Be prepared! The man who called Hurricane Sandy forecasts a rough 2021 U.S. hurricane season.

I am making this available for our readers so like last year, you can see that we put out the “numbers” in March then follow it up in April with where we believe they are going. This is to show our in-house research on all of this, though we can only show the results rather than get into the nuts and bolts of reasoning here. I will say that the warmer cycle of the Atlantic basin and enhanced MJO reactions in the Pacific ocean seem to be giving us earlier hints, so this is a good test.

The second item, and this is my OPUS, getting a more descriptive scale for hurricanes. I have been working on this for two decades and you can read it below at this link:

https://www.weatherbell.com/power-and-impact-scale

April, 2021:

  • Another big year is on the way.
  • There may be 3 predominant tracks this season.
    • One each for the eastern and central Atlantic and the other in close.
  • Late feedback development will likely be a big forecast challenge again.
  • Not as quick a start, but overall impact in worst case could rival last year and back to back challenge 04,05 tandem

Named Storms: 16-22
Hurricanes: 9-13
Major Hurricanes: 3-6
ACE: 150-200

U.S. Landfalling Hurricanes: 3-6
U.S. Major Impact Landfalls: 2-4

U.S. Hurricane conditions: 4-8

For the entire basin, I think that the overall storms will be relatively stronger than normal outside of the Main Development Region (MDR). The naming frenzy, combined with warm water farther to the north, will tend to pull the mean area to the north.

For now, the numbers remain the same as the March issuance. I have added another category, hurricane conditions, as a storm can stay offshore and still blast someone with a hurricane. The definition of landfall is a single point, but storms are not single points. If you are in the eyewall for 12 hours, even if the storm stayed offshore (this has happened quite a lot around Cape Hatteras and can happen with a stalling storm that is paralleling the coast nearby), then you could be having hurricane impacts without a technical landfall. A great example of this, perhaps the best, was Saffir-Simpson Category 4 Helene in 1958, staying offshore but still causing major hurricane impacts on the North Carolina coast. That produced Cape Fear’s strongest gust on record.

While I expect plenty of recurves and northern Atlantic spinups, a more pronounced cluster of tracks may develop. So the Windward Islands will have higher than average activity. Otherwise, the main tropical development areas and islands will be near normal. The only place with below normal conditions will be in the area of Central America that was devastated last year.

Our hurricane forecast: Another big year is on the way

The red areas represent a risk of more than 6 times the normal impact. Yellow is 3 times and green is below normal. For example, this means that if the average impact per year in an area is Saffir-Simpson 1.5 (all the years and see what the total rating is at landfall and divide by those years), then that area highlighted in red should get a total of 15. It can occur in multiple storms. Since this example would imply a total of 9, it means it is highly likely a major or two will hit there. Like using a normal snowfall and temperature to compute deviation from average, you must also look at the specific area, as those places to the northeast don’t get hit as much as the Gulf Coast.

I will use last year as a quick and dirty example of what I am talking about. Let’s take the western Gulf of Mexico outlined in the red from last year’s impact forecast:

Our hurricane forecast: Another big year is on the way 2

Talk about an advertisement for our ideas, look at the NOAA warning verification:

Our hurricane forecast: Another big year is on the way 3

This was the activity in the western Gulf of Mexico last year:

Our hurricane forecast: Another big year is on the way 4

Just in that area alone, there were 15 impact points in 2020. Over the years the estimate I came up with as an average (many years there are no hurricanes in here) is 1.5. Last year was 10 times that. So that is the metric I am trying to create to score this.

Now for the sake of argument, why would the season be less active, perhaps much less, than what I am portraying? There are seasons that looked like they should have been much bigger, like 1956, 2007, and 2013, which turned out to have much less activity. Just like this winter looked more like an El Niño at times (despite a moderate La Niña) or the 1951-52 and 2018-19 winters turned out to be opposite of what the ENSO signal gave, you can have a period when there is a large-scale driver that is overwhelming the pattern. The total tropical activity (ACE) of those 3 years above was only around 67! I always make sure I look at what can go wrong. The problem is that though I have identified these before, I have had trouble beforehand in picking them out. So that’s a concern here.

