UPDATE: TROPICAL DEPRESSION SIXTEEN FORECAST SYNOPSIS…ISSUED OCT. 04, 2017…5:20 P.M. EDT

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(T. F. “Storm” Walsh III)

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STORM W’s SEASONAL HURRICANE FORECAST
TOTAL STORMS: 14-16
HURRICANES:       6-8
MAJ. HURRICANES: 3-4

CURRENT TOTALS
STORMS: 15
HURRICANES: 10
MAJ. HURRICANES: 6

U.S. LANDFALLS: 5

Good evening everyone!

I am posting this update, as I will not be updating Saturday, and this system may make landfall early Sunday morning.  I am posting the link for local statements regarding the system, as well as the NWS Hazards and Warnings map, so you may access up to date information on your area.  I will most likely be posting on Sunday evening.  On a side note, no local statement links are available at this time.  The following map will send you to the NHC website, which will contain these links as local statements are issued.

Get up to date tracking maps and advisories from the NHC by clicking the graphic

Tropical Disturbance INVEST 90L had become better organized this morning. and is located east of Nicaragua as Tropical Depression 16.  As of the 5:00 p.m. EDT advisory from the NHC, the following was available on T.D. 16:

5:00 PM EDT Wed Oct 4
Location: 12.5°N 82.5°W
Moving: NW at 7 mph
Min pressure: 1005 mb / 29.68 in
Max sustained: 35 mph

T.D SIXTEEN FLOATER SATELLITE LOOP (CLICK ON IMAGE)

HURREVAC T.D 16 NHC TRACKING AND WIND RADII MAPS

NWS HAZARDS AND WARNINGS DISPLAY (CLICK MAP, THEN CLICK ON YOUR AREA)

Based on my analysis of the current wind shear forecast from the GFS model, indications are that upper level winds improve during the next 24 hours, with the development of an upper level anti-cyclone.  An upper level anti-cyclone is what evacuates the warm air that comes up through the center of the system, as it exits the top of the system.  This is where the strengthening process occurs, as the more air that is evacuated away from the center in the upper atmosphere, the more of a quantity of warm, moist air can be drawn in at the surface.

 

GFS WIND SHEAR FORECAST (CIRCLED AREA INDICATES UPPER ANTI-CYCLONE)


The depression is currently over an area where SST’s are 31C, or 88 degrees F. Analysis of the current OHC indicates OHC values are extremely high in and north of the area, all the way up to or near the Yucatan Channel. 

90L OHC VALUES

Based on the above factors, and depending on proximity to land, I believe Nate should develop within the next 12-18 hours.  I feel there could be a good chance for R.I. (Rapid Intensification) once the system reaches the W. Caribbean, and up through the Yucatan Channel.   Also based on these factors, IF Nate can avoid more of land, and if the wind shear forecast pans out, I cannot rule out a Category ONE or Category TWO hurricane prior to PROBABLE U.S. landfall.  However, I cannot rule out the possibility of a major hurricane at some point in its travel based on the Maximum Potential Hurricane Intensity Modeling.   The ECMWF now indicates a possible CAT 2 to low end CAT3 hurricane at landfall over the Florida Panhandle.  The GFS indicates a moderate to strong T.S. near New Orleans.  While I concur with the NHC intensity forecast at the moment, I feel it may be a little conservative for where the system will be located on Fri.

MAXIMUM POTENTIAL HURRICANE INTENSITY

NHC INTENSITY FORECAST

INIT 04/2100Z 12.5N 82.5W 30 KT 35 MPH
12H 05/0600Z 13.2N 83.1W 40 KT 45 MPH
24H 05/1800Z 14.6N 83.8W 40 KT 45 MPH…INLAND
36H 06/0600Z 16.7N 84.6W 50 KT 60 MPH
48H 06/1800Z 19.5N 85.8W 60 KT 70 MPH
72H 07/1800Z 25.0N 88.0W 75 KT 85 MPH
96H 08/1800Z 30.5N 86.0W 65 KT 75 MPH…INLAND
120H 09/1800Z 35.5N 82.0W 30 KT 35 MPH…POST-TROP/INLAND

 

Based on motion over the past 12 hours, TD 16 is moving very slowly to the NW. Based on analysis of forecast steering maps, I expect this motion to continue for the next 48 hours, with a turn more toward the north thereafter.   There is discrepancy in the global models and track guidance, and this is expected and should be considered preliminary.  However, based on analysis of the 18Z dynamic guidance models, there has been a shift to the left in the guidance.  As of the 5:00 p.m. updated map, the NHC track has shifted slightly left as well. Based on this, my conclusion is, the Florida Panhandle and/or big bend area may still be in the highest probability, however until things become more clear in forecast steering, and dynamic guidance, residents from LA to the Florida Big Bend area should monitor the progress of this system closley.  The NHC has tasked a G4 flight for tomorrow, as well as special soundings for Florida.  This should allow for models to correct and come closer together on track guidance.

18Z TRACK GUIDANCE

GFS FORECAST

ECMWF FORECAST

ECMWF EPS

I will try to have another update late on Sunday.

Elsewhere, I do not expect any Tropical Storm development during the next 7 days.

Have a blessed day!

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

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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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7 Responses to UPDATE: TROPICAL DEPRESSION SIXTEEN FORECAST SYNOPSIS…ISSUED OCT. 04, 2017…5:20 P.M. EDT

  1. originallt says:

    And Sat. afternoon this storm is rocketing Northward.! I think it’s center likely will be on or at the coast by midnight. Everyone down there take extreme care.

  2. originallt says:

    I hope Greg is “hunkering down”. The worst part may be hitting ,or near Mobile Bay and the City.

  3. dellamom says:

    Hurricane Trivia: While the eastern side is typically the worst side to be on for a hurricane or tropical storm, for Southeastern Louisiana, south and west of Lake Pontchartrain, this is not so. New Orleans is below sea level and ringed by levees. Levees also protect neighboring areas. When a storm is approaching and the northern edge crosses Lake Pontchartrain, the winds blow water into the Lake from the river and marshes to the east, threatening communities on the western half of the Lake. As the storm proceeds northward and the winds begin to blow from the north, the accumulated waters in the Lake then blow toward the south and raise the level of the lake along the southern shoreline. Should Nate come on the path currently projected, it would be at the absolute worst position for the Crescent City and her neighbors. Mac, correct me if I am wrong please, but this is the what I have been told all my life, having been raised in Chalmette in St. Bernard Parish.

  4. Dellamom says:

    thank you, Storm. has there ever been a season where the entire Gomez coastline has been hit by hurricanes? if this hits between central La. and ALa., this would be the year.

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