Halfway through the season

[DanKellFla]

So, what do you all think. It looks like the prevailing weather patterns are keeping the big storms away from CONUS this year. Of course, that can all change. So far, so good....

[vbhoutex]

So, what do you all think. It looks like the prevailing weather patterns are keeping the big storms away from CONUS this year. Of course, that can all change. So far, so good....

Agreed, but it only takes one home brew that forms off of a stalled front to make a mess of things. Overall, it has been a good season so far as nothing of a truly destructive nature, except for the flooding in the islands, has happened.

[Lurker]

I think the odds of a below normal season are increasing in terms of ACE. Only 1 of all those impressive African waves developed and we're going into the "downslope" of the activity. I think we still may get another burst that could take us near or even ahead of 2006 (ACE).

[wxman57]

I think the odds of a below normal season are increasing in terms of ACE. Only 1 of all those impressive African waves developed and we're going into the "downslope" of the activity. I think we still may get another burst that could take us near or even ahead of 2006 (ACE).

Actually, I believe that all of this year's 6 named storms developed from African waves. But only Fred and Bill developed early on in the trek across the Atlantic. The tropics are showing signs of shutting down. Plenty of shear in the Gulf/Caribbean. Models indicate significant sinking air all around through September. Good chance we'll finish 2009 with less than 10 named storms.

But we still have to watch the Gulf for close-in development. Won't be out of the woods there for another month or more.

[cycloneye]

The question is how many more systems will develop from today until November 30th.

Below is a discussion by Dr Jeff Masters on this topic.

Halfway point of hurricane season
September 10 marks the halfway point of the Atlantic hurricane season. Despite a late start (Tropical Storm Ana did not form until August 15, the latest start to a hurricane season since 1992), our number of storms has been near average. An average Atlantic hurricane season has 5 named storms, 3 hurricanes, and 1 intense hurricane by the midpoint of the season. So far this year, we've had 6 named storms, 2 hurricanes, and 2 intense hurricanes. A better measure of hurricane activity that takes into account their destructive power is the Accumulated Cyclone Energy (ACE) index. ACE for an individual storm is computed by squaring the maximum sustained winds of the storm at each 6-hourly advisory, and summing up over the entire lifetime of the storm. As of 5am EDT this morning, the seasonal ACE tally was 37.5. This number should rise to around 40 by the end of the day, thanks to the presence of Hurricane Fred. Over the period 1950 - 2005, the average ACE index for a half-season was 51, so 2009 ranks about 20% below average for the halfway point of the season. But when compared to the hurricane seasons we've been having since the current active hurricane period began in 1995, this year has been quite inactive. Between 1995 and 2008, the average ACE index for the halfway point of the season was 72. Thus, 2009 is about 45% less active than what we've been accustomed to over the past 14 years.

[jconsor]

I do agree that the odds favor less than 10 named storms, given the general lack of activity in Oct and Nov in the Caribbean and Gulf in El Nino years.

Also, the pattern through early next week does not look favorable for any new tropical development. As you said, sinking air across much of the Atlantic, and high shear in the most of the Caribbean and in the tropical east Atlantic. Beginning mid next week, the forecast pattern (strengthening and retrogression of the central Atlantic ridge and northward expansion of an upper high near the Florida Straits) suggests we need to pay attention to three areas:

1) Near the Bahamas
2) Eastern tropical Atlantic
3) Gulf of Mexico

Also, forecasts from the GFS and its ensemble have been trending more and more toward a weakening and eastward progression of the MJO. The main convection is already shifting from east Asia toward the international dateline as the MJO progresses eastward. The fact that 3 long range models develop an eastern Pacific tropical cyclone just off the Mexican coast by the middle of next week is also a sign they are sensing the eastward progression of the MJO.

Based on all of the above, I would expect the last 15 days of September to be more active than the first 15.

[Lurker]

I think the odds of a below normal season are increasing in terms of ACE. Only 1 of all those impressive African waves developed and we're going into the "downslope" of the activity. I think we still may get another burst that could take us near or even ahead of 2006 (ACE).

Actually, I believe that all of this year's 6 named storms developed from African waves. But only Fred and Bill developed early on in the trek across the Atlantic. The tropics are showing signs of shutting down. Plenty of shear in the Gulf/Caribbean. Models indicate significant sinking air all around through September. Good chance we'll finish 2009 with less than 10 named storms.

