Global model runs discussion

[Steve]

Hey Rock, there are several global teleconnections that sometimes work (some often do) depending on the time of year and various types of patterns we are in (e.g. Enso, etc.). The main one I use is based on landfalls vs. recurves in the WPAC. Eastern Asia often teleconnects with the US East Coast in a 6-10 day advance. For instance, when you have a recurve east of Japan, it usually precedes by a week +\- strong trouging off the US EC. A system moving west of Japan but recurring anyway will often show a mean trough a week later between 80-85 West or they may show the general shape of ridging a week later. . Sometimes storms will move due west or wnw south of Japan (Philippines, Taiwan, china, Vietnam, etc.). Watch those for ridging off the US EC a week or so later. This one generally tells you what to expect in the SE US the following week. This teleconnection has worked pretty well so far this season even though a couple of the telegraphs never made it past invest stage, we knew they would be western gulf systems, recurves or what have you. On rare occasions, they can teleconnect landfall zones and intensity.

There are a ton of other ones based on blocks in Scandinavia, big highs in the central US, low pressure in the gulf of Alaska, phase of MJO, etc. there are literally a ton of those that provide different clues to weather and patterns across the globe.

This post is NOT official.

[cycloneye]

Hi Steve. There is a developing storm (Usagi) forecast to become a Typhoon but will not recurve. What will this mean for the teleconnection pattern?

[Steve]

Hey Luis. What it tells me is that the trough will most likely be transient and probably will lift out a day or two after it sets up. That would be logical anyway with the current ssta profile which you can see below in the link. With the current water temperature profile in the NW Atlantic, you would expect ridging Centered off the US East Coast and south of Eastern Canada. A physicist like Aric can tell you the dynamics, but it isn't all that different from a Texas style heat ridge. At a basic explanation, the warmer water, despite some natural lift, invites generally higher pressure this time of year in that latitiude. With the recurve having happened late last week (indicating eastern trouging 6-10 days later or Friday/this weekend) and a new system moving much more westerly, after this weekend or near the end of the weekend expect high pressure to build in in the wake of the trough and front. So ultimately if the system moves toward china, expect a block in place in the NW Atlantic within a couple of days of the front blasting through there. This is the way the overall pattern has been shaping up anyway as well.

http://www.ospo.noaa.gov/Products/ocean ... index.html

[sponger]

Since its been brought up I would like to know peoples opinion on if global cooling could be the reason for the drop in activity. I know this has become a political issue (Which we should never discuss on our fine board), but climate wise isn't drier air and deeper troughs what you would expect in a cooling climate? I don't know who remembers our amateur solar forecaster who swore a link between solar activity and storm formation but could it be as simple as a climate shift underway that is having this effect on hurricane activity?

[Hybridstorm_November2001]

Well, if anything the inactivity in the North Atlantic Basin was caused by dry, stable air in the MDR (in a nutshell) which it turn can be linked to drought over the Sahel region of Western Africa. This was caused by hot, dry conditions there which helped spawn huge sandstorms from the Sahara Desert, which spread across the Atlantic and parts of Europe earlier this year.

[KBBOCA]

Well, if anything the inactivity in the North Atlantic Basin was caused by dry, stable air in the MDR (in a nutshell) which it turn can be linked to drought over the Sahel region of Western Africa. This was caused by hot, dry conditions there which helped spawn huge sandstorms from the Sahara Desert, which spread across the Atlantic and parts of Europe earlier this year.

Hi all,
Actually, this has been a pretty heavy year of rainfall in the Sahel region.
Recently 55 people were killed in flooding in Bamako, Mali, and the capital of Mauritania, Nouakchott, where I live and work part of each year, has also received heavy rains and is experiencing severe flooding in many low-lying areas.

You can check out the West Africa rainfall here:
http://www.cpc.noaa.gov/products/fews/rfe.shtml

Unfortunately, I don't know a good site that provides comparison with the long-term average. There used to be a good rainfall comparison map at FEWS (the Famine Early Warning System, funded by USAID), but I seem to recall that map is no longer available.

