Expert forecasts for 2021 North Atlantic Hurricane Season

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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: CSU=17/8/4

#61 Postby chris_fit » Fri Apr 09, 2021 8:30 am

Wow, those seem like high odds for impacts in FL. Almost a coin flip for a Major getting within 50 miles and 3 outa 4 for a hurricane.
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: CSU=17/8/4

#62 Postby Shell Mound » Fri Apr 09, 2021 10:03 am

chris_fit wrote:Wow, those seem like high odds for impacts in FL. Almost a coin flip for a Major getting within 50 miles and 3 outa 4 for a hurricane.

I would, however, bear in mind that the probabilities are based solely on a statistical methodology, not forecast steering currents, as pp. 31–2 indicate:
Net landfall probability is shown to be linked to the overall Atlantic basin Net Tropical Cyclone activity (NTC; see Table 10). NTC is a combined measure of the yearto-year mean of six indices of hurricane activity, each expressed as a percentage difference from the 1950-2000 climatological average. Long-term statistics show that, on average, the more active the overall Atlantic basin hurricane season is, the greater the probability of U.S. hurricane landfall.
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: CSU=17/8/4

#63 Postby tolakram » Fri Apr 09, 2021 10:05 am

Also keep in mind that a 'hit' on South Florida has various definitions. Having an actual landfall (eye crossing the coast) is generally not one of them.
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: Crownweather Services is up

#64 Postby Steve » Sat Apr 10, 2021 12:45 am

Audrey2Katrina wrote:
aspen wrote:
cycloneye wrote:Crownweather Services is up with 16/8/4 and a repeat of 2017?

https://i.imgur.com/acy6hGg.png

Hopefully the below-average forecast for the WCar holds. Central America really needs a break after Gamma, Delta, Zeta, Eta, and Iota all within 6 weeks.


The Central Gulf can use a break, too... after Cristobal, Laura*, Marco, Sally*, Beta, Delta*, and Zeta*... :wink:


It was a crazy season. I spent a ton of porch time staring at clouds. Zeta was the funnest In New Orleans, but it blew through in like 3 hours. Sunset landfall too which is a dream.
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: CSU=17/8/4

#65 Postby Steve » Sat Apr 10, 2021 1:01 am

chris_fit wrote:Wow, those seem like high odds for impacts in FL. Almost a coin flip for a Major getting within 50 miles and 3 outa 4 for a hurricane.


Yep. Florida, and certainly Louisiana with the H/MH threat increase in % and North Carolina all stand out as primary threat areas in that table.

To the post about 2006, lots of us on this site were still shell shocked, and lots of the preliminary indicators favored a potentiality more active season than what it was. Regardless, most of the credible signs are pointing to a strap on that seatbelt kind of season. ?
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#66 Postby Steve » Sat Apr 10, 2021 8:00 pm

Joe B @ Weatherbell put out his impact map and mentioned their 4 strongest analog years - 2005, 2008, 2017 and 2020. Like you have to be ******* with me about any of those 4 years ever being mentioned in an analog much less all 4 of them. He tied it to a cooler May for the east US with a trough in the NE US extended over into the north Atlantic which promotes ridging further south that whenever the trough pulls back, the ridge migrates into the NE US and there's the setup for US landfalls.

He likes the US impact zones exactly as it went down last year - Texas, LA, Central Gulf Coast and North & South Carolina. All those are 6x the normal on their impact scale (but I'm assuming you'd have to be a subscriber to get that info - maybe not but I wasn't planning to look for it). Florida and the Yucatan are 3x as is most of the rest of the US Coast. He forecasts less impacts for Central America which is important with all the chaos they had last year and the general upheaval.

Obviously Bastardi is a caricature/meme for overhyping. And this forecast is literally a double-down on a severe year for hype at a squared level. Just think back to US impacts from storms from those seasons - skipping all the weaker stuff:

2005 was record setting in a lot of ways and featured Dennis, Katrina, Rita and Wilma and certainly Emily in the Caribbean and Mexico.

