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Tuesday, October 27 - Special Edition for Zeta


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Good morning!

I'm not going to waste any time today, we have a lot to talk about. The confidence of the track of Zeta has increased overnight and it now appears that we may take a significant hit from Zeta right here in north Georgia.

The current track for Zeta crosses north Georgia very late Wednesday night into Thursday. As Zeta approaches the coast, it will begin to accelerate to the NE. Because of the relatively fast forward speed, Zeta won't be scrubbing off as much wind as we have seen with our past storms, and instead bringing those winds to north Georgia. Zeta rapidly accelerates and rockets from lower Alabama to Virginia in 12 hours. 

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091825_earliest_reasonable_toa_34.png.e573757eea5b81a19b68544ba209c2f5.png

 

Right now NWS Atlanta isn't saying much about the winds in the forecast discussion, but they have mentioned them briefly in the Hazardous Weather Outlook

Quote

Wednesday through Monday

Hurricane Zeta will move through parts of north and central Georgia Wednesday into Thursday. A Flash Flood Watch is in effect from Wednesday morning through Thursday evening, as rainfall totals of 2 to 3 inches and locally higher amounts could lead to flash flooding. In addition, there is a threat for strong winds and weak, short-lived tornadoes. Please continue to monitor the forecast as the situation evolves and confidence increases.

 

As the HWO mentions, we are currently under a Flash Flood Watch for Wednesday through Thursday.

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Quote

352 AM EDT Tue Oct 27 2020

  • FLASH FLOOD WATCH REMAINS IN EFFECT FROM WEDNESDAY MORNING THROUGH THURSDAY EVENING...

The Flash Flood Watch continues for

* Portions of north central Georgia...northeast Georgia...
  northwest Georgia and west central Georgia...including the
  following areas...

  • In north central Georgia
    • Barrow...  Cherokee...Clayton...Cobb...Dawson...DeKalb...Douglas...  Fannin...Fayette...Forsyth...Gilmer...Gwinnett...Hall...  Lumpkin...North Fulton...Pickens...South Fulton and Union.
  • In northeast Georgia
    • Banks...Jackson...Towns and White.
  • In northwest Georgia
    • Bartow...Carroll...Catoosa...Chattooga...   Dade...Floyd...Gordon...Haralson...Murray...Paulding...Polk...  Walker and Whitfield.
  • In west central Georgia
    • Coweta and  Heard.

* From Wednesday morning through Thursday evening

* Periods of heavy rainfall are expected across the area with
  the rain bands associated with Tropical Storm Zeta as it
  weakens and tracks across the forecast area Wednesday night
  through Thursday. Associated rainfall totals of 2 to 3 inches
  are expected on average across north and northwest Georgia
  with locally higher amounts possible where heavy rain bands
  persist for prolonged periods of time.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Watch means that conditions may develop that lead
to Flash Flooding. Flash Flooding is a very dangerous situation.
You should monitor later forecasts and be prepared to take action
should Flash Flood Warnings be issued.

 

Rainfall amounts through 8 am Friday morning from the WPC look like this. Some people could see much higher totals. This looks to have a serious upslope component to it and those east facing ridgelines in the mountains could see higher totals.

wpc-atlanta-total_precip_inch-4059200.thumb.png.729413596ed0736d398319fbb209fe34.png

 

But back to the winds. 

The next three images show accumulated maximum wind gust, so this is basically a snapshot of the wind gust over time and follows the track of Zeta. The are 10 meter readings or approximately 33 feet, or the recommended "standard" height for anemometer siting.  These winds are significant and you can see that the models are bringing some hurricane force wind gust. 

gfs-deterministic-atlanta-gust_swath_mph-4026800.thumb.png.726527bfa5738b55ebe1f38ccafcb8ef.pngnam-nest-conus-atlanta-gust_swath_mph-3980000.thumb.png.d0c7e157af22644f91f64c8923df23c0.pngecmwf-deterministic-atlanta-gust_swath_mph-4037600.thumb.png.106df96572531a1c4ff39ea045cb56f1.png

