October 2017 - Halloween Forecast/Rain Chances

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Re: October 2017 - Early Week Cold Front/Tracking TS Nate

Postby snowman65 » Thu Oct 05, 2017 4:18 pm

Just like that....it's gone :(
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Re: October 2017 - Early Week Cold Front/Tracking TS Nate

Postby DoctorMu » Thu Oct 05, 2017 7:29 pm

WTF????? GFS, Canadian, Euro, Ensemble have the front washing out over the Hill Country on Tuesday...yet Nate isn't strong :evil:

NOAA is hanging onto some cooling beginning Monday.


Edit: it appears that the front gets hung up in a swath of moisture lingering from Nate, instead of the other way around. Perhaps a shift East for Nate might help our cause.
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Re: October 2017 - Early Week Cold Front/Tracking TS Nate

Postby srainhoutx » Fri Oct 06, 2017 5:28 am

I see some folks a fretting over that cold front. While it may not be as strong as some anticipated, it still looks like the frontal boundary arrives Monday evening into early Tuesday ushering in cooler and drier air and NW breezes Tuesday afternoon into Wednesday. Nate appears to be moving NNW in the Gulf of Honduras this morning and should begin accelerating NNW today into tonight and throughout the day tomorrow before turning NNE prior to landfall somewhere near or just East of New Orleans on East toward Pensacola, Nate looks like a typical monsoonal gyre type storm where all the heaviest rainfall and wind are well to the East of the center of circulation and I expect that trend to continue (much like Cindy in June) right up to landfall. Minimal impacts expected West of the storm including here in SE Texas...unless something dramatically changes today into tonight.
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10062017 06Z GFS 102 gfs_mslp_wind_us_18.png
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Re: October 2017 - Early Week Cold Front/Tracking TS Nate

Postby srainhoutx » Fri Oct 06, 2017 7:08 am

Friday morning briefing from Jeff:

Hurricane Watch is in effect for the US Gulf coast from Morgan City, LA to the MS/AL border

Tropical Storm Watch is in effect from Morgan City, LA to Intracoastal City, LA and from the MS/AL border to the AL/FL border

Storm surge watch is in effect from Morgan City, LA to the AL/FL border including Lake Pontchartrain.

Nate will accelerate across the NW Caribbean and Gulf today and Saturday and landfall on the US Gulf coast early Sunday

Mandatory evacuations are in effect for portions of SE LA outside of hurricane protection levees

Discussion:
The center of Nate has emerged over the waters of the western Caribbean Sea overnight and recent USAF mission indicates the surface pressure has fallen from around 1000mb to 995mb with surface winds mainly to the east of the center near 45mph. Nate is a tropical cyclone embedded within a large monsoon circulation over central America which is preventing the system from developing rapidly at the moment. A NOAA high altitude mission yesterday evening sampled the air mass surrounding Nate and found an extremely moist profile with deep tropical moisture extending up to the 300mb level. Additionally, a powerful low level jet axis will be developing within the southern flank of the monsoon circulation aimed at the SW Caribbean Sea and into the eastern flank of Nate over the next 24 hours which will help to begin to accelerate the system NNW.

Track:
The rapid acceleration of Nate toward the NNW has begun with the forward motion now up to 14mph. There has been some modest changes to the forecast track guidance in the last 24 hours with several models now showing Nate hooking a harder right or NE turn just before landfall over SE LA. Given the west to east direction of the US Gulf coast a deviation of the motion toward the NE prior to landfall could potentially alter the landfall point. Models also continue to indicate a very fast forward motion of 20-30mph over the Gulf of Mexico as Nate is swung NNW/N on the western flank of a building high off the FL east coast and on the NE side of a strong upper level low over the SC Gulf of Mexico and ahead of an approaching cold front over the central US. Nate should reach the NE Yucatan tonight and then then NC Gulf of Mexico on Saturday afternoon and landfall along the SE LA/MS/AL coast early Sunday morning.

Preparations to protect life and property must be completed today along the Gulf coast as conditions will rapidly deteriorate on Saturday.

