Florence expected to become hurricane, head to Carolinas

rog1

Tyme Master Jr.
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After a slow and quiet start to the 2018 hurricane season , the tropics have come to life. This should be expected at this time of year , it is the statistical peak.

There are three reasons for this years slow start.
1.) Below average sea surface temperatures during the first half of the season.
2.) A highly stable environment of sinking air and African dust suppressing cloud formation.
3.) Higher than expected wind shear.

Earlier this week , TS Gordon struck the Gulf coast near the AL. MS. border and the weather entertainment channels tried to create this into a major disaster.

Today , however , there is a viable threat to the east coast. Major CAT4 hurricane Florence , a forecast defiant but powerful little storm , has a possibility to strike the mid east coast of the USA. Florence has surprised forecasters by rapidly intensifying to a major CAT4 storm in what appears to be a poor environment of 25 kts. of wind shear....puzzling at best. Models show high pressure building to the north of Florence which should force the storm farther to the west than originally expected a day or so ago. This may bring the storm uncomfortably close to the east coast (and Bermuda) before the high relaxes and allows the storm to turn to the north and out to sea. There are also 2 more areas of interest which we may also
be watching in a week or so from now.

Bottom line on Florence:

A recurving storm is still a very high probability , but the highly reliable ECMWF has been trending westward.

It is possible that higher wind shear will weaken Florence as it nears the USA , but the highly reliable ECMWF does show a rather significant low pressure area later in it's forecast period.

The storm is still about a week away or longer.....there is plenty of time before we buy up all the peanut butter. Keep at least one eye on this one....listen and read from the NHC , they are the ONLY hurricane authority.

I'll post if it becomes necessary , if conditions change , or if weather entertainment is scaring the crap out of you.


Models for Florence:


storm_06_ens.gif




Probability cone:



203346_5day_cone_with_line_and_wind.png
 
Thanks for the HU, and information, Rog. Stay safe, my friend.:cheers:
 
I wish I had some better news for our WIT's who live in the mid Atlantic states.

Former major hurricane Florence has been temporarily downgraded to a TS as it is in an area of wind shear. A weaker Florence will tend to move farther west. High pressure has built in along the east coast which will also push a weaker Florence farther west. The wind shear is forecast to relax in 2 to 3 days and the upper atmo conditions are expected to be favorable which will allow Florence to again strengthen , probably to major hurricane status. Also at this time, the high pressure will be displaced slightly by a troff approaching the Pacific NW USA. This will allow a stronger Florence to begin a northerly component to it's western direction. Just how much of a northerly component Florence begins is unknown at this time as the models have some disagreement in how much the high pressure is moved.

A major hurricane strike, CAT 3 or higher , on the mid Atlantic coast of the USA is very possible 6 to 8 days from now. It is still possible for this thing to come very close to the coast and turn away at the last minute if the storm timing takes a little longer than the current forecast. I've been watching this stuff for a lot of years and have noticed that rarely does a storm outrun the forecast , it usually lags a little behind so there is still some hope for it to stay in the ocean. Your model graphics and probability cone from the NHC posted above will auto update so you can quickly check in on Florence. If you live from GA. to VA. you need to keep an eye on this and have your plan ready. It is even possible for this to hit northern FL.

Elsewhere.... hurricane Olivia will probably strike the big island of Hawaii as a tropical storm in 5 days or so from now. WITS in Hawaii should monitor this event....(probably won't be that bad)

TS Helene in the very far eastern Atlantic is forecast to become a hurricane but it will recurve north somewhere around 45deg and probably not affect us.

TD 9 in the eastern Atlantic is forecast to become TS and then hurricane Isaac. The models have this one moving to the west and affecting the Islands in about 6 days as a hurricane and then tracking into the Carib Sea. Wind shear is forecast to be somewhat unfavorable at that time and keep the storm in check but this is way too far in the future to be certain of any future strength or any future track. I'll post the graphics below so you can monitor the progress of Isaac.


Models for TD 9 future Isaac :


storm_09_ens.gif




probability cone for Isaac :



085656_5day_cone_with_line_and_wind.png
 
A lot of info today so here goes....

