簽到天數: 3291 天 [LV.Master]伴壇終老
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t02436|2021-8-29 23:15
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15Z正報維持130節強度。
167
WTNT44 KNHC 291456
TCDAT4
Hurricane Ida Discussion Number 14
NWS National Hurricane Center Miami FL AL092021
1000 AM CDT Sun Aug 29 2021
Ida's rapid strengthening appears to have leveled off within the
past hour or so. NOAA and Air Force Reserve Hurricane Hunter
aircraft that have been in the storm this morning have reported
peak flight-level winds of 146 to 148 kt between 8000 and
10000 ft, and believable SFMR winds around 130 kt. Based on
these observations, the initial wind speed remains 130 kt for this
advisory. The central pressure appears to have bottomed out around
929 mb, and the latest dropsonde in the eye from the Air Force
plane supports a minimum pressure of 933 mb. Ida's satellite and
radar presentation is very impressive, as the 15-nm-wide eye is
very well-defined and surrounded by a ring of intense convection.
Within the past hour or so, there is evidence in radar imagery of a
secondary eyewall, and this has likely caused Ida's intensity to
level off for now. Although Ida's extreme winds are confined to the
inner eyewall, the aircraft data indicate that hurricane-force winds
extend outward about 45 n mi to the northeast of the center, and
based on buoy data the tropical-storm-force wind field extends
outward about 130 n mi northeast of the center.
Ida's eyewall is nearing the coast of Louisiana, and any additional
strengthening seems less likely now given the recent structural
changes of the inner core. While rapid weakening should occur after
landfall, damaging winds will penetrate well inland across
southeastern Louisiana and southwestern Mississippi through tonight.
Ida is forecast to weaken to a tropical depression over Mississippi
by late Tuesday. The global model guidance now indicates that Ida
will likely transition to an extratropical low when it nears the
east coast of the United States and the new forecast shows the
extratropical low becoming a gale center near Atlantic Canada at day
5.
Ida has begun to slow down according to the latest aircraft and
radar fixes, and the initial motion estimate is 320/11 kt. Ida's
forward speed is likely to slow further during the next 12 to 24
hours as the hurricane turns north-northwestward, and then
northward around the western periphery of a deep-layer ridge near
the southeastern United States coast. The cyclone is predicted to
turn northeastward by late Tuesday ahead of a short-wave trough
that will move across the central United States. The new NHC track
is close to the HCCA corrected consensus and the GFS ensemble mean,
and is not very different from the previous advisory.
Key Messages:
1. Extremely life-threatening storm surge inundation of 9 feet or
greater above ground level is imminent somewhere within the area
from Burns Point, Louisiana, to Ocean Springs, Mississippi.
Overtopping of local levees outside of the Hurricane and Storm
Damage Risk Reduction System is possible where local inundation
values may be higher.
2. Catastrophic wind damage will occur where the core of Ida moves
onshore along the southeast coast of Louisiana in the next few
hours. Hurricane-force winds and damaging wind gusts are expected
today within the Hurricane Warning in southeastern Louisiana,
including metropolitan New Orleans.
3. Damaging winds, especially in gusts, will spread inland near the
track of the center of Ida into southwestern Mississippi tonight
and early Monday. These winds will likely lead to widespread tree
damage and power outages.
4. Ida will continue to produce heavy rainfall today through Monday
across the central Gulf Coast from southeast Louisiana, coastal
Mississippi, and far southwestern Alabama, resulting in considerable
to life-threatening flash and urban flooding and significant river
flooding impacts. As Ida moves inland, significant flooding impacts
are possible across portions of the Lower Mississippi, Tennessee
Valley, Upper Ohio Valley, Central Appalachians and the Mid-Atlantic
through Wednesday.
FORECAST POSITIONS AND MAX WINDS
INIT 29/1500Z 28.8N 90.0W 130 KT 150 MPH
12H 30/0000Z 30.0N 90.8W 90 KT 105 MPH...INLAND
24H 30/1200Z 31.6N 91.0W 50 KT 60 MPH...INLAND
36H 31/0000Z 33.2N 90.3W 30 KT 35 MPH...INLAND
48H 31/1200Z 34.9N 88.5W 25 KT 30 MPH...INLAND
60H 01/0000Z 36.4N 85.9W 20 KT 25 MPH...INLAND
72H 01/1200Z 37.8N 82.5W 20 KT 25 MPH...POST-TROP/INLAND
96H 02/1200Z 40.5N 74.2W 30 KT 35 MPH...POST-TROP/EXTRATROP
120H 03/1200Z 43.5N 67.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
$$
Forecaster Brown
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