97L a major rainfall threat; October hurricane outlook; NC rains finally end

By: Dr. Jeff Masters , 2:08 PM GMT on October 01, 2010

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A large and complex region of disturbed weather (Invest 97L), centered about 800 miles east of the Lesser Antilles Islands, is headed west-northwest at 15 - 20 mph and will bring heavy rain showers and gusty winds to the northern Lesser Antilles Islands on Saturday and Sunday. Wind shear is a moderate 5 - 15 knots over 97L, and the waters beneath are very warm, 29°C. However, recent satellite imagery shows that the intensity and areal coverage of 97L's heavy thunderstorms have decreased this morning, thanks to some dry air being ingested into the storm. The SHIPS model predicts that wind shear over 97L will rise to the high range, 20 - 30 knots, Saturday through Tuesday, but some of the global computer models depict only moderate amounts of shear for 97L during this period. The NOGAPS model is the only model currently showing significant development 97L, and that model predicts 97L will be near Puerto Rico on Monday, the Dominican Republic on Tuesday, Haiti on Wednesday, and Eastern Cuba and the southeast Bahamas on Thursday. NHC is giving 97L a 40% chance of developing into a tropical depression by Sunday, but as of this morning, had not tasked the Hurricane Hunters to fly into the storm over the next two days. 97L will slow down to 5 - 10 mph on Sunday, bringing the potential for an extended 3 - 4 day period of heavy rains for the islands in its path. Even if 97L does not develop into a tropical depression, its slow motion may result in life-threatening flash flooding and mudslides in Puerto Rico, the Dominican Republic, Haiti, and eastern Cuba next week.


Figure 1. Morning satellite image of Invest 97L.

October hurricane outlook
October is here, and it is time to take stock of where we stand and how far we have to go before hurricane season is over. The beginning of October traditionally marks the two-thirds point of hurricane season; approximately one-third of all hurricanes and 28% of named storms occur after October 1. Tropical Storm Nicole brought us up to fourteen named storms for the year, and I expect about 4 - 5 more named storms this year with 2 - 3 of these being hurricanes. That would add up to 18 - 19 named storms for the season, putting 2010 in 3rd - 5th place all-time for most named storms. Since record keeping began in 1851, only four seasons have finished with more than eighteen named storms. These seasons were 2005 (28 named storms, with the 17th named storm, Rita, occurring by October 1); 1933 (21 named storms, with the 18th named storm occurring by October 1;) 1995 (19 named storms, with the 15th named storm, Opal, occurring by October 1;) and 1887 (19 named storms, with the 10th named storm occurring by October 1.) The most likely time to get activity is during the first two weeks of October. There are still two weeks of peak hurricane season left before the activity traditionally begins to decline steeply (Figure 2.) Given the record warm sea surface temperatures in the Atlantic this fall, the presence of La Niña in the Eastern Pacific keeping wind shear lower than average, and the observed increase in late-season activity in recent decades, I expect this year's peak portion of hurricane season will last until the end of October. I predict three named storms, two hurricanes, and one intense hurricane will form in the Atlantic this month, with two named storms and one hurricane occurring in November - December, making 2010 as the third busiest Atlantic hurricane season of all-time.


Figure 2. Climatological frequency of Atlantic named storms and hurricanes.

Jamaica cleans up after Nicole
Tropical Storm Nicole lasted only six hours as a tropical storm, but the storm's torrential rains hit Jamaica hard. Nicole's rains killed at least six people on the island, and at least thirteens others are missing and feared dead. The storm cut power to 170,000 island residents, and caused millions of dollars in damages. Wunderground member JamaicaZed wrote me to say his rain gauge in the Kingston suburb of Norbrook caught 17.39" of rain Monday through Thursday, with 11.10" coming on Wednesday.

Historic rainfall event for eastern North Carolina ends
The rains have finally ended In North Carolina, where tropical moisture streaming northward in advance of Nicole generated a historic rainfall event this week. Wilmington, NC set records this week for the heaviest 3-day, 4-day, and 5-day rainfall events in city history, and the month of September ended up as the second rainiest month ever recorded in the city. A remarkable 22.54" of rain fell on Wilmington during the 5-day period Sunday through Thursday. The previous record was 19.06", set in September 1999 during Hurricane Floyd. Fortunately, eastern North Carolina was under moderate drought conditions prior to this week's rainfall onslaught, with just 0.18" of rain falling during the first 25 days of September. Only minor to moderate flooding is occurring on North Carolina rivers, with just one river, the Northeast Cape Fear River near Chinquapin, expected to experience major flooding. Portlight.org is beginning to identify needs in Eastern North Carolina in the wake of the flooding, and expects to perform the first deployment of their new relief trailer within the next few days and send a truck loaded with water, food and personal hygiene supplies.