2008 had Ike. Gustav caused a lot of angst in the bayou/south-central Louisiana where we were at then because of the 2005 season. Luckily it never could re-stack, but I remember Mayor Nagin in New Orleans saying that it would make Katrina look like chump change as far as hurricane damage when it was expected to hit us as a 4.

2017 featured Harvey and certainly Maria and then Irma for the Leewards.

2020 had Laura, Sally and Delta along with Eta and Iota for Central America and the multiple hits on the Yucatan.

These seasons are 4 of the most extreme seasons ever. All 4 of those seasons featured damages in excess of $50MM with 2005 and 2017 having the two costliest hurricanes ever between Katrina and Harvey. All these years have different records they set from ACE to total damage to only season with multiple majors in November to first time 10 storms in a row became hurricanes, to most number of named storms ever among several other records.

I'll lift the glass of whiskey in jest at this point hoping the volcanoes or something else will render the Weatherbell forecast a joke. Here's hoping it's something to laugh at in November.
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#67 Postby chaser1 » Sat Apr 10, 2021 9:31 pm

:uarrow: Cheers Steve :37: I'll see your shot of single-malt whiskey, and raise you a double shot of tequila :wink: . God help us all if those analogue years tend to verify. I myself still find signals pointing toward the upcoming season as very murky & ill defined (including an uptick in volcanic activity not withstanding).
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#68 Postby Blown Away » Sat Apr 10, 2021 10:28 pm

Does Joe B only post his impact map to his premium customers?
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: Joe Bastardi is up

#69 Postby Shell Mound » Sun Apr 11, 2021 7:16 am

CyclonicFury wrote:
OuterBanker wrote:Why isn't GWO (Global Weather Oscilliations) included in expert forecasts.

They claim 90% accuracy. Predicted the exact landfall of seventeen hurricanes since 2016 seven months in advance.

Can you believe it? Wow!

I have yet to see if anyone here has purchased their services. (or admit they had)

Of course each zone is $300.00, and all services are $12,000.00 (again WOW).

I did want to report that I am going to purchase my zone just to see one.

Once my check for $5,000,000.00 gets here from the Nigeran government.

GWO is a scam. They edit their numbers in hindsight to make it appear as if they were right. I don't ever recall a time where they predicted a below average season.

Do you have evidence to support this? An article from March 2020 shows that GWO’s outlook was relatively accurate. So does this article from February 2019.

GWO’s outlook for 2021 (4:14, 5:13): 17 NS / 9 H / 5 MH, four to five U.S. H LF (including two MH LF); TX, LA, and NY at highest risk.
Last edited by Shell Mound on Sun Apr 11, 2021 7:32 am, edited 2 times in total.
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#70 Postby tolakram » Sun Apr 11, 2021 7:18 am

Blown Away wrote:Does Joe B only post his impact map to his premium customers?


Public next week. Here's his tweet.

 https://twitter.com/BigJoeBastardi/status/1380942142445588489


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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#71 Postby aspen » Sun Apr 11, 2021 7:51 am

Is the University of Arizona going to post pre-season numbers this year?
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#72 Postby Steve » Sun Apr 11, 2021 12:48 pm

Blown Away wrote:Does Joe B only post his impact map to his premium customers?


You can see it on yesterday’s Saturday summary on weatherbell’s home page. It’s the first thing up once he comes on. He explains how they came to the big impact year analogs and says it was first telegraphed last month with the JMA, and now the climate model is showing that NE US/N Atl trough configuration from May that migrates later and allows for high pressure in the NE for the heart of the season.
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#73 Postby CyclonicFury » Mon Apr 12, 2021 1:39 pm

TSR releases their April forecast update tomorrow...will be interesting
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#74 Postby CyclonicFury » Mon Apr 12, 2021 1:44 pm

WeatherTiger has released their April outlook. It doesn't have a precise set of numbers, but interestingly they only predicted a median ACE of 100 - a bit lower than other agencies.
https://weathertiger.substack.com/p/atl ... t-look-413
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season

#75 Postby Beef Stew » Tue Apr 13, 2021 12:17 pm

TSR's April Forecast is out: they're going with 17/8/3 and an ACE of 134.

