Tropical Depression Fifteen forms in the Caribbean

By: Dr. Jeff Masters , 7:32 PM GMT on September 23, 2010

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Tropical Depression Fifteen is here, and is destined to become Tropical Storm Matthew by late this afternoon or this evening. An Air Force hurricane hunter aircraft left the storm near 2pm EDT this afternoon, and on their final pass through the strong northeast quadrant of the storm, found a substantial area of surface winds of 40 - 45 mph with their SFMR instrument. Top flight level winds at 500 feet were 48 mph. These winds support upgrading TD 15 to Tropical Storm Matthew. Satellite loops show that TD 15's heavy thunderstorm activity continues to increase in intensity and areal coverage, with several respectable low-level spiral bands in evidence. There is some dry air to the northwest of TD 15, but it is currently not significantly affecting development.


Figure 1. TD 15 at 11:50am EDT 9/23/10, as seen by NASA's Terra satellite.

Forecast for TD 15
An upper-level high pressure system lies to the west of TD 15, near the coast of Nicaragua. The clockwise flow of air around this high will bring a moderate 10 - 20 knots of wind shear over TD 15 today and Friday. There is some dry continental air lying to the northwest of TD 15, and this shear may be able to drive dry air into the storm, slowing intensification and keeping TD 15 below hurricane strength through Saturday morning. By Saturday afternoon, TD 15 will move more underneath this upper-level high, causing the shear to decline. The SHIPS model forecasts that shear will fall to the low range, 5 - 10 knots, Saturday through Monday. This drop in shear should allow for intensification of TD 15 into a hurricane, if the center stays more than 50 miles offshore.

The future track and intensity of TD 15 depends critically upon the storm's interaction with land over the coming days. If TD 15 misses making landfall in Nicaragua and Honduras, and instead skirts the north coast of Honduras, the storm is likely to intensify into a hurricane by Sunday, as indicated in the official NHC forecast. However, if TD 15 spends significant time over or barely offshore of Honduras, the storm will likely stay below hurricane strength. TD 15 is being forced just north of due west by a strong ridge of high pressure. This ridge will keep the storm moving at 15 mph through Saturday. On Sunday, a trough of low pressure diving southwards over the Eastern U.S. will weaken the steering currents over the Western Caribbean and cause TD 15 to slow and turn more to the north. TD 15 will begin a period of slow and erratic movement on Sunday that may last many days, as the storm wanders in the Western Caribbean and over Belize, Honduras, and Mexico's Yucatan Peninsula. If the center of TD 15 spends significant time over water, the storm could easily develop into powerful and dangerous Hurricane Matthew. If the center remains mostly over land, TD 15 will still generate extremely heavy rains over Central America, but remain below hurricane strength. By late next week, the trough of low pressure over the Eastern U.S. may lift out, allowing a ridge of high pressure to build in and force TD 15 westwards across the Yucatan Peninsula and into the Gulf of Mexico's Bay of Campeche. Alternatively, the trough of low pressure over the Eastern U.S. may amplify, drawing TD 15 northwards across Western Cuba and into Florida. A complicating factor may be the development of a new tropical depression in the Central Caribbean 6 - 8 days from now, as predicted by both the GFS and NOGAPS models with their latest 12Z (8am EDT) runs. The uncertainties in the long-range fate of TD 15 are high, and depend strongly on slight variations in its track that determine how much time the storm spends over land. One thing that is virtually certain is that TD 15 will generate very heavy rains over Nicaragua, Honduras, Belize, and Mexico's Yucatan Peninsula Friday through Tuesday that will cause dangerous flooding rains and life-threatening mudslides.

Tropical Depression Lisa
Tropical Depression Lisa continues to churn the waters of the far Eastern Atlantic. By Saturday night, upper level winds out of the west are expected to increase, bringing high wind shear of 20 - 45 knots over Lisa. The high shear may be capable of destroying the storm by early next week. It appears unlikely that Lisa will affect any land areas.

Elsewhere in the tropics
The remnants of Hurricane Julia are still spinning over the far Eastern Atlantic, and are generating some sporadic heavy thunderstorm to the north of the center of circulation. Julia's remains are being given a 10% chance of re-developing by NHC.