 

The next three images depict the winds at 925mb or right about 2500 feet. I know that I'm pretty close to that level and many in the mountains are there or above, so the next three images are significant for those people. 

 gfs-deterministic-atlanta-uv925_mslp-3972800.thumb.png.c2511f7e5420a43f4a7dc53535344c38.pngnam-nest-conus-atlanta-uv925_mslp-3976400.thumb.png.2a207f4c9bc08b10f9941f98d64c4070.pngecmwf-deterministic-atlanta-uv925_mslp-3983600.thumb.png.92f740c775aebd9a593cd78297df293c.png

 

If these come to fruition, we are in for some serious wind damage across north Georgia. The soils are relatively wet and with the additional rain, there could be a significant impact on the trees, and I have a big concern about this. I can assure you that I will start securing all of our deck items today.  This storm could create more damage than Irma did a few years ago if things unfold like they are right now. 

The ultimate track of Zeta will determine where those highest winds might pass. Right now I think it would be prudent to make preparations for a high wind event across the northern 1/3 of Georgia. As the day goes on we'll know more and more about Zeta, as we are in the timeframe where almost all computer models are in the range where they have very good accuracy since we're only about 48 hours away from those potential impacts.

I'll make updates through the day so please check back. BTW, I got the little issues worked out here with images etc. when you come to this site now, it uses https instead of http, so everything is secure. Because of that fix, the app now allows you to login, or it should. Let me know if it doesn't. 

EDIT: Just asked the NWS abut their current thoughts on the winds, this is what they are saying at the moment. 

Quote

... we currently have around 40mph gusts in the metro. Realize we could see higher gusts in the mtns. Current forecast is in collaboration with NHC thinking.


I hope everyone has a great Tuesday!

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Here's the 12z NAM 3km and all images are for 10 am Thursday. Keep in mind that this is not a forecast but simply one tool of many available. 

First up are the 925 mb winds or roughly 2500 feet. 

nam-nest-conus-atlanta-uv925_mslp-3980000.thumb.png.ced284aa9eb098bc75834b5149ca0d8b.png

 

These are 10 meter wind gust (33 feet). 

nam-nest-conus-atlanta-gust_mph-3980000.thumb.png.82f589e0b0c2e9e0fbe83542d9408af5.png

 

This image shows 10 meter wind speeds, these would be steady speeds. 

nam-nest-conus-atlanta-wnd10m_stream_mph-3980000.thumb.png.cf20203c137fd08b8057050e7fc364cc.png

 

And this last image depicts the steady winds at 80 meters or about 262 feet.

nam-nest-conus-atlanta-wnd80m_stream-3980000.thumb.png.968334825ec294e0d320c81f31482c37.png

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Looking for thoughts from our NWS friends to our west in Birmingham, here is a excerpt from their afternoon discussion.

Quote

Winds:
Wind is starting to look like the main impact from this system. While we would normally not be as worried about high wind potential for a system barely at hurricane strength making landfall where it is, this system will be very fast-moving. There will also be a strong pressure gradient/fall-rise couplet as it moves through due to its strong size. Several models, including the GFS, ECMWF, and the HWRF and HMON hurricane models indicate very strong winds just above the surface (90 kts at 850 mb and 75 kts at 925mb).
While low-level stability will prevent efficient mixing of these higher values to the surface, there will still likely be some mechanical mixing. With these low-level wind fields, there is increasing concern that 50 to 60 mph wind gusts could be realized at the surface, especially in some of our southern counties. While sustained winds would likely be below tropical storm force, the
potential impacts of these wind gusts knocking down numerous trees warrants a tropical storm watch for some of our southern
counties
. It's possible this could be expanded northeastward in later updates. A wind advisory will certainly eventually be needed for areas not in a watch/warning. Models indicate the wind field will be very asymmetric with the highest winds confined to areas along and to the right of the center.

 

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While we've mostly been talking about the winds, here's the WPC Excessive Rainfall Discussion.

