Gert passes close by weather buoy 41047

Figure 1

Tropical storm Gert passed close by the weather buoy 41047 yesterday, but you would hardly have known it (fig 2), Gert is still a relatively shallow tropical storm (~1011 hpa), I’ll let you make up your minds when it came closest to weather buoy 41047 (fig 1). The gusts to 80 and 101 knots are spurious groups in the SYNOP reports, either that or my parsing isn’t doing too well with the American buoy reports.

Figure 2 – Courtesy of NHC

The latest forecast for Gert from the NHC has it close to hurricane force at T+48 early on Wednesday (fig 2), if it makes it that’ll be the second one of the season.

Figure 3 – Courtesy of the NHC

It won’t make landfall on the United States, as its forecast to take a sharp right in the next day or so (fig 4).

Figure 4 – Courtesy of the NHC

It looks like the remnants of tropical storm (possibly hurricane) Gert will find their way to this side of the Atlantic next weekend by the looks of this tracking chart from the GEFS model on the wxcharts.eu website (fig 5). The likely track looks likely to be one between the northwest of Scotland and Iceland.

NOAA: Early-season storms one indicator of active Atlantic hurricane season ahead

NOAA seem to believe that the signs are now there to indicate that the North Atlantic hurricane season is going to be a lot more lively that they thought back in June. So far we have had one short-lived North Atlantic hurricane, NOAA are now predicting between 5 and 9 this season. I’ve never seen them amend their forecast mid-season like this in the five years or so that I have been closely following the subject. I haven’t seen any tropical storm activity this year, although I could be wrong,  that has originated from around the Cape Verde Islands, which I would have thought would have been one of the prerequisites for hurricane development, but what the hell do I know.

 

Daily frequency of North Atlantic hurricanes and tropical storms

Figure 1 – Hurricane Isabel (2003) courtesy of Wikipedia

I posted a comment the other day about how quiet the North Atlantic hurricane season had been so far in 2017, forgetting of course that the season really doesn’t get going till the end of August, when the number increases from around 0.4 per day to over 3 per day by the end of August. Those figures are the average daily totals from the 1851 to 2016. Maybe I should run those figures since 1960, because with the advent of weather satellites no tropical storm escapes the NHC.

Figure 2

July 2017 – dry start for some

Another dry start to a month in July, with some places yet to see any rain, but by the look of the latest NWP for the coming week that will shortly come to an end. The small white plotted squares indicated stations reporting nil rainfall for the first eight days of this month, and as you can see from the map (fig 1) they cover quite a swathe of Central England.

Figure 1

let me know if I’ve got my programming right for the accumulations, because of the countless number of applications that I’ve written, this is the one that always gives me the biggest problems. In Japan for example, they report a 12 hourly total at 00 and 12 UTC, and a six hourly total at 06 and 18 UTC. I hadn’t realised till this week that the United States report a 3 hourly total. In France they very cleverly (in my opinion) report an hourly total, why can’t the UKMO do this? Or is that just being too darned helpful, perhaps it’s included in the Bufr coded observation, which of course we can’t access.

Anyway I’ve reworked the application to try to cope with the recent heavy rainfall event in Japan triggered by tropical cyclone Nanmadol’s. The chart below (fig 2) is for rainfall accumulations so far this July. I haven’t had time yet to check the accumulations I’ve calculated, although they look reasonably large I don’t’ seem to have captured any totals in excess of 500 mm that I’ve seen bantered about in reports. The GPM [Global Precipitation Measurement] satellite measured rainfall intensities of over 84.4 millimeters (3.3 inches) per hour in an intense band of rain in the Korea Strait, with clouds topping out at heights of over 13 kilometers or 8 miles. That’s the way to measure rainfall forget the 5″ copper gauge.

Figure 2

Tracking tropical cyclones

Figure 1 – Courtesy of NOAA

I came across this web application the other day that displays the archived track of tropical cyclones from any ocean basin of the world. It’s from NOAA, and they are using the ESRI GIS web mapping component (fig 1), and it’s very good, but not quite as good in my opinion as my old Windows application that’s knocking on twenty years old now (fig 2), but as Mandy Rice-Davies said ‘I would say that, wouldn’t I’.

Figure 2 – Courtesy of Seal Software.

