Tropical Depression 18 forms south of Jamaica

By: Dr. Jeff Masters , 3:34 PM GMT on October 22, 2012

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Tropical Depression Eighteen is here, and appears poised to become Tropical Storm Sandy by early Tuesday morning. TD 18 is over very warm waters of 29.5°C, is in a moist environment, and has light wind shear of 5 - 10 knots. These conditions are very favorable for intensification, and TD 18's heavy thunderstorms are steadily organizing into curved spiral bands, as seen on visible satellite loops. An Air Force hurricane hunter aircraft will investigate TD 18 this afternoon.


Figure 1. Morning satellite image of Tropical Depression Eighteen.

Forecast for TD 18
Wind shear is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday night. This should allow for some steady development of TD 18. On Tuesday, a trough of low pressure to the north is expected to pull TD 18 to the north-northeast, which should put the storm in the vicinity of Jamaica on Wednesday and Eastern Cuba on Thursday. The 11 am EDT NHC Wind Probability Forecast gives a 32% chance that TD 18 will be a hurricane by 8 am EDT Wednesday, when the center should be close to Jamaica. Wind shear will rise to a high 25 - 30 knots by Thursday, which should make it difficult for TD 18 to intensify. By Friday, TD 18 should be in the Central or Eastern Bahamas, and wind shear may increase further, making TD 18 more of a hybrid subtropical storm. It is unclear at this point whether or not the trough pulling TD 18 to the north will be strong enough to pull the storm all the way out to sea to the northeast; a very complicated steering environment will develop late this week, and it is possible that a narrow ridge of high pressure could build in over TD 18 and force the storm to the west-northwest, with a potential threat to the Northwestern Bahamas and U.S. East Coast by Saturday, as predicted by the ECMWF model. TD 18 will be capable of bringing heavy rains of 5 - 10 inches, with isolated amounts of up to 15 inches in mountainous areas, to Jamaica and Haiti, Monday night through Thursday. Heavy rains will begin on Tuesday in Eastern Cuba, and spread northwards into the Central and Eastern Bahamas by Wednesday. Heavy rains of 3 - 6 inches can be expected in the Cayman Islands and Dominican Republic, Tuesday through Thursday.

Invest 90L in the middle Atlantic
A small low pressure system (Invest 90L) about 700 miles east-northeast of the northernmost Lesser Antilles Islands is headed northward at about 10 mph. The disturbance has a modest area of heavy thunderstorms, as seen on visible satellite images, and is struggling with cool, dry air from the upper-level low pressure system that it is trying to form underneath. This upper-level low has provided 90L the spin it needs to become a tropical cyclone, though. Wind shear is a moderate 10 - 20 knots, and is forecast to remain in the moderate range until Wednesday morning. This may allow 90L to develop into a tropical cyclone before it encounters high wind shear of 20 - 30 knots on Wednesday. It's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 50% chance of developing into a tropical cyclone by Wednesday morning.

Jeff Masters

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214. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #7
TROPICAL DEPRESSION 25
3:00 AM JST October 23 2012
====================================

SUBJECT: Tropical Depression In Sea East Of Mindanao

At 18:00 PM UTC, Tropical Depression (1004 hPa) located at 9.2N 131.4E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as moving west at 6 knots.

Dvorak Intensity: T2.0

Forecast and Intensity
========================

24 HRS: 10.5N 128.6E - 35 knots (CAT 1/Tropical Storm) Sea East Of The Philippines
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Bonjou from Port-au-Prince...are we going to feel this one?? In the past, some of the most deadly ones didn't hit us directly, just a sideswipe...
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Another powerful blast from sunspot 1598 just occurred, M5 class this time:



Things could get real interesting if that spot holds itself together for another few days when it will be directly facing Earth.
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Member Since: April 29, 2009 Posts: 75 Comments: 14066
Quoting MAweatherboy1:
Um... yeah....



Last year's halloween for the NE was screwed up...this year's ??????
I better get my hurricane plan out.

926 ??? cat 5? lol.
Member Since: April 23, 2011 Posts: 104 Comments: 14871
Lol, center is almost on top of me in the last frame, though it is 40mb weaker.

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Quoting MAweatherboy1:
Um... yeah....



