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OCTOBER 2018 - Stormy Halloween

General Weather Discussions and Analysis

Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Mon Oct 08, 2018 1:24 pm

The afternoon Updated Climate Prediction Center temperature Outlook that extends into the weekend after next suggests below normal temperatures are possible across our Region.
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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Mon Oct 08, 2018 2:46 pm

Hurricane Michael still expected to be a Major Category 3 Cyclone at Landfall and Hurricane Warnings as well as Storm Surge Warnings have been hoisted with the latest full package Advisory...

HURRICANE MICHAEL DISCUSSION NUMBER 9
NWS NATIONAL HURRICANE CENTER MIAMI FL AL142018
400 PM CDT MON OCT 08 2018

DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT THAT WAS
IN THE STORM UNTIL ABOUT 1700 UTC CONTINUED TO INDICATE THAT THE
HURRICANE WAS DEEPENING. THE PRESSURE HAD FALLEN TO 978 MB ON
THE FINAL FIX, BUT THE AIRCRAFT WAS STILL NOT ABLE TO SAMPLE THE
NORTHEASTERN PORTION OF THE STORM DUE TO THE CLOSE PROXIMITY OF
LAND. THE INITIAL INTENSITY HAS BEEN INCREASED TO 70 KT BASED ON A
BLEND OF DVORAK SATELLITE CLASSIFICATIONS AND THE CONTINUED
DEEPENING THAT WAS OBSERVED.

THE UPPER-LEVEL OUTFLOW HAS GRADUALLY IMPROVED OVER MICHAEL BUT IT
IS STILL SOMEWHAT RESTRICTED OVER THE WESTERN PORTION OF THE STORM.
THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE INTENSITY FORECAST
THINKING. THE MODERATE SHEAR THAT HAS BEEN AFFECTING THE CYCLONE IS
NOT EXPECTED TO PREVENT STRENGTHENING WHILE MICHAEL MOVES OVER THE
WARM WATERS OF THE EASTERN GULF OF MEXICO. ALTHOUGH THE STATISTICAL
GUIDANCE IS SOMEWHAT LOWER THIS CYCLE, THE REGIONAL HURRICANE AND
GLOBAL MODELS STILL FAVOR STEADY TO RAPID STRENGTHENING, AND THE NHC
FORECAST IS CLOSEST TO THE FLORIDA STATE SUPERENSEMBLE AND THE HFIP
CORRECTED CONSENSUS MODEL.

AIRCRAFT AND SATELLITE FIXES SHOW THAT MICHAEL HAS BEEN WOBBLING AS
IT MOVES GENERALLY NORTHWARD. SMOOTHING THROUGH THE WOBBLES GIVES A
LONG-TERM INITIAL MOTION ESTIMATE OF 355/8 KT. MICHAEL IS FORECAST
TO MOVE NORTH-NORTHWESTWARD TO NORTHWARD BETWEEN A DEEP-LAYER RIDGE
OVER THE WESTERN ATLANTIC AND A TROUGH OVER THE WEST-CENTRAL UNITED
STATES. THE TROUGH IS FORECAST MOVE EASTWARD, CAUSING MICHAEL TO
TURN NORTHEASTWARD IN 36 TO 48 HOURS, AND THE CYCLONE SHOULD THEN
ACCELERATE NORTHEASTWARD AS IT ENTERS THE MID-LATITUDE WESTERLY
FLOW. THE 1200 UTC DYNAMICAL MODELS HAVE CONVERGED ON BOTH THE
TRACK AND FORWARD SPEED THROUGH THE FIRST 48 TO 72 HOURS. THE
UPDATED NHC TRACK HAS BEEN NUDGED SLIGHTLY WESTWARD THROUGH 48 HOURS
TO BE CLOSER TO THE LATEST CONSENSUS AIDS.

IT SHOULD BE NOTED THAT THE LOCATION AND MAGNITUDE OF PEAK STORM
SURGE FLOODING IS VERY SENSITIVE TO SMALL CHANGES IN THE TRACK,
INTENSITY, AND STRUCTURE OF THE HURRICANE. SINCE THERE IS STILL
UNCERTAINTY IN ALL OF THESE PARAMETERS, THE OFFICIAL NHC STORM SURGE
FORECAST AND WATCH/WARNING AREAS INCLUDES VARIOUS PLAUSIBLE
SCENARIOS. REGARDLESS OF THE EVENTUAL TRACK AND INTENSITY OF
MICHAEL, LIFE-THREATENING STORM SURGE INUNDATION IS EXPECTED ALONG
PORTIONS OF THE FLORIDA PANHANDLE AND BIG BEND/NATURE COAST, AND THE
STORM SURGE WATCH HAS BEEN UPGRADED TO A STORM SURGE WARNING FOR
PARTS OF THIS AREA.