Hurricane Florence has rapidly intensified into a CAT 3 overnight as it was forecast to do. Further increases in strength are possible today as most of the global models bring this storm to dangerous CAT 4 strength on 9/10 in the pm.

Florence has begun to "lean" more to the right , which means that the expected turn to the WNW has begun as the blocking high has been displaced somewhat. Florence will begin to pick up forward speed as it steers around this high and eventually it should turn more to the NW from the W or WNW sometime in the next 12 to 24 hours.

Florence is currently an average sized hurricane with TS force winds extending outward about 130 miles from the center. The wind field is forecast to expand. Florence currently has a small 10 to 15 mile wide eye with a fully formed eyewall.

Florence is currently in an area of low wind shear and very warm sea temps with an anticyclone above it which could lead to further strengthening and these conditions will continue for the next 2 to 3 days. RH values are not really that high and the storm seems to have less outflow in the southeast quadrant but that doesn't appear to be hindering intensification.

Florence will most likely approach the coast of SC or NC late Thursday night or early Friday if the forecast speed holds true. Some of the better global models have deviated slightly to the south or north of the track on the latest runs , but the NHC usually follows the consensus of the models or private models like the FSSE and they have not deviated much in the last few runs. Average track error in 4 days is still around 150 miles , and it can be greater. It is still possible for this thing to go outside the box but that is decreasing with time. When the 3 day portion of the cone is over you , the error dramatically decreases.

Steering currents are forecast to collapse and become very weak in the 4 to 5 day time frame which means that IF the hurricane does come ashore , it will not move very much and linger for possibly several days. It is still possible for Florence to stall offshore but this is becoming less likely with time. Some models show 15 to 20 kts of wind shear on approach to the coast and it is also possible for some drier air from the continent to be inhaled by the heat engine , so some weakening is possible , but not forecast , in the 3 to 5 day time period.

The slow movement or stalled movement forecast for this storm in the day 4 and 5 time frame can create catastrophic rains so flooding can be a major concern even well inland. Very high storm surge will be a problem for the coast regardless of impact or not , and those expected 120 to 140 mph breezes will be a big concern IF the eyewall comes ashore or is near your location.

NOW is the time to prepare as the TS force winds and some rain bands will arrive well before the main body of the hurricane. I imagine stores and gas stations are a cluster today with many older residents remembering hurricane Hugo of 1989. Expect widespread power outages that may last for weeks. Expect loss of water and sewer supply if on municipal sources. Expect slow response times for emergency services if they are needed and no response during the body of the storm. Above all , listen to your local emergency officials about any evacuations and listen to the NHC for accurate storm information. Stay safe and God Bless if this thing affects you. The graphics posted above for Florence will update so you can quickly monitor the progress of the storm with time.

Elsewhere , hurricane Helene will turn out to sea and not be an issue for USA.

Hurricane Isaac will track west into the Caribb sea where high wind shear is forecast to be late in the forecast period. That wind shear may weaken or destroy this small hurricane. The models are somewhat divergent on the future track of Isaac. Some models continue to move Isaac west while some show an opening in the high pressure due to the presence of Florence and the storm may track north in that direction. The difference in the better models spread is on the order of about 800 miles......obviously that can't be right. The graphics are posted above to follow the progress of this storm

An area of low pressure has formed in the western caribb sea and the NHC is giving it a medium chance to develop in 5 days as it moves generally to the NW towards the southern coast of TX.

Another area of low pressure has formed in the middle of the Atlantic and the NHC is giving it a medium chance to develop in 5 days as it moves away from us.

Hurricane Olivia will affect the Hawaiian Islands on Wednesday as a TS.

There are currently 7 named storms in the northern hemisphere and at least 4 or 5 invest areas.
 
​Looks like we have three storms lined up in the South Atlantic, now Rog. :no: ​Intelicast, satellite of the Atlantic.:wink:
 
Published on Sep 10, 2018
As Hurricane Florence approaches the East Coast of the United States, the governors of Virginia, North and South Carolina have issued mandatory evacuation orders affecting hundreds of thousands of residents in coastal areas.


