An active Atlantic hurricane period coming

By: Dr. Jeff Masters , 1:48 PM GMT on August 17, 2010

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The remnants of Tropical Depression Five are no longer a threat, done in by high wind shear and close proximity to land. However, an active period for Atlantic hurricanes is likely for the remainder of August, as the global atmosphere undergoes a major change to the circulation pattern that has dominated Northern Hemisphere weather during July and August. A large trough of low pressure is gathering strength over Europe, and is expected to push eastward. By Thursday, this trough should be able to push away the blocking ridge of high pressure that has given Russia its worst heat wave in history. The shift in circulation has already weakened the large region of sinking air that has brought dry, stable conditions to the tropical Atlantic over the past month. Vertical instability, which was unusually low since late July, has now returned to near normal levels over the tropical Atlantic (Figure 1), though it remains quite low over the rest of the North Atlantic. Instability is measured as the difference in temperature between the surface and the top of the troposphere (the highest altitude that thunderstorm tops can penetrate to.) If the surface is very warm and the top of the troposphere is cold, an unstable atmosphere results, which helps to enhance thunderstorm updrafts and promotes hurricane development. Since SSTs in the Atlantic were at record highs and upper tropospheric temperatures were several degrees cooler than average in July, enhancing instability, something else must have been going on to reduce instability. Dry air can act to reduce instability, and it appears that an unusually dry atmosphere, due to large-scale sinking over the Atlantic, was responsible for the lack of instability. Now that vertical instability has returned to near normal levels, Atlantic hurricane activity should increase to at least average levels over the next two weeks. This is particularly true since SSTs are at record highs and vertical wind shear is at average to below average levels over the tropical Atlantic.


Figure 1. Vertical instability (in °C) over the Caribbean (left) and tropical Atlantic between the Lesser Antilles Islands and coast of Africa (right) in 2010. Normal instability is the black line, and this year's instability levels are in blue. The atmosphere became much more stable than normal in both regions at the end of July. This lack of instability also extended to the Gulf of Mexico and North Atlantic Ocean between Europe and North America. However, in the past few days, vertical instability has returned to normal, thanks to a major pattern shift in the global atmosphere. Image credit: NOAA/CIRA.


Figure 2. The climatology of Atlantic hurricane activity shows a sharp rise in activity around August 18.

Analysis
August 18 historically marks the point where Atlantic hurricane activity makes a major spike upwards (Figure 2.) On average, we can expect to see two named storms and one hurricane during the last half of August. The last half of August usually sees a moistening of the atmosphere off the coast of Africa, as the the African monsoon kicks into high gear. This year is no exception (Figure 3.) The dry Saharan Air Layer (SAL) has retreated to the north, leaving a moist atmosphere conducive for tropical cyclone development off the coast of Africa.

It would not be a surprise to see atmospheric instability increase to above-average levels by early next week as the major atmospheric pattern shift progresses. Will this usher in a hyperactive period of Atlantic hurricane activity next week, with a parade of three or four simultaneous storms strung out across the Atlantic? Probably not, since the Madden-Julian Oscillation (MJO) only marginally favors upward motion over the tropical Atlantic, and is not forecast to change much over the next ten days. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The bottom line: I expect we will see 2 - 3 named storms in the Atlantic by the end of August, including one hurricane. Where these storms might develop and move is difficult to say. It currently appears that the global shift in circulation will bring near-average steering currents to the Atlantic over the next ten days, with a series of troughs of low pressure capable of recurving hurricanes, moving across the Atlantic. The GFS model is indicating, though, that during the few days of August, these troughs may weaken, making recurvature of hurricanes less likely, and increasing the probability of landfalling storms.

The GFS, NOGAPS, and ECMWF currently predict that one or two tropical storms will form between Africa and the Lesser Antilles Islands during the period 4 - 10 days from now. The NOGAPS model is predicting the development of a strong tropical disturbance near the coast of Honduras late this week.