THE NOAA G-IV AIRCRAFT IS CONDUCTING A SYNOPTIC SURVEILLANCE MISSION
OVER THE GULF OF MEXICO AND DROPSONDES FROM THAT MISSION WILL BE
ASSIMILATED INTO THE 0000 UTC NUMERICAL MODELS RUNS.

KEY MESSAGES:

1. LIFE-THREATENING STORM SURGE IS LIKELY ALONG PORTIONS OF THE
COASTS OF THE FLORIDA PANHANDLE, BIG BEND, AND NATURE COAST, AND A
STORM SURGE WARNING IS IN EFFECT FOR THESE AREAS. RESIDENTS IN THESE
AREAS SHOULD FOLLOW ALL ADVICE GIVEN BY THEIR LOCAL OFFICIALS.

2. A HURRICANE WARNING HAS BEEN ISSUED FOR PORTIONS OF THE FLORIDA
GULF COAST, AND EVERYONE IN THESE AREAS SHOULD PREPARE FOR
LIFE-THREATENING WINDS ASSOCIATED WITH THE CORE OF MICHAEL.
DAMAGING WINDS WILL ALSO EXTEND INLAND ACROSS PORTIONS OF THE
FLORIDA PANHANDLE, SOUTHERN GEORGIA, AND SOUTHEAST ALABAMA AS
MICHAEL MOVES INLAND.

3. HEAVY RAINFALL FROM MICHAEL COULD PRODUCE LIFE-THREATENING FLASH
FLOODING FROM THE FLORIDA PANHANDLE AND BIG BEND REGION INTO
PORTIONS OF GEORGIA AND SOUTH CAROLINA.

4. HURRICANE CONDITIONS WILL CONTINUE IN PORTIONS OF WESTERN CUBA
THROUGH THIS EVENING, WHERE A HURRICANE WARNING IS IN EFFECT.

5. MICHAEL IS EXPECTED TO PRODUCE HEAVY RAINFALL AND FLASH FLOODING
OVER PORTIONS OF WESTERN CUBA AND THE NORTHEASTERN YUCATAN PENINSULA
OF MEXICO DURING THE NEXT COUPLE OF DAYS.

FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 22.2N 85.2W 70 KT 80 MPH
12H 09/0600Z 23.7N 85.7W 85 KT 100 MPH
24H 09/1800Z 25.7N 86.4W 95 KT 110 MPH
36H 10/0600Z 27.9N 86.6W 105 KT 120 MPH
48H 10/1800Z 30.2N 85.8W 100 KT 115 MPH...NEAR THE COAST
72H 11/1800Z 34.5N 80.5W 45 KT 50 MPH...INLAND
96H 12/1800Z 39.8N 68.8W 55 KT 65 MPH...POST-TROP/EXTRATROP
120H 13/1800Z 46.2N 50.0W 60 KT 70 MPH...POST-TROP/EXTRATROP

$$
FORECASTER BROWN
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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Mon Oct 08, 2018 2:51 pm

Monday afternoon local weather briefing from Jeff:

Coastal Flood Advisory has been issued for the middle and upper TX coast into Wednesday.

Combination of typical early Fall high tides and the arrival of large long period swells from Hurricane Michael over the SE Gulf of Mexico will result in elevated tides along the upper TX coast into Wednesday and possibly Thursday. Tides are already running 1-2 feet above normal today due to sustained ESE fetch of wind off the Gulf over the weekend and lunar high tide cycles. Starting Tuesday and peaking early Wednesday large swells with periods of 11-14 seconds will begin to arrive along the upper TX coast from Hurricane Michael. These large swells will result in water level pile up along the beaches and some tidal trapping of already elevated tides. These factors will likely push total water levels along the coast into the 3.5-4.0 foot range which is getting close to or in some areas exceeding advisory criteria especially on Bolivar. Would expect some overwash of low lying marsh and coastal beach access areas during high tides and potentially impacting HWY 87 on the east end of Bolivar. With Galveston and Matagorda Bays tides will likely remain below 4.5 foot levels which usually start to result in concerns, but could see some coastal flooding in the typical low lying areas in SE Harris County around the Lynchburg Ferry Landing, Shoreacres and Seabrook.

