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WTNT41 KNHC 100258
TCDAT1
Hurricane Irma Discussion Number 44
NWS National Hurricane Center Miami FL AL112017
1100 PM EDT Sat Sep 09 2017
Irma's nearly 24-hour traversal of the north coast of Cuba appears
to have affected the hurricane's structure and intensity. An
earlier NOAA Hurricane Hunter aircraft and a more recent Air Force
reconnaissance flight both measured maximum flight-level winds near
105 kt and surface winds near 95 kt. The planes have reported
a double eyewall structure, which has also been observed in WSR-88D
Doppler radar data from Miami and Key West. Irma's intensity has
been conservatively lowered to 105 kt, and I'd rather wait to lower
the winds further until we've seen the full data set from the Air
Force mission.
Irma在古巴几乎二十四小时的旅程显示出已经影响到飓风的结构与强度
稍早一架NOAA飓风猎人机与最新的空军机侦查飞行一起测量得出近105节最大飞行高度风
以及近95节表面风力.
两机均回报发现双眼墙结构, 此结构也在西礁岛群与迈阿密的WSR-88D雷达观测到
Irma的强度已经保守地降低到105节, 我宁愿等著更加降低风力, 直到我们已收到空军机
完整的数据集
Irma has stuttered near the north coast of Cuba for the past few
hours, which may be a harbinger of the north-northwestward turn
that we've been waiting for. In any event, Irma appears to be
moving very slowly toward the northwest, or 305/5 kt, very gradually
shifting away from the north coast of Cuba. With the hurricane
located near a break in the subtropical ridge, it should turn
north-northwestward soon and accelerate near or along the west
coast of Florida during the next 36-48 hours. Because of Irma's
hesitation to move northwestward, the new track guidance has shifted
ever so slightly westward, and the new NHC track is just a little
left of the previous one. Although it is likely that the eye will
move near or over the Lower Keys Sunday morning, the hurricane's
angle of approach to the west coast of Florida makes it very
difficult to pinpoint exactly where Irma will cross the Florida Gulf
coast.
Irma在过去数小时来时断时继地在古巴北部的海岸附近, 这可能是我们一直在等待的北北
西转向的预兆。
无论如何, Irma显示似乎缓慢地以305度5节向西北方向移动, 非常缓慢地从古巴北部海岸
转离
随着飓风位于副热带高压脊缺口附近, 这应该在接下来三十六到四十八小时内快速转向
北北西, 并在佛州西海岸附近或是沿着西海岸加速移动
由于伊尔玛犹豫不决地向西北移动, 新的路径指导已经向西移动一点, 本局新的路径只比
前一报向左一点
虽然风眼可能将在周日早晨接近或是穿越下礁岛群, 但飓风向佛州西海岸的接近角度造成
很难确实定位Irma会在佛州弯曲海岸的何处通过
If an eyewall replacement occurs within the next 6-12 hours, Irma
has an opportunity to restrengthen a bit while it moves across the
Straits of Florida. After that time, however, southwesterly shear
is expected to increase to 25-30 kt in about 24 hours and then
continue increasing through 48 hours. This shear, in addition to
Irma's core interacting with Florida, is likely to cause a
weakening trend after 24 hours. The new intensity guidance calls
for an adjustment from the previous forecast, although it
conservatively lies near the upper bound of the reliable models.
Irma is still expected to approach the Florida Keys and Florida
west coast as a major hurricane, and combined with its large size,
will produce significant storm surge flooding in those areas.
如果在接下来六到十二小时内发生眼墙置换, 当Irma通过佛州海峡时有稍微增强的机会
此时之后, 西南向风切预料约在二十四小时时增加到25-30节,
接着直到四十八小时持续增强.
此风切加上Irma核心与佛州陆地交互作用, 有可能会在二十四小时后出现减弱趋势
新强度指引提出对前一报的修正, 虽然这保守地落在数值预报中可信度的上限
Irma依然预计以主要飓风接近佛州礁岛群与佛州西海岸,
结合飓风本身巨大的尺寸,这将会以上地区产生显著的风暴潮溢洪
KEY MESSAGES:
1. Irma is expected bring life-threatening wind and storm surge to
the Florida Keys and southwestern Florida as an extremely dangerous
major hurricane tonight through Sunday. Preparations in the Florida
Keys and southwest Florida should be complete since tropical-storm-
force winds are already affecting portions of the coast.
2. There is an imminent danger of life-threatening storm surge
flooding in portions of central and southern Florida, including the
Florida Keys, where a Storm Surge Warning is in effect. The threat
of catastrophic storm surge flooding is highest along the southwest
coast of Florida, where 10 to 15 feet of inundation above ground
level is expected. This is a life-threatening situation, and
everyone in these areas should immediately follow any evacuation
instructions from local officials.
3. Irma will bring life-threatening wind impacts to much of Florida
regardless of the exact track of the center. Wind hazards from Irma
are also expected to spread northward through much of Georgia
and portions of South Carolina and Alabama.
4. Irma is expected to produce very heavy rain and inland flooding.
Total rain accumulations of 10 to 20 inches, with isolated amounts
of between 20 and 25 inches, are expected over the Florida Keys, the
Florida peninsula, and southeast Georgia from Saturday through
Monday. Significant river flooding is possible in these areas. Early
next week Irma will also bring periods of heavy rain to much of the
southeast United States where an average of 2 to 6 inches is
forecast, with isolated higher amounts, from North and South
Carolina to Tennessee and eastern Alabama. This includes some
mountainous areas which are more prone to flash flooding. Residents
throughout the southeast states should remain aware of the flood
threat and stay tuned to forecasts and warnings.