2013 Steering Pattern / Early indicators

[TheStormExpert]

Am I the only one who is seeing signs of a pattern change which would allow storms to once again recurve out to sea and not affect the U.S.? And since the NAO is going negative doesn't that usually correlate towards a pattern where storms tend recurve?

[wxman57]

A negative NAO does promote early recurvature of Cape Verde storms. Not much impact on systems that form farther west (and south), like in the Caribbean.

[gatorcane]

Not only that but those graphics only go out through the next 14 days when the Cape Verde season hasn't quite started based on climatology. (typically starts Aug. 15th).

[cycloneye]

Also if a negative NAO occurs, with less strong trade winds,the MDR waters warm much more.

[NDG]

Since the middle of April, every time the NAO has gone negative (barely) has been for about a week or so, the trend has been for a persistent Positive NAO regime, doubt that will change much for the rest of the hurricane season.
NCEP Ensembles still call for strong ridging in the NW Atlantic to take over by the beginning of August and for the trough along the east coast to retrograde towards the GL and MS River valley.

[TropicalAnalystwx13]

Many of the United States' worst hurricane hits have from a negative NAO. This phase may allow for a weaker high overall, but the high is shifted farther southwest. Let's not get "weaker" confused with "weak", it's still sufficiently powerful enough to steer a strong hurricane. Right now, the Azores high is shunted way northeast near the Azores, typical of a positive NAO.

That being said, as long as the Arctic remains cool, I don't see a sudden flip in the pattern that would allow for more recurves.

[cycloneye]

I see a couple of highs south of 30N right now dominating.

[tolakram]

I'm wondering if the same pattern that avoids recurves is also a negative for CV formation, since a strong high pressure system will almost always result in increased trade winds and cooler ocean temps.

[ninel conde]

I'm wondering if the same pattern that avoids recurves is also a negative for CV formation, since a strong high pressure system will almost always result in increased trade winds and cooler ocean temps.

sst's are no problem but you may be right about the strong easterly shear. also, as cycloneye points out the highs are too far south for any development.

[Ntxw]

Wxman57 made a good post above we should all consider, -NAO does usually re-curve when you're speaking about strong CV originated systems, but those that get their act together near, west of the Islands, or just north of the Antilles usually aren't effected as much with the 're-curve' idea.

[ninel conde]

Wxman57 made a good post above we should all consider, -NAO does usually re-curve when you're speaking about strong CV originated systems, but those that get their act together near, west of the Islands, or just north of the Antilles usually aren't effected as much with the 're-curve' idea.

thats assuming anything makes it that far. the last 3 seasons had a neg NAO every month of the hurricane season, in fact that streak was finally broken last month i think, and we can see the results. very few cane hits on the US and no majors. what we saw most often was weak sheared systems past 65west.

[TheStormExpert]

I'm wondering if the same pattern that avoids recurves is also a negative for CV formation, since a strong high pressure system will almost always result in increased trade winds and cooler ocean temps.

Then how were we able to have the major cape verde storms of 2004 with this same pattern?

[wxman57]

Wxman57 made a good post above we should all consider, -NAO does usually re-curve when you're speaking about strong CV originated systems, but those that get their act together near, west of the Islands, or just north of the Antilles usually aren't effected as much with the 're-curve' idea.

thats assuming anything makes it that far. the last 3 seasons had a neg NAO every month of the hurricane season, in fact that streak was finally broken last month i think, and we can see the results. very few cane hits on the US and no majors. what we saw most often was weak sheared systems past 65west.

A negative NAO typically does result in a greater number of named storms, though a higher percentage of those named storms (compared to normal) may recurve east of the U.S. But the recurving storms are typically those that develop farther east. The farther west a storm develops, the greater the chance it won't recurve east of the Caribbean and/or the U.S.

2004, by the way, was more positive NAO than negative:

[Hybridstorm_November2001]

Interesting, nearly all the years during which my general region had a moderate to strong impact (1954, 1962, 1963, 1969, 1985, 1996, 1999, 2001, 2003, 2011), the NAO was moderately to strongly negative over all.

[ninel conde]

yea, i was going to say 2004 had a rather strong west atlantic ridge, unlikely in a neg NAO.

['CaneFreak]

Take a real good look at this current SST Anomaly map. This tells you A LOT about where the pattern has been and where it may be heading. Take a look at those strong positive SST anomalies up in the far northern and northwestern Atlantic. Why is this important? Given that the atmosphere and ocean are a coupled system and that the atmosphere tends to have a long term "memory" if you will, I would be looking for increased ridging in the northern Atlantic to persist as we head into August and September as these positive anomalies continue to get stronger and expand. This warmer than normal water will act to reinforce this ridge and allow it to persist for a longer than normal period of time. Notice the "cool" anomalies over the Bahamas and the area just north of PR and the Greater Antilles - wonder why they are there? Because there has been a fairly persistent area of lower than normal pressure with increased cloudiness and precipitation falling onto the ocean surface making it seem "cooler" on the ocean surface. However, deep below that cooler than normal water lies some very warm water that is just waiting to be upwelled back to the surface. Don't be fooled by that tongue of "cooler than normal" water - it may actually be an indication of an upcoming persistent hurricane track for the next couple of months through this area.

['CaneFreak]

I would encourage EVERYONE to read this paper (Wang et. al 2011). Great paper. For those that read it, this year's SST pattern strongly resembles a small AWP or Atlantic Warm Pool as referenced in the paper.

http://www.aoml.noaa.gov/phod/docs/Wang_etal_2011.pdf

[Kalrany]

Great paper! Learned a lot from it. Have a better handel on NASH's influence. Thanks!

I would encourage EVERYONE to read this paper (Wang et. al 2011). Great paper. For those that read it, this year's SST pattern strongly resembles a small AWP or Atlantic Warm Pool as referenced in the paper.

http://www.aoml.noaa.gov/phod/docs/Wang_etal_2011.pdf

That... doesn't sound so good.

[SFLcane]

posted here from my twitter page..

seasons storm tracks look a lot like 2004

[Steve H.]

Have to agree with 'canefreak. This has been a very rainy early summer in Florida. The SSTs are deceiving. The SW flow takes the waters at the surface east and up wells some cooler water, at least at the beaches, But offshore, these anomalies of cooler water are temporary. There is abundant warm water underneath, and that will surface with up welling and the heat from the summer temperatures. This pattern is IMO very similar to 2004 when Florida had a relatively cool and rainy early summer.