Weather:
Moist onshore flow will continue with scattered showers and thunderstorms moving inland off the Gulf of Mexico. Upper trough to our west will generally shear out into the plains on Tuesday with tail end of lift moving across SE TX. This will help to enhance rain chances mainly NW of US 59 Tuesday afternoon and evening. As Hurricane Michael intensifies into a major hurricane and landfalls along the NE US Gulf coast Wednesday the strong circulation around the hurricane will drive a “dry front” across the region allowing drier air to our NNE and NE to move into the region. This will help lower overnight lows into the 60’s by Thursday morning with highs in the mid to upper 80’s.

Another strong trough develops west of TX late this week as the remains of eastern Pacific Hurricane Sergio makes landfall over Baja and then track ENE/NE into NW TX over the weekend. This trough is able to tap some fairly cold air over the northern Rockies and will likely send a “true” fall cold front through SE TX at some point either late this weekend or early next week. GFS is fairly aggressive with this feature showing significant cold air advection behind the frontal passage and decent post frontal cooling. Upper level moisture from Sergio will likely spill across the frontal slope helping keep mostly cloudy skies in place post front which will help insulate the colder surface air from the still fairly high October sun angle. Don’t want to get too carried away with post frontal cooling nor get any hopes up, but could certainly be looking at lows into the 50’s and highs possibly only in the 60’s depending on how much post frontal cloud cover lingers.


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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby Katdaddy » Tue Oct 09, 2018 4:48 am

Hurricane Michael has sustained winds of 90MPH and has developed an eye overnight with landfall along the NW FL Coast tomorrow afternoon. The SPC has a large slight risk area across the S Plains and into the Upper MS Valley today which includes a large portion of N, Central, and S TX. Coastal Flood Advisories are in effect for the entire TX Coast due to a high risk of rip currents and swells from Hurricane Michael. The cool front arrives late tonight/early tomorrow morning bring slightly cooler but much drier weather followed by a cold front Sunday.
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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Tue Oct 09, 2018 6:23 am

The upper trough and a potent shortwave over New Mexico continue to advance E today. Very heavy rainfall with strong to possibly severe storms will continue to spread toward SE and East Texas into the afternoon/evening. Those neighbors to our West in S Central, Central and N Texas will need to be weather aware today.

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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Tue Oct 09, 2018 7:34 am

Tuesday morning Hurricane Michael briefing from Jeff:

Major hurricane landfall likely along the FL panhandle in the next 30 hours.

Severe and widespread storm surge event likely across Apalachee Bay (Big Bend area) and FL panhandle

Discussion:
Multiple aircraft are in Michael this morning and both indicate the hurricane is intensifying. Winds of 103mph were recorded and the central pressure has fallen from 973mb to 968mb. Additionally, a ring of deep convection has now developed around the large diameter eye and the satellite presentation continues to improve with expanding outflow over the western semi-circle of the hurricane and very good outflow to the east over the SW Atlantic. NOAA buoy 42003 is currently sustained at 47mph gusting to 54mph.

Track:
Track aides are in excellent agreement that Michael will continue NNW today and then turn N and NE on Wednesday and landfall along the FL panhandle roughly 40 miles either side of Panama City FL. There has been very little adjustments in the track guidance over the last 24 hours and this is a high confidence track that a major hurricane will strike the FL panhandle in about 30 hours. Near landfall the hurricane will begin to accelerate to the NE across SC GA and across the Carolinas and this accerelation of forward speed will bringing damaging winds well inland along the track of the hurricane.

Intensity:
Michael continues to show steady intensification with 24 hours pressure falls from 982mb to 968mb and increasing winds from 70mph to 100mph over 24 hours. Thus far rapid intensification was not occurred, but with the expanding outflow to the west and decreasing shear and the formation of the inner core intensification will continue up to landfall. Like Florence last month, Michael is a very large hurricane with the eye diameter of nearly 40 miles across and TS force winds extending outward nearly 200 miles. Many times these large hurricane have a tough time intensifying as their wind field is spread out over a large area instead of consolidated in the eyewall. The current NHC forecast brings Michael to the coast as a 120mph hurricane.

It should be noted…that do to the large size of the hurricane, impacts will be far reaching and the large wind field will drive a massive storm surge into the coast especially Apalachee Bay which is extremely vulnerable to storm surge flooding. In fact storm surge will penetrate upwards of 5 miles inland over the flat ground and as far as 15 miles inland along rivers south of Tallahassee.

Impacts:

This will be a devastating hurricane for the FL panhandle…potentially the strongest to strike Panama City since Eloise in 1975.

