Tropical Storm Humberto

[WxWatcher007]

The tropics are active now with three systems being monitored. This is the thread for the current central Atlantic cherry.
 

 

There has been a strong cross guidance signal for days that a central Atlantic wave will develop. The models have actually been quite robust with this wave once it develops, in similar fashion to the rapidly intensifying Gabrielle.

The AI ensembles, which have done a particularly good job sniffing the environment out, are particularly strong. Now, while the majority of guidance turns this out to sea without threatening any land masses, the amplitude and timing of a trough in the coming week will determine the eventual evolution, along with where this develops. I expect this to develop first if both waves develop. 

[GaWx]

 The 12Z UKMET threatens Bermuda:

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER  90 HOURS
              FORECAST POSITION AT T+ 90 : 22.0N  61.0W

                        LEAD                 CENTRAL     MAXIMUM WIND
      VERIFYING TIME    TIME   POSITION   PRESSURE (MB)  SPEED (KNOTS)
      --------------    ----   --------   -------------  -------------
    1200UTC 26.09.2025   96  22.5N  61.5W     1010            35
    0000UTC 27.09.2025  108  22.5N  62.5W     1008            37
    1200UTC 27.09.2025  120  23.1N  63.5W     1007            38
    0000UTC 28.09.2025  132  23.7N  64.1W     1005            45
    1200UTC 28.09.2025  144  24.5N  66.1W     1003            41
    0000UTC 29.09.2025  156  25.6N  66.8W     1000            43
    1200UTC 29.09.2025  168  27.2N  66.4W      997            45

[WxWatcher007]

This one could very well end up further west than Gabrielle. Would definitely watch in Bermuda. I expect the odds to go up at 2pm. It still has disorganized convection but it looks like it’s trying to consolidate. 

[WxWatcher007]

Good candidate for our next major…

[GaWx]

13 minutes ago, WxWatcher007 said:

Good candidate for our next major…

The 12Z slams Bermuda with this on 10/1 as a 954 MH.

[WxWatcher007]

Central Tropical Atlantic:
Shower and thunderstorm activity associated with a tropical wave 
located about midway between the Lesser Antilles and the Cabo Verde 
Islands show some signs of organization.  Environmental conditions 
are forecast to become more favorable for development by tomorrow, 
and a tropical depression is likely to form on Wednesday or 
Thursday while the system moves west-northwestward to 
northwestward across the central Atlantic.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 7 days...high...80 percent.

 

[WxWatcher007]

Good chance this becomes a TD later today or tonight. Despite westerly shear the organizational trend continues.

[hawkeye_wx]

The visible loop confirms 93L has a well-defined surface vortex.  It just needs to exit the shear zone.

[GaWx]

12Z UK just W of Bermuda
TROPICAL DEPRESSION 93L        ANALYSED POSITION : 19.7N  53.9W

     ATCF IDENTIFIER : AL932025

                        LEAD                 CENTRAL     MAXIMUM WIND
      VERIFYING TIME    TIME   POSITION   PRESSURE (MB)  SPEED (KNOTS)
      --------------    ----   --------   -------------  -------------
    1200UTC 24.09.2025    0  19.7N  53.9W     1014            33
    0000UTC 25.09.2025   12  20.6N  56.0W     1013            32
    1200UTC 25.09.2025   24  21.3N  57.4W     1012            33
    0000UTC 26.09.2025   36  21.7N  57.9W     1009            34
    1200UTC 26.09.2025   48  21.7N  58.5W     1007            35
    0000UTC 27.09.2025   60  22.0N  59.1W     1005            42
    1200UTC 27.09.2025   72  22.0N  60.3W     1003            44
    0000UTC 28.09.2025   84  22.2N  61.0W     1000            44
    1200UTC 28.09.2025   96  22.8N  63.0W      998            47
    0000UTC 29.09.2025  108  23.7N  64.5W      994            49
    1200UTC 29.09.2025  120  24.5N  66.3W      992            52
    0000UTC 30.09.2025  132  25.6N  67.8W      991            56
    1200UTC 30.09.2025  144  27.3N  68.4W      991            54
    0000UTC 01.10.2025  156  29.1N  67.8W      984            59
    1200UTC 01.10.2025  168  31.9N  66.6W      972            61

[WxWatcher007]

This one has a good shot of becoming our third consecutive major. It’s looking well on its way to being designated a TC in the next 24 hours. 

