Puna Weather
Sunday 20th September 2026
Today scattered showers with light to moderate easterly trade winds.
Monday and Tuesday very humid with moderate easterly winds and scattered showers.
Late Tuesday through early Friday very humid with heavy rain and moderate to breezy east or northeast winds. Flooding is possible.
Models agree that the remnant circulation of TD 15E moves northwest and towards our island over the next couple of days in response to a digging mid-level trough to our northwest. Both GFS and ECMWF) show moderate shear over 15E currently and for another couple of days, after which shear relaxs substaintially, possibly allowing 15E to regain a tropical cyclone structure as it stalls just south of our island Wednesday and Thursday. The European model is deeper/stronger with the mid-level feature and takes 15E, or it's remnants, over our island chain Friday and Saturday. The GFS is much weaker with this feature, and as such has north or northeast steering for 15E taking the storm to the south or southwest.
As 15E's remnants approach we initially see a rise in low level moisture on Monday for high humidity. By late Tuesday or early Wednesday deeper moisture arrives with precipitable water rising to around 2.50" and dew points in the mid to upper 70s. Winds are expected to pick up because the surface low is to our south, and possibly strengthening some. The winds push all this moisture up our mountains and promise vast amounts of rain for windward shores and slopes, especially Wednesday and Thursday.
The NHC gives 15E a 60% chance of becoming a cyclone in the next week while keeping the circulation well south of our island. The ICON model (Germany's model) shows 15E becoming a cyclone to our southeast. Neither the GFS or ECMWF develop 15E into a cyclone on approach.
Based on the top models (GFS and ECMWF) we're not expecting wind damage, but the rain event could be long lived and that increases the risk for flooding. The GFS shows 4" to 8" of rain through early Friday with the European model calling for >12" over a large portion of our island.
It is too early to know what happens after Thursday as models diverge so much on their handling of the mid-level trough/low to our our northwest.
