Drought in Guam, July 1 to 29, 2022

Area Forecast Discussion...UPDATED
National Weather Service Tiyan GU
940 PM ChST Thu Jun 30 2022

.Update...
A weak trade-wind trough moving through the region is generating
scattered showers isolated thunderstorms across Guam and Rota, with
isolated showers and thunderstorms for Tinian and Saipan.

&&

.Prev discussion... /issued 743 PM ChST Thu Jun 30 2022/

Marianas Synopsis...
Satellite and radar show isolated showers moving across the region. A
small uptick in showers is seen just east of the islands along the
leading edge of a small surge in the trade winds. Upper-level winds
continue to provide sufficient shear to limit vertical development of
showers, though a few brief thunderstorms have been noted to the west
and north of the Marianas. Buoys and altimetry data show seas of 3 to
4 feet across the region.

Discussion...
Weak trade disturbances will bring periodic increases in showers the
next couple of days before a broader-scale wetter pattern unfolds
across the region. Moderate trades will persist through the weekend
before subsiding early next week. Heading into next week, models show
a weakening, and perhaps a breakdown, of the trade-wind flow across
Micronesia with a broad, but weak convergent pattern setting up over
central Micronesia and the Marianas. With increasing atmospheric
moisture, this pattern will lead to a higher proclivity for showers.
The GFS goes so far as to depict an east-west oriented trough along
10N serving as the focusing mechanism for additional disturbances.
While other models maintain weaker trades with passing troughs, such
an eventuality will need to be watched out for in the coming weeks.

Marine...
Seas of 3 to 4 feet will increase 1-2 feet by Saturday with a slight
uptick in trades. This increase will be short-lived with winds and
seas gradually subsiding early next week. Increasing surf will result
in a moderate risk of rip currents by Friday night.

Tropical systems...
JTWC Invest Area 98W, well west of the Marianas near 19N131E,
is slowly becoming better organized and is now the subject of a
tropical cyclone formation alert by the JTWC. While this system will
not affect any of the islands in our region, it is perhaps another
reminder of our gradual transition into wet season. While computer
models show no tropical cyclones developing across Micronesia, the
trade-wind pattern will likely weaken in the coming 1-2 weeks
allowing for some disturbances to become better developed.

Eastern Micronesia...
Scattered to numerous showers are seen on satellite across most of
eastern Micronesia, from just east of Pohnpei to beyond the date
line. This activity is associated with a weakening and fractured ITCZ
that is interacting with several trade-wind troughs moving through
the region. There are a few breaks in the action between the troughs,
though a very active pattern remains across the region.

For Pohnpei, isolated showers are seen across the state this evening,
with increasing convection seen to the east and southeast. This
convection is expected to approach Pohnpei through the evening, with
numerous showers and isolated thunderstorms expected there near
midnight. Though showers are then expected to decrease a bit Friday
as the ITCZ continues to dissipate, an overall wet pattern is
expected to continue through the week. This is due to a series of
trade-wind troughs that will maintain enhanced showers across the
area for the next several days.

For Kosrae, numerous showers and isolated thunderstorms are expected
to continue through the night, though a couple hour break in the
convection is likely later in the evening as one trough exits the
area and another moves in from the east. Kosrae has already received
nearly 4 inches of rainfall over the last 24 hours from these
showers. As with Pohnpei, an overall unsettled pattern is then
expected to continue through the week.

For Majuro, isolated showers are currently seen across the area with
increasing convection seen to the east. This convection is expected
to move across the atoll later this evening, around midnight.
Numerous showers and isolated thunderstorms are then expected to
continue across the area through Friday afternoon or early evening.
Shower coverage is then likely to decrease, though an overall wet
pattern looks to be the rule through the week.

Fresh to occasionally strong winds with gusts in the 30 knot range
are expected to continue through the night, maintaining a Small Craft
Advisory across eastern Micronesia. The SCA is currently set to
expire Friday morning, though the latest model guidance now indicates
the enhanced winds could continue into Saturday. Will let the night
shift take a look at the situation and decide whether the SCA needs
to be extended.

Western Micronesia...
A fairly dry pattern is currently in place across western Micronesia.
This resulted in big changes for the short-term forecast. Shower
coverage was decreased to isolated for all 3 forecast points.

For Palau, showers will begin to increase Friday evening as the
first of a series of trade-wind troughs approaches the republic.
Then, an overall wet pattern will continue across Palau through the
middle of next week.

Yap will see dry conditions for a bit longer, with isolated showers
continuing through Saturday. By Saturday afternoon, trade-wind
troughs moving into the region from eastern Micronesia will drift far
enough north to increase convection over the state. This wetter
pattern will then continue across Yap State through the middle of
next week.

Chuuk will see an increase in convection Friday evening as a trough
moving out of Pohnpei approaches the state. This will signal the
beginning of a wet pattern for Chuuk State as well. This pattern will
continue through most of next week.

Overall, marine conditions look to remain fairly benign, with light
to gentle trade winds and combined seas between 3 and 5 feet.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
MP...None.
Marianas Waters...None.
&&

Update: Kleeschulte
Marianas: Aydlett
Micronesia: Kleeschulte