Atlantic Tropical Action 2013

[HM]

Thanks so much for the very detailed response...it is good to see that my views were in line with what you were seeing. I have also noticed that the E Pacific seems to be especially responsive to surface wind stress late in meteorological spring. For instance, in the 10-day period before our recent Kelvin wave crossed 120˚W, a period of -OLR / increased trades due to an enhanced Hadley in the SE Pacific was enough to cool NINO 1-2 by a good several degrees (May 1-10 period). The lag continued for the next several days even as the Kelvin wave-induced + U-anomalies at 250 mb migrated eastward. This trend, whose feedback loop will also serve to reinforce the SE Pacific Hadley, is yet another factor that will slow the advance of warm subsurface anomalies, especially without an "active" MJO signal. The latent (meaning enhanced but not "true") MJO signal, which supports a feedback favoring a slow N-PAC SSTA progression to a more neutral PDO configuration, looks to last into most of the first half of June or perhaps beyond. This should produce, in my view, a more typical early start to the Atlantic season, meaning fewer prospects of early development before the start of July. At least that is how I see it, but please feel free to voice your assessment/corrections.

 

Earlier, when the scale was slightly tilted "nino" on the global pattern, I thought it would be possible to pull something off, tropical-wise, in the Atlantic sometime in May/start of June. There is still time with the CCKW but a solid subsidence period will follow for a bit. So your thoughts about the June-early July period seem reasonable to me. July will probably grow more interesting as the waves return.

[Superstorm93]

CPC is starting to hint at an early-season cyclone:

 

 

A large scale ridge predicted over the southern CONUS and Gulf of Mexico during Week-2 is expected to reduce wind shear and provide favorable conditions for tropical cyclone development across the northwestern Caribbean Sea. Due to the reduced wind shear in an area of enhanced convection, the development of an early season tropical cyclone is favored for the northwest Caribbean Sea. The GFS model has been consistent in developing a potential tropical cyclone in the northwestern Caribbean Sea in early June.

 

 

6z NCEP ensembles were pretty bullish in the Caribbean for D5-10

 

 

[Eyewall2005]

Superstorm93 can you post a link to those ncep ensemble probability maps?

[crownweather]

Link to the NCEP ensemble probability charts: http://www.emc.ncep.noaa.gov/gmb/tpm/emchurr/tcgen/

[Eyewall2005]

Link to the NCEP ensemble probability charts: http://www.emc.ncep.noaa.gov/gmb/tpm/emchurr/tcgen/

 

Thanks rob had misplaced link.

[crownweather]

No problem. I think we all are now looking for our hurricane season links, in fact I had to Google the ensemble link.

Rob Lightbown

Crown Weather Services

http://www.crownweather.com

[Ed Lizard]

Model gazing...

 

At least Texas is protected by both cool water and a ridge.

 

 

[phlwx]

that gulf/fl threat is modeled on the EC as well (weaker, east, but still there) in about ten days.

 

If anything develops, rain probably the bigger calling card.

[HurricaneJosh]

So not gonna get sucked into early-season fake-outs this year.  No, sirree.

[WxFreak11]

So not gonna get sucked into early-season fake-outs this year.  No, sirree.

Liar, liar, pants on fire!

[HurricaneJosh]

Liar, liar, pants on fire!

 

Quiet.  

[bluewave]

The models generally agree on a sloopygyre development next week. This looks like

a very broad system with the potential to produce significant rainfall wherever it ends

tracking. Development will hinge on how far away from Central America the system

tracks. Barry developed in a similar manner during the beginning of June 2007.

 

 

[klw]

So not gonna get sucked into early-season fake-outs this year.  No, sirree.

[Ground Scouring]

The models generally agree on a sloopygyre development next week. This looks like

a very broad system with the potential to produce significant rainfall wherever it ends

tracking. Development will hinge on how far away from Central America the system

tracks. Barry developed in a similar manner during the beginning of June 2007.

