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

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

Share this Blog
3
+

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
()

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 218 - 168

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16Blog Index

Quoting RyanFSU:
From a simple comparison of actual SSTs between 2009 and 2010, the "record" warmth isn't apparent to me any longer. The Gulf is 1-2C cooler than this time last year, no surprise with the dry cold front that just blew through the Gulf coast.



With the Pacific experiencing a near-record strength La Nina episode for this time of the year, it is not clear to me how the very-cool SSTs will teleconnect to the Atlantic hurricane formation region.
Any atmospheric influence, then, for a La Nina apparently downing TC formation late in hurricane season?

La Ninas are known for dry falls in CONUS, but October/November aren't really home-brew TC months anyway.
Member Since: Posts: Comments:
Quoting RyanFSU:
From a simple comparison of actual SSTs between 2009 and 2010, the "record" warmth isn't apparent to me any longer. The Gulf is 1-2C cooler than this time last year, no surprise with the dry cold front that just blew through the Gulf coast.



With the Pacific experiencing a near-record strength La Nina episode for this time of the year, it is not clear to me how the very-cool SSTs will teleconnect to the Atlantic hurricane formation region.

Thanks for that.
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
I don't think the season has been over this early since 1993. I remember that year the last storm died on September 21, Hurricane Harvey. That was the year light snow fell all afternoon in Atlanta during Halloween.
The season is certainly not over but this front and all the shear dampening things down for the moment and any cooling will affect later development. But even as a downcaster at this point it would really surprise me if there are not a couple more storms out there.
Member Since: Posts: Comments:
From a simple comparison of actual SSTs between 2009 and 2010, the "record" warmth isn't apparent to me any longer. The Gulf is 1-2C cooler than this time last year, no surprise with the dry cold front that just blew through the Gulf coast.



With the Pacific experiencing a near-record strength La Nina episode for this time of the year, it is not clear to me how the very-cool SSTs will teleconnect to the Atlantic hurricane formation region.
Member Since: Posts: Comments:
Quoting cat5hurricane:
LOL!

Wow...shocked that even down there yours has already got color. It could be the different soil content too. Depending on the soil & topography of the land, that could have quite an impact on it's growing season. I don't believe Sugar Maples are indigenous to the area.
Well, regardless, it seems to love it down here. Grows a solid 3 feet every year.

Hmmm, could be my highly acidic, red clay, "soil". (I am not in the usual river sediment/alluvial soils associated with LA)
Member Since: Posts: Comments:
Quoting Jeff9641:
Interesting! Vorticity near Barbados with all os that convection in the area.

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8vor4.html

Good afternoon...
a good weather site in Barbados--
www.brohavwx.com
Member Since: Posts: Comments:
all that matters is hits numbers are good for surfers troughs can be bad as this yr for the carib.
Member Since: September 11, 2010 Posts: 1 Comments: 4731
Quoting Relix:


Models? lolz =P

They don't have a firm grasp on where the center is. The center, as 101 pointed out, can be clearly seen. Its farther north than what the models forecast and moving WNW. Should pass 150-200 miles north of the islands. More rain of course.

Because the bogus center was off when model was run does not mean you can translate the track adding a vector from the bogus center to the actual center. It only means the track you have is worthless. Also the L on the Chart is not necessarily the bogus center used when the model was run. There are a different ways they pick the bogus center for each model.
Member Since: Posts: Comments:
The sure La Ninas in that period were 1950, 1955 and 1964.

7 storms prior to onset of October, 6 in October alone for 1950. So, roughly half there.

Only 2 of 1955's 13 storms came in October and November.

2 of 1964's 12 storms came in Oct/Nov (though, Hilda was active for part of October, forming in very late September).
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Quoting Cotillion:
Thaale, wouldn't you mean 2007?

2008 wasn't a La Nina as far as I recall.

(Regardless, 2007 was mostly inactive post-September. Noel and Olga for October and November).

(1950-70: 1950, 1954/55/56, 1962, 1964, 1967. All had episodes according to: this)
Ehhh, good catch. The building La Nina was through the '07 season....
Member Since: Posts: Comments:
197. Seriously? Like... for real? We still have TWO MONTHS LEFT in the 2010 season!
Member Since: Posts: Comments:
Quoting cat5hurricane:
Oranges beginning to fade away on this map...but beginning to emerge on the Sugar Maples in WI & MI.

A true tell-tale sign of October.