The most remarkable thing about Wilmington's second-wettest month in history is that it came without a hurricane affecting North Carolina. All four of the other top-five wettest Septembers in history were due, in large part, to hurricanes:

#1 23.41 inches 1999 (Hurricanes Dennis and Floyd)
#2 22.72 inches 2010 (plume of tropical moisture in advance of TS Nicole)
#3 20.10 inches 1877 (Hurricane Four)
#4 18.94 inches 1984 (Hurricane Diana)
#5 16.93 inches 1924 (Hurricane Five and Tropical Storm Eight)


Figure 3. Radar-estimated precipitation for North Carolina since Sunday shows that the precursor moisture from Nicole has brought widespread rain amounts of fifteen inches (white colors.)

Heavy rains and flooding for New England
The plume of tropical moisture that affected North Carolina is now triggering heavy rains in New England, and flood warnings are posted throughout most of New Jersey, eastern Pennsylvania, eastern New York, Delaware, and Vermont this morning. In New York City, heavy rains this morning have overwhelmed one section of the city's subway system, and flooding closed several key road arteries in the city, snarling the morning commute. About two inches of rain have fallen so far this morning in the city. Severe weather is not expected, and no tornadoes were reported yesterday in association with this weather system.

Elsewhere in the tropics
Disturbed weather continues in the Central Caribbean, where the remnants of Tropical Storm Nicole will bring isolated heavy rain showers today to Hispaniola, Jamaica, Cuba, the Cayman Islands, and northern Honduras. The GFS model predicts this activity will concentrate near Hispaniola over the weekend, then push northwards into the Bahamas, with a subtropical or extratropical storm forming over the Bahamas on Sunday or Monday. This storm could bring 2 - 4 inches of rain to the Bahamas Sunday and Monday. The storm will then move north-northeastwards, parallel to the U.S. East Coast, and not affect any other land areas. Several of the models are predicting the formation of a tropical depression in the Mid-Atlantic 5 - 7 days from now, in a location that would not be of any danger to land areas.

Next update
I'll have an update Saturday morning.

Jeff Masters

Flooding (jdwagon)
Shannon Hills, Ridgeway, VA
Flooding
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Wondering if anyone saw this?
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Quoting WatchingThisOne:


Um, when the lettering on the chart is less than 1 point in size (for anyone on a high res monitor), could you (and other posters) please do us the favor of typing e.g. "OOZ NAM +84". Would save me dragging out the Windows magnifying glass each time. Thanks in advance.

WTO


Maybe this will help -

Right-click the image and select View Image. You see it full-sized. The hit the back button to get back to where you were in the blog.

(Works in Firefox, wouldn't know about IE tho)
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315. JLPR2
Quoting JRRP:


I was going to post that XD
We got a low with our CATL disturbance.
Member Since: September 4, 2007 Posts: 7 Comments: 8697
Quoting ShenValleyFlyFish:
A blown down house is a reason for a party? Anything like an Amish Barn-Raisin' after a fire?


Only if you have it insured for more than it's worth is it a reason for a party. Otherwise, I think we'll stick to the WU-birthday party. A lot less clean-up required afterward.
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Quoting TropicalAnalystwx13:
I see people giving out their 2011 Atlantic Hurricane Season.

What the heck...I'll give mine.

12-16........................ Named Storms
6-9...........................Hurricanes
3-5.......................... Major Hurricane Hurricanes
I believe 2011 will be active, but not as active as this year. Your prediction sounds very reasonable to me. I'll try to release a 2011 outlook on Christmas, or New Years.
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Quoting CaptnDan142:


Sounds like a good reason for a double 'birthday' party next year. We can get Amy to bring the forks.
A blown down house is a reason for a party? Anything like an Amish Barn-Raisin' after a fire?
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I believe this month will feature up to 4 named storms, and November/December bringing 1.

14+5 = 19 named storms :)
Member Since: July 6, 2010 Posts: 113 Comments: 32046
I see people giving out their 2011 Atlantic Hurricane Season.

What the heck...I'll give mine.

12-16........................ Named Storms
6-9...........................Hurricanes
3-5.......................... Major Hurricane Hurricanes
Member Since: July 6, 2010 Posts: 113 Comments: 32046
Quoting KerryInNOLA:
To my fellow Gulf Coast neighbors. We made it thru the meat of the season. It's Oct 1st and our shields are up at 100% force. The 10 day forecast is for clear and cool. Nothing is on the horizon. We can safely drop our guards for the next 2 weeks with a reevaluation then for declaring the Northern Gulf season over if the fronts keep coming. Laissez le bon temps rouler!


Fais do do! I was so jealous when I saw y'all with that front pass by you. I can't believe it made it all the way down to me in Florida. Whoo hoo! Christmas came early this year.
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Quoting WatchingThisOne:


Looks to me like the Ford will be swept away before the buggy will. Those things are actually built to cross a fair amount of moving water (large spoked wheels and high clearance).
In actuality they can float and the horse can swim. Flood water still dangerous due to current once everything is out of contact with the ground but otherwise getting up and down the bank is the real concern.
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305. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5813
303. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5813
Quoting Huracaneer:

and live to blow your house down!