[NorthHillsWx]

3 minutes ago, WxWatcher007 said:

This one has a good shot of becoming our third consecutive major. It’s looking well on its way to being designated a TC in the next 24 hours. 

It looks like a TD already. Modeling is catching up, hurricane models are very aggressive. Also I feel very strongly this wave is a fish storm. East coast surfers are having a hell of a summer

[WxWatcher007]

3 hours ago, NorthHillsWx said:

It looks like a TD already. Modeling is catching up, hurricane models are very aggressive. Also I feel very strongly this wave is a fish storm. East coast surfers are having a hell of a summer

Might be declared at 5pm with that LLC tucking under the convection on IR.

[Maggie Valley Steve]

NHC will initiate Advisories for TS Humberto at 5 PM.

[WxWatcher007]

Close to MH status by day 5.

Tropical Storm Humberto Discussion Number   1
NWS National Hurricane Center Miami FL       AL082025
500 PM AST Wed Sep 24 2025
 
Satellite data indicates that Invest 93L over the central tropical 
Atlantic has now developed into Tropical Storm Humberto. Visible 
satellite imagery shows that throughout the day, the low-level 
center has become well-defined, with persistent and organized deep 
convection mainly located over the eastern side of the system. 
Subjective Dvorak intensity estimates from TAFB and SAB were both 
data-T/2.5 35 kt. DPRINT and DMINT Objective intensity estimates 
from UW-CIMSS range from 31 to 35 kt. Using these data, the 
initial intensity is set to 35 kt.

The system is estimated to be moving west-northwestward at 300/13 
kt, but this is of low confidence since the center has only recently 
formed.  A west-northwestward to northwestward motion is 
anticipated through the next several days along the southwestern 
periphery of a mid-latitude ridge. Towards the end of the forecast 
period, an approaching trough moving offshore the east coast of the 
United States will erode the ridge and allow the system to turn more 
northward. However, there is quite a bit of uncertainty with the 
forward speed and cross-track spread of the system. This is 
increasingly apparent beyond day 3 as there are complex steering 
components with timing differences in the global models, including 
the approaching trough and potential binary interaction with Invest 
94L. The NHC track forecast lies near the consensus aids given some 
of these uncertainties, and there is lower than normal confidence in 
the track forecast.

The storm is within a favorable environment for strengthening with 
warm sea surface temperatures near 29C and moist mid-level RH 
values. The system will be dealing with some moderate westerly wind 
shear for the next day or so that will likely cause an asymmetric 
storm structure. EC and GFS SHIPS guidance depict the shear slightly 
weakening in the day 2 to 4 time frame, and with increasing 
divergence aloft, a slightly greater rate of strengthening is shown 
at that time. The latest NHC forecast follows these trends and lies 
near the consensus intensity aids. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/2100Z 20.1N  54.9W   35 KT  40 MPH
 12H  25/0600Z 20.9N  56.0W   40 KT  45 MPH
 24H  25/1800Z 21.6N  57.0W   45 KT  50 MPH
 36H  26/0600Z 22.0N  57.5W   50 KT  60 MPH
 48H  26/1800Z 22.5N  58.2W   55 KT  65 MPH
 60H  27/0600Z 22.9N  59.0W   60 KT  70 MPH
 72H  27/1800Z 23.6N  60.6W   70 KT  80 MPH
 96H  28/1800Z 26.0N  64.3W   90 KT 105 MPH
120H  29/1800Z 29.1N  67.1W   95 KT 110 MPH
 
$$
Forecaster Kelly