But we still have to watch the Gulf for close-in development. Won't be out of the woods there for another month or more.

Yeah I meant the time period where Fred developed. During that time there were about 4 waves that all looked like they could be a "go". But only Fred developed. The negative conditions won out otherwise we could have had an impressive outburst.

[Lurker]

I do agree that the odds favor less than 10 named storms, given the general lack of activity in Oct and Nov in the Caribbean and Gulf in El Nino years.

Also, the pattern through early next week does not look favorable for any new tropical development. As you said, sinking air across much of the Atlantic, and high shear in the most of the Caribbean and in the tropical east Atlantic. Beginning mid next week, the forecast pattern (strengthening and retrogression of the central Atlantic ridge and northward expansion of an upper high near the Florida Straits) suggests we need to pay attention to three areas:

1) Near the Bahamas
2) Eastern tropical Atlantic
3) Gulf of Mexico

Also, forecasts from the GFS and its ensemble have been trending more and more toward a weakening and eastward progression of the MJO. The main convection is already shifting from east Asia toward the international dateline as the MJO progresses eastward. The fact that 3 long range models develop an eastern Pacific tropical cyclone just off the Mexican coast by the middle of next week is also a sign they are sensing the eastward progression of the MJO.

Based on all of the above, I would expect the last 15 days of September to be more active than the first 15.

I agree with you. I think there will be one more burst before the season ends.

[StormClouds63]

We may have seen the last of the "major" hurricanes this season with Fred. It could be that the Cape Verde season is also just about done for 2009. Any additional systems will probably form closer to home (off U.S. Atlantic coast, Bahamas, GOM). I predicted 10/5/2 at the start, and will stick with it. It may be a stretch, though, to think we'll reach 10 named storms.

Whether anything forms in the Gulf or not, could bring us some beneficial rain and officially end the drought for 2009. With shear so high, shouldn't have to worry about a big wind event.

[cycloneye]

This is where things stand as of yesterday.

[Frank2]

The 10-day H5 GFS loop shows the northern jet retreating and a weak to moderate ridge in the Western Atlantic from 5-8 days from now, so we'll see - perhaps this is what the 300-hour models were indicating last week...

http://weather.unisys.com/gfsx/loop/gfsx_500p_loop.html

[Stormcenter]

IMO I'm seeing the beginning of the end for at least anything "Major-Cat.3 or higher" affecting the U.S. coastlines during this hurricane season. Again just my opinion.

[ConvergenceZone]

I think this season will end after the I storm. So in spite of their being no sign of "g", "h" or "i"....I still think we will have 3 more before the season ends, and probably a couple of tropical depressions besides that....

Other then that, bring on 2010..............

[DanKellFla]

I think this season will end after the I storm. So in spite of their being no sign of "g", "h" or "i"....I still think we will have 3 more before the season ends, and probably a couple of tropical depressions besides that....

Other then that, bring on 2010..............

May 2010 be as quiet as this year.

[HurricaneJoe22]

I like this lead paragraph in this story in Friday's Miami Herald.

Hurricane season hit its official peak Thursday and the year so far can perhaps be best summed up this way: El Niño, you da man!


El Niño shows manly strength, keeps hurricane season quiet
http://www.miamiherald.com/1374/story/1227791.html

[cycloneye]

It looks like December but its almost mid September and this is how the Atlantic basin looks in the upper levels.

[gatorcane]

Have to agree with Jconsor, there are signs we are about ready to pick up again in the Atlantic and I think the last half of September could produce a couple of systems to monitor. Main reason is the favorable MJO moving eastward from the EPAC, along with less troughiness across the Atlantic as long-range H5 models seems to be favoring a more zonal flow across the Atlantic and less of an amplified pattern (and less W and SW wind shear we have been seeing the past couple of weeks as a result).

One thing to be careful about, however, is saying that the season is over for the CONUS from any significant hit. We have a long way to go and the Caribbean and GOM has certainly been very quiet so far. Although El nino is around, keep in mind it is a fairly weak el nino. I would think something will get going in the GOM or Western Caribbean before this season is done -- alot of untapped SST heat content is there.

[CrazyC83]

The Pacific could be an area to really watch though, I think it is far from done there...