Weather Details & Aloha Paragraphs

As the trade winds fade away, our weather will remain pretty good for the time being. Although with the relatively close proximity of an upper level low pressure to the east-northeast of the Big Island, our atmosphere remains unstable enough that there may be a continued threat of heavy showers locally. Looking at the clouds around the Hawaiian Islands Thursday evening, they seem to have a rather pronounced vertical development…indicating the presence of cold air aloft. When we see these towering cumulus clouds, with a weakening wind field, the chance of locally heavy showers, although spotty at the moment…increases.

After nearly a week’s worth of flip flops in the computer forecast models, they seem to be in fair agreement that we will see a wet weekend coming up. The upper level low to our ENE now is expected to fill and move away soon. This doesn’t help us much, as a new long wave trough of low pressure is expected to swing down from the middle latitudes, depositing a cutoff low pressure center to the NW of Kauai by Saturday. These cutoff lows are called Kona lows when they form within range of the Hawaiian Islands. They are infamous for being heavy rain producers, at least sometimes. When these low pressure systems form to the west and NW of Hawaii they can funnel large amounts of tropical moisture up over the islands. It’s not a complete certainty yet, but there’s a good chance that we could see heavy showers, even ones heavy enough to cause localized flooding starting Saturday, and remaining a threat into early next week.

Back to the winds, as they become lighter and from the southeast, there will be several influences in our local Hawaiian Island weather pattern. The first will be for an increase in vog over the Kona side of the Big Island, reaching up over the islands of Maui County. This SE orientation will put most of the state in the wind shadow of the Big Island, with much lighter winds than have been blowing during the recent long term trade wind episode. SE winds too can bring rich tropical moisture up from the deeper tropics, fuel for the showers that are expected due to the instability created by the Kona low’s closeness. Cloud plumes can be carried from one island to the next, which can concentrate their associated showers for long enough to cause localized flooding rainfall. Finally, rather warm and muggy weather can take place with such a SE wind flow.

There seems to still be enough uncertainty, that this may or may not manifest completely as drawn out in the paragraphs above. However, most of the computer forecast models are now suggesting that some form of trough or Kona low will come close to, or over the islands over the next 4-5 days. There are still some wild cards in the mix, but in sum…unsettled weather coming our way, with the best prospect for the heaviest showers between Saturday and Sunday or Monday. Between now and then, there seems to be a distinct lack of clouds over us, and upstream, which will limit the shower outbreaks temporarily. Later Friday things should become more interesting, and hopefully put an end to whatever drought prone pockets that still remain in place across the Hawaiian Islands. Looking further ahead, by about Tuesday we should see improvement in these unsettled weather circumstances, as the trade winds return 

It’s Thursday evening here in Hawaii as I begin updating this last paragraph of today’s narrative. As you can see from the information in the paragraphs above, we have a good chance of a wet weekend coming up. There’s still a part of me that wants to hedge my bet on this unfolding as the computer models indicate. All this week I’ve been asking for just one or two more days to fully make up my mind in regards to this rain event. It’s finally the judgement day though, and the models are all just too lined up together in their forecast, in lock step if you will…to overlook their weather solution. So, with just a little leftover reluctance, I’ll finally submit to the good chance of increasing showers Saturday through next Monday or Tuesday! I think folks should be ready for the chance of some good soaking rains during that time frame, with the possibility of flooding rainfall not out of the question. The cold air associated with the upper low may onof both Mauna Kea and Mauna Loa on the Big Island! ~~~ I’ll be back very early Friday morning, well before dawn, with your next new weather narrative, I hope you have a great Thursday night wherever you happen to be spending it! Aloha for now…Glenn.