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Hurricane Florence

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On ‎14‎/‎09‎/‎2018 at 08:08, mb018538 said:

Indeed - the wind was never going to be the main problem with this storm. The fact that up to 40 inches of rain could fall in places will be the ultimate disaster, much like Harvey last year.

Hi Guys...

Has anyone seen the rainfall totals that Florence accumulated?

Did we manage to get the 3 - 4 feet promised?

I think that 10 -12 inches are fairly normal for a Hurricane.

I have actually 'been through' 24 inches from a storm in Aussie, so what are the actual figures inn terms of wind and rainfall?.

MIA

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8 minutes ago, Midlands Ice Age said:

Hi Guys...

Has anyone seen the rainfall totals that Florence accumulated?

Did we manage to get the 3 - 4 feet promised?

I think that 10 -12 inches are fairly normal for a Hurricane.

I have actually 'been through' 24 inches from a storm in Aussie, so what are the actual figures inn terms of wind and rainfall?.

MIA

The largest totals of rainfall from the start appear to be around 40 inches in parts of North Carolina which is more then what a fair few places get in the UK annually.

https://www.bbc.co.uk/news/world-us-canada-45544424

The winds luckily eased off a bit before landfall although they were still at 110mph. The floodwaters may carry on rising and peak on Tuesday. Given Florence is having a foray further inland the risk of landslides is also high.

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5 hours ago, Quicksilver1989 said:

The largest totals of rainfall from the start appear to be around 40 inches in parts of North Carolina which is more then what a fair few places get in the UK annually.

https://www.bbc.co.uk/news/world-us-canada-45544424

The winds luckily eased off a bit before landfall although they were still at 110mph. The floodwaters may carry on rising and peak on Tuesday. Given Florence is having a foray further inland the risk of landslides is also high.

QS..

Thanks for your reply.

I was asking for actual rainfall numbers not MSM versions.

 I think that your version is a bit  'off the mark'.

CNN have just reported that Wilmington (live report) has received around 15 inches, over 4 -5 days.

It appears to be in the middle of the rainfall charts.

I think that 40 inches would have produced similar results to those in the Philippines.

So far I have seen people wading around in about 1 foot of water, although rivers clearly are in spate.

I have also watched  Storm Chases like Bret Adair and he seems to be freely moving around the area, with no rain falling.

I watched him on Thursday when the storm hit and from the front, ( not the island in front of Wilmington),  he reported wind speeds of 75 mph.  Right on the Cat 1 lower limit.  This continued for a few hours before dropping to 40 - 60 mph gusts.   (this was all live).

Also note the Met Office have just issued warnings of similar gusts for the North of the UK for Wednesday. 

MIA

 

Edited by Midlands Ice Age

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DnPUff2UcAAVhX8.thumb.jpg.7531606071827930b86faa7c199e44cc.jpg

Edited by Mapantz
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5 hours ago, Midlands Ice Age said:

QS..

Thanks for your reply.

I was asking for actual rainfall numbers not MSM versions.

 I think that your version is a bit  'off the mark'.

CNN have just reported that Wilmington (live report) has received around 15 inches, over 4 -5 days.

It appears to be in the middle of the rainfall charts.

I think that 40 inches would have produced similar results to those in the Philippines.

So far I have seen people wading around in about 1 foot of water, although rivers clearly are in spate.

I have also watched  Storm Chases like Bret Adair and he seems to be freely moving around the area, with no rain falling.

I watched him on Thursday when the storm hit and from the front, ( not the island in front of Wilmington),  he reported wind speeds of 75 mph.  Right on the Cat 1 lower limit.  This continued for a few hours before dropping to 40 - 60 mph gusts.   (this was all live).

Also note the Met Office have just issued warnings of similar gusts for the North of the UK for Wednesday. 

MIA

 

StormTotalQPF_SFC1.png

 

40 inches of rain in the most exposed areas sounds entirely reasonable in the most exposed areas the highest totals from Florence updated as of today are:

Elizabethtown: 35.93 inches                   
Swansboro: 33.89 inches                  
Gurganus: 30.38 inches                                      
Hofmann Forest: 29.62 inches                                      
Hampstead: 29.52 inches                                      
Sunny Point: 27.44 inches                
Oak Island: 26.98 inches                                      
Wilmington: 26.58 inches                                    
Whiteville: 25.91 inches                                      
Newport/Morehead City: 25.20 inches               
Mount Olive: 25.04 inches  

https://edition.cnn.com/us/live-news/florence-flooding-north-carolina/index.html

So Wilmington has got more then the 15 inches you mentioned earlier. Thankfully its beginning to clear though some GFS runs suggest it will do something similar to Ivan and curve back I hope this isn't the case.