My sugar maple in SE LA, too.
(not sure why, but that tree only fully covered from Memorial day to Labor day. Maybe it heard someone speaking french and figured it was in Canada...)
Member Since: Posts: Comments:
Quoting Jeff9641:
GFS and NOGAPS both take 97L to FL now later next week. More rain Great News!

http://www.dejongonline.com/weather/weathermodel.htm


With a weakening Bermuda High and a strong persistent trough over the eastern 2/3, it would have to stay undeveloped and far south(e.g. Florida Straights). And even at that, it'll get detoured and absorbed by an early season front. Just sayin'.;)
Member Since: Posts: Comments:
I only wonder if 97L wil be a tropical storm or hurricane?
Member Since: Posts: Comments:
Quoting hydrus:
What a beautiful day for the entire Gulf coast...The NAM model has it in for Puerto Rico.Link

It's coming at us from the East and West!!!!
The ULL is increasing our instability but the shear is keeping organization from happening.
I am all about unorganized convection. Use that TCHP/OHC up!!!
Member Since: Posts: Comments:
Thaale, wouldn't you mean 2007?

2008 wasn't a La Nina as far as I recall.

(Regardless, 2007 was mostly inactive post-September. Noel and Olga for October and November).

(1950-70: 1950, 1954/55/56, 1962, 1964, 1967. All had episodes according to: this)
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Quoting sailingallover:
SST's in the GOM are dropping. Before the front came through there was no 29deg C line..
Now there is one about 150nm offshore along the coast and the 28 line is pushing off near Galveston.
One strong EARLY front for sure. Enjoy the cooler weather.

I am definitely enjoying our 3 weeks of autumn.
Member Since: Posts: Comments:
2011 Atlantic Hurricane Season

Just an Early Prediction
13-16 NS
7-9 H
3-5 MH
Member Since: Posts: Comments:
Thanks Dr. Masters! Your blogs are the best and I always enjoy reading them.

probably a crazy thought in my head but I can only wonder what the 2011 hurricane season will bring and what the steering currents, bermuda high, etc.. will be.

I believe next hurricane season will be ENSO Neutral correct?
Member Since: Posts: Comments:
SST's in the GOM are dropping. Before the front came through there was no 29deg C line..
Now there is one about 150nm offshore along the coast and the 28 line is pushing off near Galveston.
One strong EARLY front for sure. Enjoy the cooler weather.
Member Since: Posts: Comments:
Quoting Thaale:

Sorry, got stuck at JiffyLube, aka HourLube.

Yes, I did that from the HURDAT data set. The most recent La Nina years I looked at were since 1970. The following shows eight La Nina years, total # of TSs, and date of formation of the median storm:

1970 -- 8 - 08/30/70
1973 -- 7 - 09/03/73
1975 -- 8 - 09/07/75
1988 - 12 - 09/07/88
1995 - 19 - 08/23/95
1998 - 14 - 09/17/98
1999 - 12 - 09/10/99
2008 - 16 - 08/30/08

The median storm formation for all those eight years, 96 TSs, is September 3. Their seasons were cumulatively 78% complete by Oct 1.

It's similar for hurricane median formation dates for those eight years - two seasons hit the halfway point in August, three more before Sept 10, two on 9/11, and one on 9/22. However, the median hurricane of the 56 that formed in those 8 years formed on 9/11, and the hurricane (as opposed to TS) season was 75% complete as of Oct 1, at least as far as hurricanes forming.
Thanks for following up. Very intriguing.

Like you said, though, the sample size is fairly small.

Sitting here trying to come up with a clear synoptic scale dynamical reason for a less busy than average late season brought on by a La Nina regime...
Quoting JeffMasters:


You're right, I was guilty of muddled writing. I've rephrased the blog so it makes sense! According to NHC climatology, 2 of our 6 hurricanes in an average season (1/3) occur after Oct 1, and 3 of 11 (27%) of named storms. This would argue for 5 more named storms this year (19 total), with three more hurricanes, assuming the season stays proportionally busy to what it has been.

Jeff Masters
Dr. M? Any thoughts about the apparent tendency of late season behavior during a La Nina?
Member Since: Posts: Comments:
Quoting NRAamy:
You pick it up....you put it in a cage....you take it someplace high and dry....end of story...

usually best to leave bunny alone. it may jump into water from fear of approaching humans, then it could drown or die from exhaustion. depends on if it's a neighborhood bunny used to people or not. they also can scratch and or bite if scared enough. best to leave nature alone.
Member Since: Posts: Comments:
Another wave about to exit africa.

Member Since: Posts: Comments:
179. TDogg
Quoting kwgirl:
I was going to say the same thing, but if it is wild, someone trying to rescue it will scare it even more. It's high and dry and even has some greens to eat.