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Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Tue Oct 27 2020
 
Day 2
Valid 12Z Wed Oct 28 2020 - 12Z Thu Oct 29 2020 

  • THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF THE CENTRAL GULF COAST INLAND ALONG/NEAR THE PATH OF ZETA

Southern Louisiana across Alabama into Far Northern Georgia 
The main concern for flash flooding remains associated with the land falling tropical storm Zeta early Wednesday afternoon. There has been some agreement on the potential for rainfall to develop near an fairly weak low level boundary ahead of Zetas arrival... but the mechanisms are still out of phase for a well-defined predecessor rainfall event.  Rainfall directly related to Zeta should be arriving during the late afternoon over far southeast Louisiana and then continue to spread north and then northeast. The axis of heaviest rainfall was along and displaced a bit to the east of the NHC forecast track in response to the anticipated asymmetric rainfall pattern resulting from deep layer shear across the storm.  Many pieces of numerical guidance were considerably slower than the NHC track and could not be used directly or within a blend.  The exception tended to be the GFS which was close to the track and speed but seemed to be too aggressive in its rainfall amounts inland.  For that reason, we nudged the axis of the Slight Risk eastward a bit from  Mississippi/Alabama towards the southern end of the Appalachians.  Also made sure to cover some areas of northern Georgia in the Slight Risk area which had some heavy rainfall a few days ago. The amounts remain fairly modest...2 to 4 inches with isolated higher amounts...due to the accelerating forward speed.

Also tended to make only minor changes in the Marginal Risk area which surrounds the Slight Risk area.  The deformation axis associated with an anomalously deep mid-latitude system will be able to tap some of the moisture which had streamed northward ahead of Zeta.  There was a broadening of the range of solutions since the previous outlook... which precluded upgrading any of the area to a Slight Risk.  

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Quote

Tonight through Wednesday Night

Current satellite loop shows TS Zeta just NW of the Yucatan peninsula. Zeta is still moving to the NW but it is expected to turn NE Wed morning and quickly move into the US Gulf coast by Wed evening. The current forecast shows it strengthening to a Hurricane over the next few hours and then making landfall across the SE LA coast Wed evening. Zeta is expected to weaken to a depression by Thu morning as it tracks across N GA. Precipitation ahead of the storm has already begun moving onshore the FL/AL coast and should see showers move into central GA tonight. The outer most rain band is expected to push northward through the
state tonight with most of the state seeing some precip before daybreak.
The short term hi-res models are showing we may see a bit of a break in the precip after this first band pushes through but showers and thunderstorms begin to develop state wide Wednesday afternoon. Precipitation continues Wednesday night with winds picking up as well. We are looking at rainfall totals in the 2-4 inch range across N GA (Mainly along and north of the Interstate 85 corridor) with isolated higher amounts to 5 inches. Will see winds increase from west to east as the center of Zetas remnants move across the region. Will see winds winds in the 15-25 mph range with gust 30-40 mph by day break Thursday.

With this amount of precipitation expected and strong gusty winds we will be issuing a Tropical Storm Watch this evening. This watch will include a good portion of the counties that are already in the Flash Flood Watch but will include Harris, Meriwether, and Troup counties. This watch will go into effect at 5pm this evening and continue through 11am Thu.

Thursday through Tuesday

The long term period begins Thursday morning with the remnants of Zeta moving across portions of north and central Georgia from southwest to northeast as it is steered by an upper-level low over the ArkLaTex region. Have maintained likely to categorical PoP's across north Georgia and much of central Georgia through Thursday as the heaviest and most widespread rain moves through. Storm total QPF is 2 to 4 inches across north and western Georgia with locally higher totals possible. A potential limiting factor to rainfall totals will be the fast movement of Zeta, though the anticipated rainfall efficiency coupled with already-high stream flows and fallen leaves still make for a flash flooding concern. Sustained winds of 20 to 30 mph with gusts of 30 to 40 mph are expected as the center of circulation moves through the area Thursday. In addition, a few weak, short-lived tornadoes will be possible across southern portions of the CWA as the rainbands pass through.