Intensity:
Nate is in an overall favorable environment, but the competing forces from the larger monsoon circulation that Nate is within may help to mitigate rapid intensification. USAF mission this morning is not finding very strong winds near the center of Nate suggesting the inner core is weak at the moment, however systems over the western Caribbean Sea do not always need much time to develop and Nate could be near hurricane intensity as it approaches the Yucatan later today. Once in the Gulf of Mexico overall conditions appear to continue to favor intensification, with the exception of the increasing forward speed. Nate will become embedded within a very strong mid level SSE flow across the central Gulf of Mexico and while strong winds are likely across the eastern flank of the system, Nate’s fast forward motion may make it hard for convection and strong winds to wrap around the west side. This could help to throw off the balance needed near the inner core for any sort of rapid deepening in favor of more modest intensification.

NHC brings Nate to a 80mph cat 1 hurricane at the 48 hr forecast point, but Nate could continue to increase in intensity up to landfall around 50-54 hrs from now.

Impacts:

Storm Surge:
Storm surge flooding of 4-6 feet above the ground near the coast will be possible over SE LA including the N/W shores of Lake Pontchratrain eastward along the MS/AL coasts including Mobile Bay. Given the exact track over/near SE LA large portions of SE LA outside hurricane protection systems will be covered in sea water…in some cases to several feet deep.

Storm Surge Inundation Map:
http://www.nhc.noaa.gov/refresh/graphic ... n#contents

Winds:
Tropical storm force winds will arrive into SE LA early afternoon on Saturday and build to hurricane force Saturday night and spread inland over MS/AL/western FL panhandle. Core winds of Nate will landfall over SE LA early Sunday morning and then spread rapidly NE across much of MS/AL on Sunday and well into N GA/TN Sunday night. Large areas of power outages will be possible given that Nate’s wind field will move very far inland.

Rainfall:
Due to the rapid forward motion of Nate rainfall amounts of 5-8 inches will be possible along the track of the system with isolated totals up to 15 inches.

SE TX Impacts:
Moisture will be increasing on the NW flank of Nate across the NW Gulf of Mexico today and tonight. A few outer rain bands may approach the upper TX coastal waters tonight into Saturday and a few of these may move inland along the coast.

Winds will increase out of the ENE/NE into Saturday night with speeds on average of 10-15mph inland, 15-20mph along the coast, and 20-25mph across the waters.

Tides are already running 1-2 feet above normal and this will continue with ENE winds and larger swells moving into the coastal waters on Saturday. Could see values push near 3.0-3.5 feet on Saturday of total water which may cause minor overwash near Hwy 124/87 on Bolivar.
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Re: October 2017 - Early Week Cold Front/Tracking TS Nate

Postby DoctorMu » Fri Oct 06, 2017 9:06 am

GFS, Canadian, Ensemble models nudge the front and Nate farther east this morning. Nate is also projected to move faster ahead of the front. Hope this trend continues. Tuesday and Wednesday bring now slightly cooler and drier air. 70s highs are gone, though.
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Re: October 2017 - Early Week Cold Front/Tracking TS Nate

Postby tireman4 » Fri Oct 06, 2017 1:01 pm

Remember, we see this all the time. Models ( especially the GFS) will lose a cold front in a 5-7 day period before it arrives. The pro mets can tell you, models still have a hard time with cool/cold air and timing thereof. Just because it lost it or lessens the intensity does not mean it will not be a cool down. I have learned over my many years of following weather that trends are your friend.
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Re: October 2017 - Early Week Cold Front/Tracking TS Nate

Postby tireman4 » Fri Oct 06, 2017 1:04 pm

XUS64 KHGX 061830
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
130 PM CDT Fri Oct 6 2017