It sounds like you are trying to play down the impacts of the storm MIA but apart from the unexpected weakening prior to landfall it has been exceptionally well forecast. It still made landfall as a category 2 hurricane and I don't think the winds in the UK compare to anything observed by Florence.

I know climate change deniers won't like it but in the North Atlantic the relationship between ACE and tropical Atlantic SST is undeniable, especially when you take the influence of ENSO away. I spent a whole dissertation looking at this....

We may not see more tropical storms forming but the intensification of them will be greater and stronger hurricanes will track over higher latitudes, you only have to look at Ophelia last year as an example. 

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Here is a 104 hr loop of Florence,no wonder there is flooding.

 

Edited by Allseasons-si

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1 hour ago, BornFromTheVoid said:

Fake weather!

a5d0e83.thumb.jpg.63fe27d747e1622f6c6efa477dd49360.jpg

Still they go on!.

Love the guy walking across with his pumps on in the post by Soft Lad.

I had a greater depth of water over my golf shoes today, here in the Midlands!. 

Love the 500 million without power...

As you say typical MSM.

MIA

 

Edited by Midlands Ice Age

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32 minutes ago, Midlands Ice Age said:

Still they go on!.

Love the guy walking across with his pumps on in the post by Soft Lad.

I had a greater depth of water over my golf shoes today, here in the Midlands!. 

Love the 500 million without power...

As you say typical MSM.

MIA

 

I'll agree for the last two pics...

The thing that worries me is that the MSM can exaggurate things and when this seeds distrust between the public and scientists (when scientists aren't to blame) then there is trouble. Still even the BBC isn't anywhere near as bad as the example from BFTV!

A lot of people seemed to heed the advice of the NHC forecasts and evacuated North Carolina, seems things have got better since Katrina. One criticism I found with some media outlets is there were focusing far too much on the Category of the hurricane rather then emphasising the rainfall threat.

Hopefully the flooding won't be too bad. Though there have been huge rainfall totals, soil moisture is lower then what I thought it would be prior Florence's landfall.

Interesting a few GFS runs have been producing a zombie Florence in recent runs, would be remarkable if it persisted still as it formed later on in August I think, so it would be a remarkably long lived storm system.

Looking into the future and I've noticed some cooler SSTs are showing in the MDR again. Due to this I reckon the rest of the Atlantic Hurricane season to only have average activity, with Florence being the main storm for this year. Isaac really didn't get anywhere in the Gulf of Mexico so I'm not convinced too much will happen in this region during October (activity tends to be more focused there later on into the hurricane season).

anomg.9.20.2018.gif

 

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9 hours ago, Quicksilver1989 said:

I'll agree for the last two pics...

The thing that worries me is that the MSM can exaggurate things and when this seeds distrust between the public and scientists (when scientists aren't to blame) then there is trouble. Still even the BBC isn't anywhere near as bad as the example from BFTV!

A lot of people seemed to heed the advice of the NHC forecasts and evacuated North Carolina, seems things have got better since Katrina. One criticism I found with some media outlets is there were focusing far too much on the Category of the hurricane rather then emphasising the rainfall threat.

Hopefully the flooding won't be too bad. Though there have been huge rainfall totals, soil moisture is lower then what I thought it would be prior Florence's landfall.

Interesting a few GFS runs have been producing a zombie Florence in recent runs, would be remarkable if it persisted still as it formed later on in August I think, so it would be a remarkably long lived storm system.

Looking into the future and I've noticed some cooler SSTs are showing in the MDR again. Due to this I reckon the rest of the Atlantic Hurricane season to only have average activity, with Florence being the main storm for this year. Isaac really didn't get anywhere in the Gulf of Mexico so I'm not convinced too much will happen in this region during October (activity tends to be more focused there later on into the hurricane season).

anomg.9.20.2018.gif

 

QS..

 You mentioned a high ACE value in a previous post.

