Is Hurricane Alex a Sign?

18 01 2016

Dale C. S. Destin |

By now you may have heard of Hurricane Alex, the first Atlantic hurricane to form in January since the only other one in 1938, according to HURDAT2. Alex is also only the third hurricane to exist over the Atlantic in January. There was Alice2 which formed late December 1954 and continued over into January 1955.

Hurricane Alex, as seen via a NASA satellite image on Jan. 14, 2016.

Hurricane Alex, as seen by a NASA satellite on January 14, 2016.

I suppose a few of the questions raised in some persons minds by Alex are: what does this mean for the upcoming hurricane season; does a January storm equate to an active or inactive season and was Alex caused by climate change?

Looking back at the three other times tropical cyclones – the generic name for depressions, tropical storms and hurricanes – formed in January for clues, I see none.

In 1978, there were 12 named storms (NS), 5 hurricanes and 2 major hurricanes (MH). In 1951, there were also 12 NS, with 8 becoming hurricanes and 3 MH. In 1938, the record shows that after Hurricane One in January, the eventual totals for the year were 9 NS, 4 hurricanes and 2 MH. Nothing unusual!

Based on El Nino Southern Oscillation data, which go back to 1950, Tropical Storm One of 1951 occurred during a moderate La Nina, whereas the 1978 system occurred during a weak El Nino. Of course, Alex formed in one of the strongest, if not the strongest El Nino on record.

Looking at the preceding hurricane seasons to the four January tropical cyclones, I also see nothing interesting.

In 1977, there were 6 NS, 5 hurricanes and a MH; 1950 had 16 NS, 11 hurricanes and 6 MH and 1937 had 11 NS, 4 hurricanes and a MH.  And of course, in 2015, we had 11 NS, four hurricanes and 2 MH. Except for 1950, the other prior years had near normal number of storms.

Of the three previous years with January tropical cyclones, only one had a second preseason tropical cyclone formed before the official hurricane season – June 1 to Nov 30. This was 1951 with Hurricane Able in May. So, one cannot really say that January storms are a precursor to other preseason ones.

Looking a bit more broadly, there have been, at least, six years with preseason hurricanes (May 1970, May 1951, Jan 1938, March and May 1908, May 1889, May 1863) on record since 1851 prior to Alex. For such small sample sizes, no definite conclusions can be made. However, it may be instructive that these six seasons had near normal number of NS and hurricanes.

Here is what Dr. Rick Knabb – Director of the U.S. National Hurricane Center (NHC) – had to say on the meaning of Alex and preseason tropical cyclone activity:

The activity of a hurricane season is more closely linked to the existing climate during the given season. This climate is very difficult to predict in advance of the season, which is evident by the fact that the best performing hurricane season forecasts are those issued around early August.

In speaking with Phil Klotzbach of Colorado State University via email, he shared the view that, “any tropical cyclone forming in January to be more responding to last year’s climate forcings than anything that would be present in 2016.”

So, Alex can be considered a super late hurricane that may be best credited to the 2015 hurricane season as opposed to being a super early system, which will be credited to the 2016 season.

Then there is the question of climate change, which has nothing to do with Alex. The previous three tropical cyclones forming in January occurred before 1979, pretty much predating climate change as an issue. This shows that January cyclones were more frequent before climate change was a concern.

Although HURDAT2 only has three tropical cyclones on record in January, it is a widely known fact that a number of such cyclones were missed prior to the satellite era and possibly shortly thereafter. This is especially so for those short-lived (lasting less than 48 hours) and forming in a similar area to that of Alex.

Given the advanced weather monitoring enterprise that exists today, we in the meteorological fraternity are pretty confident that no such system has formed in the past 20 years, at least. Thus, it would stand to reason that such January tropical cyclones like Alex are becoming fewer with climate change.

Further, according the IPCC, climate change is likely to cause a reduction in the number of tropical cyclones. Thus, based on our understanding of the science, it would be reasonable to expect that out-of-season tropical cyclones, such as Alex, will become even rarer as the more ideal conditions of the summer months would be required for their formation.

One of the things that climate change will alter, that will lead to fewer storms, is the lapse – the change of temperature with increasing height. It will cause it to decrease, leading to a less unstable, hurricane unfriendly atmosphere. In Alex’s case, the environmental lapse rate was very large contrary to the decreasing trend being caused by climate change.