Storm Surge:
Life threatening storm surge is likely as angle of approach of Michael will drive a massive surge into Apalachee Bay which is one of the most storm surge prone locations along the US coast. The concave shape of the bay will amplify the surge to “incredible” heights near St. Mark and areas south and southeast of Tallahassee. Additionally, the large wind field of Michael and favorable SSW fetch on the eastern flank of the circulation will drive a significant surge into the Apalachee Bay. Based on the tight track clustering the greatest storm surge will likely be from near Seaside eastward to Panama City and then across all of Apalachee Bay to Cedar Key. Based on the latest storm surge height forecasts, it is likely that coastal dune defenses from Destin to Port St. Joe will be overtopped and breached allowing large destructive wave action to impact the first floors of the dense hotel and resort areas along the beach fronts of the barrier islands. Some of the barrier islands will suffer extreme erosion and new cuts will be formed.

The following are forecasted storm surge heights above the ground:

Indian Pass to Cedar Key, FL: 8-12ft
Cedar Key to Crystal River FL: 6-9 ft
Indian Pass FL to Destin: 6-8 ft

Wave heights over the eastern Gulf are forecast to build to 25-35 ft on Tuesday and due to the angle of the offshore shelf off the coast of the FL panhandle very large wave actions as experienced during both Opal and Ivan will arrive onto the coast with the storm surge. Coastal barrier islands will likely be completely overrun by the storm surge with large destructive wave pounding coastal structures to failure. Many of the large resorts and hotels along the barrier islands will suffer extensive damage to their first floors and in many cases the storm surge will completely destroy the first floor of any structures on the ground. Even well built structures along the Gulf facing beaches will see heavy erosion and some may collapse and be washed away. In and around Apalachee Bay surge heights will be magnified and near St Mark, FL values may rise higher than roof levels. In some areas near the head of Apalachee Bay the storm surge will extend many miles inland flooding entire towns as such: St. George Island, St. Vincent Island, Sopchoppy, Carrabelle, Medart, Panacea, and Alligator Point

The damage to the barrier islands along the FL panhandle will be extensive and rival both Ivan, Opal, and Eloise.

NHC Interactive Storm Surge Forecast Inundation Mapping:

https://www.nhc.noaa.gov/refresh/graphi ... n#contents

Winds:
Coastal winds of 115-125mph sustained with gust over 140mph will be likely along the coast of FL from Port St. Joe to Destin including: Seaside, Mexico Beach, Panama City, and Miramar Beach. A larger area of winds of 75-100mph will impact areas from Pensacola to Tallahassee and then well inland over all of the FL panhandle and into much of central and southern GA. Tropical storm force winds will extend across much of northern FL north of Tampa to potentially as far east as Jacksonville and then NE across much of coastal SC and NC.

Winds near the landfall of the eye of Michael will result in extensive damage to even well built structures. Winds will increase 20-30mph at the top of high rise buildings built on the barrier islands. Upper floors of these builds will experience significant damage from both wind driven rain and structural failures.

Rainfall:
Due to the increasing forward motion of the hurricane…rainfall amounts will average 4-8 inches. Inland freshwater flooding is a secondary threat in this hurricane when compared to the storm surge and wind threats.
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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Tue Oct 09, 2018 7:55 am

10092018 mcd0954.gif


Mesoscale Precipitation Discussion 0954
NWS Weather Prediction Center College Park MD
936 AM EDT Tue Oct 09 2018

Areas affected...Central Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 091336Z - 091800Z

Summary...Several lines of thunderstorms tracking through central
to north-central TX will be capable of producing hourly totals up
to 1.5" and may lead to some flash flooding.

Discussion...Recent IR imagery continues to show deep convection
developing across portions of central Texas. Aloft, water vapor
imagery depicts a strong shortwave pushing into west-central TX,
aiding the upper level support. In the low levels, there is a
corridor of high PWATs and moisture transport feeding into the
current convection.

Radar imagery from the area shows hourly rates of 1 to locally 2".
This activity is expected to move eastward over the next several
hours and potentially uptick with building instability. As this
moves into areas with lower FFG (1-hr around 1.5"), some localized
flash flooding will be possible.

Taylor

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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Tue Oct 09, 2018 9:31 am

Severe weather threat growing across W and NW portions of SE Texas this afternoon. Stay weather aware...