 
Florence update 9-11-18

The NHC forecast philosophy has not changed from yesterday concerning Florence. Florence is a very dangerous CAT 4 hurricane with winds right now around 130 mph. Florence is in conditions where it can strengthen further and become larger. Florence is moving WNW at around 16 mph and a further turn to the NW is expected. Florence is forecast to most likely strike the coast of NC very late Thursday or early Friday and then slow down or stall for a day or so, The wind will wind down if Florence does come ashore but the torrential rain can cause flooding well inland. The storm surge on the coast can possibly be upwards of 10 feet on the windward side of the storm. Wind shear is forecast to increase as the hurricane approaches the coast and some weakening is forecast and possible , but a major hurricane is still forecast to be in the affected neighborhoods. I believe I heard that about 1 million people have been ordered to evacuate.

Now some observations...

Florence completed a rather lengthy concentric eyewall replacement cycle last night. (ERC) This is when a new eye forms farther out from the existing eye and replaces that eye. This expands the size of the eye which can eventually lead to further wind speed and it also increases the size of the overall wind field and hurricane itself. Florence increased the size of it's eye from about 10 miles to roughly 30 miles. Storms do temporarily weaken during ERC's and Florence is down to 130 mph but it is forecast to spin up and peak around 150 mph before dropping down to 140mph. Strength models , like all weather aids , are better now than years prior , but we are still poor in forecasting strength.

Florence seems to have better outflow (exhaust) on both sides where yesterday it looked a little weaker on the southern right side. ( warm moist air rises inside of the eye to the top of the hurricane , cools , and is evacuated by a reverse spin High anticyclone over the top of the storm. This air cools , loses moisture , and then sinks and becomes fair weather beyond the confines of the storm,,,,,{"the calm before the storm } )

If you look at the Florence probability cone in post #1 above , you might notice that it looks like it has an unusual shape. This is caused by how the cone is generated. The storm will be first moving fast and then slow down. The cone is created by drawing a series of concentric circles which represent the average error of the NHC for the last 5 years , at 12 hour and then 24 hour expected forecast positions. When all plotted 5 day positions are circled with their average error circles , the circles are then smoothed out to give a cone shape as NHC error does increase with time. A fast moving storm gives the illusion that the cone is thin , and likewise , a slow moving storm gives the illusion that the cone is fat. It is possible for a very slow moving or stationary storm to have a probability cone that is just a single circle as the 5 day circle , being larger , would surround all the other forecast point circles....it has happened. Notice the NHC 5 day position of Florence. You can just about make out the drawn 5 day circle even though it is partially covered by the non opaque 3 day circle. Notice that some of that 5 day circle , about 1/6 of it , is still over water. That is why I have been saying that it is still possible for Florence to slow or stall before the coast. That probability is still within the margin of error , but becomes less likely with time. In all probability, the storm will move ashore and slow as forecast by the NHC. ( The probability cone has since updated since this post , so it is now not possible to see the effect that I described above )

Wind shear is expected to increase as Florence approaches the coast and weaken the storm somewhat and it is possible some dryer air might also be ingested further weakening the storm. If an ERC was also happening at this time , it surely wouldn't hurt and might drop this thing to a strong but manageable CAT 2, I hope , but that stuff is pure speculation . A slow off shore storm of this power would also wreak havoc on the coastal beach areas with massive storm surge and rain.

To me , the latest sat pic of Florence looks to be a little eroded in the upper right quad , might be a little dryer air or RH getting sucked in ( we can only hope) , maybe a little shear , maybe the start of another ERC , but the Central dense overcast looks to be unaffected. If something nice happens , I'll post later

Elsewhere:

TS Olivia will affect the Hawaiian Islands Wednesday.....won't be bad , they need the rain.

Hurricane Helene will recurve very far away , possible affect Azores.

Models say an area of low pressure will form west of the Azores , could possible develop into a TS or Sub TS , not a concern for us.

