Tropical Depression Five a heavy rain threat; the smoke clears in Moscow
Tropical Depression Five is currently weak and disorganized, but it has the potential to organize into a potent rain-maker that may bring extremely heavy rains to Louisiana, Mississippi, Alabama, and Georgia over the next four days. Outer rain bands from TD 5 are already affecting the New Orleans region, where as much as two inches of rain has fallen in isolated regions. TD 5 has only limited heavy thunderstorm activity at present, thanks to an infusion of dry air early this morning from an upper-level low pressure system over the Gulf of Mexico. However, TD 5 is steadily recovering from this blow, and water vapor imagery shows the atmosphere is moistening in the eastern Gulf of Mexico as TD 5 builds more heavy thunderstorms. Wind shear is currently a moderate 10 - 15 knots over TD 5, and water temperatures are very warm, 31°C. The Hurricane Hunters have left TD 5, and a new aircraft is scheduled to arrive this afternoon.
Figure 1. Morning radar image of TD Five from the New Orleans radar.
Forecast for TD 5
The latest SHIPS model forecast predicts that wind shear will drop to the low range, 5 - 10 knots, by tonight, and remain low for the remainder of TD 5's life. The main hindrance to development will be the current large, disorganized nature of the storm's circulation. Without a tight, well-defined center of circulation, it will take time for the storm to intensify, and I don't expect TD 5 will have time to become more than a 50 mph tropical storm. NHC is giving TD 5 just a 2% chance of reaching hurricane strength. The main threat from TD 5 will be rainfall. This is a slow-moving storm, and the steering currents pushing the storm towards the coast are expected to weaken Thursday and Friday. TD 5 will likely slow to a crawl on Thursday and Friday, moving at just 3 - 5 mph. This will allow the storm to dump very heavy rains in excess of eight inches in isolated regions.
93L
There is not much new to report on the tropical wave (Invest 93) in the middle Atlantic Ocean that has been close to tropical depression status for three days now. The disturbance has a well-defined surface circulation, but only a limited amount of heavy thunderstorm activity, thanks to dry air aloft and wind shear of 10 - 20 knots. Wind shear is expected to stay in the moderate range, 10 - 20 knots, over the next three days, which is low enough that 93L could become a tropical depression at any time during that period. NHC is giving 93L a 70% chance of developing into a tropical depression by Friday morning. The GFS, GFDL, and HWRF models predict 93L will develop, and the GFDL forecasts that the storm will become a hurricane. A strong trough of low pressure moving across the central Atlantic is recurving 93L to the north, and the system should only be a concern to shipping interests. None of the reliable computer models are forecasting tropical cyclone development in the Atlantic over the next seven days, other than for 93L.
Moscow's air clears, but it is still extraordinarily hot
A thunderstorm blew through Moscow early this morning, bringing a little rain and a very welcome shift of wind direction. The wind shift freed the city from the persistent wild fire smoke that had plagued the city for seven straight days. Temperatures at Moscow's Domodedovo airport hit 35°C (95°F) today, the 29th day in row that temperatures have exceeded 30°C (86°F) in Moscow. The average high temperature for August 11 is 21°C (69°F). Moscow's high temperatures have averaged 15°C (27°F) above average for the first eleven days of August--a truly extraordinary anomaly. There is some modest relief in sight--the latest forecast for Moscow calls for high temperatures of 30 - 31° (86 - 88°F) Thursday through Sunday. This is still 20°F above normal, but will be a welcome change from the extreme heat of the past two weeks. Long range forecasts from the ECMWF and GFS models show no major change to the ridge of high pressure locked in over Russia, for at least the next seven days. However, both models suggest that a trough of low pressure may be able to erode the ridge significantly 8 - 10 days from now, bringing cooler temperatures of 5°C (8°F) above average.
Next update
I'll have an update this afternoon between 3 - 4 pm EDT.
Jeff Masters
Reader Comments
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Wow, that is wild! You can easily see the energy transfer from one area over to the other! :O
Sure, the perfect storm was also an example of a "subtropical hurricane" as was Hurricane Vince in 2005.