That's an insanely powerful extra-tropical (or tropical?) system.
Member Since: July 8, 2005 Posts: 259 Comments: 23619
Quoting MAweatherboy1:
Um... yeah....

Happy Halloween to 50 million people!!
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Euro at 120...hmmmmmm...interesting
Member Since: September 30, 2008 Posts: 0 Comments: 108
Quoting LostTomorrows:


I wonder if that will be a Nor'easter or a hurricane still? It's not as though it's THAT late in the season, and water temperatures are still quite warm in that area compared to what is average for October, especially along the coast up to and around the Maritimes.

It's interesting to think that if it consolidates enough, it could maintain hurricane/tropical status for longer. But that is quite the doom scenario, no matter how you look at it.

That would definitely be extratropical by the time it got here, but it really wouldn't make a difference. A 926mb low is going to cause mass destruction no matter what it's technically called.
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Post 198 that looks like a Halloween mask.
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Quoting MAweatherboy1:
Um... yeah....



I wonder if that will be a Nor'easter or a hurricane still? It's not as though it's THAT late in the season, and water temperatures are still quite warm in that area compared to what is average for October, especially along the coast up to and around the Maritimes.

It's interesting to think that if it consolidates enough, it could maintain hurricane/tropical status for longer. But that is quite the doom scenario, no matter how you look at it.
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Quoting MAweatherboy1:
Um... yeah....



926mb?!!!!?!

CMC showed a 939mb low. this is crazy.
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Quoting stormpetrol:
TD# 18 could well be a hurricane by late tonight, its just in that sweet spot for this time of year.


That would be sort of insane. I'd project it to become a hurricane in 36 hours or so. needs to build an inner core.
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Quoting MAweatherboy1:
Um... yeah....



If that happens Manhattan would have very serious problems
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Link
Join us
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Um... yeah....

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Quoting Tropicsweatherpr:
12z Euro at 168 hours,wow!!
Member Since: April 29, 2009 Posts: 75 Comments: 14066
12z Euro at 168 hours,wow!!

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Lots of readings now near 1003 mbs flying near 750 feet !. Must be really calm out there LOL
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Good afternoon. I see we have TD 18. It looks pretty good right now I think, recon may find Sandy:



NHC forecast seems very reasonable to me, maybe a tad conservative on intensity after it crosses Cuba.
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Quoting CybrTeddy:


Suspect, was recorded while descending.


Agree a suspect reading
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Is it to early to ask if( Sandy maybe) could pump the ridge?
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Quoting CybrTeddy:


Suspect, was recorded while descending.


Not flagged though but subsequent readings rising
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Quoting kmanislander:
Pressure of 1001.8 and 38 MPH already found and nowhere near the center


Suspect, was recorded while descending.
Member Since: July 8, 2005 Posts: 259 Comments: 23619
New Jersey coast here anxious about the potential for a Nor'Sandy. Prep supplies are a go. Camera a go. Storms like this are very rare, but not without precedent.
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Pressure of 1001.8 and 38 MPH already found and nowhere near the center
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Quoting reedzone:
The 12Z EURO (still running) is wayy off of the model guidance.


Could it be the start of a new trend. Will the other models play monkey see monkey do?
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TD 18 without a doubt is getting its act together. RI in the cards?



On another note if the models pan out I may have to put up with a storm of dynamic and perhaps historic proportions. Snow to my west and wind and rain here in central VA. Crazy and unusual setup.
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So I decorated for halloween! Last time I did that was the year of Wilma! Uggghhhh! I am never decorating again during hurricane season!
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184. 7544
Quoting Tropicsweatherpr:
12z Euro more west.

120 hours.



hmm more are shifting west today interesting
Member Since: May 6, 2007 Posts: 0 Comments: 6694
This is an interesting map. It shows the 925 mb vort displaced well to the West of where the surface center is currently positioned, suggesting that the system may be tilted in height from West to East.

Recon will sort this out.

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Quoting yqt1001:


It happened this year. TD 7 developed and then dissipated, after that TD 8 became Gordon. However, a week or so later TD 7 redeveloped into Helene in the GoM.


