HURRICANE FLORENCE / INVEST 95L SHORT SYNOPSIS…ISSUED SEP 13, 2018…10:20 P.M. EDT

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(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!

I had to make this short, as I am exhausted and need to retire earlier tonight.

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

8:00 PM EDT Thu Sep 13
Location: 33.9°N 76.4°W
Moving: NW at 5 mph
Min pressure: 955 mb / 28.20 in
Max sustained: 100 mph

HURREVAC NHC ERROR CONE AND WIND RADIUS FORECAST

RAMSDIS FLOATER SATELLITE LOOPS (CLICK)

Florence has been slowing down during the day, and continues to slow.  As of 8:00 p.m., the forward motion was NW at 5 mph.  Current Doppler Radar loop imagery however, suggests Florence may have now stalled.  Based on analysis of the forecast ridge and trof pattern, a shortwave trof has weakened the portion of the ridge north and east of the hurricane (seen dipping down in water vapor loop imagery).  This has weakened the steering currents.  This ridge is forecast to remain in place, however in a weakened state, and this should induce a very slow west to WSW motion, as shown in the forecast track.  Based on this, I concur with the NHC track, and the consensus model guidance.  This situation will allow for massive amounts of rainfall to accumulate, and prolong the endurance of storm surge action.

NWS DOPPLER RADAR LOOPS (CLICK IMAGES)

RAMSDIS WATER VAPOR LOOP (CLICK)

The following are forecast rainfall totals for the next 7 days from the ECMWF and GFS models.

Hurricane Florence began weakening very early this morning.  I did some quick analysis this evening to see what could have caused this, as analysis of the various maps (i.e. wind shear forecast, Ocean Heat Content) over the past few days indicated that conditions were highly favorable for Florence to maintain at least category 4 intensity, and should have become a category 5 storm briefly.  Based on analysis going back 12-18 hours, it appears the culprit was wind shear on the southern portion of the hurricane.  It seems that what occurred is, the hurricane and upper level anti-cyclone became displaced from each other, with the center of the upper level anti-cyclone being south of the eye of the hurricane, thus the outflow imparted about 20 knots of shear on the southern periphery.  At any rate, the wind field continues to expand, and an outer eyewall appears to be taking shaped on radar.  Based on this, the hurricane should not change much in intensity if the trend continues.  In addition, shear values are forecast to remain low, and Florence has stalled over the Gulfstream.

Residents should continue to heed ALL NWS statements and warnings.

NWS LOCAL STATEMENTS LINK:
https://www.nhc.noaa.gov/text/refresh/index_hls1+shtml/140031.shtml?

PLEASE, use the following link for the current advisory, which lists all the current hazards associated with Florence:

NHC PUBLIC ADVISORY LINK
https://www.nhc.noaa.gov/text/refresh/MIATCPAT1+shtml/132356.shtml?

Prayers are with everyone in the path of this dangerous hurricane.

INVEST 95L GOMEX DISTURBANCE:

INVEST 95L remains poorly organized.  As of 8:00 p.m. EDT, the center of the disturbance was located approximately near  25.2°N and 95.4°W. The current intensity was 25 kt and the center was moving just north of due west.  Maximum winds were estimated to be 30 mph.  Est. pressure was 1008 mb or 29.77 in.  Based on forecast steering maps, and current track guidance, the disturbance should move on a WNW trajectory until landfall, which should occur either near the TX/MX border, or Hartigen, TX in about 18 hours.

GOES 16 GOMEX SATELLITE LOOP (CLICK IMAGE)

18Z GUIDANCE

Based on analysis of the current shear forecast, upper level winds should improve by tomorrow, with an established upper level anti-cyclone developing just prior to landfall.  Wind shear and upper level winds maps indicate this may be occurring now.  NHC has dropped the probability to 50% for development of a depression.  This COULD become a depression, but at this time, I believe the chances are slim given the time over Gulf waters will be short.  However, a depression is possible, albeit it would be short lived.

BROWNSVILLE DOPPLER RADAR LOOP (CLICK IMAGE)

TEXAS 7 DAY TOTAL RAINFALL FORECAST

ECMWF

GFS

I will NOT have an update tomorrow evening, as my wife and I will be spending her Birthday together.

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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