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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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.
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What a beautiful day for the entire Gulf coast...The NAM model has it in for Puerto Rico.Link
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What a mess. I can't imagine how long its going to take for this to get organized.


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000
ABPZ30 KNHC 011235
TWSEP
MONTHLY TROPICAL WEATHER SUMMARY
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM PDT FRI OCT 01 2010

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

ONE TROPICAL STORM AND TWO TROPICAL DEPRESSIONS FORMED IN THE
EASTERN NORTH PACIFIC BASIN DURING SEPTEMBER. THESE NUMBERS ARE
WELL BELOW THE LONG-TERM AVERAGES OF 3 TROPICAL STORMS...2
HURRICANES...AND 1 MAJOR HURRICANE. IN FACT...SINCE THE SATELLITE
ERA BEGAN IN 1971...THIS IS THE QUIETEST SEPTEMBER ON RECORD IN
TERMS OF ACCUMULATED CYCLONE ENERGY...ACE...WHICH MEASURES THE
COMBINED STRENGTH AND DURATION OF TROPICAL STORMS AND HURRICANES.

SO FAR THIS SEASON...OVERALL TROPICAL CYCLONE ACTIVITY OBSERVED TO
DATE IS ABOUT 46 PERCENT OF 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/2010EPAC.SHTML

SUMMARY TABLE

NAME DATES MAX WIND (MPH)
-------------------------------------------------
TS AGATHA 29-30 MAY 45
TD TWO-E 16-17 JUN 35
TS BLAS 17-21 JUN 65
MH CELIA 19-29 JUN 160
MH DARBY 23-28 JUN 120
TD SIX-E 14-16 JUL 35
TS ESTELLE 6-10 AUG 65
TD EIGHT-E 20-22 AUG 35
H FRANK 21-28 AUG 90
TD TEN-E 3-4 SEP 35
TD ELEVEN-E 3-4 SEP 35
TS GEORGETTE 21-23 SEP 40

$$
FORECASTER BRENNAN

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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

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That bunny's dynamite!
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159. Relix
Quoting CaribBoy:


but... global models move it towards your area.


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.
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Portlight stands ready to help and as the situation becomes clearer,,we will have more words later this afternoon.

Patrick

Relief and Communications Coordinator.

http://portlight.org/


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Quoting Relix:


That should pass well north of the islands. Will leave a lot of rain behind though


but... global models move it towards your area.
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Have a great afternoon. I'll be back later to see what's going on with 97L. SSTs are warm, there is no dry air issue, vorticity is fine... shear is marginal so it shouldn't dissipate.
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154. Relix
Quoting Hurricanes101:
vorticity is now vertically stacked and a circulation is showing up on visible imagery around 16N 51W



That should pass well north of the islands. Will leave a lot of rain behind though
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Quoting StormJunkie:
Good afternoon all.

Portlight has been working all morning to gain an understanding of the flooding in eastern NC due to the recent rains associated with what was TS Nichole. We have spoken with the Jacksonville EOC as well as several local governments in the area. At this point, it seems some of the hardest hit areas are in Onslow county in the vicinity of Bear Creek, Hubert, and Swansboro. We have also spoken with a local church in Jacksonville which reported significant flooding along Piney Green Rd where many homes are flooded as well as an apartment complex. When asked to provide a guesstimate of how many homes were flooded in the Hubert/Swansboro area the lady provided us with a very rough guess of 300.

From this very early information, we expect that there will be significant needs in Eastern NC and While we are still looking for more specific information from the hardest hit areas; we are also preparing a truck and trailer load of supplies to carry up. While delivering these supplies we will also work with local officials, churches, and citizens of these communities in order identify the most pressing needs of the under-served and forgotten people. Please consider making a donation to help support the North Carolina flood victims.

Busy day ahead as preparations are being made, so please leave any response to this on the Portlight Blog. As more media starts coming out about the impacted areas, please feel free to post it to the blog. Thanks everyone


Hey SJ, good post. Hope things are well with you. Glad to hear Portlight is on the job, as usual.
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vorticity is now vertically stacked and a circulation is showing up on visible imagery around 16N 51W

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97L in the process of poof.
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Quoting VAbeachhurricanes:
I think we are all missing the point of the blog...
Look at that poor bunny... looks so sad and scared!
LOL hey at least it picked a good spot to camp...food, AND PLENTY OF WATER! =)
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Quoting TropicalMan2010:

one thing you forgot this hasnt been in the carribean yet the last few storms didnt develop until there so yea you have to give it a few days.


