"An active Atlantic hurricane period coming" - Jeff Masters

[ColinDelia]

Since this is the biggest debate going this year::

An active Atlantic hurricane period coming

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.

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.

Source: http://www.wunderground.com/blog/JeffMasters/show.html

[CourierPR]

The tropical weather discussion yesterday at Crown Weather mentioned that going into September, the tropics may become very active with as many as 13 storms during the month.

[ConvergenceZone]

Do you have that link to the crown weather discussion? I was trying to find it yesterday and somehow I deleted it out of my favorites....

[boca]

Here's the link to crown weather.

http://www.crownweather.com/

[ROCK]

Dr Master's is right on with his take....you can see it in every long range model...We could be tracking 3 storms at one time next week...

[boca]

I'm to the point now that when I see I'll believe it.I'm taking everything with a grain of salt

[Stormcenter]

Haven't we heard this song before?
After all it's very obvious this season is not following
the script at all. They way I undestood it we were going
to have storms forming left and right from the get go like 2005.
Well that hasn't been the case. Oh don't get me wrong I'm sure
we willl have activity ramp up the next few weeks and I expect
to see at least 2-3 big boys form in the next month but will they
survive or come close to U.S. mainland is the key. We shall see.

Dr Master's is right on with his take....you can see it in every long range model...We could be tracking 3 storms at one time next week...

[Portastorm]

On the contrary, from what I have read the season is following along as many experts suggested it would. This idea of "storms forming left and right from the get go" certainly didn't come from any respected tropical forecaster I read. Have the overall numbers been shaved down a bit, yep. So I'm not sure where your expectations for this season came from?

You also seem to be mixing and matching your criteria. You appear to be criticizing calls for an active season, yet you say the "key" is whether or not we see US mainland landfall. Which is it?

Haven't we heard this song before?
After all it's very obvious this season is not following
the script at all. They way I undestood it we were going
to have storms forming left and right from the get go like 2005.
Well that hasn't been the case. Oh don't get me wrong I'm sure
we willl have activity ramp up the next few weeks and I expect
to see at least 2-3 big boys form in the next month but will they
survive or come close to U.S. mainland is the key. We shall see.

Dr Master's is right on with his take....you can see it in every long range model...We could be tracking 3 storms at one time next week...

[ConvergenceZone]

I'm also in the "believe it when I see it" camp. All that Dr Masters is saying is
that the tropics getting busy is what "suppose" to happen. But we all know that the
weather doesn't always do what it "suppose" to..... So I'm not sold on it getting "really busy"
until I see it...

[KWT]

We will see CZ, remember 1961 that had nothing in August at all and then went mental in September...

Given both the ECM and CFS long range models are picking up on the same hyperactive period in September, it'll be worth keeping a close eye on...

Also FWIW I feel the CFS has done surprisingly well, it didn't show much at all for the first half of August which looks to have been a good call.

[hurricaneCW]

I'm definitely in the wait and see boat as well since everything has fizzled thus far. Now I don't even know what to make out of the activity of the African coast. Will anything even develop out of that mess?

[StormClouds63]

The tropical weather discussion yesterday at Crown Weather mentioned that going into September, the tropics may become very active with as many as 13 storms during the month.

A storm named every 2-3 days? I'd be willing to take that bet ... the "under 13" that is.

[boca]

The tropical weather discussion yesterday at Crown Weather mentioned that going into September, the tropics may become very active with as many as 13 storms during the month.

A storm named every 2-3 days? I'd be willing to take that bet ... the "under 13" that is.

I'll take that bet too this is child's play.LOL

[KWT]

That 13NS is NOT JUST for September, its for the rest of the season, that comes from Joe B yesterday who said what the long range ECM shows...CFS shows something similar....

[robbielyn]

wait and see been dealing with tutts ull's this year

[Stormcenter]

My expectations came from NOAA and other so called experts who through out numbers ranging from 14-23 named storms. I just don't see the benefit of it at all. What is the point of putting numbers out there? All you do is leave yourself open for criticism. Wouldn't it be easier just to say we are expecting an active or average season. When the "Average Joe" sees numbers like that they "expect" a busy season from the beginning. Anyway my key has always been the quality of the storms and where they make landfall and not the quantity. It only takes 1 Katrina type storm to make it an active season for many.

On the contrary, from what I have read the season is following along as many experts suggested it would. This idea of "storms forming left and right from the get go" certainly didn't come from any respected tropical forecaster I read. Have the overall numbers been shaved down a bit, yep. So I'm not sure where your expectations for this season came from?

You also seem to be mixing and matching your criteria. You appear to be criticizing calls for an active season, yet you say the "key" is whether or not we see US mainland landfall. Which is it?

Haven't we heard this song before?
After all it's very obvious this season is not following
the script at all. They way I undestood it we were going
to have storms forming left and right from the get go like 2005.
Well that hasn't been the case. Oh don't get me wrong I'm sure
we willl have activity ramp up the next few weeks and I expect
to see at least 2-3 big boys form in the next month but will they
survive or come close to U.S. mainland is the key. We shall see.

Dr Master's is right on with his take....you can see it in every long range model...We could be tracking 3 storms at one time next week...

[TYNI]

Regardless of the numbers right now, I, for one, am learning a lot this season, just by looking at the reasons hindering complete formation. The conditions have been favourable (or so we think) several times, yet we have had nothing really substantial to track from start to finish. A lot of "what ifs", and "almosts". I love reading our pro mets discussions about how the MJO, Bermuda high, tutt, SAL, steering currents and water temps affect creation, sustainability, and growth, and ultimately to this point this season, the reasons for lack of development.

Wait and see, and learn from the so-called hindrances as much as the positives of tracking a named storm. Watch what Dr. Masters and others are telling us about the African climatology changes, and see how the CV systems form and track.

[StormClouds63]

That 13NS is NOT JUST for September, its for the rest of the season, that comes from Joe B yesterday who said what the long range ECM shows...CFS shows something similar....

KWT:

I really enjoy your posts, and appreciate your knowledge of the tropics. I always learn a great deal from your posts. However, I don't think we end up with 13 remaining storms for even the entire season ... with Alex, Bonnie, and Colin, that would mean a minimum total of at least 16 NS for the 2010 season.

I believe a range of 10-15, with 15 being the maximum, is what to expect through the end of the 2010 tropical season. With Alex, Bonnie, and Colin, that would mean a minimum of 7 and maximum of 12 named storms for the remainder of the season. I don't see the overall patterns changing that dramatically.

If you're right, (16 or over), and you usually are, I'll be the first to acknowledge it.

[Macrocane]

Again, I understand that it only takes one to make this season a memorable one, but DESTRUCTIVE is not the same as ACTIVE and they shouldn't be used as synonyms.

[SootyTern]

Well said! (to TYNI)

I just am not getting this fixation on absolute numbers of storms predicted for a season. This site isn't just about betting on scores it's about learning about the wonders of the weather and also getting important information to help with decision making when a storm threatens.