.AVIATION...
VFR. Few CU over the area with dry air draped over the area. Light
easterly winds should veer slightly by 10-30 degrees but still
light. Moist axis associated with the surface trough south of
Louisiana will shift westward and bring an increase in clouds
mainly MVFR CIGS near 12z Saturday to the GLS/IAH area along with
the threat of showers. By 15z Saturday expect SHRA and a few TSRA
along and east of the surface trough axis which should be near an
LBX/HOU/IAH line. Intermittent MVFR CIGS/VISBY 15z Saturday and
beyond with the axis going nearly stationary.
45
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Re: October 2017 - Early Week Cold Front/Tracking TS Nate

Postby snowman65 » Sat Oct 07, 2017 7:45 am

Looking like we may just skip fall altogether and go straight into winter in December sometime...thank you, La Nina...lol.
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Re: October 2017 - Early Week Cold Front/Tracking Nate

Postby srainhoutx » Sat Oct 07, 2017 8:18 am

Saturday morning briefing from Jeff:

Hurricane racing toward the US Gulf coast

Preparations to protect life and property must be rushed to completion across SE LA, MS, AL, and the FL panhandle

Discussion:
Near continuous USAF missions into Nate overnight have revealed a lopsided hurricane with strong winds mainly confined to the eastern side of the circulation. Overall the satellite appearance is not one suggesting rapid intensification and the pressure has only fallen about 4mb since late yesterday evening. There is deep convection near/around the center, but Nate lack a well defined inner core or well defined eyewall which is likely helping to mitigate a more rapid pace of intensification. As Nate arrives on the US Gulf coast this evening the current wind pattern if it holds suggests area west of the center may see very little impact.

Track:
Nate is racing NNW at 22mph on the east side of a building mid level ridge east of FL and an upper level low over the southern Gulf of Mexico and ahead of an approaching deep layer trough over the central US. Nate may turn a little NW for a period today and then back NNW and N this evening. On this track the hurricane will approach and likely make landfall over SE LA (Mississippi River Delta) and then track NNE toward a second landfall on the MS coast. Nate will then accelerate inland over MS/AL Sunday.

Intensity:
Nate is gradually intensifying and while conditions in the Gulf of Mexico are favorable for intensification, the lack of a well defined inner core should preclude significant intensification prior to landfall. With that said, Nate still has 16-18 hours over a very warm Gulf of Mexico and a 90-100mph hurricane at landfall is certainly possible…high end cat 1 or low end cat 2. After landfall, Nate will begin to decay, but the fast forward motion will bring strong winds well inland over much of MS/AL/N GA and TN

Impacts:

Storm Surge:

Major storm surge flooding is likely along coastal MS and AL and into Mobile and Pensacola Bays.

Significant and life threatening storm surge flooding is likely over extreme SE LA and coastal MS/AL/NW FL panhandle. Storm surge values of 5-9 feet above normally dry ground near the coast will be possible over coastal MS and AL including Mobile Bay and the portions of SE LA outside of hurricane risk reduction systems (levees) S and E of the metro New Orleans area. Maximum storm surge values will be found near and just right of the landfall of the center which appears most likely along and east of the SW MS coast or east of the Gulfport, MS area. Water levels currently being forecast will overtop HWY 90 along the MS coast. Given the current forecast track, storm surge values into Lake Pontchratrain are not expected to reach levels of hurricane Issac in 2012.

http://www.nhc.noaa.gov/refresh/graphic ... n#contents

Winds:
Winds of 85-95mph will be possible near and east of the center landfall location especially across the lower MS River Delta and then into coastal MS and AL. Given the fair weak wind field on the western side of the system, winds across metro New Orleans may be significantly weaker than those along the MS coast, however any wobble of the center only a slight distance to the west would bring hurricane conditions to New Orleans.

Rainfall:
Rainfall amounts of 3-6 inches will be possible along the track of Nate as the fast forward motion will help to reduce overall totals.
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Re: October 2017 - Early Week Cold Front/Tracking Nate

Postby DoctorMu » Sat Oct 07, 2017 2:06 pm

Nate is charging along at 27 mph - more like an east coast October hurricane. Lake Ponchatrain is susceptible to that east wind ahead of the center.


The cold front washes out tonight and Sunday and merges with Nate.

A second front moves our way on Tuesday.


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