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Tropical Depression Ernesto - 35 mph - 1004 mb - W 14 mph


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You think its going through an ERC or just dry air intrusion with diurnal min?

I think it's just trying to find out what type of eyewall it can get away with at this point. Not really a full-blown EWRC, but still in the formative phase.

This morning the closed wall was 6nm wide (or just under) and as the day moves on, the eye is becoming larger. Once convection can blossom later today/tonight, this should have no trouble finishing off an impressive core and becoming a decent system.

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Agree 100%. In fact, I would argue that there are three outflow channels, one enhanced by the upper low in the southern Gulf, one enhanced by the upper low just east of the Bahamas, and the third on the south side possibly being enhanced by the passage of the Kelvin wave. Ernesto has great dynamical support aloft. The ocean heat content is quite high as well, although not quite as high as further north. The inner core structure looks good too in microwave, with a eye confirmed on visible and by recon.

RI doesn't tend to happen in a straight line, it's usually more like a staircase. Thus, we may not actually see much intensification during the day today, but I would watch the overnight period tonight for the next major step down in pressure based on some of Jason Dunion's preliminary work on diurnal processes.

I think a major hurricane landfall is a distinct possibility. This has a lot of time left...

Agree and precisely what I was thinking earlier. I think tonight's diurnal maximum may be very, very interesting as long as dry air is not entraining too much.

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After some data/model checking, this is a good candidate for RI in the next 24-36 hrs up to landfall...SHIPS RI index will probably go a bit crazy next few runs...I wouldn't even discard a major, though that's not something I'm daring to forecast still...also, I would heavily lean toward MX rather than BZ. ~300 degree motion should continue until landfall.

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Not liking the OFB's propagating out in front of Ernie:

erniee.jpg

I am noticing something I noted about 3 days ago, which is rare. Usually arcus clouds just race away as skinny little low coud lines, but these are trying to pop new storms. Just an observation. It was actually more pronounced about 3 days ago.

One other thing about the arc clouds, a couple of days ago there was a healthy spread between temp and dewpoint, and before the plane started climbing, the T/Td spread was much smaller, so maybe it was just a little burp, not a major dry air issue.

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I am noticing something I noted about 3 days ago, which is rare. Usually arcus clouds just race away as skinny little low coud lines, but these are trying to pop new storms. Just an observation. It was actually more pronounced about 3 days ago.

It probably means the environment ahead of it is quite moist in a large area surrounding the inner core.

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Ernesto still has the same problem it did a few days ago, the rainband structure in the inner core is not well developed. I think westerly shear + dry air is still causing problems. It has no convection at all on the western side of the circulation, not even any lower-level rain bands. I only expect slow intensification overnight. There is no indication that RI will occur tonight.

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Ernesto still has the same problem it did a few days ago, the rainband structure in the inner core is not well developed. I think westerly shear + dry air is still causing problems. It has no convection at all on the western side of the circulation, not even any lower-level rain bands. I only expect slow intensification overnight. There is no indication that RI will occur tonight.

That is true, a dry slot has indeed formed off Honduras and is going into Ernesto in the mid-levels. The cloud tops have warmed incredibly as well.

We'll have to wait and see as it appears the last chance to really stengthen will be tonight. By Wednesday AM it will be close to land.

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Ernesto still has the same problem it did a few days ago, the rainband structure in the inner core is not well developed. I think westerly shear + dry air is still causing problems. It has no convection at all on the western side of the circulation, not even any lower-level rain bands. I only expect slow intensification overnight. There is no indication that RI will occur tonight.

That is true, a dry slot has indeed formed off Honduras and is going into Ernesto in the mid-levels. The cloud tops have warmed incredibly as well.

We'll have to wait and see as it appears the last chance to really stengthen will be tonight. By Wednesday AM it will be close to land.

While I agree that the system is not rapidly intensifying at this time, the system is obviously under the most favorable conditions of its lifetime. There is little shear impinging on the storm with deep layer easterlies overhead, and the warming of cloud top temperatures today is more of a diurnal cycle rather than true dry air entrainment. In fact, there is copious precipitable water surrounding the circulation at this time. I fully expect convection to return with vengeance tonight.

2mzywwn.gif

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Observation here so don't shoot me down..If there is an upper level low in the GOM..which was progged to move westwards before Ernesto so he could track into Mex and bay of Campeche,wouldn't this upper level low still present in the GOM haul Ernesto's ass into the GOM and the track would of course be changed. A , the models were supposed to keep Ernesto a 45kt low and now that its a 65mph storm close to cane strength and its been ever so slowly nudging more n or nw during the day today. To me,that upper level low is pulling Ernesto more north then progged..but hey what do I know,I'm just a Maine weather weenie.

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Good day all,

What really determines the movement of a tropical system (or even a thunderstorm complex) is how well it's "rooted" in the atmosphere. Shallow systems, say, with circulation weakening above 10,000 feet (700 MB) as with sheared storms (like Florence for example) - Move with the low level flow.

If a system is "tall" (taking up the entire air column, or at least 40,000 feet or so), then the storm is steered more by the mean (average) atmospheric flow (with emphasis on this average direction dictated more so by the winds above 10,000 feet, such as the 500 MB heights).

Sheared storms are even stranger because the "upper" part of the system tilts away from it's lower portion until is "rips off" (called de-coupling) from the lower part and becomes an upper-air feature that dissipates, causing the low level feature to "start over" again IF the shear relaxes. In that case, the upper portion would have a more NW motion while the lower area would be more westerly.

In Ernesto's case, that has happened already a couple of times. This accounts for the westward motion (when it was weaker). The "recovery" from the shear also may cause a large burst of convection (like we saw this morning) to the northeast of the partly exposed surface low. This removes lots of air, and creates a secondary "wake low" or "mesoscale vortex" that may become the "dominant" low and even consolidate the remnants of the original low level circulation to the SW of it. This is why such systems appear to "JUMP" from the SW to NW as the new low forms under the new convection.

With thunderstorm complexes (especially supercells) in the central USA, sometimes you see the same behavior, although shear is required for their existance. A developing storm may develop in a wind profile where the surface flow is SE, then SW at 10,000 feet (700 MB), and NW above 18kft / 6 KM (500 MB). The developing storm, still "shallow", will move north, then NE. After a while, when it becomes affected by the upper / mean flow, it's final movement will be ESE or SE.

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Ernesto, IMO, is not going to strengthen rapidly over the next 18 hours, and will ultimately move back to the due west into Belieze. I'm not even sure this makes it back to the BOC/GOM...

If it can travel at 287º, 286º roughly, it should make the MX/BZ border, if I used the Excel asin atan function correctly.

ETA, about 315º to come up the Ship Channel

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