Note: this is not to deny that there have been major dust storms / severe SAL pushed out into the Atlantic, but I do not believe it has been unusual SAL this year. The Harmattan season (December - March) was quite light in terms of dust storms in Nouakchott. We did experience a major heat wave and extreme low humidity in May, and perhaps that was unusual, but the June - August period seemed quite light on dust in our city.

[KBBOCA]

Following up to my previous comment on rainfall in the Sahel, I just happened to come across this interesting study (from Nov 2012) about rainfall patterns in the Sahel

http://www.hindawi.com/isrn/meteorology/2013/453521/

Here's the abstract:

The West African Sahel is well known for the severe droughts that ravaged the region in the 1970s and 1980s. Meteorological research on the region has flourished during the last decade as a result of several major field experiments. This paper provides an overview of the results that have ensued. A major focus has been on the West African monsoon, a phenomenon that links all of West Africa. The characteristics and revised picture of the West African monsoon are emphasized. Other topics include the interannual variability of rainfall, the atmospheric circulation systems that govern interannual variability, characteristics of precipitation and convection, wave activity, large-scale factors in variability (including sea-surface temperatures), and land-atmosphere relationships. New paradigms for the monsoon and associated ITCZ and for interannual variability have emerged. These emphasize features in the upper atmosphere, as well as the Saharan Heat Low. Feedback mechanisms have also been emphasized, especially the coupling of convection with atmospheric dynamics and with land surface characteristics. New results also include the contrast between the premonsoon and peak monsoon seasons, two preferred modes of interannual variability (a latitudinal displacement of the tropical rainbelt versus changes in its intensity), and the critical importance of the Tropical Easterly Jet.

[chaser1]

Following up to my previous comment on rainfall in the Sahel, I just happened to come across this interesting study (from Nov 2012) about rainfall patterns in the Sahel

http://www.hindawi.com/isrn/meteorology/2013/453521/

Here's the abstract:

Feedback mechanisms have also been emphasized, especially the coupling of convection with atmospheric dynamics and with land surface characteristics.

Hmmm, any chance that stronger than normal or severe precip. conditions over the desert regions might actually serve as a mechanism to "kick up" a significant amount of dust particles, only to somehow remain suspended within some sort of height level or within some quasi stationary blocked pattern until such level winds were to be later dispersed? That almost seems unlikely though.... I almost wonder if there are simply other primary origins or sources of dust, sand, ash that were not anticipated or even noticed, and that these particulates somehow migrated to be absorbed within the lower latitiude tropical wind belts of the N. Hemisphere affecting both the Atlantic and the Pacific???

[Hybridstorm_November2001]

@KBBOCA The recent, August rainfall, went against the long term Spring & Summer trend (thus why we had Gabby & Humberto). The August upsurge had more to do with a much needed boost from the MJO, imo, than any other factor. -

http://www.fews.net/docs/Publications/a ... 6_2013.pdf *

http://reliefweb.int/sites/reliefweb.in ... 130718.pdf

http://reliefweb.int/sites/reliefweb.in ... st%201.pdf


* Warning all links require PDF reader.

[Steve H.]

Why has this thread deteriorated into a discussion about African rainfall. Seems a bit off topic.

[chaser1]

Why has this thread deteriorated into a discussion about African rainfall. Seems a bit off topic.

Good question, but I think I know the answer. Not to sound funny but, models are inconsistent and flip flopping with 95L - and thats just with trying to forecast the near to mid term time frame. Geez, I miss the days of magical Cat. 5 hurricanes spun up arbitrarily by CMC; when NOGAPS would develop a storm where the GFS didn't even see a wave, and the good 'ol days when the GFS actually bit onto something - 14 days out - AND actually carried the same system for at least 3 to 4 days before sometimes dropping it altogether. Heck.... we can't even seem to have a mid to long term model forecasting development and expect to even see that same feature on the following run?!

