts: 113 Comments: 32530
847. LargoFl
4:24 PM GMT on September 09, 2012
.......looks like the rains are going to end soon near my area,they are moving inland to the NE
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846. SFLWeatherman
4:23 PM GMT on September 09, 2012
Member Since: May 23, 2012 Posts: 0 Comments: 4957
845. SFLWeatherman
4:21 PM GMT on September 09, 2012
Member Since: May 23, 2012 Posts: 0 Comments: 4957
844. Maineweatherguy20023
4:20 PM GMT on September 09, 2012
Quoting Methurricanes:
because Micheal is the deeper system, wouldn't he technicly be favored to abosrb leslie, not vise-versa?

leslie is bigger
Member Since: August 1, 2012 Posts: 0 Comments: 269
843. SFLWeatherman
4:20 PM GMT on September 09, 2012

Member Since: May 23, 2012 Posts: 0 Comments: 4957
842. wxchaser97
4:17 PM GMT on September 09, 2012
Quoting washingtonian115:
Trade winds have been strong in the caribbean and instability has been below average...So I really have my doubts.

Trade winds aren't so much of a problem before but instability is lacking. Anyway the storm would leave the Caribbean, I think we should see a storm.
Member Since: March 16, 2012 Posts: 127 Comments: 7959
841. wxchaser97
4:15 PM GMT on September 09, 2012
Michael is an interesting looking storm, only reason for the lowering of intensity is probably the warming of cloud tops.
Member Since: March 16, 2012 Posts: 127 Comments: 7959
840. AegirsGal
4:11 PM GMT on September 09, 2012
Quoting MAweatherboy1:

I'm already getting excited for winter... especially after the disappointment last year. It's hard to keep my mind fully on the tropics at this point, lol.
Honestly, me too. I've mentioned before that I just moved to NE this summer. I haven't seen a true winter in over 30 years, since I lived in Wyoming.
Member Since: August 2, 2011 Posts: 0 Comments: 291
839. Tropicsweatherpr
4:09 PM GMT on September 09, 2012
We have a new invest in the EPAC!

BEGIN
NHC_ATCF
invest_ep902012.invest
FSTDA
R
U
040
010
0000
201209091549
NONE
NOTIFY=ATRP
END
INVEST, EP, E, , , , , 90, 2012, DB, O, 2012090912, 9999999999, , , , , , METWATCH, , EP902012
EP, 90, 2012090912, , BEST, 0, 115N, 940W, 20, 0, DB, 0, , 0, 0, 0, 0,
Member Since: April 29, 2009 Posts: 75 Comments: 14571
838. Grothar
4:04 PM GMT on September 09, 2012
Member Since: July 17, 2009 Posts: 71 Comments: 26895
837. StormDrain
4:03 PM GMT on September 09, 2012
Sept 9, 2012 06z GFS
Leslie and Michael





images credit: http://moe.met.fsu.edu/tcgengifs/
Member Since: October 9, 2005 Posts: 13 Comments: 495
836. wxchaser97
4:02 PM GMT on September 09, 2012
Quoting GeorgiaStormz:



Isnt that what snowflakes are supposed to do?
Oh yeah, i live in GA...



That would make my snow year....3" is enough to cover my grass and its a big snow event if i get that much.

Snowflakes are obviously supposed to melt, well up here snow accumulates instead of melting on most surfaces. Also we get a good 40-50" a year, last winter was a big let down.
Member Since: March 16, 2012 Posts: 127 Comments: 7959
835. Grothar
4:01 PM GMT on September 09, 2012
Member Since: July 17, 2009 Posts: 71 Comments: 26895
834. washingtonian115
4:00 PM GMT on September 09, 2012
Quoting robert88:
Long range GFS says CV season comes to an early close....shows even stronger cold fronts coming through as well. Conditions have been pretty horrible in the Atlantic this season. It will be interesting to see if we can even get any homegrown for the remaining of the season.
Trade winds have been strong in the caribbean and instability has been below average...So I really have my doubts.
Member Since: August 14, 2010 Posts: 10 Comments: 17486
833. robert88
3:58 PM GMT on September 09, 2012
Long range GFS says CV season comes to an early close....shows even stronger cold fronts coming through as well. Conditions have been pretty horrible in the Atlantic this season. It will be interesting to see if we can even get any homegrown for the remaining of the season.
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832. GeorgiaStormz
3:54 PM GMT on September 09, 2012
Quoting washingtonian115:
We only had 2 1/2 inches for the whole winter!!!!.It sucked!.Every time you saw snow flakes they would melt when they hit the ground...



Isnt that what snowflakes are supposed to do?
Oh yeah, i live in GA...

Quoting wxchaser97:

I know how you feel, the most in one event was a mere 3"(wet).


That would make my snow year....3" is enough to cover my grass and its a big snow event if i get that much.
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831. AussieStorm
3:53 PM GMT on September 09, 2012
Quoting Tazmanian:



i dont even think wounderBlogAdmin is real



dr m him may be a better pick


WunderBlogAdmin
WunderBlogAdmin is a generic handle used by our employees to interact with bloggers. This gives a single point of contact for our members to report issues and dispute bans. As noted in our terms of service, Weather Underground does not maintain 24/7 watch over the blogs and administration is not real time. Administrators will deal with problems and answer notes when they can, so please be patient.
For questions about these rules please contact WunderBlogAdmin.
Member Since: September 30, 2007 Posts: 9 Comments: 15962
830. aislinnpaps
3:52 PM GMT on September 09, 2012
Quoting aislinnpaps:


Thanks, I wondered about the 'F' word, but didn't want to ask that directly as I know what happens when someone does. Also wondered since I know what a Fujiwara is, if instead one could absorb the other since there is a discrepancy in size.