Hurricane Karl's moisture causing flooding in Minnesota, Wisconsin
A plume of very moist air associated with what was Hurricane Karl last week has surged northwards over the Central U.S. over the past two days. This moisture is now being lifted over a warm front draped over Minnesota and Wisconsin, and has generated flooding rains in excess of six inches in southern Minnesota this afternoon. Flood warnings and flood watches are posted for a wide swath of the upper Midwest today, including most of southern Minnesota, northern Wisconsin, and Michigan's Upper Peninsula. These types of rain events are called Predecessor Rain Events (PREs), because they typically precede the actual arrival of the rain shield of a tropical storm.


Figure 2. Radar estimated rainfall over Minnesota.

Next post
I'll have an update on TD 15 Friday morning.

Jeff Masters

L 95 21st Sept. 2010 (TriniGirl26)
Neighbors help a driver to move his vehicle from the flood waters
L 95 21st Sept. 2010

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2888. largeeyes
7:59 PM GMT on September 24, 2010
I love the cone from the NHC. No way it ends outside that thing!
Member Since: August 22, 2006 Posts: 0 Comments: 1459
2887. hcubed
3:50 PM GMT on September 24, 2010
Quoting smartinwx:
why are so many messages on here hidden?


Troll activity.
Member Since: May 18, 2007 Posts: 289 Comments: 1639
2886. stormhank
3:12 PM GMT on September 24, 2010
Morning....Does anyone feel October could be an active month for the carribean and GOM?? I fear would could have a couple US hits next month??
Member Since: September 8, 2005 Posts: 0 Comments: 1386
2884. smartinwx
2:51 PM GMT on September 24, 2010
why are so many messages on here hidden?
Member Since: September 22, 2010 Posts: 0 Comments: 88
2882. RobbWilder
2:23 PM GMT on September 24, 2010
Quoting btwntx08:

u know they have a life u know drakoen has college and the same with 23


u know usually when stuff starts to cocern florida they pop up. u know they are both pretty knowledgeable. u know
Member Since: August 3, 2006 Posts: 0 Comments: 154
2881. sarahjola
2:18 PM GMT on September 24, 2010
this morning the news on the front that was expected to pull matthew n. is going to flatten out over e.tx./la. what else could turn mat. n. maybe the front is going to push it s. like the models show mat. doing and then back out into the Caribbean as remnants, and reform once it gets out in water like that image tampaspin posted(2824). i think that post tells the story of mat. best. yesterday the word was that this front was going to be strong, now its not. the models started picking up on this yesterday. which was reflected in the model runs that first started turning it s. or dissipating mat. i think that tampaspins model is awesome. i would like to see a longer range for that model. i do not know much about weather, and i am getting my front information from twc.:)but my opinion comes from what the models started saying yesterday, and what i heard this morning about the front flattening out. just using common sense thinking with the front flattening out,the front might push the storm s. & e. causing mat. to reform once it enters the Caribbean. if i am wrong or way off can someone please explain to me why, and tell me what will be the steering factor for mat.? thanks in advance
Member Since: September 10, 2008 Posts: 0 Comments: 1294
2878. swlavp
2:08 PM GMT on September 24, 2010
Quoting btwntx08:

u know they have a life u know drakoen has college and the same with 23


We know...u know
Member Since: June 16, 2010 Posts: 0 Comments: 117
2876. sailingallover
1:59 PM GMT on September 24, 2010
Quoting RobbWilder:
Where is Drakoen or Hurricane23?
Have not seen Drak for weeks...
Member Since: September 1, 2009 Posts: 23 Comments: 1007
2874. breald
1:59 PM GMT on September 24, 2010
Quoting flsky:

Thanks for your guess. Oh, and thank you for the new addition to my list of dubious vocabulary - "slown." haha


Leave him be he has been watching too many Sarah Palin interviews....LOL.

Taco back away from fox news before it is too late.
Member Since: May 28, 2008 Posts: 38 Comments: 5303
2871. sailingallover
1:57 PM GMT on September 24, 2010
The little disturbance at 57W 13N is what is supposed to run into the Low pressure area that is left by Mathew. And since it looks like his convection is getting sheared off to the W because the upper level winds are stronger then the low level at least for the moment he will be relatively weak happily for Honduras/Roatan/Belize
Member Since: September 1, 2009 Posts: 23 Comments: 1007
2870. RobbWilder
1:57 PM GMT on September 24, 2010
Where is Drakoen or Hurricane23?
Member Since: August 3, 2006 Posts: 0 Comments: 154
2869. Couillon
1:56 PM GMT on September 24, 2010
Quoting jasoniscoolman2010xo:
GOING TO HIT LAND SOON..