10092018 mcd1548.gif


Mesoscale Discussion 1548
NWS Storm Prediction Center Norman OK
1019 AM CDT Tue Oct 09 2018

Areas affected...Parts of central Texas

Concerning...Severe potential...Watch possible

Valid 091519Z - 091715Z

Probability of Watch Issuance...60 percent

SUMMARY...Gradually intensifying convection into early afternoon may
be accompanied by increasing severe weather potential, mainly
strong, potentially damaging wind gusts. This could require a watch
within the next couple of hours.

DISCUSSION...Near the southeastern periphery of stronger cyclonic
mid-level flow (30-50 kt around 500 mb), associated with large-scale
troughing now shifting northeast of the southern Rockies, a line of
thunderstorms is gradually evolving across the Texas Hill Country
southward into the Rio Grande Valley. This appears supported by
inflow of seasonably high moisture content, which may be
contributing to CAPE as high as 2000+ J/kg.

A gradual further upscale growth and intensification seems probable
into early afternoon, as the boundary layer continues to warm ahead
of it, and activity becomes increasingly based within the boundary
layer. Despite trends toward shrinking low-level hodographs with
weakening of low-level flow to the south of the Red River, strong
deep layer shear may contribute to further organization, and it is
possible that the risk for potentially damaging wind gusts could
increase with a strengthening surface cold pool.

Otherwise, mid-level lapse rates appear generally modest to weak,
but there may also be some risk for severe hail. While low-level
hodographs appear to be in the process of becoming modest to weak,
an isolated tornado or two may still not be out of the question.

..Kerr/Grams.. 10/09/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...HGX...FWD...CRP...EWX...
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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Tue Oct 09, 2018 11:16 am

10092018 mcd0955.gif


Mesoscale Precipitation Discussion 0955
NWS Weather Prediction Center College Park MD
105 PM EDT Tue Oct 09 2018

Areas affected...South-Central, Central, and North Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 091704Z - 092200Z

Summary...An extensive band of heavy rain and embedded
thunderstorms is expected to persist in the general vicinity of
the I-35 corridor in Texas into the early-mid afternoon. Localized
areas may see rain rates approach 2 in/hr, which could lead to
flash flooding.

Discussion...Regional radars showed a fairly extensive squall line
extending from the south side of DFW Metro, to near Killeen, to
near Uvalde. The squall line was making steady progress east, but
may begin to slow down as it moves further off a surface cold
front. Visible satellite imagery showed sufficient clearing ahead
of the squall line in central and south-central Texas to generate
strong instability. RAP analysis already indicated MLCAPE of
2000-3000 j/kg ahead of the convection. Hi-res models struggle to
maintain the southern end of this squall line, but given the
available instability and relatively strong convergence along the
associated outflow boundary, it should continue for at least
another few hours. There also appears to be large-scale support
for vertical motion as additional convection was developing in the
low-level inflow region from near Killeen and Austin south to near
Corpus Christi and Port Lavaca. The atmosphere was destabilizing,
but there was also strong upper level divergence noted on RAP
analysis as well. The scattered convection developing ahead of the
main squall line may eventually coalesce, leading to a larger band
of convection in some spots, and thus potentially longer duration
of heavy rain. Estimated rain rates in this region were already
peaking in the 1-2 in/hr range per WSR-88D dual pol and MRMS.
Therefore, rain rates peaking around 2 in/hr seems to be a
reasonable expectation as convection continues. This may lead to
flash flooding, particularly if it occurs over urban areas or in
the vicinity of the typically flash flood prone Balcones
Escarpment.

Further to the north, in North Texas around the DFW Metro Area to
near the Red River, instability was weaker, owing to more dense
cloud cover. This was even true ahead of an outflow boundary, with
some scattered mid-level clouds limiting destabilization in the
I-20 corridor between DFW and Tyler. Nevertheless, as the
afternoon progresses, the RAP shows the LLJ lifting north and the
nose of the LLJ becoming more focused in North Texas. Therefore,
it is possible that convection will become increasingly
concentrated further north and may pose more of a flash flood
threat with time. However, confidence is lower given how far east
the outflow boundary has pushed, and the ongoing cloud cover in
advance of that outflow boundary. Flash flooding will be possible
if convective bands can redevelop in areas that have already
received heavy rainfall this morning (including some parts of the
DFW Metro Area), or if destabilization can occur further north to
increase rain rates.

Lamers

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Re: OCTOBER 2018 - Tracking The Tropics/Fall Cold Front

Postby srainhoutx » Tue Oct 09, 2018 2:33 pm

No change expected regarding to cooler air headed our way throughout the extended period. Next week into early the following week look delightful, temperature wise...
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