Had a squirrel get blown 30 feet into my yard during Floyd. Poor little guy was terrified...what I thought was trembling was it breathing a 100 times a minute. I covered it up with a dark cloth and you could see it slowly relax. Within 10 minutes it was peeking out, and was scampering up and over my fence in the next 20.
Member Since: Posts: Comments:
You pick it up....you put it in a cage....you take it someplace high and dry....end of story...

Member Since: Posts: Comments:
Quoting tropicfreak:
What a mess. I can't imagine how long its going to take for this to get organized.


We'll probably wake up to a CAT 5 over night! LOL
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:


Reread the first three sentences or so of it.

Out of the eight that FORMED during the month. Not the ones that were active.
Thanks.! I,m tired already and its only 1:30 P.M. here..:)
Member Since: Posts: Comments:
Quoting hydrus:
I thought Earl was a major hurricane during September also..?


Reread the first three sentences or so of it.

Out of the eight that FORMED during the month. Not the ones that were active.
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:
000
ABNT30 KNHC 011156
TWSAT
MONTHLY TROPICAL WEATHER SUMMARY
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT FRI OCT 01 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

EIGHT TROPICAL STORMS FORMED IN THE ATLANTIC BASIN DURING THE MONTH
OF SEPTEMBER. THREE OF THESE STORMS...IGOR...JULIA...AND KARL...
BECAME MAJOR HURRICANES...AND LISA REACHED HURRICANE STATUS. THESE
NUMBERS ARE WELL ABOVE THE LONG-TERM (1944-2009) AVERAGES OF 4
TROPICAL STORMS...2 HURRICANES...AND ABOUT 1 MAJOR HURRICANE FOR THE
MONTH OF SEPTEMBER. ALSO...THE FORMATION OF EIGHT NAMED STORMS
TIES 2002 FOR THE RECORD NUMBER OF NAMED STORMS FORMING IN THE
MONTH OF SEPTEMBER. IN TERMS OF ACCUMULATED CYCLONE ENERGY...
ACE...WHICH MEASURES THE COMBINED STRENGTH AND DURATION OF TROPICAL
STORMS AND HURRICANES...TROPICAL CYCLONE ACTIVITY IN SEPTEMBER WAS
ABOUT 78 PERCENT ABOVE AVERAGE.

SO FAR THIS SEASON...OVERALL TROPICAL CYCLONE ACTIVITY TO DATE IS
ABOUT 53 PERCENT ABOVE THE LONG-TERM MEDIAN.

REPORTS ON INDIVIDUAL CYCLONES...WHEN COMPLETED...ARE AT THE WEB
SITE OF THE NATIONAL HURRICANE CENTER...USE LOWER-CASE
LETTERS...HTTP://WWW.NHC.NOAA.GOV/2010ATLAN.SHTML

SUMMARY TABLE

NAME DATES MAX WIND (MPH)
----------------------------------------------------
H ALEX 25 JUN-2 JUL 105
TD TWO 7-8 JUL 35
TS BONNIE 22-24 JUL 40
TS COLIN 2-8 AUG 60
TD FIVE 10-11 AUG 35
MH DANIELLE 21-31 AUG 135
MH EARL 25 AUG-5 SEP 145
TS FIONA 30 AUG-4 SEP 60
TS GASTON 1-2 SEP 40
TS HERMINE 6-8 SEP 65
MH IGOR 8-21 SEP 155
MH JULIA 12-20 SEP 135
MH KARL 14-18 SEP 120
H LISA 21-26 SEP 80
TS MATTHEW 23-26 SEP 60
TS NICOLE 28-29 SEP 40


$$
FORECASTER KIMBERLAIN/BRENNAN/BLAKE

I thought Earl was a major hurricane during September also..?
Member Since: Posts: Comments:
Quoting tropicfreak:
What a mess. I can't imagine how long its going to take for this to get organized.


Things change so fast out there.. It looks like the wave near Barbados has a better chance at development once it is west of the islands. there is a lot of moisture for sure.....
Member Since: Posts: Comments:
Quoting NRAamy:
Somebody needs to rescue that poor bunny!!!!!!
I was going to say the same thing, but if it is wild, someone trying to rescue it will scare it even more. It's high and dry and even has some greens to eat.
Member Since: Posts: Comments:

Viewing: 218 - 168

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16Blog Index

Top of Page

About

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

Local Weather

Mostly Cloudy
68 °F
Mostly Cloudy