I thought matthew's coc was pounding Honduras.
Member Since: August 8, 2010 Posts: 0 Comments: 167
2868. BobinTampa
1:55 PM GMT on September 24, 2010
NEW BLOG
Member Since: August 14, 2008 Posts: 0 Comments: 546
2867. Neapolitan
1:55 PM GMT on September 24, 2010
NEW BLOG
Member Since: November 8, 2009 Posts: 4 Comments: 13611
2864. flsky
1:54 PM GMT on September 24, 2010
Quoting tacoman:
guys its pure and simple matthew has no where to go but over land..he hasn't slown down and continues to move a little n of due west...matthew will be on shore in hondouras and continue to truck through beliez causing copious amounts of rain im saying 25 inches is not out of possibility..it will then go over the yucatan where if he is lucky he will make it all the way to the boc loking like a wounded duck.....this will be late tuesday or wednesday if this happens..i think by that time the cut off low centered over the se will be out and the high will be building back in...thats the way i see it now ...i have been 100% on the money...imo matthew doesnt survivie the long track over land...which is going to pain all you fla people...be patient you may get nikki

Thanks for your guess. Oh, and thank you for the new addition to my list of dubious vocabulary - "slown." haha
Member Since: October 24, 2006 Posts: 0 Comments: 2047
2863. Times2
1:54 PM GMT on September 24, 2010
Only time will tell how many times someone on the blog says "only time will tell", lol. Sorry it's just funny to me...does any of us have a job?
Member Since: September 11, 2008 Posts: 0 Comments: 153
2862. Grothar
1:54 PM GMT on September 24, 2010
If Matthew is fizzling, no one told him. Look at those incredible cold cloud tops.

Member Since: July 17, 2009 Posts: 71 Comments: 26889
2859. CyclonicVoyage
1:54 PM GMT on September 24, 2010
Quoting Times2:
If only we had someone on here who KNEW WHAT THEY WERE TALKING ABOUT!!!!!! There is no scenario right now that has any solid validity. JMO


I haven't seen anyone discuss any scenario solidly. There is still extreme differences in the models and equal chances of Matthew dying over CA or a Cat 5 developing in the Gulf of Honduras. I personally prefer the GFS's handling of Matthew and how this will all evolve. A lot of opinions flying around today as there are many options on the table. However, at this point Matthew is still disorganized enough to not strengthen all that much over the next 24hrs, again IMO.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
2856. Dakster
1:52 PM GMT on September 24, 2010
Quoting Orcasystems:
Matthew is only taking the southern track long enough to get under the Box :)





It is almost like it knows... Somehow.
Member Since: March 10, 2006 Posts: 0 Comments: 10572
2855. FSUCOOPman
1:51 PM GMT on September 24, 2010
Quoting FLdewey:
Geez hopefully this thing is out in 16 days... but Dizzneee rarely closes.... they bolt down the tea cups pretty securely.


Shoot, that far out, I'd be worried about one of these other supposed systems that's going to hit in FL in October.
Member Since: August 29, 2008 Posts: 0 Comments: 376
2852. reedzone
1:51 PM GMT on September 24, 2010
Soooo the GFS creates a Superstorm out of Matthew or Nicole. Does the same thing it wanted to do with Wilma in 2005.
Member Since: July 1, 2008 Posts: 13 Comments: 7423
2851. Grothar
1:48 PM GMT on September 24, 2010



Member Since: July 17, 2009 Posts: 71 Comments: 26889
2850. sailingallover
1:48 PM GMT on September 24, 2010
Mathew is the topic of the day but this si really interesting(to me as a sailor anyway).
Lisa has reversed the trade winds below below 15N between 30-45W. Now yes a hurricane always changes them as it go's by but this is a more sustained event over a longer swath of ocean since Lisa has just been sitting there of the CV islands
look at the low level winds here
http://www.ssd.noaa.gov/goes/east/tatl/loop-rgb.html
Member Since: September 1, 2009 Posts: 23 Comments: 1007
2847. kimoskee
1:46 PM GMT on September 24, 2010
Met Service of Jamaica

NEWS RELEASE
September 24, 2010 – 5:00 a.m.

***TROPICAL STORM MATTHEW MOVING QUICKLY WESTWARD TOWARD CENTRAL AMERICA***

*** LISA MOVING NORTHWESTWARD ***

At 4:00 a.m. the centre of Tropical Storm Matthew was located near latitude 14.2 degrees north and longitude 79.3 degrees west or about 445 kilometres east of Puerto Cabezas, Nicaragua.