Have you access to the current value for 2018, we are now just over 2/3 of the way through the season, and an update would be appreciated.

I have the ACE values for  both the  Atlantic and Pacific detailed below -

 

Categories[edit]

330px-Atlantic_ace_timeseries_1850-2014.
 
Atlantic basin cyclone intensity by Accumulated cyclone energy, timeseries 1850-2014

A season's ACE is used by NOAA and others to categorize the hurricane season into 3 groups by its activity.[4] Measured over the period 1951–2000 for the Atlantic basin, the median annual index was 87.5 and the mean annual index was 93.2. The NOAA categorization system divides seasons into:

  • Above-normal season: An ACE value above 111 (120% of the 1981–2010 median), provided at least two of the following three parameters are also exceeded: number of tropical storms: 12, hurricanes: 6, and major hurricanes: 2.
  • Near-normal season: neither above-normal nor below normal
  • Below-normal season: An ACE value below 66 (71.4% of the 1981–2010 median), or none of the following three parameters are exceeded: number of tropical storms: 9, hurricanes: 4, and major hurricanes:

 

 

 

File:Hist east pac ace trend 1981-2015.gif

 

and these show little change in intensity   (if you accept a drop in the 19th century due to no satellite measurements).

The item I used above also contains lists of the number of storms and hurricanes each year and there is little apparent change in the numbers.

I understand you have studied l the situation in detail. Could you give us a clearer picture?

MIA 

Edited by Midlands Ice Age

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53 minutes ago, Midlands Ice Age said:

QS..

 You mentioned a high ACE value in a previous post.

Have you access to the current value for 2018, we are now just over 2/3 of the way through the season, and an update would be appreciated.

I have the ACE values for  both the  Atlantic and Pacific detailed below -

 

Categories[edit]

330px-Atlantic_ace_timeseries_1850-2014.
 
Atlantic basin cyclone intensity by Accumulated cyclone energy, timeseries 1850-2014

A season's ACE is used by NOAA and others to categorize the hurricane season into 3 groups by its activity.[4] Measured over the period 1951–2000 for the Atlantic basin, the median annual index was 87.5 and the mean annual index was 93.2. The NOAA categorization system divides seasons into:

  • Above-normal season: An ACE value above 111 (120% of the 1981–2010 median), provided at least two of the following three parameters are also exceeded: number of tropical storms: 12, hurricanes: 6, and major hurricanes: 2.
  • Near-normal season: neither above-normal nor below normal
  • Below-normal season: An ACE value below 66 (71.4% of the 1981–2010 median), or none of the following three parameters are exceeded: number of tropical storms: 9, hurricanes: 4, and major hurricanes:

 

 

 

File:Hist east pac ace trend 1981-2015.gif

 

and these show little change in intensity   (if you accept a drop in the 19th century due to no satellite measurements).

The item I used above also contains lists of the number of storms and hurricanes each year and there is little apparent change in the numbers.

I understand you have studied l the situation in detail. Could you give us a clearer picture?

MIA 

ACE is currently running at 80, which is above average at this point but not especially so...

I looked at Atlantic Hurricanes for my undergrad dissertation and here are the general things that are happening:

- The number of tropical storms is not increasing but the rate at which they become major hurricanes is.

- ENSO and tropical Atlantic SSTs are the main contributing factor towards Atlantic hurricane activity

- ACE is underestimated before 1950 as the number of ships moving around in the Atlantic is far less (especially during the world wars).

We can create a regression model dividing years into La Nina, El Nino or neutral years:

image.thumb.png.e62121551d679c1f5c37c682e1623de1.pngimage.thumb.png.40c4764ffad89525091611c924e333fa.pngimage.thumb.png.34c6754d4e356b2f0870a2681b5a5581.png 

Interestingly an El Nino year will typically see below average activity regardless of SSTs. La Nina years can be hyperactive if a La Nina is particularly strong as long as SSTs aren't too far below average. 

Bear in mind the tropical North Atlantic is warming rapidly and this is a concern as ENSO neutral years show a strong relationship between SST anomaly and ACE. Therefore we can conclude the only way activity can drop in this basin is if we see an increase in El Nino events. If you do a multiple linear regression you get the folllowing:

image.thumb.png.d6db2df0c095eeb8002d8993b2e57a38.png

The increase in hyperactive seasons since 1995 is marked and this is because tropical Atlantic SSTs were so warm. The period from 1950-1969 was also active but tropical Atlantic SSTs weren't as warm but there was more La Nina's
 

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1 hour ago, Midlands Ice Age said:

 

Wrong thread?