Tropical cyclones in January and preseason hurricanes in general over the Atlantic are very rare; hence, the sample size is very small. Thus, one cannot be dogmatic about what Hurricane Alex means for the upcoming season. Notwithstanding, I am very confident that Alex is an aberration, virtually a freak hurricane, and means nothing for the upcoming hurricane season. It is also clearly not the fault of climate change, which is making it harder for hurricanes to form. Rather, it is simple natural climate variability.

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A Rare January Atlantic Hurricane?

8 01 2016

Dale C. S. Destin |

The fourth ever January tropical cyclone (generic name for depressions, tropical storms and hurricanes) could form in the next five days. Weather models have been indicating, with varying degrees of confidence, that a powerful extratropical cyclone centred near Bermuda could transition into a tropical cyclone.

Extratropical cyclone with centre marked by X, next to the red L. 1200 UTC, Jan 8, 2016

Extratropical cyclone, centre marked by X next to the red L. 1200 UTC, Jan 8, 2016 Surface Chart

How often does this happen? This has happened only three other times over the past 165 years, the last being 1978. On average, the probability of a tropical depression, tropical storm or hurricane developing in January is around 2%. This means that it happens once in about every 50 Januarys/years.

What’s the situation? Already, the extratropical cyclone has winds of 57 knots (65 mph). The winds are of similar strength to a strong tropical storm. However, it lacks tropical characteristics such as a warm core, organized deep convection and strong winds close to its centre of circulation – all features required for it to be classified as a tropical storm or hurricane.

Satellite image of the extratropical cyclone that could transition to tropical cyclone

Satellite image of the extratropical cyclone that could transition into a tropical storm or hurricane

What are the chances of a tropical cyclone this January? Currently, the United States National Hurricane Center (NHC) has given the system a 30% chance of developing into a subtropical or tropical cyclone in the next five days. However, the usually very reliable ECMWF model has the chance greater than 90% for the 48 hours starting from 8 am, Saturday, January 9, 2016.

ECMWF model forecast, valid 8 am Sat, Jan 9 to 8 am Mon, Jan 11, 2016

ECMWF model forecast, valid 8 am Sat, Jan 9 to 8 am Mon, Jan 11, 2016

Will it impact the Caribbean? Whether or not the system develops into a tropical cyclone, it is not expected to have a direct impact on Antigua and the rest of the Caribbean. The centre and storm/hurricane force winds will stay well away from our islands. Notwithstanding, the cyclone will push large battering swells to our shores, making for hazardous marine conditions, especially for sea bathers.

Wave height (ft). Valid 8 pm, Mon, Jan 11, 2016. Issued Jan 8 at 6 pm

Wave height (ft). Valid 8 pm, Mon, Jan 11, 2016. Issued Jan 8 at 6 pm

Wind speed (knots). Valid 8 pm, Mon, Jan 11, 2016. Issued Jan 8 at 6 pm

Wind speed (knots). Valid 8 pm, Mon, Jan 11, 2016. Issued Jan 8 at 6 pm

Where else will it affect? The cyclone will likely make life extremely difficult and dangerous for Team Wadadli and the rest of the rowers taking part in the Atlantic Challenge. In addition to it generating large northerly swells across the preferred path of the race, it is expected to cause strong southerly, westerly and northerly winds during next week.

Swells are expected to reach Africa and Europe during the upcoming week as the system moves east over the eastern North Atlantic.

Where has it affected? Today it caused storm force winds of 43 knots (50 mph) and rain across Bermuda. It has and still is generating very hazardous seas around this island also. Swells from the system have reached the United States east coast and the Bahamas.

What are the other Atlantic January Tropical cyclones? According to NHC’s database – HURDATA2, which dates back to 1851, the three times that there have been tropical cyclones in January are:

None affected any land mass directly.

Has the Caribbean ever receive a direct impact in January? Incidentally, Antigua and the northeast Caribbean were once struck by a Hurricane in January. This happened with Hurricane Alice, which actually formed on December 30, 1954 and crossed over into January 1955, impacting the islands during the first week of the year.

If the extratropical storm does develop into a tropical cyclone it would be called Alex. We will be keeping an eye on this once in a half a century event.

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