Figure 3. Saharan Air Layer (SAL) analysis shows that the dry air and dust of the SAL (orange colors) lies well to the north of the hurricane breeding grounds off the coast of Africa, near the Cape Verdes Islands. Image credit: University of Wisconsin/NOAA Hurricane Research Division.

Smoke bedeviling Moscow again
Light easterly winds over the past few hours have brought smoke from wildfires back into Moscow today. Temperatures at Moscow's Domodedovo airport hit 29°C (84°F) today, which is 11°C (20°F) above average. The latest forecast for Moscow predicts that just one more day remains for Russia's greatest heat wave in recorded history. On Thursday, a strong trough of low pressure will move through European Russia, finally bringing below average temperatures.

Jeff Masters

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Quoting smuldy:
didnt read that i'm drunk and lazy but again youre usually cool so i wont join any permaban bandwagon or even start a 24hr ban/dwagon people need to be able to cross a line and step back once in a while; and you question the veracity of a computer model run 200+hours out on a system not yet formed? are you crazy? already bought all my friends still in nyc tickets here to miami beach since we're obviously much safer (just a joke in case it came off dry/harsh with heightened tensions around tonight); and has anyone posted or seen the euro 315am run yet? been watching tony bourdain in rome and warren the ape in prison but not seen the euro here when checking in during commercials


have not seen it yet....drink one for me pardner!!
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2349. xcool
;p;
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2348. JLPR2
Well, I just cranked up the A/C, fixed the sheets which were all twisted up and added a pillow. Wish me luck! XD

Also the 00z ECMWF says Fish or close one for Bermuda.


Goodnight everyone!(again)
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Quoting JLPR2:


Pero hombre, no puedo dormir y tu me dices eso! :S

I want to sleep, but I cant and you're not helping. LOL!


hehehe sorry, my bad, I was in shock, have passed 12 years since Puerto Rico experience it last hurricane, and it was a major one, Hurricane Georges!!!
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2346. smuldy
Quoting KerryInNOLA:
Read post 2307. I already apologized. I come on the blog 1/2 hr ago and can't understand half of what is being said. Spanish has NEVER been spoken on this blog before, and I don't think Dr Masters wants his bloggers to need translators if all sorts of languages are being spoken. It could ruin the blog.
didnt read that i'm drunk and lazy but again youre usually cool so i wont join any permaban bandwagon or even start a 24hr ban/dwagon people need to be able to cross a line and step back once in a while;
Quoting traumaboyy:


I can see it now....Cantore on top of the Empire State building.....with his beady little glasses on.....lmfao..
and you question the veracity of a computer model run 200+hours out on a system not yet formed? are you crazy? already bought all my friends still in nyc tickets here to miami beach since we're obviously much safer (just a joke in case it came off dry/harsh with heightened tensions around tonight); and has anyone posted or seen the euro 315am run yet? been watching tony bourdain in rome and warren the ape in prison but not seen the euro here when checking in during commercials
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Quoting TORMENTOSO83:


thank you a lot
You are most welcomed dear.And thanks Trauma you as well.Toodles for now.
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Quoting mrsalagranny:
Well off to bed 5:00 comes early.Have a blessed night everyone.And xcool welcome back.


Good night maam...sweet dreams!
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Quoting mrsalagranny:
I pray Peurto Rico will be spared.


thank you a lot
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Quoting xcool:
mrsalagranny:.thanks.
You are most welcome.See you all tomorrow and Xcool keep them models out to sea for us.LOL!!!!!
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Quoting JLPR2:


Hola! :)
I hope to be here only a little while, the bed is calling me but I'm wide awake.


Hope you can get your ZZZZ's man we need you rested for the next few days!!

Look foreward to what Storm will have to say this morning.....as usual
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2340. xcool
mrsalagranny:.thanks.
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2339. xcool
traumaboyy haha
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2338. JLPR2
Quoting mrsalagranny:
Well off to bed 5:00 comes early.Have a blessed night everyone.And xcool welcome back.


Good night!
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Quoting xcool:
traumaboyy .hey .how was new orleans..?


Wow was it fun.....and that red dress run they had Saturday was off the chain....never saw so many guys with dresses on in my life (note) I did not participate...lol
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Well off to bed 5:00 comes early.Have a blessed night everyone.And xcool welcome back.
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2335. JLPR2
Quoting traumaboyy:

Hola JLP



Hola! :)
I hope to be here only a little while, the bed is calling me but I'm wide awake.
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Most definately Trauma.It would be awful a hurricane of that magnitude struck NY City or any one for that matter.
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2333. xcool
traumaboyy .hey .how was new orleans..?
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2332. xcool
ECMWF right idea outt sea
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Quoting xcool:
hey just got home


morning xcool
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I pray Peurto Rico will be spared.
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2329. JLPR2
Quoting TORMENTOSO83:
el ltimo modelo del GFS muestra que un huracn intenso podra afectar directamente la Isla del Encanto, Puerto Rico, a mediados de la semana entrante!!!


Pero hombre, no puedo dormir y tu me dices eso! :S

I want to sleep, but I cant and you're not helping. LOL!
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Quoting mrsalagranny:
I know the feeling.I dont like trouble.So what is your thoughts on what the models are showing?


Awful early....but could be historic and tragic....I am pulling for a fish storm!
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Quoting TORMENTOSO83:
el último modelo del GFS muestra que un huracán intenso podría afectar directamente la Isla del Encanto, Puerto Rico, a mediados de la semana entrante!!!
thank you Tormentoso
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2326. xcool
gfs I'm not putting much faith bull 384hrs
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2325. JLPR2
I guess this area is the one supposed to spark development?

PGI30L and PGI31L aren't doing that wonderful right now. XD
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2324. xcool
hey just got home
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el último modelo del GFS muestra que un huracán intenso podría afectar directamente la Isla del Encanto, Puerto Rico, a mediados de la semana entrante!!!
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Quoting traumaboyy:

Hola JLP

Morning Maam.....I am just here for the free coffee...don't want no trouble.....lol
I know the feeling.I dont like trouble.So what is your thoughts on what the models are showing?
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Quoting JLPR2:


The best post I read here. XD
Jeez, you guys can get into a fight so easily, some people speak Spanish, deal with it! And remember, just cause you cant understand what it says doesn't mean you have to open up your wrists! -.-

This was an ugly surprise for a sleep deprived person as myself! darn insomnia T_T!

Hola JLP
Quoting mrsalagranny:
Good morning Trauma and everyone.I see the models are forecasting a pretty strong hurricane.I hope they dont turn and switch directions on the next runs.


Morning Maam.....I am just here for the free coffee...don't want no trouble.....lol
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Good morning Trauma and everyone.I see the models are forecasting a pretty strong hurricane.I hope they dont turn and switch directions on the next runs.
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2318. JLPR2
Quoting NRAamy:
Donde esta el bano?


The best post I read here. XD
Jeez, you guys can get into a fight so easily, some people speak Spanish, deal with it! And remember, just cause you cant understand what it says doesn't mean you have to open up your wrists! -.-

This was an ugly surprise for a sleep deprived person as myself! darn insomnia T_T!
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discrimination will never ends, either racist people, as well some americans discriminates latin people, eventhough some are USA citizens as Puertoricans, Puertoricans also discriminates against the dominicans, England people and French people discriminates against americans...etc... it's a hater chain!!!!

I'm a U.S.A. citizen because I was born and raised in Puerto Rico, (and maybe I have more hurricanes experiences than other people)and I don't asked for the USA citizenship, it just became in the 70's and it was given by the USA Goverment itself through the Jone's Law...only God knows when all racism will end!!!

