HURRICANE FLORENCE FORECAST SYNOPSIS…ISSUED SEP. 12, 2018…10:40 P.M. EDT

Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, and I am solely responsible for the content.  As always, follow the NHC and Local NWS office guidelines, and your local Emergency Management officials for emergency decisions.
(T. F. “Storm” Walsh III)

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StormW’s 2018 HURRICANE SEASONAL FORECAST

TOTAL STORMS: 12 – 13
HURRICANES: 5 – 6
MAJOR HURRICANES: 2 – 3

2018 CURRENT SEASON TOTALS

TOTAL STORMS: 10
HURRICANES: 5
MAJOR HURRICANES: 1

U.S. LANDFALLS: 2

Greetings everyone!

The following information was available on Hurricane Florence as of the 8:00 p.m. intermediate advisory from the NHC:

8:00 PM EDT Wed Sep 12
Location: 31.5°N 73.2°W
Moving: NW at 16 mph
Min pressure: 956 mb / 28.23 in
Max sustained: 115 mph

HURREVAC NHC TRACKING MAP PRODUCTS

FLORENCE SATELLITE LOOP IMAGES (CLICK GRAPHICS)

NWS DOPPLER RADAR WILMINGTON NC (CLICK FOR LOOP)

NWS DOPPLER RADAR LOOP SOUTHEAST (CLICK IMAGE)

Florence is a CAT3 hurricane at the moment with winds at 115 mph.  She has weakened over the past few hours, mainly due to inner core and outer wind field expansion, and due to the eye being centered north of the center of the upper level anti-cyclone.  The wind shear forecast indicates however, the upper level anticyclone becomes better established, with an expanding outflow.  So, during the next 24 hours, as Florence moves over higher OHC, some strengthening could occur.  I do not anticipate significant strengthening base don the fact of the expanding core and outer wind field.  In about 36 hours or so, the hurricane will be leaving the higher OHC, and due to the fact she is forecast to slow, and possibly stall briefly, upwelling of colder shelf waters should cause her to begin the weakening phase.  Regardless, Florence should be a category 3 hurricane at landfall, and I have to concur with the NHC intensity forecast:

NHC INTENSITY FORECAST
INIT 12/2100Z 30.9N 72.5W 105 KT 120 MPH
12H 13/0600Z 32.1N 74.1W 110 KT 125 MPH
24H 13/1800Z 33.4N 75.9W 110 KT 125 MPH
36H 14/0600Z 33.9N 77.1W 105 KT 120 MPH
48H 14/1800Z 34.0N 77.9W 100 KT 115 MPH…NEAR THE COAST
72H 15/1800Z 33.6N 79.2W 70 KT 80 MPH…NEAR THE COAST
96H 16/1800Z 34.0N 81.7W 30 KT 35 MPH…INLAND
120H 17/1800Z 35.6N 83.4W 20 KT 25 MPH…POST-TROP/INLAND

As we know by now, there has been a shift in track and guidance.  This is basically attributed to weakening of the system, and the orientation of the ridge north and NE of Florence.  The eastern half of the ridge is forecast to move in such a fashion (SSW), which in turn should cause the storm to bend left, briefly, and as the ridge retrogrades and orients more east – west, the track should reflect that brief motion to the west, and possibly land fall.  The push toward the SW is most likely due to a very large weakness SSE and east of the hurricane.  You’ll see the ridge blocking her, and the weakness circled in the ECMWF map.  My opinion is, the hurricane should try to begin a loop to head for the weakness.  However, before a loop can be made, the ridge strengthens, and its orientation after landfall becomes such that a WNW and eventually NW motion should occur as shown in the tracking map.  During this west motion, Florence could briefly stall, which will make the rainfall and flooding impacts more severe.  Based on this information, I agree with the NHC track and current dynamic guidance

ECMWF 500 MB NORMALIZED ANOMALY MAP

00Z DYNAMIC GUIDANCE

FROM THE NHC:

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for
* South Santee River South Carolina to Duck North Carolina
* Albemarle and Pamlico Sounds, including the Neuse and Pamlico Rivers

A Storm Surge Watch is in effect for…
* Edisto Beach South Carolina to South Santee River South Carolina
* North of Duck North Carolina to the North Carolina/Virginia border

A Hurricane Warning is in effect for… * South Santee River South Carolina to Duck North Carolina
* Albemarle and Pamlico Sounds

A Hurricane Watch is in effect for
* Edisto Beach South Carolina to South Santee River South Carolina

A Tropical Storm Warning is in effect for…
* North of Duck North Carolina to the North Carolina/Virginia border

A Tropical Storm Watch is in effect for…
* North of the North Carolina/Virginia border to Cape Charles Light Virginia
* Chesapeake Bay south of New Point Comfort

Interests elsewhere in the southeastern and mid-Atlantic states should monitor the progress of Florence.

A Storm Surge Warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline, during the next 36 hours in the indicated locations. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. This is a life-threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.

A Storm Surge Watch means there is a possibility of life- threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm- force winds, conditions that make outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.

HAZARDS AFFECTING LAND

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground if peak surge occurs at the time of high tide…

Cape Fear NC to Cape Lookout NC, including the Neuse, Pamlico, Pungo, and Bay Rivers…9-13 ft
North Myrtle Beach SC to Cape Fear NC…6-9 ft
Lookout NC to Ocracoke Inlet NC…6-9 ft
South Santee River SC to North Myrtle Beach SC…4-6 ft
Ocracoke Inlet NC to Salvo NC…4-6 ft
Salvo NC to North Carolina/Virginia Border…2-4 ft
Edisto Beach SC to South Santee River SC…2-4 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: Florence is expected to produce heavy and excessive rainfall in the following areas…

Coastal North Carolina…20 to 30 inches, isolated 40 inches. This rainfall would produce catastrophic flash flooding and significant river flooding.

South Carolina, western and northern North Carolina…5 to 10 inches, isolated 20 inches. Elsewhere in the Appalachians and Mid-Atlantic states…3 to 6 inches, isolated 12 inches.

WIND: Hurricane conditions are expected to reach the coast within the hurricane warning area late Thursday or Friday. Winds are expected to first reach tropical storm strength on Thursday, making outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

TORNADOES: A few tornadoes are possible in eastern North Carolina beginning late Thursday morning.

SURF: Swells generated by Florence are affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

The following are revised SLOSH Surge data maps for a CAT 3 hurricane, moving to the west a 5 mph.  Both MEAN tide and HIGH tide are shown.  Values are accurate to plus or minus 20%.

CAT 3 HURRICANE SURGE MEAN TIDE

HIGH TIDE

ECMWF AND GFS FORECAST 10 DAY PRECIPITATION FORECAST

NHC FLASH FLOODING POTENTIAL MAP

PLEASE follow your local NWS for impacts and actions to be taken in your area!

LOCAL NWS PRODUCTS LINK:
https://www.nhc.noaa.gov/text/refresh/index_hls1+shtml/130036.shtml

Against my better judgement, I will not be updating on Florence tomorrow evening, but will try to have a real quick post on INVEST 95L in the GOMEX.  PLEASE use the linked Tropical Weather Outlook map for information on the other systems that are ongoing

NHC TWO (LINKED TO NHC HOME PAGE)

Have a blessed evening!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS

 

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About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc. I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.
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2 Responses to HURRICANE FLORENCE FORECAST SYNOPSIS…ISSUED SEP. 12, 2018…10:40 P.M. EDT

  1. originallt says:

    Thanks, Storm. It is now quite a large storm in area, but winds continue to go down. At 12pm EDT thursday , they are down to 105mph. But still really dangerous because of it’s overall size and very slow movement . Still moving NW at 10-12mph, but i guess as you said it should really start to slow down.

  2. Linda Marie Simpson says:

    Thank you Storm aka Thomas Walsh!

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