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Atlantic Tropical Action 2012 - Part II


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If we can go to the middle of September without a major hurricane, it will mark something only done once in the last decade.

And yet if Leslie gets named tomorrow or the next day, we'd be right on or just one day off 2005's pace in terms of named storms.

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The caveats of 10-day model output notwithstanding, the 00Z ECM shows 98L/proto-Leslie making a very close run at the New England coast, with the center about 70-80 miles SE of Nantucket at H240. Has Maine ever had a TC landfall? :lmao:

Edna 1954.

But :lmao:, it has it doing a Fujiwhara with Isaac's remnant. Oh what has become of the mighty Euro.

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The upper low off the southeast US coast that does a Fujiwhara with Leslie-to-be pinches off from a trough moving off the east coast in a few days. It is not the remnants of Isaac.

Edna 1954.

But :lmao:, it has it doing a Fujiwhara with Isaac's remnant. Oh what has become of the mighty Euro.

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The upper low off the southeast US coast that does a Fujiwhara with Leslie-to-be pinches off from a trough moving off the east coast in a few days. It is not the remnants of Isaac.

The remnant H85 vort energy from Isaac is pretty easily trackable on the high-res ECM. It's pretty complex (and humrous to watch happen), but Isaac's remnants rotate around the back side of that H50 low that pinches off from the western Atlantic trough, and then the H50 low gets absorbed into proto-Leslie, with Isaac's remnants lagging behind a few hundred miles to the south.

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Great illustration Mike. This strongly suggests that the model is not correct in projecting a similar string of activity like we just saw the last 5-10 days. I agree with you that we should see much more limited activity than we had had over the past 2 weeks thanks to the unfavorable MJO state.

its looking like the model was correct after all.

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8AM TWO for 98L:

SATELLITE IMAGES INDICATE THAT A TROPICAL DEPRESSION IS LIKELY

FORMING OVER THE CENTRAL ATLANTIC OCEAN ABOUT 1250 MILES EAST OF

THE LESSER ANTILLES...AND ADVISORIES WILL PROBABLY BE INITIATED

LATER THIS MORNING. THIS SYSTEM HAS A HIGH CHANCE...NEAR 100

PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS

AS IT MOVES WEST-NORTHWESTWARD AT 15 TO 20 MPH.

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its looking like the model was correct after all.

With respect to developing a tropical cyclone, or pair of tropical cyclones... yes the model did verify. Whether these tropical cyclones develop into strong Hurricanes is yet to be seen.

With regards to forecasting the MJO/Kelvin waves, the model forecast did not verify. I was pointing out a potential flaw in the model forecast that could affect it's medium-to-long-range prediction. I try to look at all aspects of model forecasts to understand the underlying risk in each run.

To illustrate the GFS forecast from an earlier post and what actually verified:

ex_vp200_bad.png

Now for what actually happened:

vp.anom.30.5S-5N.gif

The relative magnitude in differences for the GFS forecast and what actually happened are quite striking. Forecasters need to look at all aspects of tropical circulation becuase it will dramatically affect the mid-latitude circulation X days into the future.

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so are we still looking at a quieter interlude regarding TC activity?

With regards to the current intraseasonal state.. I still think we will enter a period of inactivity until mid September. I have been forecasting this lull in activity since August 9.

http://www.atmos.albany.edu/student/ventrice/real_time/txt_forecast/8_9_2012.pdf

I was off with regards to two tropical cyclones developing instead of only one. I didn't expect Kirk to develop, but there are times when you are right, and there are times when you are wrong. When your forecast is right, there's no need to boast. But when it's wrong, you need to figure out what went wrong and why. I expected 1 tropical cyclone to develop between the end of August and mid September. My error lies in that I did not account for any genesis north of 20N, as did Kirk.

Kirk looks pretty spectular by the way.. hurricane kirk at 11am?

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With regards to the current intraseasonal state.. I still think we will enter a period of inactivity until mid September. I have been forecasting this lull in activity since August 9.

http://www.atmos.alb...st/8_9_2012.pdf

I was off with regards to two tropical cyclones developing instead of only one. I didn't expect Kirk to develop, but there are times when you are right, and there are times when you are wrong. When your forecast is right, there's no need to boast. But when it's wrong, you need to figure out what went wrong and why. I expected 1 tropical cyclone to develop between the end of August and mid September. My error lies in that I did not account for any genesis north of 20N, as did Kirk.

Kirk looks pretty spectular by the way.. hurricane kirk at 11am?

No doubt...RIC currently going on....and probably a 75kts one.

post-29-0-50272600-1346336637_thumb.jpg

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its looking like the model was correct after all.

Indeed, the models were right in terms of TCG, but as for the overall atmospheric pattern in the tropics it was off the mark. Perhaps the TCs in the domain are small enough that they don't contribute to a large part of the synoptic flow. Kirk is certainly a smaller than average TC (and well outside of the MDR).

With regards to the current intraseasonal state.. I still think we will enter a period of inactivity until mid September. I have been forecasting this lull in activity since August 9.

http://www.atmos.alb...st/8_9_2012.pdf

I was off with regards to two tropical cyclones developing instead of only one. I didn't expect Kirk to develop, but there are times when you are right, and there are times when you are wrong. When your forecast is right, there's no need to boast. But when it's wrong, you need to figure out what went wrong and why. I expected 1 tropical cyclone to develop between the end of August and mid September. My error lies in that I did not account for any genesis north of 20N, as did Kirk.

Kirk looks pretty spectular by the way.. hurricane kirk at 11am?