2007 was a case of the ridge being too far to the south over the Southeast. Modeling this year is showing the ridge in the classic banana arc over the top.

Our hurricane forecast: Another big year is on the way 5

These are the 5-highest impact years in the current warm era:

Our hurricane forecast: Another big year is on the way 6

A close-up of the 500 mb forecast:

Our hurricane forecast: Another big year is on the way 7

So right off the bat, the signature is there. The old-timers used to call the positives over the Maritimes the “Newfoundland wheel” because higher than average surface pressures are pulled northward and anything under it would be wheeled into the U.S.

The non-years have the ridge over the Heartland and a trough in the opposite areas:

Our hurricane forecast: Another big year is on the way 8

So that is the opposite of what is being forecasted here. Given the evolution of the spring pattern, I am pretty confident we are not going to see the inactive sample.

Another element that could slow the season down is that we will not be getting the “forecast gift” of the MJO this year. For those of you that read our forecasts last year, you don’t know how many nights I thanked God for that change in the MJO regime we caught so that we could give everyone a heads up about the activity that we were going to see. I did not, nor have I seen, any writeup in previous years jump on the change in the MJO like that. In fact, it was the winter season debacle that actually helped me since when I figured that out and understood the opposite phases for cold were also the strongest hurricane hit correlations, it became clear.

So you cannot ignore the MJO. Phase 4 is the phase that correlates to high northwestern Gulf of Mexico activity.

Our hurricane forecast: Another big year is on the way 9

By and large, the storms hit on the opposite side of the MJO hemisphere that we saw the MJO in during the prior winter.

January-March 2020 MJO:

Our hurricane forecast: Another big year is on the way 10

July-September 2020:

Our hurricane forecast: Another big year is on the way 11

You can’t get much more opposite.

So to catch a change in that major hemispheric driver meant it was going to hold in some form for several months. Not only do we not have that tool this year, but there is always a danger that pattern is still driving all this now because we are in a long-standing pattern that has been undetected. So the best I can do is try to line up the analog season tropical precipitation with the modeling ideas.

Of late the MJO has been tending to go opposite of last year, but I think that is because there are changes in the Pacific going on that will then level off and allow it to be weaker this year or in Phases 3 & 4. That is not etched in stone.

So you see there are two “negative” influences, but also in this section the countering strong model correlation to it being the opposite at 500 mb to those negative years.

Recently the MJO has been gaining amplitude and a move into those phases in May and June ( 8,1,2,3) could improve on the hints I am seeing from this far out:

Our hurricane forecast: Another big year is on the way 12

European Model ACE forecast

The average of the April European ACE forecasts over the past 5 years has averaged a bit over 70% of normal. Every one of those years they had below normal activity. Its greatest blunder was 2017, where it had about 70% of normal. The average ACE of all these years was 175 or about 160% of the average ACE.

The implications are startling. If they have not changed the way they compute that, then for it to be seeing that large of an ACE forecast when it had below normal activity during two hyper-active years, then it must be seeing something. I suspect they may have made some kind of correction, but it’s very tough to dig into the weeds to find that stuff.

Global precipitation pattern

Here is the forecasted pattern for August-October:

Our hurricane forecast: Another big year is on the way 13

That shows a lot of convection from the Indian Ocean eastward to Indonesia. This would line up with the JMA upward motion forecast for summer along with its precipitation forecast.

Our hurricane forecast: Another big year is on the way 14

It is displaced a couple of months from the heart of the season, though. This lines up with the analog pattern over Indonesia into the eastern Indian Ocean, but also notice the drier western Indian Ocean in the analogs and the JMA showing sinking air over the Gulf of Mexico.

Our hurricane forecast: Another big year is on the way 15

The Euro’s forecast precipitation pattern: