Headings/Angles for Coastal Impact (10am Central update)

[mtm4319]

Hoping you did the math correctly, and used the proper variable distances between longitude, since the earth is indeed a sphere. Not gonna do the math myself to verify, just hope you did it right!

I'm not a math expert, but 315 degrees is one degree north and one degree west. Gulfport is located at 30.37 and 89.09, which is 4.47 degrees north and 4.19 degrees west of the current location. Intuitively, that would be slightly greater than 315 (more northerly than a pure NW heading), and it is at 316.9 degrees. Remembering high school trigonometry, I just used the arctangent of (4.47/4.19), then converted radians (which MS Excel uses) into degrees.

I know that a degree of latitude and a degree of longitude are slightly different at this latitude, but by how much?

[dolebot_Broward_NW]

Close enough I suppose, but if you want to be really technical and very accurate...

1 degree latitude and 1 degree longitude difference at this latitude is not perfectly 315 degrees. It's more like 318°08′43″. This is because as you go north, the difference in distance between longitude degrees decreases from 69 miles @ the equator, to 0 miles at the poles. 3 degrees off might be big enough to make a difference here.

[mtm4319]

At 30 degrees North, a degree of latitude is 69.17 statute miles, and a degree of longitude is 59.96 miles. The 6pm update will be delayed until I take this slight adjustment into account.

[mtm4319]

Okay, I think I've made the necessary corrections.

6pm Central time update

As of 6pm Central time, the 6-hour motion of Dennis was 1.1 degrees North and 0.9 degrees West (a heading of 324.7 degrees). The position of Dennis as of 6pm Central time was 26.1 N and 84.9 W.

Here is the average heading Dennis would need to take from now (6pm Central time) on in order to reach the coast at the positions listed above:

319.6 Gulfport, MS
321.1 Biloxi, MS
323.3 Pascagoula, MS
324.7 MS/AL state line
326.4 Fort Gaines, AL
329.8 Gulf Shores, AL
331.5 AL/FL state line
336.4 Pensacola Beach, FL
341.1 Fort Walton Beach, FL
342.1 Destin, FL

The current 6-hour heading, if sustained until landfall, would take Dennis ashore near the MS/AL state line.

Keep in mind, a NNW (or 330-degree heading) is expected to gradually occur overnight.

My apologies for any mathematical errors I've made that may have misled people.

[mtm4319]

7pm Central time update

As of 7pm Central time, the 6-hour motion of Dennis was 0.9 degrees North and 0.8 degrees West (a heading of 322.4 degrees). The position of Dennis as of 7pm Central time was 26.2 N and 85.0 W.

Here is the average heading Dennis would need to take from now (7pm Central time) on in order to reach the coast at the positions listed above:

319.6 Gulfport, MS
321.2 Biloxi, MS
323.4 Pascagoula, MS
324.9 MS/AL state line
326.6 Fort Gaines, AL
330.1 Gulf Shores, AL
331.8 AL/FL state line
336.9 Pensacola Beach, FL
341.7 Fort Walton Beach, FL
342.8 Destin, FL

The current 6-hour heading, if sustained until landfall, would take Dennis ashore between Biloxi and Pascagoula, MS.

Keep in mind, a NNW (or 330-degree heading) is expected to gradually occur overnight.

[mtm4319]

To shed some light on why the 6-hour heading decreased slightly this hour: the movement from 12pm to 1pm (25.0/84.0 to 25.3/84.2, a .3N/.2W movement) was replaced by the 6pm to 7pm movement (.1N/.1W, which is NW instead of more NNW). However, the 2-hour heading (from 5pm to 7pm) is .3N/.1W, which is 330 degrees. The rolling average of 6-hour headings might begin to move back toward 330 degrees next hour.

[patsmsg]

7pm Central time update

As of 7pm Central time, the 6-hour motion of Dennis was 0.9 degrees North and 0.8 degrees West (a heading of 322.4 degrees). The position of Dennis as of 7pm Central time was 26.2 N and 85.0 W.

Here is the average heading Dennis would need to take from now (7pm Central time) on in order to reach the coast at the positions listed above:

319.6 Gulfport, MS
321.2 Biloxi, MS
323.4 Pascagoula, MS
324.9 MS/AL state line
326.6 Fort Gaines, AL
330.1 Gulf Shores, AL
331.8 AL/FL state line
336.9 Pensacola Beach, FL
341.7 Fort Walton Beach, FL
342.8 Destin, FL

The current 6-hour heading, if sustained until landfall, would take Dennis ashore between Biloxi and Pascagoula, MS.

Keep in mind, a NNW (or 330-degree heading) is expected to gradually occur overnight.

This is a really excellent effort! I love the format, and it makes a lot of sense. None of this is to say that Dennis will continue in a straight line, but it's always nice to know what it's been doing as of late with respect to city-references.

[Frank P]

this is great information, please continue to update if you can...

excellent

[mtm4319]

Just worked it out in Google Earth, and it pretty much confirms my calculations are fairly accurate. Glad to know.





(Hope I'm not breaking any copyright laws... but the interests of public safety might overrule that. )

[mtm4319]

8pm Central time update

As of 8pm Central time, the 6-hour motion of Dennis was 0.8 degrees North and 0.7 degrees West (a heading of 322.8 degrees). The position of Dennis as of 8pm Central time was 26.3 N and 85.1 W.

Here is the average heading Dennis would need to take from now (8pm Central time) on in order to reach the coast at the positions listed above:

319.6 Gulfport, MS
321.2 Biloxi, MS
323.5 Pascagoula, MS
325.0 MS/AL state line
326.8 Fort Gaines, AL
330.4 Gulf Shores, AL
332.2 AL/FL state line
337.5 Pensacola Beach, FL
342.4 Fort Walton Beach, FL
343.5 Destin, FL

The current 6-hour heading, if sustained until landfall, would take Dennis ashore between Biloxi and Pascagoula, MS.

Keep in mind, a NNW (or 330-degree heading) is expected to gradually occur overnight.

Fort Walton Beach and Destin are becoming less and less likely destination possibilities, IMO.

[mtm4319]

[dolebot_Broward_NW]

EXCELLENT work MTM.. Wish I knew how to overlay this stuff into google earth

[mtm4319]

Disclaimer: This is not a forecast; it is an extrapolation of current trends. The current heading can, and probably will, change over time.

9pm Central time update

As of 9pm Central time, the 6-hour motion of Dennis was 0.8 degrees North and 0.6 degrees West (a heading of 327.0 degrees). The position of Dennis as of 9pm Central time was 26.5 N and 85.2 W.

Here is the average heading Dennis would need to take from now (9pm Central time) on in order to reach the coast at the positions listed above:

318.9 Gulfport, MS
320.6 Biloxi, MS
322.9 Pascagoula, MS
324.5 MS/AL state line
326.3 Fort Gaines, AL
330.1 Gulf Shores, AL
332.0 AL/FL state line
337.5 Pensacola Beach, FL
342.7 Fort Walton Beach, FL
343.8 Destin, FL

The current 6-hour heading, if sustained until landfall, would take Dennis ashore between Fort Gaines and Gulf Shores, AL -- somewhere in south Mobile County.

Keep in mind, a NNW (or 330-degree heading) is expected to gradually occur overnight -- and in fact seems to be occurring as we speak.

[mtm4319]

[rtd2]

TOTALLY AWESOME WORK!

[Ixolib]

Looks like he's "stair stepping".

[drezee]

I am sorry to rain on your parade, but you should place a disclaimer on this. Your calculations are wrong!

0.8N and 0.6W is not 327degs!!!
right triangle: 3 4 5
Use this:

sin (Angle) = 0.8 / 1.0 = 53.2degs

270 + 53.2 = 323.2 angle of movement

Please redo all your calculations before you resume.

[mtm4319]

I am sorry to rain on your parade, but you should place a disclaimer on this. Your calculations are wrong!

0.8N and 0.6W is not 327degs!!!
right triangle: 3 4 5
Use this:

sin (Angle) = 0.8 / 1.0 = 53.2degs

270 + 53.2 = 323.2 angle of movement

Please redo all your calculations before you resume.

That was the method I was using at first, before someone noted that a degree of longitude is less than a degree of latitude (69.17 statute miles for a degree of latitude versus 59.96 miles for a degree of longitude). Using your method would place the extrapolated point of landfall a good bit west of where it is shown/estimated on the map.

Woohoo, 100th post!

[Valkhorn]

I am sorry to rain on your parade, but you should place a disclaimer on this. Your calculations are wrong!

0.8N and 0.6W is not 327degs!!!
right triangle: 3 4 5
Use this:

sin (Angle) = 0.8 / 1.0 = 53.2degs

270 + 53.2 = 323.2 angle of movement

Please redo all your calculations before you resume.

A right triangle is only 3, 4, and 5 on a flat surface.

The earth is a curved surface. Plus distances between latitude and longitude points are not always equal.

[air360]

mtm4319..is that a overlay you are using that updated automatically or did you manually imput those to great that graphic?

Edit: I figured out how you did it...you entered the lat/long and marked each place then used the distance tool to pull the line out and over the markers and then saw where it came ashore....at least i think thats how you did it anyways..good maps!