The GFS ensemble mean seems to anticipate that the UL anticyclone associated with the down-welling Kelvin wave / developing TC (convection) in the EPAC will spread into the Atlantic in about six days as the MJO finally begins to revive and move into Phase 1. The EPAC convection should serve to both heighten and warm the upper troposphere, meaning an expansion of the 250-mb anticyclone. Both the GFS and the ECMWF show a trend toward a +NAO in the same time frame, which would favor UL divergence, a relaxation in vertical shear, and a pressure vacuum (lower pressures) in the SW Caribbean Sea. The strong convection ongoing near Indochina should help to foster added energy to the East Siberian vortex and thus erode the ridge near Japan, thereby introducing lower heights to the Bering region. This would help set the Atlantic pattern change in motion. Past experience with Kelvin wave-induced transitions suggests that the general pattern set-up appears reasonable to expect over the next six days. So the idea of development in the SW Caribbean next week, while still highly uncertain, is gaining some traction in my outlook. I initially expected no development, but now I may need to revise my expectations.

[Ed Lizard]

The models generally agree on a sloopygyre development next week. This looks like

a very broad system with the potential to produce significant rainfall wherever it ends

tracking. Development will hinge on how far away from Central America the system

tracks. Barry developed in a similar manner during the beginning of June 2007.

 

GFS_3_2013052806_F216_PWATIN_SURFACE.png

 

00zeurotropical500mbSLP240.gif

 

 

From my standpoint as a pure amateur, seeing lowest 500 mb heights well displaced to the Northeast of lowest surface pressures suggests to me Euro is seeing a badly sheared system.

[phlwx]

So not gonna get sucked into early-season fake-outs this year.  No, sirree.

 

you know you like 50 mph slopical storms.  they're the new hawtness.

[Ground Scouring]

Both 12Z runs of the GFS and the ECMWF are trending toward a larger system that already shows signs of organizing in about five days...but the key disagreement seems to concern whether the "TC" forms on the east or west side of the Yucatán peninsula. The GFS first develops an organized low-level vorticity center in the Bay of Campeche as early as this Saturday, then stalls the low just offshore between Poza Rica and Veracruz. The ECMWF shows less development until day seven, then starts developing a highly asymmetric, sheared low west of Campeche. Both models have significantly trended toward a larger system: each model suggests that remnant vorticity from the current EPAC depression will favor UL divergence and a thermal expansion resulting in a larger UL anticyclone over the W Caribbean, beginning in about five days.

 

Both models suggest that convection related to the current TD 2 in the EPAC will linger over the Isthmus of Tehuantepec through day five, then get drawn northward as a mid-level trough dips down into the NE Gulf of Mexico. As early as Thursday morning (EDT), the GFS absorbs the EPAC TD 2 into the broad monsoonal gyre after its having moved inland by Wednesday evening near Salina Cruz. It then seems to reform a new TC just offshore in the EPAC which moves inland Thursday evening, which indirectly plays a role in the development of the BOC low on Saturday. The ECMWF seems to favor the eastern (Campeche) solution, with TC development about a day later. Nevertheless, the proximity of the low to an upper low means that some baroclinicity and cooler temperatures at H5 are likely playing a role in development, hence the sloppy, broad, and sheared structure.

 

In short, the support for increased TC genesis beginning in five days, most likely somewhere in the BOC, continues to grow, but uncertainties re: location and track remain.

[Ground Scouring]

you know you like 50 mph slopical storms.  they're the new hawtness.

Would you pay $0.25 to hear my scintillating three-paragraph-long prognosis on a slop-gyre hitting FL? 

[OKpowdah]

For what it's worth .........

 

For the projected phase of the QBO this season, here is the TC density standardized anomaly ... notice above normal activity in the GoM (especially the western Gulf). Also, the positive anomaly up around New England is the highest of all the phases.

 

[Ground Scouring]

For what it's worth .........

 

For the projected phase of the QBO this season, here is the TC density standardized anomaly ... notice above normal activity in the GoM (especially the western Gulf). Also, the positive anomaly up around New England is the highest of all the phases.