An area of low pressure is near the Yucatan channel. It has a medium chance to develop as it moves WNW or NW across the favorable environment of the GOM. Interests from northern Mexico through TX. and LA. should watch this. (IMHO I don't think it will become very much.)

Former hurricane Isaac is now a TS. This small storm has had trouble getting it's act together since it formed being affected by wind shear and outflow from the other storms. Isaac is forecast to MAYBE regain at least CAT 1 strength as it moves W. Stronger wind shear in the Carib sea will again weaken Isaac as it continues W. If Isaac remains strong it may turn to the north but this is unlikely. (IMHO , I think Isaac will just go away in the strong wind shear of the Carib.)
 
Addition....

Florence actually completed it's somewhat very long ERC an hour or so ago and not this morning. The storm now looks very symmetrical and the new larger eye has gained enough energy and angular momentum to begin getting stronger. Winds are now up to 140 mph in the eyewall with gusts to 165 mph. The best atmo conditions will exist for about the next 24 hours and the wind speed is forecast to peak at 155 mph during this time....borderline CAT 5. The size of the wind field has also expanded with hurricane force winds extending outward about 40 miles from the eye and tropical storm force winds extending out about 150 miles from the eye , a much larger storm then yesterday. After 24 hours the conditions are forecast to deteriorate , but just how much power this storm looses before it's forecast landfall is questionable if it achieves it's forecast peak and it also depends on the storms speed as it nears the coast. We can hope that the future atmo conditions are worse than currently forecast.
 
The NHC has made what I would consider a major forecast track adjustment in the future path of Florence at 5 am this morning.

Yesterday , our consensus models were showing a track that would bring Florence onshore somewhere in southern NC. On the other hand as I mentioned in posts above , some of our better global models were a becoming a little divergent as the storm approached the coast. Some were trending a little north while slowing the approach , and some were trending a little south while doing the same. Now that hurricane hunter planes are flying frequent missions to gather the data which initializes the models so they perform better , the NHC has adjusted the future path to the south. This adjustment may leave Florence in the ocean a little longer before coming ashore and she may come ashore farther south than most of the prior forecasts have shown. This may help to weaken Florence somewhat in the expected poorer conditions forecast at that time. It is very possible that Florence may not be a major hurricane when it comes ashore if it is in poorer conditions for a longer time. Although the NHC has adjusted the forecast track to the left with this advisory, they are on the right side of the model guidance which means further track adjustments to the left may be made with today's 11am and 5pm cone updates if the future model runs remain consistent.

Bottom line:

Hopefully Florence will remain in poor conditions longer and weaken it lower than a major hurricane before it comes ashore possible farther south than prior forecasts , still a bad event but possibly not catastrophic.

Florence has weakened overnight from 140mph to 130 mph winds. This may be due to unexpected shear , dryer air ingested , cooler water upwelled in front of Florence by large hurricane induced waves , interference in conditions caused by the possibly developing TS moving into the GOM towards TX. , the building high on the continent is stronger , or the onset of another ERC.

I have mentioned several times in my above posts that it was still within the margin of error that Florence might stall offshore and weaken , there is still hope and the forecast aids may be trending that scenario. Time will tell.
 
https://www.cnn.com/us/live-news/hurricane-florence-dle/index.html


Here are a few key events to watch for today


We'll have our eyes on a few key events scheduled throughout the day. From a 9:15 a.m. FEMA briefing in Washington to the North Carolina governor's press briefing at 5 p.m., here's the current outlook. (Note: This will surely be updated.)

  • 9:15 a.m. ET: FEMA Briefing in Washington, DC.
  • 10 a.m. ET: North Carolina Gov. Roy Cooper holds briefing at Joint Force Headquarters in Raleigh
  • 10:15 a.m. ET: Virginia Sen. Tim Kaine heads to FEMA for a closed-door briefing and a media avail
  • 11 a.m. ET: The National Hurricane Center will release an updated forecast.
  • 12:30 p.m. ET: Cooper visits hurricane staging site in Kinston
  • 2 p.m. ET: The National Hurricane Center will release an updated forecast.
  • 5:05 p.m. ET: Cooper holds media briefing at Joint Force Headquarters in Raleigh
  • 5 p.m. ET: The National Hurricane Center will release an updated forecast.
  • 6:00 p.m. ET: More than 2000 North Carolina National Guard soldiers will report to duty for Hurricane Florence response.
  • 8 p.m. ET: The National Hurricane Center will release an updated forecast.