Also wondered if they would 'bounce' off each other. Appreciate the answers!
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829. aislinnpaps
3:50 PM GMT on September 09, 2012
Quoting Dakster:


Two possibilities, one storm will absorb the other one OR they will rotate around each other (fujiwara).

Depends on how close in strength to each other they are and what the environmental conditions are at the time.
Quoting AussieStorm:

Sorry, I was watching the stream from Bermuda.

If they get close enough, we could see the Fujiwara effect take place.
Quoting wxchaser97:

Well either a Fujiwara effect happens or one of the storms absorbs the other. Sorry I didn't see your question earlier.


Thanks, I wondered about the 'F' word, but didn't want to ask that directly as I know what happens when someone does. Also wondered since I know what a Fujiwara is, if instead one could absorb the other since there is a discrepancy in size.
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828. trHUrrIXC5MMX
3:50 PM GMT on September 09, 2012

THIS IS THE ONLY STORM THAT HAS BEEN SO GOOD LOOKING FOR SO LONG
Member Since: April 23, 2011 Posts: 104 Comments: 14873
827. washingtonian115
3:48 PM GMT on September 09, 2012
We only had 2 1/2 inches for the whole winter!!!!.It sucked!.Every time you saw snow flakes they would melt when they hit the ground...
Member Since: August 14, 2010 Posts: 10 Comments: 17486
826. wxchaser97
3:46 PM GMT on September 09, 2012
Quoting MAweatherboy1:

I'm already getting excited for winter... especially after the disappointment last year. It's hard to keep my mind fully on the tropics at this point, lol.

I know how you feel, the most in one event was a mere 3"(wet).
Member Since: March 16, 2012 Posts: 127 Comments: 7959
825. GeorgiaStormz
3:40 PM GMT on September 09, 2012
Quoting MAweatherboy1:

There's more to it, but in that case at least some people would get some snow or mix, and in the one I posted in 809 there would certainly be some people getting measurable snowfall in northern MI, northern NY, and Canada.


not really:



maybe in canada...

We arent going to go so far away from climatology to september snows this year..this isnt 1942 again.... i dont think..
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824. Grothar
3:35 PM GMT on September 09, 2012
Member Since: July 17, 2009 Posts: 71 Comments: 26895
823. MAweatherboy1
3:34 PM GMT on September 09, 2012
Quoting GeorgiaStormz:


That doesnt mean it will snow in september in Wisconsin and Michigan....there is more to it than that line....

Thats almost certainly at best a cold rain.

There's more to it, but in that case at least some people would get some snow or mix, and in the one I posted in 809 there would certainly be some people getting measurable snowfall in northern MI, northern NY, and Canada.
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822. Grothar
3:33 PM GMT on September 09, 2012
Member Since: July 17, 2009 Posts: 71 Comments: 26895
821. Tropicsweatherpr
3:33 PM GMT on September 09, 2012
The 12z Best Track for 91L came out very late but here it is.

AL, 91, 2012090912, , BEST, 0, 149N, 278W, 25, 1008, LO
Member Since: April 29, 2009 Posts: 75 Comments: 14571
820. Grothar
3:32 PM GMT on September 09, 2012
Member Since: July 17, 2009 Posts: 71 Comments: 26895
819. SFLWeatherman
3:31 PM GMT on September 09, 2012
12Z GFS is coming out now!!:)
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818. MAweatherboy1
3:31 PM GMT on September 09, 2012
Quoting Methurricanes:
because Micheal is the deeper system, wouldn't he technicly be favored to abosrb leslie, not vise-versa?

It's more of a size issue though. Logically you would think the deeper system would win out but it's almost always the bigger one.
Member Since: February 11, 2012 Posts: 84 Comments: 7948
817. washingtonian115
3:31 PM GMT on September 09, 2012
Quoting MAweatherboy1:

I'm already getting excited for winter... especially after the disappointment last year. It's hard to keep my mind fully on the tropics at this point, lol.
I know.I'm done with the tropics just about.I had my fun to track this year and most of the storms have been non interesting.Bring on the cold and snow!!.
Member Since: August 14, 2010 Posts: 10 Comments: 17486
816. GeorgiaStormz
3:31 PM GMT on September 09, 2012
Quoting SFLWeatherman:


That doesnt mean it will snow in september in Wisconsin and Michigan....there is more to it than that line....

Thats almost certainly at best a cold rain.
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815. Grothar
3:30 PM GMT on September 09, 2012
Member Since: July 17, 2009 Posts: 71 Comments: 26895
814. Methurricanes
3:30 PM GMT on September 09, 2012
because Micheal is the deeper system, wouldn't he technicly be favored to abosrb leslie, not vise-versa?
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813. SFLWeatherman
3:30 PM GMT on September 09, 2012
Member Since: May 23, 2012 Posts: 0 Comments: 4957
812. washingtonian115
3:29 PM GMT on September 09, 2012
Quoting MAweatherboy1:
Another 6z GFS ensemble member, this one at 288 hours. This would bring some wintry weather a little sooner than usual...

Ohhh I hope that's true after the non existing winter we had this year...
Member Since: August 14, 2010 Posts: 10 Comments: 17486
811. MAweatherboy1
3:28 PM GMT on September 09, 2012
Quoting wxchaser97:

I would hope that verified, better than last winter.

I'm already getting excited for winter... especially after the disappointment last year. It's hard to keep my mind fully on the tropics at this point, lol.
Member Since: February 11, 2012 Posts: 84 Comments: 7948

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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