5pm (Update) Tuesday, Hurricane Florence Information

By -
140 mph winds Hurricane Florence
4:50pm Tuesday
5pm National Hurricane Center: Hurricane Warning Now in Effect from South Santee River, South Carolina north to Pimlico and Albamarle Sounds. 
Dark brown is the hurricane-force winds and amber is the tropical storm-force winds. The wind field will likely grow in diameter between now and landfall. Thus, don't worry too much about the point of landfall. Just about all of the information you need is below.
Basemap by Capital Weather Gang
Closeup of Hurricane Warning Area With Major Cities
First, I hope you have used the checklists in the postings below to prepare yourself and your family for the oncoming storm.

Here is the timing of sustained 40 mph winds (with gusts to 60 mph). You should be gone by these times.


Below, I am going to provide details as to the threat areas for the three types of hazards:
  • Saltwater storm surge
  • Wind damage
  • Freshwater (river and stream) major to catastrophic flooding
Many of these suggestions are already covered by local emergency evacuation information but I want to reiteration and provide some of the weather science behind those evacuation orders.

Storm Surge
Click to enlarge
This map does not include wave action. In addition to a 20' storm surge, there could be 20' waves on top. This is combination is extremely destructive. 

My advice? The Outer Banks should be completely evacuated!
If you live 22' above sea level or lower, GET OUT!! You may want to raise that to 24-25' to be sure. 
Courtesy of Jim Reed, Twitter
This is what storm surge does (this was Hurricane Ike in Galveston in 2008)! You don't want to be there!

 Peak Wind Speeds

These are two different but plausible forecasts of peak wind gusts. Find your location and then pick the worst case scenario. If you are in the bright red, dark brown, white or pink areas, you are in an area that could be possibly have power failures or street blockages due to falling trees. Along the South Carolina coast, the highest winds may be delayed until the weekend. 

If you are in the winds of 80 mph or higher, if it were me, I'd get out. Trees could fall on your home or structural damage could occur exposing your family to danger or even extreme danger. 

Below, courtesy of Jim Reed, is what Category 4 wind damage looks like. 
You don't want to be there when winds like this are in progress. 

Flooding
Again, I am going to present two maps. The map immediately below shows a situation where heavy rains falls in the Appalachians. If this occurs, the amounts are likely too low. Near the coast, amounts are more than 30 inches.
click to enlarge
And, another scenario.



At 4:30pm, the NWS issued its rainfall forecast for the next seven days. While it is intentionally smoothed a bit (so it doesn't display the absolute maxima), the pattern is very reasonable.
If this is correct, there will be massive flooding.

Although the locations vary, both maps indicate the potential for more than 30 inches. If the wrong things come together, amounts could be heavier and more widespread. Major to catastrophic flooding is likely, especially given the recent wet conditions. Exact amounts may vary (per the two model patterns depicted). The bottom line: major to catastrophic flooding. 

While this is from Hurricane Harvey, this is the type of flooding to be expected from Florence. One of the things said right after Harvey was, "there was a failure of imagination" with regard to the amount of flooding. Don't let that be the case here. 

Comments

Post a Comment

Popular posts from this blog

Hilary's Forecast Path Shifts West; Updated 9:20am PDT

By -
Image
The forecast path of the center of Hilary has shifted a bit to the west. This increases the threat to the Southland, especially in terms of flooding.  Rainfall Note the heavy rains are forecast for Los Angeles County. Serious flash flooding may result. Because the forecast path has shifted to the west, that increases the threat of serious flooding in Los Angeles County north into Yosemite and the southern Sierra. It lessens the threat in Utah and western Arizona. While the threat of widespread flooding in Utah and Arizona lessens, note that some thunderstorms with localized heavy rain show up on the map.  In Nevada, the more western path increases the risk of serious flooding around Mt Charleston and into the central part of the state.  Here is the updated  (9am PDT) flash flood risk map. Wind There are already about 40,000 people without power in California, mostly in the center of the state.  The maps above are the peak gusts forecasted with the storm. The highest winds, in general,
Read more

Dangerous Travel Conditions - People Reportedly Stranded

By -
Image
-- Note, more current info available. Scroll up. --- Updated Information as of 8am PDT You are risking your life if you attempt to travel through the purple area.  While the rain has not begun in coastal California, I would urge you to use this time to make any preparations. Power outages have occurred already in southeast California. Here is the latest radar as of 7:55am PDT. As of 6:40am PDT , the radar indicates moderate to heavy rain falling over desert areas of Southern California and far western Arizona (click to enlarge).  Rainfall amounts for the 24 hours ending at 7am PDT show more than two inches have already fallen. There are reports from reliable sources that roads are already washed out and that people are stranded in isolated parts of the desert.  Below is a high-resolution computer model's rainfall forecast from 5am PDT to 11pm PDT Sunday. More than a foot of additional rain is forecast to fall. This will lead to catastrophic flooding.  Here is a map of current watc
Read more

Update on Tornado and Wind Potential; 12 Noon PDT

By -
Image
There was at least one tornado and at least one funnel cloud yesterday.  --- original forecast --- Hilary (the swirly symbol) continues to move NNW paralleling the coast of Baja California, Mexico. The area outlined in red has a significant risk of tornadoe s the rest of the afternoon.  Below is a list of peak wind gusts so far.  Peak winds may increase farther north as the afternoon progresses.  Addition at 12 noon PDT: Sure enough, winds have increased.  Note: If you are in the San Diego area, I recommend not  traveling east on I-8. Heavy rains may cause flash flooding that will involve the highway. 
Read more