So, I have 3 possible answers as to why this thread has deteriorated into a discussion about African rainfall (which I DO find interesting by the way).

1) This thread was hijacked by the creation of a thread: "Thoughts on activity as heart of season has passed". This seems like a general long term prognostication topic that could well fit within this thread (at least I think so) thus rendering this thread as simply redundant.
2) As I've already alluded to in the paragraph above...., perhaps the models have been tinkered with just enough to really suck! Therefore little reason to anticipate even prior year levels of reasonable mid to long term forecast skill. Even less reason to anticipate any consistency from one model run to the next.
3) Maybe the Model Runs don't really suck, and maybe the 2013 Atlantic Season is what REALLY sucks! Therefore perhaps many just figure "why look if it ain't comin' ".

AND, A BONUS REASON - Perhaps its because most everyone are over in the "Active Storm" Threads talking about 95L and beyond this system, many would probably agree that this season "feels" like its already toast therefore who even cares about what models think might develop out in the North Atlantic in the weeks to come. Reality is though, that we could easily see a major hurricane develop in the Caribbean in the weeks to come. When 95L drops us like a bad Prom date sometime during the next few days or week, the migration will come back on over here as their last bastion of hope. Finally once again, the Global Model Run Discussion will ring loudly "Give me your tired, your poor, your huddled masses yearning to breathe free...."

[Hurricaneman]

The 0zGFS has another area in the Caribbean at about 240hrs heading NW into the gulf, that area would need to be watched especially since that area has produced hurricanes in October in the past and when the list of hurricanes from this area from the monsoon trough the second half of the season are as follows since 1960 and the Tampa Bay hurricane of 1921

2012 Sandy
2011 Rina
2010 Karl
2010 Paula
2010 Richard
2009 Ida
2008 Omar
2008 Paloma
2005 Stan
2005 Wilma
2005 Beta
2001 Michelle
2000 Gordon
2000 Keith
1999 Irene
1999 Lenny
1998 Mitch
1996 Lili
1996 Marco
1995 Opal
1995 Roxanne
1994 Gordon
1987 Floyd
1984 Klaus
1981 Katrina
1980 Jeanne
1969 Laurie
1969 Martha
1968 Gladys
1964 Isbell
1961 Hattie
1921 Tampa Bay Hurricane

so as can be seen the western Caribbean is a hot spot from September 15th on even in a dull season, just look a 2009 as an example not much going on but a hurricane in Ida threatened the gulf coast in November of that year so the moral to the story is the Caribbean is the place to really watch until November is over

[alienstorm]

I agree the heat content lack of activity this year will in all likelihood produce the CAT 3 / CAT 4 in October

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The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Macrocane]

The WPAC has entered in a period with more favorable conditions, maybe that will move to the EPAC and the ATL in a couple of weeks because of the teleconnection things.

[cycloneye]

I think this was not looked by the model fans. 00z ECMWF has something near the CV islands at 240 hours.

[ROCK]

12Z GFS wants to bring a low into the GOM in the long range....along with this ATL TS that swings out to sea.
12Z CMC has a TS in the ATL but out to sea
12Z NAVGEM sees the same as the CMC

so to sum up there is potential for something in the ATL soon that could rack up some ACE....

wouldnt rule out a subtropical storm riding up this front thats swinging thru either.

[supercane4867]

12Z ECMWF hints a weak system develop from Cape Verde start at 192HR

[supercane4867]

00Z GFS come into agreement with ECMWF

Finally there will be a FISH

[Hammy]

I'm seeing a very intense low on the Euro at days 7-9 but it is difficult to tell if it is tropical or not.

[BigB0882]

I'm seeing a very intense low on the Euro at days 7-9 but it is difficult to tell if it is tropical or not.

Near CV or somewhere else?