The debate on it comes from the fact that subtropical cyclones aren't supposed to have wind maxima close to the center, which is a characteristic generally reserved for tropical cyclones. However, if you have such a storm like Karl, Grace, or Vince with wind maxima near the center and the structure of a tropical cyclone, yet it's cold-core aloft, you can't call it fully tropical. There are several different ways you can have a subtropical cyclone which is why even having the term is controversial.
Well there seems so be some kind of system there but perhaps develop might be too strong a word to use.
The ECMWF takes the system almost due northwards immediately after it gets its toes in the water.
See post #804.
StormW or Levi....I noticed a lot of convection generated today in the system near 55W but at the same time seems that the ULL over Puerto Rico is pulling all that convection way north from the main circulation. Can we expect a strong rain event in the islands or dou you think that the system could develop into something stronger? Appreciate your response.
Even with Tornado Warning
he writes in quatrains.
i will forgive you but admit i was thinking gosh, there are a lot bigger fish to fry here than smiley faces :)
it is very red! and there is a green blob around bermuda that has developed a face like the man in the moon. or is it.... SATAN
But that was before satellite, so we don't know how many never hit land.
I collated some additional data relating to these 16 seasons, then looked for additional trends. I gathered information about the formation date of the FINAL storm in each of these seasons, the total number of named storms, and the total number of major hurricanes.
Final Hurricane Formation Date
The formation date for the final storm of the selected seasons ranged from 4 Oct to 9 Dec, and the mean formation date was 3 November. 9 of the 16, or 56.5%, formed on or after 1 November. [NOTE: while I did not record dissipation dates, many storms forming after 20 Oct continued into November.] 67% of seasons with above-average ACE ended with a storm that formed after 31 Oct; the average date was 4 Nov. Again, 1995 fell into the anomalous category, with its 19th storm forming on 27 Oct.
Total Number of Named Storms
As has been presented in other research, La Nina seasons tend to have above average numbers of named storms. The average of these 16 seasons is 11.81, which can be rounded to 12. The smallest number is 8, seen in the 1956 and 1973 seasons, and of course 1995 has the largest, 19. Interestingly enough, seasons with above average ACE only averaged 0.97 more storms than the sample mean, though they did see 2.21 more storms on average than the 10.57 mean of years that had average and below average ACE. However, even storms with average and below average ACE beat the seasonal average of named storms.
Total Number of Major Storms
For the La Nina years Kotzbach focused on, number of major hurricanes varied from 1 to 8 per season. There was a high correlation between seasonal ACE and number of major storms; average and below average seasons [seven] had a mean of 1.86 cat 3 - 5 hurricanes, while the above 100 ACE seasons averaged 5 major storms. The mean across the set was 3.86 major hurricanes per season. Only one high ACE season, 1954, had fewer than three major hurricanes, and every below 100 ACE season except 1971 and 1973 had at least two major storms.
I'm adding some final conclusions and observations to this stuff in my blog... eventually. I'll post a comment about it when I'm done...
1. Anybody who expects 12 - 15 named storms this year is well within the climatology. Anybody who expects 19 likely believes there are some climatologically anomolous conditions which would predispose the basin towards much higher than average activity levels, both in term of named storms and in terms of ACE.
2. We can reasonably expect the season to last beyond 1 Nov, regardless of number of named storms and / or ACE. One low ACE season had 15 named storms; another initiated its final storm on 9 Dec.
3. There seems to be no immediately obvious correlation between number of storms and number of major hurricanes. 1950 and 1973 both had 13 named storms; both had their second hurricane form on 20 Aug; both seasons ended in mid-Oct [18th and 16th respectively]. 1950 had eight majors; 1973 had one.
I'm sure there are other things to think about from this data. But it is interesting to note that five of the 7 low or average ACE years took place between 1970 and 1975...
Exactly. As I recall from reading as well as listening to a well-respected hurricane expert (Dr. Neil Frank), seasons before the advent of satellites are likely to have had multiple missed storms because they formed too far east and never ventured far enough west to be reported. The 1933 season is, I believe, through to have had somewhere between 3 and 5 more storms than officially reported. Additionally, small storms like Marco, even forming in well-traveled waters, may have been missed. I seriously doubt 1914 had a lone tropical cyclone like the official record indicates.
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