[HM]

After reviewing the latest maps, I thought this was deserving of a new thread. I knew that if I put this into the ENSO thread, that it would be either completely dismissed or taken out of context (as in proof of a certain forecast ENSO strength through implication). Therefore, I wish to discuss the recent developments and share some pretty impressive images and what that may mean down the road.

The MJO has some legs with all variables that go into the EOFs saying "it's a go" here with -h2 anomalies, +h85 anomalies and -OLR anomalies. Finally, some progression was noted on the 9/26 update and this was explained why in the ENSO thread.

http://i10.photobucket.com/albums/a127/HMisdead/phaseLast40days.gif
http://i10.photobucket.com/albums/a127/HMisdead/hov_u200gif.png
http://i10.photobucket.com/albums/a127/HMisdead/hov_u850gif.png
http://i10.photobucket.com/albums/a127/HMisdead/tlon_vpot_mjo.gif

There is a +6 SD h85 positive anomaly located around 150E with actual MEAN surface winds out of the west here! It is quite an +u anomaly at the surface when the actual mean winds are coming out of the west INVOF a classic atmospheric Kelvin Wave (please don't confuse this with the oceanic type). What also is classic is the coupling going on here with a retrograding Rossby Wave across 5-10°N around 120E. In between the two systems, you'll find the MJO signal in a classic position with a strong water vapor/divergence gradient right near the Kelvin Wave. This system is very organized and straight out of a book! That westerly surface wind is heading right for the Dateline!

http://i10.photobucket.com/albums/a127/HMisdead/sfcwnd_01afnl26.gif
http://i10.photobucket.com/albums/a127/HMisdead/sfcwnd_01afnl27.gif
http://i10.photobucket.com/albums/a127/HMisdead/sfcwnd_01afnl28.gif
http://i10.photobucket.com/albums/a127/HMisdead/sfcwnd_01afnl29.gif
http://i10.photobucket.com/albums/a127/HMisdead/sfcwnd_01afnl30.gif

Another sign that this system is classic is how it is also impacting the subtropics and water. The negative tendency to the AAM that has persisted for so long around 10°N is now over as the -AAM propagates into the Mid Latitudes and westerly momentum is added across the subtropics from the organized convective system. Expect the mean AAM to become more positive over the next couple of weeks as this system propagates east towards the Dateline. Also, anticipate the SST to cool across the Maritimes somewhat where the MJO-related -OLR has focused and cooled the water. There is already some anecdotal indication of that in the dailies focused around 140-150E but I want to wait for some SST change maps to verify this. It will be interesting to see how this Westerly Wind Burst handles the -u vector pool focused over the Tropical Pacific right now. If it can get beyond this increasingly hostile battle in the ENSO regions, it may be able to start warming the western edges.

The -AAM propagation into the Mid Latitudes has already been discussed and is the reason the Pacific has had such a radical shift in the modeling. The anticyclonic wave breaking has been rather persistent lately and the mean geopotential flow is expected to shift poleward some, giving a more La Niña-like appearance to general circulation and less meridional. However, this should be brief if this system in the tropics holds the course and it continues to add +AAM to the subtropics. This would help to extend the Pacific Jet some, position a classic El Niño-like Aleutian low and initiate a Rossby Wave Train perhaps in later week 1 or week 2. We'll see what happens here!

But what a classic system down there!

[HM]

Also, for you tropical fans, just hold out. Despite what has been a pretty lackluster year so far and peak, this wave shows no signs of stopping and should arrive into the Atlantic during latter week 1, but especially week 2. They tend to speed up once they get to the Dateline and this behavior can already be seen in the early stages when looking at a CHI loop (time sensitive)-->

http://www.cpc.ncep....m_monthly.shtml

I correctly predicted 1 storm during the peak of hurricane season and a rather boring peak. I said the next wave of potential would come later in the month with the next CHI wave. I may have rushed the second wave in the original call but the general idea is right. There could potentially be more named storms POST peak than during the peak if my ideas (both seasonal and medium range) are correct.

The El Niño is not the only reason for the lackluster season. I warned of the potential for subtropical lows this year in the upper troposphere given the timing of the +QBO descent. The latest 50mb winds are beginning to weaken and mean temperatures are beginning to cool here. This may combine with the next wave in CHI to perhaps bring some more named storms, despite climatology and El Niño.

