Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
336 AM EDT Wed Apr 07 2021

Valid 00Z Thu Apr 08 2021 - 00Z Thu Apr 15 2021

Once again the models and ensembles agree fairly well for the
overall forecast through the weekend into early next week though
some differences in details and moisture arise toward the middle
of next week.  The large scale pattern will support relatively dry
conditions with below normal precipitable water values prevailing
into late this week.  Then shortwave energy approaching from the
northwest/north will lead to a gradual increase of moisture during
the weekend, with some models starting to hint at a corresponding
increase of showers.  Guidance consensus shows moisture decreasing
again early next week as the upper trough axis drifts east of the
main islands after Monday.  Around Tuesday the 00Z ECMWF closes
off a low center to the east somewhat closer to the state than
most other guidance.  This may play a role in the model's moisture
return from the east by Wednesday but the 00Z GEFS/12Z ECMWF means
also hint at a modest rebound in moisture at that time--in
contrast to the 00Z GFS that maintains lower precipitable water
values.

Over the coming days expect the trades to weaken toward the
light-moderate range as mid-latitude high pressure weakens and
eventually moves eastward, with the approaching shortwave energy
this weekend leading to additional weakening of the surface
pressure gradient.  Remains of low pressure to the northeast of
the state could reach closer to the area as well.  By the middle
of next week high pressure building into the central Pacific may
help to strengthen the trades somewhat.  

Rausch