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Tropical Tropical Depression Four

Storm5 said:
I'm not . Just pointing out that run . I for one hope we get something like the 12z euro . At least it would be interesting


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I bet the 18Z GFS will provide plenty of interest later in an hour. I am sure we will see another 980mb low or stronger on that run just because its the 18Z. The real test is the next 3 days in runs, because that will determine if we could look at a stronger or weaker system.
 
ForsythSnow said:
I bet the 18Z GFS will provide plenty of interest later in an hour. I am sure we will see another 980mb low or stronger on that run just because its the 18Z. The real test is the next 3 days in runs, because that will determine if we could look at a stronger or weaker system.
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Our system looks like it's gonna deal With some drier air over the next 36 hours or so. Will be interesting to see what it looks like Wednesday into Thursday

I sold out on a weaker system yesterday. At least it's something to track regardless

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The spread on this is just crazy.
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Pretty big shift south . Most take it to tropical storm strength briefly

Edit : not really a shift south just a little more agreement which tightens the 00z set
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94L's odds for TCG have skyrocketed to 70/80 after a recent ASCAT pass revealed a closed, yet slightly elongated circulation. Even a slight increase in organization would result in a tropical depression...
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The aforementioned ASCAT pass shows a fully closed, well defined circulation with 94L embedded within the monsoon trough, it's just a little broad atm... Again, it wouldn't take much at all for this to become Tropical Depression Four and/or Tropical Storm Don.

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Notice, 94L is pulled further west 6zgfs because of how weak it is.
 
If you ask me this has good potential to be a close call for the SE coast with the weekend trough lifting out and the next loading in the lakes there might be ebbing ridging to force it west

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This distance tool on Levi's site is absolutely fantastic... Using 94L as an example you can take any TC vortex hold shift and measure the distance at any time step from the TC or other area of interest to any point on earth. It's friggin cool...

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He's also implemented another tool that allows for area averaged soundings that would essentially allow you to adequately sample the environment directly over and surrounding any TC, including being able to gauge upper level shear, moisture/RH, etc. as opposed to using singular vortex points which are susceptible to considerable noise often unrelated to the environment itself.

Here's one for the GFS at 66hr for 94L...

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Interaction between 94L and a PVS (potential vorticity streamer) (indicated by the string of deeper yellow and red colors associated with a mid-latitude trough in the 355K potential vorticity surface image below) emanating from a equatorward cyclonic rossby wave breaking event over the western Atlantic will likely induce unfavorable upper level westerly wind shear over 94L once it passes north of the Greater Antilles late this week and into this weekend, and the further north 94L travels, the more interaction that's liable to occur w/ this PVS. Thus, 94L will have a 72-96 hr window for intensification before conditions become unfavorable for tropical cyclogenesis and intensification. Equatorward rossby wave breaking here in the western Atlantic isn't surprising given passage of a suppressed MJO regime. Anomalous upper level westerly winds in the wake of a suppressed MJO regime allow for effective mid latitude RW propagation into the tropics by enhancing upper level westerly wind ducts that ultimately allow these RWs to conserve more angular momentum and therefore penetrate deeper into the tropics and subtropics (& occasionally even across the equator and into the other hemisphere!). Increasing RW penetration in the tropics increases the probability for the appearance of PVSs and unfavorable upper level wind shear in the Atlantic, along with large-scale subsidence/sinking, dry air, and decreasing in lower level relative vorticity that also accompanies the passage of a convectively suppressed phase of the MJO or a CCKW...

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Really not buying this scenario (at least not yet anyways) but worth mentioning that the UKMET re-intensifies 94L after day 5, implying that 94L's interaction w/ this PVS is limited, at least enough to allow it to remain intact enough to take advantage of what appears to be at least a marginal environment in the SW Atlantic. Verbatim still looks a little too close to call for the SE US and eastern seaboard...
 
12z Gfs basically washes out the system NE of the Bahamas.

12z euro has an extremely weak wave in the Bahamas days 8-10


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Outflow boundaries are apparent on both sides of 94L atm even in the moist monsoon southwesterly flow to its south, indicative of large-scale sinking/stable air in its surrounding environment which is significantly attributable to the passage of the suppressed phase of the MJO... It's still quite amazing we even have a legitimate chance of development given the unfavorable intraseasonal forcing and climatology.
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Im really not sure what in the hell the NHC is waiting for but Im pretty sure 94L is at least a tropical depression atm. Im sorry but tropical wave axes rarely have consolidated moderate-deep, consistently pulsating convection like this for nearly 24 hours, not to mention there was a low-level swirl on visible satellite yesterday that was quickly covered by convection last night during diurnal maximum...
 
Webberweather53 said:
Im really not sure what in the hell the NHC is waiting for but Im pretty sure 94L is at least a tropical depression atm. Im sorry but tropical wave axes rarely have consolidated moderate-deep, consistently pulsating convection like this for nearly 24 hours, not to mention there was a low-level swirl on visible satellite yesterday that was quickly covered by convection last night during diurnal maximum...
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They probably aren't doing anything because they think it won't develop into anything or it "Isn't developed". Honestly when they begin dropping chances of cyclone formation that pretty much puts the last nail in the coffin for the system for now at least.

It does look healthy though, so I have no idea why it isn't at least a PTC.
 
ForsythSnow said:
They probably aren't doing anything because they think it won't develop into anything or it "Isn't developed". Honestly when they begin dropping chances of cyclone formation that pretty much puts the last nail in the coffin for the system for now at least.

It does look healthy though, so I have no idea why it isn't at least a PTC.
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Potential tropical cyclones are only designated if a tropical disturbance poses an immediate threat to a landmass (don't worry this tripped me up for a second as well)... However, yes I don't understand why they've lowered the chances when the organization has only improved throughout the day and given the recent ASCAT pass which showed a closed, but a zonally oblong circulation with a lot of earth relative westerly winds to the south, it's very close to becoming a tropical cyclone, especially if organizational trends continue
 
Tropical Depression Four certainly looks similar to the precursor to Tropical Storm Ana (2009) (Tropical Depression Two) with a low-level circulation near the eastern edge of a moderate-deep sheared, circular, symmetrical CDO, although Four doesn't look quite as sheared as Two (2009) did due to its slower forward movement...
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Webberweather53 said:
Tropical Depression Four certainly looks similar to the precursor to Tropical Storm Ana (2009) (Tropical Depression Two) with a low-level circulation near the eastern edge of a moderate-deep sheared, circular, symmetrical CDO, although Four doesn't look quite as sheared as Two (2009) did due to its slower forward movement...
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.Is it possible it can become a TS?
 
Basing off of the current situation, the Euro appears to be in the lead for winning, since it kept a weak system, but if it strengthens later on, or surprises us, another model will win, for long range at least. Short range right now is the HWRF.
 
Doesn't look that bad right now, but it could look better. Probably surviving because it is pulling moisture from the south with the dry air in front of it countering it. If it was dry to the south, this system would be dissipated.
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Cary_Snow95 said:
The CMC actually tried to do that the other day as well
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Interesting NHC takes note of what the UKMET is showing as well.... keep one eye on that possibility

There is one important caveat to note and
that is the UKMET model, which continues to show less weakening and
even strengthening in 96 and 120 h when the system is approaching
the Bahamas. Although the other global and regional models do not
show regeneration at this time, they do however show similar
improving upper-level wind conditions east of Florida by 120 h. For
now, the official intensity forecast remains similar to the previous
advisory and the consensus model IVCN through 48 h, after which the
forecast is lower than the intensity consensus.
 
Just started looking at this one. With the path it is showing now, definitely have to keep an eye on it.
 
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