 
The NHC 11am forecast has been released. (The forecast updates at the two 11's and the two 5's during the day are the only updates which adjust the cone)

Hurricane Florence has not gained strength but the pressure has slightly lowered , it is still at 130 mph , a borderline CAT 4 hurricane. The reasons for this may be from my last post above , or just because Florence is around 30 deg N Lat. Hurricanes usually don't get stronger north of there. The wind field has increased slightly in size and the central donut area has maintained its structure , but in the last few Sat pics , the cloud tops appear to be warming which could be a sign of some slow weakening. The hurricane will have its best conditions to gain strength during the overnight hours.

There has been no further adjustment to the future path as the models are in better agreement. Florence is still forecast to move very near the southern coast of NC. or the northern coast of SC. , stall somewhat , drift south , and then possibly move inland in SC. It is forecast to be a CAT 2 storm when it moves inland , but coming ashore as a CAT 3 is still within the forecast error. It should be noted that the NHC strength forecast is on the higher end of the strength models...(err on the side of caution is always a good thing) Hopefully the storm will be weaker , possibly much weaker. Storm surge and rains will still be significant , but structural failure decreases dramatically if the storm weakens to CAT 2 because wind speed is exponential. It is also possible that the strongest winds might not make it all the way to the surface. Sometimes this can happen if the cloud tops warm in the CDO.
 
Florence weakens to CAT 3

Since the 11am advisory Florence has weakened to a CAT 3 storm with winds of 120mph and the pressure has also risen. Florence's wind field , on the other hand , has expanded. Hurricane force winds extend out about 70 miles from the center and tropical storm force winds extend outward about 200 miles from the center. The forecast cone has been nudged a little bit to the right due to the storm wandering a wee bit to the N in the short term since 11am , but the forecast philosophy has remained the same. Florence will approach the coast of NC. as possibly a CAT 3 hurricane , slow down , wander to the south , and go ashore as a CAT 2 hurricane. The new expanded wind field , however , will bring poor conditions much farther away from the center. Storm surge of around 10 ft. and excess rain of possibly 10 to 20 inches can cause possible flooding even well inland. This remains a large concern. There is a window for Florence to regain strength as it passes over the gulf stream this evening with warm water and low wind shear expected. If you are in the cone , rush your plan to completion quickly tomorrow , if not already completed. If you were thinking evacuation , you should already be gone.

Elsewhere ....

TS Isaac will continue to travel due west in the near term. After the Islands , some models dissipate it while others regenerate it as it moves to the NW over Fl. or into the GOM.

CAT 1 Helene will not be a threat to us , possibly to the Azores as a TS.

Newly formed sub TS Joyce will strengthen some and move towards the Azores before being absorbed in the jet stream.

Invest 95L near the Yucatan has a high probability to develop into a TD or TS as it moves towards the coast of South TX. or North Mexico. Just bring your garbage cans in for this one if necessary.

TS Olivia is affecting the southern Hawaiian Islands with 45 mph breezes and rain.


Florence opinion:

I don't think Florence will strengthen later tonight in the better expected conditions. The larger wind field would need larger angular momentum to spin up , think of a skater with her arms extended and not tucked in , tough to spin.

Florence's eye appears to have shrunk in the latest microwave image and the cloud tops
noticeably have warmed in the southern quadrants while the pressure has risen. Could be the onset of an ERC and she might recover over the gulf stream , she could be feeling the building high on the continent , but hopefully this is the beginning of a further weakening trend.

I am cautiously optimistic that when Florence moves onshore , it will be in the CAT 2 range (hopefully weaker) , but let's see what it looks like in the morning.
 
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