PEACE & LOVE
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Quoting smuldy:
gfs actually put a cat 4 or higher at first landfall in nyc; why im dying to see the euro


I can see it now....Cantore on top of the Empire State building.....with his beady little glasses on.....lmfao..
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2315. smuldy
Quoting traumaboyy:


Actually...being sort of buzy the last few hours here where I work, I have not looked at anything yet....but the way this year has been going if they say east coast....Galveston better look out...lol
gfs actually put a cat 4 or higher at first landfall in nyc; why im dying to see the euro
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Quoting CoffinWood:


Hola, muchacho traumatico (?). What do you think of the new GFS runs taking a major to the east coast?


Actually...being sort of buzy the last few hours here where I work, I have not looked at anything yet....but the way this year has been going if they say east coast....Galveston better look out...lol
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so the MJO - when is that suppose to end? Dr. Masters says that it stays in place for 30-60 days but doesn't say when it began. I know it has been in place for about 4 weeks at least? Will the MJO be gone in Sept? Anyone that can explain this further? Thanks in advance for the knowledge :)
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2312. smuldy
Quoting KerryInNOLA:
A permaband? Have you people ever heard of "sticks and stones"?
i would say just let it be and shut lips; i TOTALLY disagree with you on this stance tonight and i flagged the one WB post you made too, but you didnt start it the idiot that did get banned did, and i had an off night when i ripped all rural southerners in 2 posts after having a few and you're usually ok and post more than i do so I'd chalk it up to something like that and absolutely not think you deserve a permaban for one off night, but seriously if they want to speak spanish, c'est la vie or however live and let live is really said in french, again with you id say off night youre usually cool but def not the issue to take one blocked line and make a stand on that could cost you your account, and for anyone not able to read back i was one of the people orginially ripping the guy that came on mscasino for not being tolerant so please dont lump me in with the anti-spanish crowd for defending someone that is usually much less troublesome but whom is having one off night



modified ps: anyone have the euro runs yet? 45 min late now and only one i saw was a 0z that would be 8pm eastern
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Quoting traumaboyy:
Buenos Diaz (sp?) WU night shift!!


Hola, muchacho traumatico (?). What do you think of the new GFS runs taking a major to the east coast?
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Buenos Diaz (sp?) WU night shift!!
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Quoting StSimonsIslandGAGuy:
CoffinWood, A ! I flagged that also. 2293 is out of bounds and unacceptable. And deserves a permaban.


Agreed. You can argue about what language Dr. Masters exclusively wants on the blog til the cows come home, but when you spew racist filth you've crossed the line. Perma-banning seems an appropriate response.
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Quoting RainyEyes:
Darn, I log in to see what is going on in the tropics and every other comment is removed? I will say that if I went on a prodimantly Spanish blog, and wanted to contribute then I would respectively use google translator to post...just makes sense to me. I think the danger lies in miscommunications or skipped information when a serious tropical threat is headed towards land..JMHO

Totally True
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Quoting LakeWorthFinn:
Tormentoso, no grites - LOL
Hasta mañana everybody, thanks for great graphics and info.


hahaha no gritaré
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Darn, I log in to see what is going on in the tropics and every other comment is removed? I will say that if I went on a prodimantly Spanish blog, and wanted to contribute then I would respectively use google translator to post...just makes sense to me. I think the danger lies in miscommunications or skipped information when a serious tropical threat is headed towards land..JMHO
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another one??? OMG this is endless, better to ignore
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Quoting KerryInNOLA:
Whats with all the ******** on this blog tonight?


Completely racist and inappropriate. Flagged and reported.

Additionally, consider that Dr. Masters has not stated that this is an English-only blog, and that many of our blogging friends in the Caribbean are Spanish-speaking, and come here for life-saving information about tropical events that may affect their islands.

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Tormentoso, no grites - LOL
Hasta mañana everybody, thanks for great graphics and info.
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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