What's interesting is that while this diagram, based upon MQI, shows some of the highest activity in the N and W Gulf and near New England, none of the reliable TC forecasts that I have seen highlights those areas--in fact, most current forecasts show most of the activity hitting FL through the Carolinas. Most seem to expect low activity in the W Gulf and near New England. Nevertheless, most recent landfall-probability forecasts have not performed well. It will be interesting to see whether MQI beats everyone else's forecast.

[Ed Lizard]

People in the I-35 corridor a couple of hundred miles West of here don't want it, but providing it doesn't stall, I'd welcome an early season TC passing over water barely 26ºC to drop a few inches of rain on the lawn.

 

Early signs seem to suggest a 39/2/59 split between Mexico/Texas/Eastern Gulf/Florida *if* anything does develop.

[phil882]

The models generally agree on a sloopygyre development next week. This looks like

a very broad system with the potential to produce significant rainfall wherever it ends

tracking. Development will hinge on how far away from Central America the system

tracks. Barry developed in a similar manner during the beginning of June 2007.

 

GFS_3_2013052806_F216_PWATIN_SURFACE.png

 

00zeurotropical500mbSLP240.gif

 

 

you know you like 50 mph slopical storms.  they're the new hawtness.

 

Central American gyres are actually an area I've been doing focused research on the last year in grad school. In terms of intensity I think CA gyres often get a bad rap because they often don't become much of anything in terms of a well organized tropical cyclone. There are some notable exceptions though such as Wilma (2005), Opal (1995), and Roxanne (1995). There is also a bimodal peak in gyre activity with a first peak taking place in the early portion of the hurricane season (May, June) with a secondary peak in the latter half (Sep, Oct, Nov).

 

We are obviously right in the early peak season for gyre activity, so its not surprising to see the models want to spin something up in the long range. There are a couple of additional factors that increase the likelihood of gyre development. First, we have a predecessor TC (Barbara) that is likely to make landfall over the next few days over CA. This provides an initial source region for vorticity over CA. In addition the background flow is already setting up for anomalous westerly low-level flow in the East Pacific south of CA and anomalous easterly low-level flow in the Atlantic (Caribbean and Bahamas due to an enhanced subtropical ridge). This creates a large region of cyclonic shear vorticity over CA which oftentimes can lead to broad gyre development. 

 

 

Source: Kyle MacRitche's webpage: http://www.atmos.albany.edu/student/macritch/showhovs.php?bknum=1&lat=75N15N

 

 

Oftentimes this type of favorable low-level wind regime is cause by a propagating MJO event. Indeed, a normalized OLR hovemoller with MJO spectrum wave filtering show a significant MJO event underway across CA (note the positive red contours between 90-120 W). 

 

 

 

 

 

Source: Kyle MacRitche's webpage: http://www.atmos.albany.edu/student/macritch/showhoriz.php

 

 

 

In addition, this MJO event appears to be superimposed over a developing Equatorial Rossby (ER) wave over the same region. You can see this in the horizontal plots above where the -OLR band associated with the MJO is intersecting the -OLR band associated with the ER wave. This type of pattern obviously promotes lots of convection over CA, but also large scale gyre development on the backside of the MJO, which is now forecast by both the GFS and the ECMWF in the medium range.

 

Any TC that does develop would be most likely to occur on the southern (East Pacific) or eastern flank (Western Caribbean/Eastern GOM) of the gyre circulation, as this is typically where the mesovorticies and convection associated with the gyre are focused. Think like Barry (2007), Nicole (2010), or Debby (2012).  

[Bryan Wood]

What's interesting is that while this diagram, based upon MQI, shows some of the highest activity in the N and W Gulf and near New England, none of the reliable TC forecasts that I have seen highlights those areas--in fact, most current forecasts show most of the activity hitting FL through the Carolinas. Most seem to expect low activity in the W Gulf and near New England. Nevertheless, most recent landfall-probability forecasts have not performed well. It will be interesting to see whether MQI beats everyone else's forecast.

 

It's because most landfall forecasts are just based on straight climo mixed with "hunches" (sometimes based on actual data).

