Weather

029 
fxhw60 phfo 112021 
afdhfo 


Area forecast discussion 
National Weather Service Honolulu HI 
1000 am HST Sat Oct 11 2008 


Synopsis... 
trade winds will weaken as a low develops north of the islands 
Sunday night. Clouds and showers will increase over Kauai Monday and 
then over Oahu early Tuesday as the front weakens to a surface 
trough. Southeasterly winds on Monday and Tuesday could carry the 
volcanic haze from The Big Island onto the other islands until 
the trade winds begin returning Wednesday afternoon. 


&& 


Discussion... 
satellite imagery shows scattered clouds and mainly light showers 
east of the islands moving in an easterly trade wind flow. Shower 
activity tonight through Sunday night will be mainly isolated and 
still focused near mountain or windward areas. A low will form on 
the front about 600 miles north of our islands on Sunday. The front 
will approach Kauai on Monday...weakening and stalling as a surface 
trough near Kauai Monday night...then finally retreat westward on 
Tuesday. The accompanying moisture is expected to produce wet 
weather over Kauai Monday afternoon and Oahu Monday night through 
Tuesday with a chance of thunderstorms. Other islands on Monday and 
Tuesday should see mainly scattered clouds and showers with more 
activity during afternoon convective heating. The southeast wind 
flow will produce more humid conditions and also raises the 
possibility of volcanic haze from the Kilauea Volcano area moving 
onto the other islands by Monday afternoon...then moving back south 
of the islands Tuesday night. Varying amount high cloudiness is 
expected Sunday...clearing Monday but may return Tuesday and 
Wednesday. Moderate trades are expected Wednesday becoming stronger 
Thursday and Friday under the influence of a new strong high 
pressure center that moves in from the north. 


Models still have some disagreement in handling the low that 
develops Sunday on the frontal band north of the islands. The GFS 
places the surface low...and the nearly vertically stacked upper 
low...about 400 miles north northwest of Kauai Monday afternoon 
moving it to about 600 miles northwest of Kauai Tuesday afternoon. 
The European and Navy models place it several hundred miles to the 
east Tuesday afternoon. This affects the position of the surface 
trough and the onset of the light southeast winds east of the 
trough. The general picture however is for surface trough to form 
near Kauai east of the weakening front Monday morning. Moisture from 
the old front will move into this trough and linger into 
Tuesday...hence the focus of unsettled weather and chance of 
thunderstorms over Kauai and Oahu through Tuesday evening. 


&& 


Marine... 
the large northwest swell will arrive on Kauai and Oahu Sunday 
midday or afternoon and affect exposed north facing shores of all 
islands except Lanai and Kahoolawe. Surf should be just under 
advisory criteria for west facing shores. This high surf advisory 
will be issued this afternoon and will be effective beginning Sunday 
through Tuesday afternoon. 


&& 


Hfo watches/warnings/advisories... 
none. 


&& 


$$ 


Hoag