Yea Kirk looks great... and in my opinion higher than the 65 knots they assigned for this advisory. I don't think these TCs that develop in the mid-latitudes are as susceptible to the unfavorable conditions typically associated with the subsiding MJO and Kelvin phases. Equatorial waves are by definition centered on the equator and decay exponentially as you increase poleward from the Equator. By the time you are N/S of 30 degrees, equatorial waves don't have much of a direct influence (but indirectly they interact with extratropical disturbances). With that said, that doesn't explain the apparent organization of TD#12.

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Indeed, the models were right in terms of TCG, but as for the overall atmospheric pattern in the tropics it was off the mark. Perhaps the TCs in the domain are small enough that they don't contribute to a large part of the synoptic flow. Kirk is certainly a smaller than average TC (and well outside of the MDR).

This goes back to what I said earlier about the MJO... it's a useful tool outside of the very peak of hurricane season, but in the past, I've seen an unfavourable MJO come at the peak of hurricane season and systems will still develop. If models are constantly showing TC generation... if it's the peak of hurricane season, regardless of the status of the MJO, it's probably best to go with the models.

That said, while Kirk is small, I don't think the same can be said for 12L. Kirk initially formed with a lot of dry air and shear around it, so it naturally started out small which leads to its current size.

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This goes back to what I said earlier about the MJO... it's a useful tool outside of the very peak of hurricane season, but in the past, I've seen an unfavourable MJO come at the peak of hurricane season and systems will still develop. If models are constantly showing TC generation... if it's the peak of hurricane season, regardless of the status of the MJO, it's probably best to go with the models.

That said, while Kirk is small, I don't think the same can be said for 12L. Kirk initially formed with a lot of dry air and shear around it, so it naturally started out small which leads to its current size.

We are still in "favorable" MJO state according to Wheeler and Hendon's RMM phase space diagram:

phase.TotAnom.Last90days.gif

Some of my work, including others show that TC genesis is still favorable during RMM phase 3. I didn't quite expect the hold up in RMM phase 3 though. I thought we would be in RMM phase 4-5 at this point, but that didn't happen.

mwr-d-10-05028.1-f15.gif

Fig. 15 from my 2011 paper.

*Edit*

The VP200 filtered fields are something brand new that I have been developing. I do need to put more research into it.. but it still suggests the bulk of the suppressed MJO state is still over East Pacific.

http://www.atmos.albany.edu/student/ventrice/real_time/maps/waves/global/28.gif

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With regards to the current intraseasonal state.. I still think we will enter a period of inactivity until mid September. I have been forecasting this lull in activity since August 9.

http://www.atmos.alb...st/8_9_2012.pdf

I was off with regards to two tropical cyclones developing instead of only one. I didn't expect Kirk to develop, but there are times when you are right, and there are times when you are wrong. When your forecast is right, there's no need to boast. But when it's wrong, you need to figure out what went wrong and why. I expected 1 tropical cyclone to develop between the end of August and mid September. My error lies in that I did not account for any genesis north of 20N, as did Kirk.

Kirk looks pretty spectular by the way.. hurricane kirk at 11am?

Any way of knowing the synoptic pattern and/or steering currents during the mid-September uptick in tropical actvity you are forecasting?

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Mike following the CCKW and the GEFS MJO forecast which takes it back into phase 1 around Sept 2-3... and is somewhat backed up by the Euro (that it will at least try to work back into phase 2). It appears that the CCKW (now over C. America) would arrive near Africa around Sept. 4. So if the MJO is in phase 1 over Africa Sept.4 and amplifying through the 11th in phase 1 wouldn't the 2 waves be collocated with one another at some point during that time frame and increase activity sooner than mid Sept. say...during the time of Sept. 4-11? Or would the conjunction of the two take place to far inland over the continent to exert influence on the Atlantic basin since the MJO is transitioning 2 to 1 instead of 8 to 1 positioning further east in the phase 1 domain?

All this hings on if the GEFS was to verify of course.

NCPE_phase_21m_small.gif

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Does anyone know where you can find model position errors bias anymore or something that looks like this. It came off Brian Tang's site at MIT http://wind.mit.edu/...Home/TCGuid.htm but it says it was moved to NCAR here http://www.ral.ucar....canes/overview/ and I still can't find it. I see he has joined some of you guys at Albany. Maybe you guys could shed some light on where it went. It was a great product.

post-3697-0-45914500-1346358358_thumb.jp

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Mike following the CCKW and the GEFS MJO forecast which takes it back into phase 1 around Sept 2-3... and is somewhat backed up by the Euro (that it will at least try to work back into phase 2). It appears that the CCKW (now over C. America) would arrive near Africa around Sept. 4. So if the MJO is in phase 1 over Africa Sept.4 and amplifying through the 11th in phase 1 wouldn't the 2 waves be collocated with one another at some point during that time frame and increase activity sooner than mid Sept. say...during the time of Sept. 4-11? Or would the conjunction of the two take place to far inland over the continent to exert influence on the Atlantic basin since the MJO is transitioning 2 to 1 instead of 8 to 1 positioning further east in the phase 1 domain?

All this hings on if the GEFS was to verify of course.

NCPE_phase_21m_small.gif

To summarize it, most dynamical models have been predicting the MJO poorly over the past month (as of August 22). The Canadian Model stands above all for medium-long range prediction. That being said, I'm not sold on the backward track into RMM phases 1-2. Now if this were to verify, yes, we might expect another period of enhanced TC activity much earlier than mid-September. I just would't double down on it yet.

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I haven't been keeping track and don't want to take this thread off track, but that burgeoning El Nino looks sickly off South America.

As a result from intraseasonal convective patterns in the tropics, trade winds have picked up over the eastern Pacific during the past two weeks. This has caused recent upwelling in the east Pacific and and retreat of the 28 deg isotherm to about 155W. We might expect the 28deg Isotherm to begin to slide back to the east when equatorial westerly winds pick up during the next convectively active MJO passage later in early-to-mid September.

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/wkxzteq.shtml

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