[Ground Scouring]

Shear will be relaxing considerably over the next two days in the SW Caribbean just N of Honduras. The ECMWF ensemble mean actually develops a weak low in this area on Friday--something that is hinted at but not shown by the GFS. I think that the difference between the ECMWF and the GFS solutions can be explained by their differences in handling convection from Barbara in the E Pacific. The GFS develops a vigorous secondary vorticity maximum SW of Barbara overnight into Thursday, while the ECMWF gives more emphasis to moisture pooling / orographic convergence on the east side of Barbara, which serves to draw Barbara's remnant vorticity more to the NNE and just into the SE Bay of Campeche on Saturday. The GFS seems to show a bias toward a secondary low, especially when dealing with large gyres forming near a coastal mountainous terrain, so I would tend to favor the ECMWF, which could allow development to begin on either side of the Yucatán as early as late Sunday.

 

Please let me know whether my analysis seems correct or logical...thanks!

[Ground Scouring]

The 12Z GFS brings the vorticity of Barbara across the Tehuantepec Isthmus intact and thence into the southern BOC on Thursday evening.

[icebreaker5221]

For what it's worth .........

 

For the projected phase of the QBO this season, here is the TC density standardized anomaly ... notice above normal activity in the GoM (especially the western Gulf). Also, the positive anomaly up around New England is the highest of all the phases.

 

tcstanomdens60.png

 

 

It's a nice product, but it looks extremely noisy to me - especially when you have maxima immediately adjacent to minima like that.  Does the QBO really do something that supports enhanced TC activity off the coast of NJ and GA/SC, but suppressed TC activity between the two off the coast of NC? 

 

I think your other products on overall activity, or something between the two (e.g. overall activity in 3 different sub-sections of the Atlantic) is more meaningful, but I guess we need to try it out for a few seasons to see how it actually does!

[weatherdude888]

The 12Z GFS brings the vorticity of Barbara across the Tehuantepec Isthmus intact and thence into the southern BOC on Thursday evening.

 

Interesting.....A few housekeeping questions:

 

1) Assuming the circulation remains intact to some degree over the mountainous terrain, this would be called Barbara in the Atlatic as well correct?

 

2) Has it ever happened that the first named storm in the atlatic would be a cross over from the EPAC

 

3) Would the atlatics "B" name still be used in the event we get to that storm

 

 

Just curious

 

 

 

-Matthew

[am19psu]

Interesting.....A few housekeeping questions:

 

1) Assuming the circulation remains intact to some degree over the mountainous terrain, this would be called Barbara in the Atlatic as well correct?

 

2) Has it ever happened that the first named storm in the atlatic would be a cross over from the EPAC

 

3) Would the atlatics "B" name still be used in the event we get to that storm

 

 

Just curious

 

 

 

-Matthew

1. No

2. Yes - most recently 2008 (Alma/Arthur)

3. N/A

[OKpowdah]

It's a nice product, but it looks extremely noisy to me - especially when you have maxima immediately adjacent to minima like that.  Does the QBO really do something that supports enhanced TC activity off the coast of NJ and GA/SC, but suppressed TC activity between the two off the coast of NC? 

 

I think your other products on overall activity, or something between the two (e.g. overall activity in 3 different sub-sections of the Atlantic) is more meaningful, but I guess we need to try it out for a few seasons to see how it actually does! 

 

 

 

Yeah no I definitely agree. The noisy extrema I don't take to mean anything. It's the larger more consistent areas like that in the western Gulf that I take to be some degree of a signal. Perhaps I could smooth this out a bit more. Right now, it's TC 6hrly points interpolated to a 1deg/1deg grid. Maybe I'll try lower resolutions ... heck, at least the program would run faster haha.

The QBO can modify overall tropical activity, as well as the extratropical wave pattern ... which is what theoretically connects it to localized distribution of TC activity. What is actually statistically significant ... that's something I'll be working on.

[Ed Lizard]

1. No

2. Yes - most recently 2008 (Alma/Arthur)

3. N/A

 

 

I was under the impression if a Basin crosser remained a TC (not a remnant that redeveloped) it would keep the original name, ie, if Barbara emerged in the BoC as a TD it'd be TD Barbara.  Not that I expect that.