I was going to say that the NOAA might have one distinct advantage over my program, and that is you can plot this year’s tropical cyclones and also get a forecast track for them. A quick fiddle with the application, and I find that this is not the case, which is a bit of a let down, and no better than my application in that regard. What I will say that the mapping component is clarity itself and very responsive, the other components in the design let the whole thing down I’m afraid, and rather clunky. I’m not sure how long the NOAA hurricane tracker has been around but overall it’s a very useful tool for anyone interested in tropical cyclones and the part they play in the weather and climate of the world around us.

The Met Office does have a tropical cyclone web application called Storm Tracker. I’m sure that at one time you could plot archived events from the HURDAT2 database using it, but now it looks like they just stick to current events, plotting the track of the tropical cyclone so far, and the anticipated forecast track from one of their global NWP models. The screenshot (fig 3) is of the latest look at Cyclone Donna in the western Pacific. What can I say, it works and it’s free to view, but the satellite imagery is quite low resolution. It seems to me as an organisation the Met Office seem to have scaled back their effort in recent years in making a go commercially, of selling NWP information about cyclone tracks, even though their models are highly regarded, perhaps there are just too many organisations at it.

North Atlantic hurricanes – reviewing last season and looking forward to 2017

Figure 1 – Hurricane Sandy courtesy of NASA

The 2016 North Atlantic season ended up being slightly above average, with seven of the fifteen tropical storms reaching hurricane status, there were three category 1’s, two category 3’s and a category 4 & 5 hurricanes (fig 3 & 4). It was the highest number of hurricanes in a year since the ten in 2012.

Figure 2 – Raw HURDAT2 data courtesy of the NHC

Some of the tropical cyclones in 2016 were very long-lived. Hurricane Nicole survived over 15 days, and Hurricane Alex, which started life on the 7th of January, and became the first Hurricane to form in January since 1938, travelled almost nine thousand nautical miles in its ten-day life.

Figure 3

The most severe Hurricane of the season was undoubtedly Hurricane Matthew, which flirted with the eastern seaboard of the United state and reached category five status in so doing , the first category five hurricane since 2007.

Figure 4

I always reckon the best way to compare individual years is by the combined ACE of all tropical cyclones (fig 5), and using that as a yardstick 2016 was the most active year since 2010.

Figure 5

2016 Predictions

If you want to look at the NHC Forecast verification report for 2016 be my guest, you can find the PDF of the report here. To me, it tells you very little about the season, or what the verification says about the various forecasts that the NHC made. I love the old fashion verification system which has just two outcomes, right or wrong, hit or miss I’m afraid. Most of the pundits who made a prediction for how 2016 would turn out were generally correct, including me!

  • Accuweather weather 14/8
  • Met Office 14/8
  • NWS ~ 13/6

Those aren’t the odds but the count of North Atlantic tropical cyclone/hurricanes in the 2016 season, which ended up 15/7.

2017 Predictions

I’ve managed to find some early predictions for 2017 courtesy of Wikipedia

  • Tropical Storm Risk 11/4
  • Colorado State University 11/4
  • The Weather Company 12/6
  • North Carolina State University ~13/5

The general consensus from them is that it’s going to be an average season, although the big players haven’t thrown their hats into the ring yet, probably because the season doesn’t officially start till the 1st of June. The season has already started though because we’ve already seen one tropical storm this month already.

Cyclone Debbie

Figure 1- Courtesy of BOM

Here are some plotted observations from the aerodrome on Hamilton Island in Queensland Australia (WMO #94368), which seems to have been very close to the path of Cyclone Debbie. As is usual with SYNOPs from Australia they don’t include a gust group. I’m slightly suspicious of the wind speeds in the days before Debbie appeared on the scene at this station, because even without a cyclone, they seem to have been experiencing gale force winds since Saturday. Perhaps it’s just a very windy place, but if these winds are indeed correct then Debbie is one hell of a slow-moving cyclone, with hurricane strength winds for at least 12 hours or more on the island.

Figure 2

According to news reports from Australia, Hamilton Island was one of the few islands that wasn’t ordered to evacuate before Debbie’s arrival.