 MIA

Nope. Kevin was the Flag atop frying pan tower that was ripped to shreds. Became a bit of an internet sensation.

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8 hours ago, Quicksilver1989 said:

ACE is currently running at 80, which is above average at this point but not especially so...

I looked at Atlantic Hurricanes for my undergrad dissertation and here are the general things that are happening:

- The number of tropical storms is not increasing but the rate at which they become major hurricanes is.

- ENSO and tropical Atlantic SSTs are the main contributing factor towards Atlantic hurricane activity

- ACE is underestimated before 1950 as the number of ships moving around in the Atlantic is far less (especially during the world wars).

We can create a regression model dividing years into La Nina, El Nino or neutral years:

image.thumb.png.e62121551d679c1f5c37c682e1623de1.pngimage.thumb.png.40c4764ffad89525091611c924e333fa.pngimage.thumb.png.34c6754d4e356b2f0870a2681b5a5581.png 

Interestingly an El Nino year will typically see below average activity regardless of SSTs. La Nina years can be hyperactive if a La Nina is particularly strong as long as SSTs aren't too far below average. 

Bear in mind the tropical North Atlantic is warming rapidly and this is a concern as ENSO neutral years show a strong relationship between SST anomaly and ACE. Therefore we can conclude the only way activity can drop in this basin is if we see an increase in El Nino events. If you do a multiple linear regression you get the folllowing:

image.thumb.png.d6db2df0c095eeb8002d8993b2e57a38.png

The increase in hyperactive seasons since 1995 is marked and this is because tropical Atlantic SSTs were so warm. The period from 1950-1969 was also active but tropical Atlantic SSTs weren't as warm but there was more La Nina's
 

QS...

By complete coincidence it would seem that NOAA have been looking into hurricanes in the Atlantic and have issued a paper. 

They say that any warming effects from CO2 will not have any impact until later in the 21st century.

https://www.gfdl.noaa.gov/global-warming-and-hurricanes/

Not on the total number but on Cat 5's.   

Looks like it has been issued to kill the hype that seems to be prevalent when even a Cat1 hits land.

Summary says it all really -

Quote -

In summary, neither our model projections for the 21st century nor our analyses of trends in Atlantic hurricane and tropical storm counts over the past 120+ yr support the notion that greenhouse gas-induced warming leads to large increases in either tropical storm or overall hurricane numbers in the Atlantic. While one of our modeling studies projects a large (~100%) increase in Atlantic category 4-5 hurricanes over the 21st century, we estimate that such an increase would not be detectable until the latter half of the century, and we still have only low confidence that such an increase will occur in the Atlantic basin, based on an updated survey of subsequent modeling studies by our and other groups.

Therefore, we conclude that despite statistical correlations between SST and Atlantic hurricane activity in recent decades, it is premature to conclude that human activity–and particularly greenhouse warming–has already caused a detectable change in Atlantic hurricane activity. (“Detectable” here means the change is large enough to be distinguishable from the variability due to natural causes.) However, human activity may have already caused some some changes that are not yet detectable due to the small magnitude of the changes or observation limitations, or are not yet confidently modeled (e.g., aerosol effects on regional climate).

We also conclude that it is likely that climate warming will cause Atlantic hurricanes in the coming century have higher rainfall rates than present-day hurricanes, and medium confidence that they will be more intense (higher peak winds and lower central pressures) on average. In our view, it is uncertain how the annual number of Atlantic tropical storms will change over the 21st century. All else equal, tropical cyclone surge levels should increase with sea level rise as projected for example by IPCC AR5. These assessment statements are intended to apply to climate warming of the type projected for the 21st century by prototype IPCC mid-range warming scenarios, such as A1B or RCP4.5.

The relatively conservative confidence levels attached to our tropical cyclone projections, and the lack of a claim of detectable anthropogenic influence on tropical cyclones at this time contrasts with the situation for other climate metrics, such as global mean temperature. In the case of global mean surface temperature, the IPCC AR5 presents a strong body of scientific evidence that most of the global warming observed over the past half century is very likely due to human-caused greenhouse gas emissions.