Just noticed CaptDan142 that we both opened our account on the exact same date, what are the chances of that! (100% apparently).


Sounds like a good reason for a double 'birthday' party next year. We can get Amy to bring the forks.
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Quoting Huracaneer:
It's beautiful here today in the Tampa Bay Area of Florida, feels like autumn, first comfortable weather (lowest dew point) since April, nice blue skies, it's hard to believe that there is still a couple of months left in the hurricane season.

It's even harder to believe that we only have 2 more months left in the yr. Where does the time go?
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Quoting CaptnDan142:


Sometimes, patients on life support do recover.

and live to blow your house down!

Just noticed CaptDan142 that we both opened our account on the exact same date, what are the chances of that! (100% apparently).
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Quoting CaptnDan142:


Sometimes, patients on life support do recover.

Great Post!
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Havn't been on in awhile so I may be behind on some things.Anyway I see Nicole has left her mark.I've been feeling her for a couple of days now with almost non-stop rain.Tempetures are also cooler here.I think we could see an early fall.
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Quoting Neapolitan:


I remember when that was said about Danielle. And Igor. And Katrina. And Andrew... ;-)


Sometimes, patients on life support do recover.
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Quoting Cat5hit:
I love rabbits.

They taste just like chicken.


I'm rooting for bunny. You can buy chicken.
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It's beautiful here today in the Tampa Bay Area of Florida, feels like autumn, first comfortable weather (lowest dew point) since April, nice blue skies, it's hard to believe that there is still a couple of months left in the hurricane season.
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294. Relix
Quoting Neapolitan:


I remember when that was said about Danielle. And Igor. And Katrina. And Andrew... ;-)


It will probably explode overnight to make me look bad =P
Member Since: August 3, 2006 Posts: 0 Comments: 2723
Quoting Relix:
97L on life support


I remember when that was said about Danielle. And Igor. And Katrina. And Andrew... ;-)
Member Since: November 8, 2009 Posts: 4 Comments: 13531
Quoting wunderkidcayman:
quoting wunderkidcayman:

well let us put it this way It is lightly overcast with a few good showers in places and I am not calling it a front because it is not a front it is a trough with what seems to be two lows forming and may very well explode when D-Max kicks in GTcooliebai

or should say hsa formed

Well I was about to say "Remarkable" if it had cleared you area. So I take it the airmass is still tropical down there?
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Quoting angiest:


Snark Flag: ON
See, when you don't watch TV, you don't get the invaluable advice from the news readers: Turn around, don't drown! He'll probably rot out the axles on his carriage.


Looks to me like the Ford will be swept away before the buggy will. Those things are actually built to cross a fair amount of moving water (large spoked wheels and high clearance).
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Quoting xcool:


Um, when the lettering on the chart is less than 1 point in size (for anyone on a high res monitor), could you (and other posters) please do us the favor of typing e.g. "OOZ NAM +84". Would save me dragging out the Windows magnifying glass each time. Thanks in advance.

WTO
Member Since: Posts: Comments:
quoting wunderkidcayman:

well let us put it this way It is lightly overcast with a few good showers in places and I am not calling it a front because it is not a front it is a trough with what seems to be two lows forming and may very well explode when D-Max kicks in GTcooliebai

or should say hsa formed
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Quoting Cat5hit:
What is the deal with 97L?



97L

http://rammb.cira.colostate.edu/ramsdis/online/loop_640.asp?product=tropical_ge_4km_visir2_floater_ 2
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Quoting Relix:
97L on life support


Why, you think 97l can't maintain convection?, I don't have a clue about it. All conditions are in favor of development, but 97l never keep it's convection.
Member Since: Posts: Comments:
well let us put it this way It is lightly overcast with a few good showers in places and I am not calling it a front because it is not a front it is a trough with what seems to be two lows forming and may very well explode when D-Max kicks in GTcooliebai
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Quoting beell:


Big bunny.
They get bigger now. Less competition for resources.
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280. Relix
97L on life support
Member Since: August 3, 2006 Posts: 0 Comments: 2723
Quoting wunderkidcayman:
hey guys I think two weak lows have formed one near 16.0N 84.0W moving NE-ENE and the other near 17.0N 73.0W moving ENE-E

Hey the weather must be clearing out nicely down there, has the front cleared you guys yet?
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276. xcool
<<<< for me tonight

Sunny Clear Sunny Clear
84°F 49
Member Since: September 26, 2009 Posts: 2 Comments: 15671
275. beell
Quoting Jeff9641:


Bunny's becoming scarce in FL due to phythons. One was caught in the Everglades this summer of 23 feet long.


Big bunny.
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Quoting jasoniscoolman2011xz:
flood warning
He better slow down, he'll splash water in his horse's engine and short out the electrical system or flood out the air intake.
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273. xcool


12z ECM ensembles
Member Since: September 26, 2009 Posts: 2 Comments: 15671
hey guys I think two weak lows have formed one near 16.0N 84.0W moving NE-ENE and the other near 17.0N 73.0W moving ENE-E
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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.