Actually I meant the tropical atlantic between africa and the antilles. The caribbean sea is better for sustained convection, you are right.
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144. JRRP
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Quoting Hurricanes101:


I wouldnt laugh, he is right

you obviously have a lack of patience


Yes that's true.. well i need to take a break.
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Quoting Hurricanes101:


Wow you are fickle


Just like most of the tropical systems :)
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Quoting CaribBoy:


lool


I wouldnt laugh, he is right

you obviously have a lack of patience
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Quoting TropicalMan2010:

havent said this in a while...lack of patience, etc


lool
Member Since: October 6, 2007 Posts: 0 Comments: 6164
That's always a problem to sustain convection in the ATL even with no SAL.
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Quoting CaribBoy:
Well 97L back to 30% Ok NEXT...


Wow you are fickle
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Well 97L back to 30% Ok NEXT...
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Somebody needs to rescue that poor bunny!!!!!!
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after reading dr masters blog notice he said one more major. most likely it will be in the carib?
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Good afternoon all.

Portlight has been working all morning to gain an understanding of the flooding in eastern NC due to the recent rains associated with what was TS Nichole. We have spoken with the Jacksonville EOC as well as several local governments in the area. At this point, it seems some of the hardest hit areas are in Onslow county in the vicinity of Bear Creek, Hubert, and Swansboro. We have also spoken with a local church in Jacksonville which reported significant flooding along Piney Green Rd where many homes are flooded as well as an apartment complex. When asked to provide a guesstimate of how many homes were flooded in the Hubert/Swansboro area the lady provided us with a very rough guess of 300.

From this very early information, we expect that there will be significant needs in Eastern NC and While we are still looking for more specific information from the hardest hit areas; we are also preparing a truck and trailer load of supplies to carry up. While delivering these supplies we will also work with local officials, churches, and citizens of these communities in order identify the most pressing needs of the under-served and forgotten people. Please consider making a donation to help support the North Carolina flood victims.

Busy day ahead as preparations are being made, so please leave any response to this on the Portlight Blog. As more media starts coming out about the impacted areas, please feel free to post it to the blog. Thanks everyone
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Quoting atmoaggie:
Are you getting that from HURDAT yourself, or is there something written you can point to concerning that point?

Not doubting. Good post, which I find interesting and want to look further into...

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.
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129. JeffMasters (Admin)
Quoting clubjuggle:
From Dr. Masters:

"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 named storms and hurricanes in the Atlantic season occur after October 1. Tropical Storm Nicole brought us up to fourteen named storms for the year, so we should expect about four more named storms this year with one or two of these being hurricanes."

If this is the two-thirds point, shouldn't we be expecting seven more named storms, since 14 is 2/3 of 21?


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
I think we are all missing the point of the blog...
Look at that poor bunny... looks so sad and scared!
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Quoting DarIvy959810:

Thanx


you're welcome :)
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Quoting kmanislander:
Good morning everyone

The current situation in the Atlantic is interesting. There are in fact two areas from which development could come. There is a low that is easily seen in the visible loops approaching Barbados near 13 N and 57W. 97L is further out in the Atlantic and can also be seen in this loop which shows the two areas I am referring to.

The 850 mb vorticity map shows where these two lows are located and in particular you will see that the signature just East of Barbados has become much better defined this morning. Either one of these, or both, could develop in the days ahead but the low closest to the islands would not likely develop right away due to generally less favourable conditions in the eastern Caribbean.


Good update
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Quoting CaribBoy:
12Z GFS, NOGAPS, CMC and NAM Computer Models all move 97L toward to Leewards, PR, then DR

Thanx
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wow, that is pretty unanimous support; however, up to that point the high might be strong then maybe something makes it recurve. Or, maybe the high will be even stronger to force a more westward push

anyhow, somehow the models are not latching onto development as much as the previous days
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Quoting Jeff9641:
FL may want to watch what could be OTTO next week as he looks like he may miss the turn North and head WNW.

First the Islands and Greater Antilles must watch this
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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.

Been busy this morning and just checking in after Your update....That is one bold prediction Dr. M and I guess you are not second guessing any of the major prediction outlets (NOAA-Gray, etc.) in terms of numbers. Problem is no one can predict the track and "where" they might go. With activity shifting to the West, I supposed you are also suggesting that the Gulf is not forclosed yet from possibly seeing a major before the season ends?.........Just Sayin........ :)
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Center is close to 16N 51W, and it's exposed.
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12Z GFS, NOGAPS, CMC and NAM Computer Models all move 97L toward to Leewards, PR, then DR
Member Since: October 6, 2007 Posts: 0 Comments: 6164
What, only 116 comments? Everybody must be enjoying the break....

Well, it's raining like crazy here.... must be the FROPA, since I'm not seeing any obviously tropical type developments via satellite....



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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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