 

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Tropical Storm Zeta Local Statement Advisory Number 13
National Weather Service Peachtree City GA  AL282020
545 PM EDT Tue Oct 27 2020

This product covers NORTH AND CENTRAL GEORGIA

**Tropical Storm Zeta is expected to impact north and central Georgia
 late Wednesday into Thursday.**

NEW INFORMATION
---------------

* CHANGES TO WATCHES AND WARNINGS:
    - A Tropical Storm Watch has been issued for Bartow, Carroll,
      Catoosa, Chattooga, Cherokee, Clayton, Cobb, Coweta, Dade,
      Dawson, DeKalb, Douglas, Fannin, Fayette, Floyd, Forsyth,
      Gilmer, Gordon, Gwinnett, Hall, Haralson, Heard, Lumpkin,
      Meriwether, Murray, North Fulton, Paulding, Pickens, Polk,
      South Fulton, Towns, Troup, Union, Walker, White, and Whitfield

* CURRENT WATCHES AND WARNINGS:
    - A Tropical Storm Watch is in effect for Bartow, Carroll,
      Catoosa, Chattooga, Cherokee, Clayton, Cobb, Coweta, Dade,
      Dawson, DeKalb, Douglas, Fannin, Fayette, Floyd, Forsyth,
      Gilmer, Gordon, Gwinnett, Hall, Haralson, Heard, Lumpkin,
      Meriwether, Murray, North Fulton, Paulding, Pickens, Polk,
      South Fulton, Towns, Troup, Union, Walker, White, and Whitfield

* STORM INFORMATION:
    - About 840 miles south-southwest of Atlanta GA or about 750
      miles south-southwest of Columbus GA
    - 22.7N 90.3W
    - Storm Intensity 65 mph
    - Movement Northwest or 310 degrees at 14 mph

SITUATION OVERVIEW
------------------

Tropical Storm Zeta is moving northwest and is expected to turn
northeast on Wednesday morning and quickly move onto the southeast
Louisiana coast Wednesday evening. Zeta will then weaken as it moves
inland. Winds in our area will increase from west to east as the
center of the remnants of Zeta move across the region. Maximum
sustained winds are expected to be in the 25-35 mph range with gusts
as high as 45 mph. Furthermore, the outermost rain bands are expected
to push northward through Georgia tonight and rain bands will continue
to impact the forecast area through Thursday afternoon. Rainfall totals
are expected to range from 2 to 4 inches, with some locally higher
amounts possible.


POTENTIAL IMPACTS
-----------------

* WIND:
Prepare for hazardous wind having possible limited impacts across
NORTH AND CENTRAL GEORGIA. Potential impacts include:
    - Damage to porches, awnings, carports, sheds, and unanchored
      mobile homes. Unsecured lightweight objects blown about.
    - Many large tree limbs broken off. A few trees snapped or
      uprooted, but with greater numbers in places where trees are
      shallow rooted. Some fences and roadway signs blown over.
    - A few roads impassable from debris, particularly within urban
      or heavily wooded places. Hazardous driving conditions on
      bridges and other elevated roadways.
    - Scattered power and communications outages.

* FLOODING RAIN:
Prepare for dangerous rainfall flooding having possible significant
impacts across north Georgia. Potential impacts include:
    - Moderate rainfall flooding may prompt several evacuations and
      rescues.
    - Rivers and tributaries may quickly become swollen with swifter
      currents and overspill their banks in a few places, especially
      in usually vulnerable spots. Small streams, creeks, canals,
      arroyos, and ditches overflow.
    - Flood waters can enter some structures or weaken foundations.
      Several places may experience expanded areas of rapid
      inundation at underpasses, low-lying spots, and poor drainage
      areas. Some streets and parking lots take on moving water as
      storm drains and retention ponds overflow. Driving conditions
      become hazardous. Some road and bridge closures.