Figure 3

Starting to motor on Cairngorm

The wind speed on Cairngorm is starting to get a little extreme even for Cairngorm. The mean wind speed reported by the SAWS at 12 UTC on Christmas day was 86 knots (99 mph) from 240°, and at 13 UTC a gust to 129 knots or 148 mph was recorded. This gust could well have been due to the passage of the cold front at around this time. Interestingly this wind speed is still not as high as the 255 kph reported by Typhoon Nock-Ten which has just made landfall in the Philippines. The mean wind speeds quoted for Typhoons and hurricanes are usually 1 or 2 minute means and not the 10 minute means that are used in SYNOP reports.

Rainfall from Matthew

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Here are the rainfall totals as best I can make them out for the east coast of the United States for the last week. Obviously there are a fair few missing observations from the hurricane affected stations right on the coast. It looks like there was 6 to 12 inches of rain generally, but SYNOP coverage is fairly sparse as you can see. ToDo: fix the legend.

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How much do we really know about hurricanes?

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Hurricane Matthew – courtesy of Reuters and the Boston Globe.

I noticed an article in the September 2016 Weather magazine from the Royal Meteorological Society entitled “Understanding hurricanes” by Roger K. Smith and Michael T. Montgomery. It was very informative and it starts:

“Hurricanes are among the most fascinating of all atmospheric phenomena. Much of their intricate dynamics and thermodynamics can be explained within the realm of classical physics. However, some of their secrets are yet to be unlocked.”

I like the phrase “some of their secrets are yet to be unlocked“, secrets like how much will they intensify and where are they going next. It’s exemplified by the two tropical cyclones hurricane Matthew and tropical storm Nicole that are currently cruising the waters off the eastern seaboard of the United States. I’ve been reading the forecast discussion on each storm from the National Hurricane Centre [NHC] avidly as I have done for many years. I noticed that in past years many would be hurricanes never made it because of upper wind shear that stopped any further intensification and the storm ended up as  a post tropical cyclone to be absorbed by a trough, or even a worst indignity of being gobbled up by an extratropical low. But this season has been a little odd.

Hurricane Matthew

Matthew developed into a category five hurricane on September 30th despite considerable wind shear, and against what more NWP models than you can shake a stick at were forecasting at the time. There is no doubt that Matthew was bound to be a hurricane, the early guidance suggested a category one or possibly two hurricane, but category 5 which is what it reached for a time was most unexpected. The track of Matthew has been quite well forecast up till now (6 October), but at the moment there is a lot of uncertainty and  little agreement in all the various NWP models about where it will go next. Here’s a look at the Saffir-Simpson hurricane wind scale.

2016-10-06_091125

Courtesy of NHC

Theses are some extracts from the NHC forecast discussion about Matthew as it developed and intensified to category five status despite the wind shear that should have severely limited its development.

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Now a category five hurricane after an early forecasts of a maximum category two event and despite all that shear.2016-10-06_090515

Tropical Storm Nicole

Nicole seemed to spring out of nowhere on the 4th of October, as most tropical storms often do. The early discussions again talked about a strong wind shear which they thought would inhibit any further real development of the system. Here are a few more extracts from the NHC discussion this time about Nicole.

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So despite early forecasts of Nicole fizzling out due to unfavourable conditions, it now looks quite likely that Nicole will reach at least category one hurricane status later today, not bad for a storm that should now be a subtropical depression or remnant low.

Conclusion

So what is going on this season in the Atlantic basin? Tropical storms seem to be doing what they want, totally ignoring the rules laid down in classical physics about tropical cyclone development. Despite all the satellite imagery and sophisticated NWP models we don’t seem to have that firm a grasp about why cyclones rapidly intensify as Matthew has done. Forecasting the track of a tropical cyclone, although good with Matthew and Nicole up to now, is far from perfect, and I’m sure that you’ll remember the “left hook” that hurricane Sandy gave to New York in 2012. But thanks to George Bernard Shaw there is one thing I do know about hurricanes, and that is that in Hertford, Hereford and Hampshire hurricanes hardly ever happen!

Finally I would like to thank the NHC and the forecast discussion they make public, I love the candour that you get from the forecasters there, it would be good to see Met Office show that same quality of openness in the thinking that went on behind their forecasting.

 Addendum

Last night Nicole was updated to Hurricane status despite early forecasts of a quick demise.

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