[HM]

Here is the MJO SST gradient and +u winds from TAO

Attached File(s)

•  MJOsst926.jpg (108.35K)
  Number of downloads: 8

[WX1996]

Quote

There is a +6 SD h85 positive anomaly located around 150E with actual MEAN surface winds out of the west here! It is quite an +u anomaly at the surface when the actual mean winds are coming out of the west INVOF a classic atmospheric Kelvin Wave (please don't confuse this with the oceanic type). What also is classic is the coupling going on here with a retrograding Rossby Wave across 5-10°N around 120E. In between the two systems, you'll find the MJO signal in a classic position with a strong water vapor/divergence gradient right near the Kelvin Wave. This system is very organized and straight out of a book! That westerly surface wind is heading right for the Dateline!

Hey
Hard for me to follow, which system are we talking about?

[HM]

WX1996, on 27 September 2009 - 10:45 PM, said:

Hey
Hard for me to follow, which system are we talking about?

Sorry for the confusion! The first use of system refers to the Kelvin Wave and Rossby Wave system. In a classic MJO model, you will have 2 symmetrical (about the equator) RWs moving westward positioned west of the MJO and 1 KW moving eastward positioned east of the MJO. This places the MJO right smack in the middle of these two waves. Therefore, the final use of the word system is referring to the entire process just outlined.

This whole thing right now is about as classic as it gets and comes right at a time when it should, given the QBO behavior and the repositioning warm pool in the Western Tropical Pacific. I am glad I got the this early autumn MJO wave right, even if I was a little quick with its genesis in the seasonal outlook. However, I did say that it would be in phase 4 for most of early September...but I didn't think it would stay that way right through the end of the month.

[VAwxman]

Solid post HM and I think we can see the results of all of this starting to show up in the modeling. It's nice to see some of the "confused" signals in the atmosphere seemingly coming together to give a better signal, at least for now. Should hammer away at the "nina like" atmosphere after the first week or so of October.

[HurricaneJosh]

HM, on 27 September 2009 - 10:26 PM, said:

Also, for you tropical fans, just hold out. Despite what has been a pretty lackluster year so far and peak, this wave shows no signs of stopping and should arrive into the Atlantic during latter week 1, but especially week 2. They tend to speed up once they get to the Dateline and this behavior can already be seen in the early stages when looking at a CHI loop (time sensitive)-->

Hey, thanks for covering the tropical angle. :thumbsup:

I assume the pattern change will also have a positive impact on E-Pac activity?

[nynjpaweather]

All I can say is I love this stuff that HM posts. I always learn something new! THANK YOU!!

[wxmann_91]

I've definitely been noticing the impact of this latest westerly wind burst in the WPAC. Impressive indeed.

[snowman]

Hm, nice post, and always enjoy reading them , although I don't always understand all you say. From what I gather, based on your explanation, the sst are about to change a bit and the atmosphere is going to change to more el nino like. What would that mean for sensible weather. It has been very nice , dry here in the mid atlantic for a while now. Thanks in advance. I hesitate to intrude on a thread that is obviously intended for the more knowledgable and educated on the board. My apologies.!!!

[Glacier Point]

Some deep convection showing up on latest OLR totals centred 170W ahead of the MJO wave:

 map_last3days.JPG (589.5K)
Number of downloads: 4

Westerly mean zonal wind anomalies also increasing once again behind the MJO wave in the Indian Ocean which should help bolster the convective centres further east, possibly nudging it towards the dateline:

 TAO zonal.JPG (328.68K)
Number of downloads: 4

So every prospect for continued enhanced forcing 170W-180 corresponding with projections into phase space Octants 6 and 7. However, as observed, the extratropical ocean-atmosphere dynamic is not fully embracing the tropical signals and September's phase 4 stall was a good example of shackling that the GWO is currently exerting on the tropics.

Relative angular momentum is still below climo as per last Friday (we seriously need these to update faster):

http://www.cdc.noaa....g1-21.90day.gif

and the GWO is unlikely to orbit quickly into phases coherent with the MJO for the time being until we see mean westerly zonal wind propagation polewards in addition to strong tropical forcing (mid October ??).

Probably the best summation for the pattern would be for a GWO phase 4 type (although long range modelling looks to have conflicting signal with Atlantic trough):

 phase 4 nino.JPG (159K)
Number of downloads: 2

with increasing tendency towards phase 5 / 6 type into October:

 phase 5 nino.JPG (160.21K)
Number of downloads: 1

[usedtobe]

HM, Glacier Point,

Good posts. I think HM is right about the mjo helping to tilt the GLAAM to more positive nino like conditions in a couple of weeks time.