"The TSR (Tropical Storm Risk) April forecast update for North Atlantic hurricane activity in 2021
anticipates a season with activity that is ~25-30% above the long-term norm and slightly above the 2011-
2020 10-year norm level."

https://www.tropicalstormrisk.com/
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: TSR April Forecast up / Bastardi graphic up

#76 Postby cycloneye » Tue Apr 13, 2021 12:54 pm

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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: TSR April Forecast up / Bastardi graphic up

#77 Postby toad strangler » Tue Apr 13, 2021 1:18 pm

cycloneye wrote:JB high risk areas.



The entire US East Coast.... and then some :lol: :lol:
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: TSR April Forecast up / Bastardi graphic up

#78 Postby cycloneye » Tue Apr 13, 2021 6:06 pm

This is the 2021 one.

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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: TSR April Forecast up / Bastardi graphic up

#79 Postby jconsor » Wed Apr 14, 2021 6:25 am

University of Arizona outlook also indicates a more active season than usual, though not as active as last year.

https://has.arizona.edu/article/2021-hurricane-forecast-kyle-davis-and-xubin-zeng
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Re: Expert forecasts for 2021 North Atlantic Hurricane Season: TSR April Forecast up / Bastardi graphic up

#80 Postby tolakram » Wed Apr 14, 2021 7:07 am

jconsor wrote:University of Arizona outlook also indicates a more active season than usual, though not as active as last year.

https://has.arizona.edu/article/2021-hurricane-forecast-kyle-davis-and-xubin-zeng


Pasting the text of that document here. Very interesting way of calculating seasonal activity.

Forecast of the 2021 Hurricane Activities over the North Atlantic
Kyle Davis and Xubin Zeng
Department of Hydrologic and Atmospheric Sciences
University of Arizona, Tucson, AZ
13 April 2021

Coming off a record-breaking 2020 hurricane season, we provide our view of the 2021 season, which runs from June 1 to November 30. The prediction includes total numbers of named storms, hurricanes, major hurricanes, and accumulated cyclone energy (ACE, defined as the sum of the squares of the 6-hourly windspeeds in knots above tropical storm strength). Our forecast combines dynamic forecasts with machine learning as informed by our physical understanding of hurricane activities.

Specifically we utilize a Random Forest approach based on seasonal forecast data from the European Centre for Medium-Range Weather Forecasts (ECMWF). We utitlize the forecast July/August/September tropical Atlantic area-averaged sea surface temperatures (SSTs) in the same region used in our June predictions (Davis, Zeng, and Ritchie 2015; Davis and Zeng 2019) as well as August/September area-averaged SSTs in the Nino 3.4 region. Our method uses 25 ensemble members from 1993-2016 and 51 members from 2017-2021.

We calibrate the model using data from 1982 to 2006: we first train the model on the first ensemble member (from the model control run) on all data from 1993 to 2006; use it to predict for the other members from 1993 to 2006; and average predictions from all members for a year as our prediction for that year. Then we validate the model using data from 2007 to 2020 in “real time” (for example, for 2015, we would train the model using data from 1993 to 2014 and use the 2015 data to make a prediction for 2015).

Figure 1 compares our model’s performance during the calibration and validation periods against observations and the 5-year running average, or a no-skill metric. Table 1 shows that our model during the calibration and validation periods beat the average error for the 5-year running average in all categories. We began to predict all four quantities, starting from 2020, and Table 2 shows that our April 2020 prediction has a smaller error in each of the quantities than those from two groups with the longest history in hurricane seasonal prediction.

For our April 2021 forecast, we expect above-average hurricane activities over the North Atlantic:

2021 Prediction Probability Range Median Since 1980
Hurricanes 8 6-10 (66%) 7
Major Hurricanes 4 3-5 (74%) 2
Named Storms 18 15-21 (64%) 13
ACE 137 97-177 (59%) 103

Atlantic SSTs are forecast to be warm across the main development region during July, August, and September. In the Pacific, an ENSO-neutral state is most likely to prevail in August and September though a La Niña is possible.

We will update our prediction in early June 2020.


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