 

 

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59 minutes ago, Midlands Ice Age said:

QS...

By complete coincidence it would seem that NOAA have been looking into hurricanes in the Atlantic and have issued a paper. 

They say that any warming effects from CO2 will not have any impact until later in the 21st century.

https://www.gfdl.noaa.gov/global-warming-and-hurricanes/

Not on the total number but on Cat 5's.   

Looks like it has been issued to kill the hype that seems to be prevalent when even a Cat1 hits land.

Summary says it all really -

Quote -

In summary, neither our model projections for the 21st century nor our analyses of trends in Atlantic hurricane and tropical storm counts over the past 120+ yr support the notion that greenhouse gas-induced warming leads to large increases in either tropical storm or overall hurricane numbers in the Atlantic. While one of our modeling studies projects a large (~100%) increase in Atlantic category 4-5 hurricanes over the 21st century, we estimate that such an increase would not be detectable until the latter half of the century, and we still have only low confidence that such an increase will occur in the Atlantic basin, based on an updated survey of subsequent modeling studies by our and other groups.

Therefore, we conclude that despite statistical correlations between SST and Atlantic hurricane activity in recent decades, it is premature to conclude that human activity–and particularly greenhouse warming–has already caused a detectable change in Atlantic hurricane activity. (“Detectable” here means the change is large enough to be distinguishable from the variability due to natural causes.) However, human activity may have already caused some some changes that are not yet detectable due to the small magnitude of the changes or observation limitations, or are not yet confidently modeled (e.g., aerosol effects on regional climate).

We also conclude that it is likely that climate warming will cause Atlantic hurricanes in the coming century have higher rainfall rates than present-day hurricanes, and medium confidence that they will be more intense (higher peak winds and lower central pressures) on average. In our view, it is uncertain how the annual number of Atlantic tropical storms will change over the 21st century. All else equal, tropical cyclone surge levels should increase with sea level rise as projected for example by IPCC AR5. These assessment statements are intended to apply to climate warming of the type projected for the 21st century by prototype IPCC mid-range warming scenarios, such as A1B or RCP4.5.

The relatively conservative confidence levels attached to our tropical cyclone projections, and the lack of a claim of detectable anthropogenic influence on tropical cyclones at this time contrasts with the situation for other climate metrics, such as global mean temperature. In the case of global mean surface temperature, the IPCC AR5 presents a strong body of scientific evidence that most of the global warming observed over the past half century is very likely due to human-caused greenhouse gas emissions.

 

 

It's a difficult one to judge, in the Pacific I agree that not much may change, given that SSTs across much of the basin are so warm. In the Atlantic SSTs in the main development region however are borderline for tropical storm development so any change in SSTs is likely to have a marked impact.

The whole article does go through some potential consequences of increased global temperature on tropical cyclone activity, with some of the key points:

  • Tropical cyclone rainfall rates will likely increase in the future due to anthropogenic warming and accompanying increase in atmospheric moisture content.  Modeling studies on average project an increase on the order of 10-15% for rainfall rates averaged within about 100 km of the storm for a 2 degree Celsius global warming scenario. (Higher SSTs mean more fuel for storms)
     
  • Tropical cyclone intensities globally will likely increase on average (by 1 to 10% according to model projections for a 2 degree Celsius global warming). This change would imply an even larger percentage increase in the destructive potential per storm, assuming no reduction in storm size.  Storm size responses to anthropogenic warming are uncertain.

     
  • The global proportion of tropical cyclones that reach very intense (Category 4 and 5) levels will likely increase due to anthropogenic warming over the 21st century.  There is less confidence in future projections of the global number of Category 4 and 5 storms, since most modeling studies project a decrease (or little change) in the global frequency of all tropical cyclones combined.

There is a clear relationship between SSTs and Atlantic ACE when we don't have El Nino events but there are a few exceptions to the rule. 2013 and 2007 for example should have been hyperactive seasons but were rather quiet. Saharan dust and wind shear changes may hamper a rise in ACE in association with increasing SSTs. If  El Nino states become more common under a warming climate expect Atlantic hurricane activity to get quieter in a warming climate.

However my take on it all is that if  we don't see any systematic change in ENSO behaviour then ACE will continue to generally increase. Whether that is the case we shall see.

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