I didn't count that in my mind because, as you said, TD 7 did technically dissipate.
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Quoting LostTomorrows:


It's happened before with storms that were declared TD beforehand, and then upgraded to a TS after another TS formed after it did. It's happened recently I think, in 2007 once or twice. Humberto got named before Ingrid even though she formed as a TD sooner on the same day.


It happened this year. TD 7 developed and then dissipated, after that TD 8 became Gordon. However, a week or so later TD 7 redeveloped into Helene in the GoM.
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HH descending now.
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Update from Kingston Jamaica. Light showers periodically from before daybreak this morning. By all indications, this system is ready to dish us our share of HUrricane Season 2012. It will be interesting to see what this system will be by the time i leave out for the gym and get back.
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12z Euro more west.

120 hours.

Member Since: April 29, 2009 Posts: 75 Comments: 14066
The 12Z EURO (still running) is wayy off of the model guidance.
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Quoting caribnewsman:
Question:
If Invest 90L were to become TD#19 and then a tropical storm before TD#18 reaches tropical storm status, would it be named Sandy or Tony?
If the answer to that question is Sandy, and I think it is, does anyone know when the last time storm names were out of sequence with the TD numbers (taking into consideration, of course, that there are no 'Q' storms).


It's happened before with storms that were declared TD beforehand, and then upgraded to a TS after another TS formed after it did. It's happened recently I think, in 2007 once or twice. Humberto got named before Ingrid even though she formed as a TD sooner on the same day.
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Quoting stormpetrol:
TD# 18 could well be a hurricane by late tonight, its just in that sweet spot for this time of year.


I hope not but we have seen it happen before.
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TD# 18 could well be a hurricane by late tonight, its just in that sweet spot for this time of year.
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Quoting superpete:


Ok to be on the edge so long as the twigs & bark dont start 'flying' LOL
Just drove thru S.Sound ,gusty out of the E-NE now at a decent clip
East End is pretty gusty too and seas are getting pretty choppy.
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The aircraft will start descending shortly. Near 15 N now.
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from Levi:

TD 18 will likely be east coast bound if it takes on a wrapped, unbroken comma shape north of the Bahamas and bombs out its NW quadrant, thereby trapping its moisture bubble and dumping the outflow heat north and east of itself, which would help the storm stay west. Otherwise, if the GFS is right and energy splits away from the storm to the east, it will likely follow the stream flow south of the upper low to its east and head out to sea. Still too soon to sell out on either one until we see what the storm looks like in 2-3 days.
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170. Skyepony (Mod)
Quoting jeffs713:

CMC initialized very badly. WAY too far SW.


Most the models initialized badly that run. Check out the 99L model error (0hr) in nm here.
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Quoting superpete:


Ok to be on the edge so long as the twigs & bark dont start 'flying' LOL
Just drove thru S.Sound ,gusty out of the E-NE now at a decent clip


I am at home now. Feels like the typical Xmas breeze. Lovely day out.
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It doesn't get much better than this overhead a tropical system. Well established anticyclone.

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Quoting kmanislander:


We are on the edge of the woods :-).

It may drift West close to 80 but unless the trough is weaker and shallower than forecast I do not see this coming our way at this time.


Ok to be on the edge so long as the twigs & bark dont start 'flying' LOL
Just drove thru S.Sound ,gusty out of the E-NE now at a decent clip
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Quoting CybrTeddy:
90L could, and probably will, be upgraded to TD19 later today. The question will be in that case, which one becomes Sandy, and which one becomes Tony.


TD18 is ramping up, the satellite presentation has improved remarkably since 8 hours ago.


is it possible 90L could make it to TS right away at 5PM ???
Member Since: April 23, 2011 Posts: 104 Comments: 14871
Quoting ncstorm:
the CMC is also back to bombing back over the NC/VA and DC



939 MB.."Elizabeth, Im coming to join you with a CMC doom model"


939mb...this is doom if it verified eventually
Member Since: April 23, 2011 Posts: 104 Comments: 14871
Question:
If Invest 90L were to become TD#19 and then a tropical storm before TD#18 reaches tropical storm status, would it be named Sandy or Tony?
If the answer to that question is Sandy, and I think it is, does anyone know when the last time storm names were out of sequence with the TD numbers (taking into consideration, of course, that there are no 'Q' storms).
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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