[gil888]

HM, on 27 September 2009 - 10:11 PM, said:

After reviewing the latest maps, I thought this was deserving of a new thread. I knew that if I put this into the ENSO thread, that it would be either completely dismissed or taken out of context (as in proof of a certain forecast ENSO strength through implication). Therefore, I wish to discuss the recent developments and share some pretty impressive images and what that may mean down the road.

Agreed totally. I noticed this before reading your post this morning and I posted something about it in the El Nino thread earlier. Your discussion here expounds on what I was thinking very well.

[flwxwatcher45]

nynjpaweather, on 28 September 2009 - 04:54 AM, said:

All I can say is I love this stuff that HM posts. I always learn something new! THANK YOU!!

Agree with your statement 100%!!!.. I also hope we can get some late season Tropical action close to Florida to save the year :popcorn:

[wxmx]

Great thread. This Niño could well become an interesting study case. There's a significant probability, in my eyes, that this time there will be a more sensible warming in the ENSO regions, but until I see a definite shift of the main forcing from near Indonesia & N of Australia to near the dateline, any WWB will encounter a brave resistance from the SOI/equatorial easterlies. OLR near the dateline has become more Niño-like during September, which hints at an eastward shift, but SSTAs are still above normal near Indonesia and N Australia (during El Niño episodes they are commonly below average), which has depressed SLPs there (Darwin has been a bit below normal). So let's say, let Round 3 begin!

[rfhpsu]

Why does a strong MJO event help tilt the GLAAM?

I'm trying to expand my wx knowledge beyond a 7 day forecast :)

usedtobe, on 28 September 2009 - 09:00 AM, said:

HM, Glacier Point,

Good posts. I think HM is right about the mjo helping to tilt the GLAAM to more positive nino like conditions in a couple of weeks time.

[DixieBlizzard]

Very interesting post, HM, and I appreciate what you do for us here!

[usedtobe]

rfhpsu, on 28 September 2009 - 09:43 AM, said:

Why does a strong MJO event help tilt the GLAAM?

I'm trying to expand my wx knowledge beyond a 7 day forecast :)

Behind the mjo induced convection, the easterlies are suppressed and there often is warming of the pacific and actually there can be westerly flow near the equator. That will tend to change the GLAAM towards positive values. As the convection shift eastward towards the dateline you also often get a pattern change away from an rpna towards a pna. A couple of Weickmann and Berry articles discuss the impact.

These papers explain it better than me. The first explains how the mjo can change the low level winds and how it can help with the nino.

http://www.bom.gov.a...racts/HWZ07.pdf

The next is a paper by weickmann and Berry that explains how the convection moving eastward across the pac to near the dateline can help induce a nino like pattern.

http://www.cdc.noaa....ions/wb2006.pdf

Finally, the latest Weickmann and Berry article. Figure 3 shows how as the convection changes locations in response to the mjo and gwo, the GLAAM tendencies change.

http://www.cdc.noaa....vised_final.pdf

Hope this helps.

The

[HM]

VAwxman, on 28 September 2009 - 04:10 AM, said:

Solid post HM and I think we can see the results of all of this starting to show up in the modeling. It's nice to see some of the "confused" signals in the atmosphere seemingly coming together to give a better signal, at least for now. Should hammer away at the "nina like" atmosphere after the first week or so of October.

I am fully on board for the ideas expressed on the models in the 6-10 day period of an Aleutian Low developing. This one will be more classic of a west-based El Niño setup whereas the last North Pacific low (before the anticyclonic wave breaking) was more like that of an East-Based event. I don't know about you, but I like a cold eastern 1/3 for November and December! :scooter: :popcorn:

[HM]

HurricaneJosh, on 28 September 2009 - 04:50 AM, said:

Hey, thanks for covering the tropical angle. :thumbsup:

I assume the pattern change will also have a positive impact on E-Pac activity?

No problem Josh! For the most part, I think the experimental calls this year went pretty darn well. So, I am excited to try this again but in a year a little bit more active than this one! :arrowhead:

Anyway, this current MJO system is already responsible for producing a couple of TDs in the Western Pacific and now the divergence anomalies have spread all across the tropical Pacific. It is quite possible the East Pacific produces another named storm very soon and they will likely be the first to feel the effects of this wave, before it heads into the Atlantic. But usually, the lag is very short because the anomalies like to pulsate quickly beyond the Dateline.