932 
FXHW60 PHFO 311942
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
942 AM HST Wed Jul 31 2019

.SYNOPSIS...
Expect moderate to breezy trade winds across local waters through
Friday. Hurricane Erick will weaken as it approaches the area 
from the east. Wet weather will spread from east to west across 
all islands Thursday into the weekend as Erick passes just south 
of the state Thursday and Friday. Additional impacts from Erick 
such as high surf, strong winds, heavy rain and flash flooding are
possible, especially over the Big Island. Hurricane Flossie may 
bring additional weather impacts to the islands early next week.

&&

.DISCUSSION...
In general, a ridge far to the north of the main Hawaiian Islands
will keep moderate to breezy trade winds through the week with 
clouds and showers favoring windward and mountain areas.
Instability will keep enhanced showers over the islands through 
Thursday morning. Less shower activity is forecast over leeward 
sections of each island. Water vapor imagery shows an upper level 
trough north and west of the islands, providing the instability. 
Two tropical cyclones, Erick and Flossie, are noted in satellite 
imagery drifting towards the islands, with Flossie still in the 
eastern North Pacific east of 140W.

Tropical Cyclone Erick is about 615 miles southeast of Hilo 
moving west at 13 MPH. The Central Pacific Hurricane Center is 
forecasting a steady weakening trend with Erick as the center of 
the system drifts closer to the islands. Winds will increase 
statewide from Thursday afternoon into Friday, especially over 
waters south of the Big Island. A wind advisory may be considered 
along the east to southeastern slopes of the Big Island. Deep 
tropical moisture and instability will spread across the eastern 
islands starting on Thursday, with active showers spreading to all
islands from Friday into the weekend. Additional impacts 
associated with Erick's passage, such as high surf and stronger 
winds are possible. More details will be provided in the next 24 
hours as the system tracks closer to the island chain.

A Tropical Storm Warning remains in effect for local waters south
of the Big island. However, at this time no islands are included 
in this Tropical Storm Warning. Due to the increasing threat for 
heavy rain associated with Tropical Cyclone Erick, a Flash Flood 
Watch remains in effect for the Big Island of Hawaii from Thursday
afternoon through Saturday morning.

Hurricane Flossie is is in the eastern North Pacific about 1975 
miles east-southeast of Hilo moving west-northwest at 15 MPH. 
Models show Flossie moving into the local area by next Monday or 
Tuesday. We are fairly confident that another round of tropical 
humid weather with active showers will develop over Hawaii for the
first half of next week. However, impact details have low 
confidence this far out. Island-specific impacts associated with 
Flossie will depend upon the size, intensity and track of this 
tropical cyclone as drifts westward over the next six days.

&&

.AVIATION...
Due to breezy trade winds, low level turbulence is possible in 
areas south through west of the mountains. Most shower activity 
should be confined to the windward slopes although, in areas with
higher wind speeds, some of these showers may spill into leeward 
sections. Expect only passing MVFR conditions on the windward 
slopes of all islands except the Big Island and VFR conditions 
elsewhere. Low ceilings should remain in the north through east 
sections of the Big Island so an AIRMET for mountain obscuration 
has been needed and this should be the case most of the day. This 
may spread into windward areas of Maui as well so we will extend 
the AIRMET to include that island if it becomes needed.

Tropical Cyclone Erick should begin to impact areas on and around
the Big Island and possibly Maui through the day on Thursday. This
will mainly affect wind speed and wind direction.

AIRMET Sierra remains in effect for areas above 2,500ft on north 
thru east sections of the Big Island due to reduced visibility and
low ceilings from SHRA.

AIRMET Tango remains in effect south thru west of terrain on all
islands below 8000 feet due to tempo moderate turbulence. 

&&

.MARINE...
Locally strong trade winds are expected to continue through
tonight due to high pressure north of the state. Beginning
tomorrow, the effects of Tropical Cyclone Erick will begin to be 
felt over some of the coastal and offshore waters south of the Big
Island. 

A Tropical Storm Warning is in effect for the waters south of the
Big Island, with tropical storm force winds possible over those
waters beginning tomorrow morning. Erick will bring hurricane
conditions to the offshore waters south of the islands as early as
tonight. In addition to the increase in winds, seas will also be
on the increase and will be a factor in both the coastal and
offshore waters.

Outside of Erick, the pressure gradient over the islands is
producing Small Craft Advisory (SCA) level winds for the typical
windier spots. Expect the SCA to be expanded to additional coastal
waters for a combination of winds and seas as Erick passes to the
south of the islands.

The fresh trades will continue to produce choppy surf along east 
facing shores. Southern hemisphere swells will produce small surf
along impacted shorelines. Starting tonight into Thursday, we 
should see long-period swell from Erick arriving along exposed 
southeast and east exposures of the Big Island. The latest
readings from Buoy 51004, about 205 nautical miles southeast of
Hilo, has seen an increase in wave height to around 9 feet, which
is a slower than the models had been predicting. Will continue to
monitor the buoy recordings.

The swells generated by Erick will likely produce surf above the 
High Surf Advisory (HSA) levels along east facing shores of the 
Big Island starting tonight, with warning level surf possible 
Thursday and Friday. The HSA may be required for east facing 
shorelines of the smaller islands Thursday through Friday, but 
swells from Erick will be partly blocked by the Big Island. After 
Erick passes south of the Big Island, south swells from the system
may affect the smaller islands for a short time.

Tropical Cyclone Flossie remains in the Eastern Pacific. It is
expected to cross into the Central Pacific basin a hurricane late
Friday or Friday night. The current forecast track has Flossie 
tracking further north than Erick. This will allow less shadowing 
for the smaller islands and may bring higher surf later this 
weekend into early next week along east facing shores.

&&

.CLIMATE...
We remain suspicious of the unusually high temperature readings 
measured by the sensor at Kahului Airport (PHOG). Technicians are
expected to visit the site today to check it. Until then, the 
Kahului Airport temperature will be set to missing (M) in our 
climate reports. 

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from Thursday afternoon through Saturday 
morning for Big Island.

Tropical Storm Warning for Big Island Leeward Waters-Big Island 
Southeast Waters. 

Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel.


&&

$$

DISCUSSION...Powell
AVIATION...Chevalier
MARINE...M Ballard