Prepare for locally hazardous rainfall flooding having possible
limited impacts across north Georgia.

Elsewhere across CENTRAL GEORGIA, little to no impact is anticipated.

* TORNADOES:
Prepare for a tornado event having possible limited impacts across
west-central Georgia. Potential impacts include:
    - The occurrence of isolated tornadoes can hinder the execution
      of emergency plans during tropical events.
    - A few places may experience tornado damage, along with power
      and communications disruptions.
    - Locations could realize roofs peeled off buildings, chimneys
      toppled, mobile homes pushed off foundations or overturned,
      large tree tops and branches snapped off, shallow-rooted trees
      knocked over, moving vehicles blown off roads, and small boats
      pulled from moorings.

Elsewhere across NORTH AND CENTRAL GEORGIA, little to no impact is
anticipated.

PRECAUTIONARY/PREPAREDNESS ACTIONS
----------------------------------

* OTHER PREPAREDNESS INFORMATION:
Now is the time to check your emergency plan and emergency supplies
kit and take necessary actions to protect your family and secure your
home or business.

When making safety and preparedness decisions, do not focus on the
exact forecast track since hazards such as flooding rain, damaging
wind gusts, storm surge, and tornadoes extend well away from the
center of the storm.

Closely monitor weather.gov, NOAA Weather Radio and local news
outlets for official storm information. Listen for possible changes
to the forecast.

There is a threat from tornadoes with this storm. Have multiple ways
to receive Tornado Warnings. Be ready to shelter quickly.


* ADDITIONAL SOURCES OF INFORMATION:
- For information on creating an emergency plan see ready.ga.gov
- For information on appropriate preparations see ready.gov
- For additional disaster preparedness information see redcross.org

NEXT UPDATE
-----------

The next local statement will be issued by the National Weather
Service in Peachtree City GA around 11 PM EDT, or sooner if
conditions warrant.

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I worry more about the comparisons to Irma, and the fact that Steve is mentioning them (he's not one to hype needlessly). I remember that well enough...I went on into work because my boss couldn't call me to tell me to stay home...all the power, cellphone, and landline phone service was out.

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3 hours ago, KingOfTheMountains said:

Really hoping they'll go ahead and cancel school up here for Thursday. If this is anything like Irma there'll be tons of kids that won't be able to get home by the afternoon, not to mention the risk of trees falling during the morning bus routes. 

As a a teacher "up here", I am hoping they do as well. It could be hazardous and our high school kiddos definitely don't need to be out driving in that nor our bus drivers on mountainous roads that are wooded on both sides. If this forecast holds up through tomorrow afternoon, I feel pretty confident that they will. They do a good job in being cautious in these regards. 

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1. Sorry for asking this at such an odd time.

2. 

Quote

* TORNADOES:
Prepare for a tornado event having possible limited impacts across
west-central Georgia. Potential impacts include:
    - The occurrence of isolated tornadoes can hinder the execution
      of emergency plans during tropical events.
    - A few places may experience tornado damage, along with power
      and communications disruptions.
    - Locations could realize roofs peeled off buildings, chimneys
      toppled, mobile homes pushed off foundations or overturned,
      large tree tops and branches snapped off, shallow-rooted trees
      knocked over, moving vehicles blown off roads, and small boats
      pulled from moorings.

Elsewhere across north and central Georgia, little to no impact is
anticipated.

The way I am understanding that segment is that us in north Georgia, like Dawson and surrounding counties, are at a little to no chance of tornadoes, it is more central Georgia, such as Atlanta, that has tbe higher risk? Am I understanding correctly, or am I completely wrong?

 

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1 hour ago, Asperman1 said:

1. Sorry for asking this at such an odd time.

2. 

The way I am understanding that segment is that us in north Georgia, like Dawson and surrounding counties, are at a little to no chance of tornadoes, it is more central Georgia, such as Atlanta, that has tbe higher risk? Am I understanding correctly, or am I completely wrong?

 

You should be sleeping. 🙂 Yes, little to no chance

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