329 
fxhw60 phfo 181338 
afdhfo 


Area forecast discussion 
National Weather Service Honolulu HI 
338 am HST Friday Jul 18 2008 


Synopsis... 
strong high pressure far north of the state will maintain trade 
winds through next week. A trough aloft will keep the shower 
activity more active than normal. Showers will be most frequent 
over windward areas during night and morning hours and showers will 
spread to leeward areas on the smaller islands as well. 


&& 


Discussion... 
a 1033 mb high north of the main Hawaiian islands will maintain 
trade winds through next week. The forecast models remain in very 
close agreement keeping the strong high north of the islands. 


Besides the increase in trade winds...the weather has turned to a 
wetter pattern last evening and overnight. Satellite imagery and 
regional radars show moisture riding in with the trade winds. Rain 
gage reports overnight have not been overly impressive...since a 
lot of these showers have been racing by under the brisk trade flow. 
The forecasts were adjusted accordingly to account for this increase 
in shower activity...particularly over the windward coastal waters 
and the windward mountains. These showers have made it over into 
leeward sections as well. The enhanced shower activity is due in 
part by a trough aloft...which has kept the trade wind inversion a 
bit higher than normal. The morning soundings show this capping 
layer around 11 thousand feet...which allows clouds to grow taller 
resulting in enhanced shower activity. However...the speed at which 
these showers were moving has not caused any significant flooding 
problems. 


Forecast models do show the trough aloft slowly moving off to the 
northwest over the next few days but develops a new low west of the 
islands early next week. This persistent troughiness aloft will keep 
the atmosphere over the islands a bit unstable so showers will 
remain more active than usual for July. A weak consensus in the 
forecast models during the early part of next week will make it 
tricky to determine when the greatest instability will affect the 
islands. 


Forecast models show increases in low level moisture over the next 
few days. Moisture...combined with the effects of the upper trough 
will probably keep the showers a bit more active than usual. Models 
are hinting at a more significant increase in low-level moisture 
during the middle of next week as the remnants of Hurricane Elida 
moves west over the islands. That could make the weather wetter 
around next Wednesday. However...forecasting the movement and 
strength of old tropical systems is difficult to Pin Point this far 
out so confidence remains low at this point. 


&& 


Marine... 
trade winds will remain locally strong for the next several days. 
The Small Craft Advisory remains posted for the pailolo and 
alenuihaha channels...Maalaea Bay and waters south of The Big 
Island. South swells will continue...but surf will remain below the 
high surf advisory threshold. 


&& 


Hfo watches/warnings/advisories... 
Small Craft Advisory for pailolo and alenuihaha channels...Maalaea 
Bay and waters south of The Big Island. 


&& 


$$ 


Elau