#370 Postby arlwx » Fri Nov 25, 2016 4:49 am
TROPICAL STORM OTTO ADVISORY NUMBER 18...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL EP222016
300 AM CST FRI NOV 25 2016
Corrected to use Central Standard Time instead of Central Daylight
Time.
...HEAVY RAINS FROM OTTO STILL AFFECTING PORTIONS OF COSTA RICA AND
NICARAGUA...
SUMMARY OF 300 AM CST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...10.5N 86.9W
ABOUT 135 MI...220 KM WNW OF CABO BLANCO COSTA RICA
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...W OR 265 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
None.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Tropical Storm Warning is in effect for...
* Puntarenas Costa Rica to Puerto Sandino Nicaragua
For storm information specific to your area, please monitor
products issued by your national meteorological service.
DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 300 AM CST (0900 UTC), the center of Tropical Storm Otto was
located near latitude 10.5 North, longitude 86.9 West. Otto is
moving toward the west near 14 mph (22 km/h). A faster motion
toward the west-southwest is expected later today and tonight,
followed by a westward motion on Saturday. On the forecast track,
the center of Otto will continue to move away from the coast of
Central America today.
Maximum sustained winds have decreased to near 60 mph (95 km/h) with
higher gusts. Little change in strength is forecast during the next
48 hours.
Tropical-storm-force winds extend outward up to 70 miles (110 km)
from the center.
The estimated minimum central pressure is 998 mb (29.47 inches).
HAZARDS AFFECTING LAND
----------------------
RAINFALL: Heavy rains associated with Otto will continue to affect
portions of northern Costa Rica and southern Nicaragua into early
this morning. These rains are expected to move offshore of Costa
Rica and Nicaragua into the eastern Pacific later today.
Additional rainfall amounts of 2 to 4 inches are possible early this
morning across northern Costa Rica and southern Nicaragua. Earlier
heavy rains and the potential additional rainfall will continue to
pose the threat of life-threatening floods and mudslides across
these regions.
WIND: Tropical storm conditions will continue in portions of the
warning area along the Pacific coasts of Costa Rica and Nicaragua
for the next few hours. These winds will begin to diminish later
today.
SURF: Swells generated by Otto are likely to cause life-threatening
surf and rip current conditions over the next several days along the
coasts of Panama, Costa Rica, and Nicaragua. Please consult
products from your local weather office. High surf is likely
to occur during the next few hours over portions of Lago Nicaragua.
NEXT ADVISORY
-------------
Next intermediate advisory at 600 AM CST.
Next complete advisory at 900 AM CST.
TROPICAL STORM OTTO DISCUSSION NUMBER 18...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL EP222016
300 AM CST FRI NOV 25 2016
Corrected for Central Standard Time instead of Central Daylight
Time in product header.
The cloud pattern of Otto is rather ragged this morning after the
circulation moved offshore of Central America. Shortwave infrared
imagery suggests that there may now be some tilt to the circulation,
with the low-level center possibly located south of the mid-level
center. However, this is quite uncertain given the lack of microwave
imagery overnight. Based on this apparent decrease in organization,
the initial intensity is set to 50 kt, a little below the latest
Dvorak estimates of T3.5/55 kt from TAFB and SAB.
The intensity forecast is problematic. Most of the guidance suggests
that Otto will maintain its current intensity for the next 48 hours
or so while the cyclone moves over SSTs of 28-29C but with
continued southeasterly shear of 15-20 kt. Through this time the
NHC intensity forecast is near or a bit below the IVCN intensity
consensus. By day 3, the shear begins to decrease, but the
atmosphere dries out as Otto interacts with outflow from a Gulf of
Tehuantepec gap wind event. The global models show Otto weakening
late in the period, and that trend is reflected in the official
forecast, which continues to show Otto becoming a remnant low at day
5. However, given the uncertainty in the current structure of Otto
and the interplay between several competing environmental factors
during the forecast period, confidence in the intensity forecast is
lower than usual.
The initial motion estimate is a somewhat uncertain 265/12. I
shifted the initial position a little to the south to account for
the possible tilt in the circulation mentioned above. This resulted
in a southward shift of the track guidance envelope and the NHC
forecast even though the synoptic reasoning has not changed. An
amplifying mid-level ridge will steer Otto south of due west at
around 15 kt for the next 48 hours. Then, as the ridge weakens late
in the period, a slowing forward speed and gradual poleward turn are
expected. The new NHC track is close to the latest multi-model
consensus, but lies north of the latest GFS and ECMWF predictions.
FORECAST POSITIONS AND MAX WINDS
INIT 25/0900Z 10.5N 86.9W 50 KT 60 MPH
12H 25/1800Z 10.1N 88.8W 50 KT 60 MPH
24H 26/0600Z 9.5N 91.6W 50 KT 60 MPH
36H 26/1800Z 9.2N 94.6W 50 KT 60 MPH
48H 27/0600Z 9.0N 97.5W 45 KT 50 MPH
72H 28/0600Z 9.3N 103.0W 40 KT 45 MPH
96H 29/0600Z 10.5N 106.0W 35 KT 40 MPH
120H 30/0600Z 12.5N 107.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
$$
Forecaster Brennan
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