Matthew is moving toward the west near 28 km/h. This general motion is expected to continue for the next 48 hours. On the forecast track, the centre of the Matthew is expected to be near the Nicaragua/Honduras border on Saturday.

Maximum sustained winds are near 75 km/h, with higher gusts. Strengthening is forecast during the next 48 hours and Matthew could become a hurricane today.

Showers and thunderstorms from the outer bands of Matthew are forecast to continue affecting the cays and banks south of Jamaica today and tonight. Sections of southern parishes are expected to experience increased rainfall today and tonight as the system moves south of the island.

Fishers and other marine interests, particularly over southern waters, are still being advised not to venture far from port as thunderstorms, above-normal wave heights and strong gusty winds are likely.

The Meteorological Service will continue to monitor the progress of this system.

The Meteorological Service will continue to monitor the progress of this system.

Meanwhile...

At 4:00 a.m. the centre of Tropical Storm Lisa was located near latitude 18.4 degrees north and longitude 27.7 degrees west or about 475 kilometres northwest of the Cape Verde Islands.

Lisa is moving toward the northeast near 7 km/h and a turn toward the north and north-northwest is expected tomorrow with an increase in forward speed.

Maximum sustained winds are near 65 km/h, with higher gusts. Lisa could strengthen slightly today but is expected to weaken to a Tropical Depression over the weekend.


Tropical Storm Lisa is not a threat to Jamaica.
cdj
Member Since: August 17, 2008 Posts: 0 Comments: 672
2846. Matt1989
1:46 PM GMT on September 24, 2010
Looks like matthew is crashing right into the Yucatan and fizzling.
Member Since: November 8, 2009 Posts: 0 Comments: 137
2845. TampaSpin
1:46 PM GMT on September 24, 2010
Quoting Times2:
If only we had someone on here who KNEW WHAT THEY WERE TALKING ABOUT!!!!!! There is no scenario right now that has any solid validity. JMO


Try the blog down the road its really good. LOL...Actually anyone that claims they know what Matthew will do is clueless right now. That is a fact!
Member Since: September 2, 2007 Posts: 179 Comments: 20448
2844. GS121
1:46 PM GMT on September 24, 2010
Quoting FLdewey:
Geez hopefully this thing is out in 16 days... but Dizzneee rarely closes.... they bolt down the tea cups pretty securely.
mostly talking about any storms behind matthews. hope they will be effecting land after the trip this far out & not even formed yet
Member Since: September 11, 2010 Posts: 0 Comments: 24
2843. kimoskee
1:46 PM GMT on September 24, 2010
Met Service of Jamaica

September 25, 2010 at 5:00 a.m.

LOCAL WEATHER FORECAST

SIGNIFICANT FEATURES…Spiral bands associated with Tropical storm Matthew south of Jamaica.

Comment
Comment… Outer rain bands associated with Tropical storm Matthew are expected to produce increased rainfall especially over southern parishes today as the system moves westward away from Jamaica.


24-HOURS FORECAST
This Morning… Cloudy with outbreaks of showers and thunderstorms mainly over southern parishes.
This Afternoon… Cloudy with outbreaks of showers and thunderstorms across sections of most parishes.
Windy along southern coastal areas.
Tonight… Cloudy with isolated thunderstorms.

3-DAYS FORECAST (after tomorrow)
Sat… Isolated morning showers across eastern parishes. Scattered showers and thunderstorms across most
parishes during the afternoon.
Sun&Mon… Widespread showers and thunderstorms across the island.

Regionally… Tropical storm Matthew located 390 kilometres east of Puerto Cabezas, Nicaragua.
Tropical storm Lisa located 475 kilometres northwest of the Cape Verde Islands.

cdj
Member Since: August 17, 2008 Posts: 0 Comments: 672
2841. CyclonicVoyage
1:44 PM GMT on September 24, 2010
Quoting MahFL:


That output has the low too far north over Honduras.


We'll see how it plays out today and tomorrow, Mattie is still taking in some shear today and multiple LLC's were noted on the 5am from the NHC.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
2839. GS121
1:42 PM GMT on September 24, 2010
Quoting cat5hurricane:

Yeah, we're keeping an eye on the Gulf Coast, Central America, and NOW perhaps the Mid-Atlanic down the road. Let's hope not any of the three!

I personally do not see him surviving his run-in with the rugged terrain of Hunduras; but by no means am I letting my guard down for anybody just yet.



leave for walt disney world in 16 days. live on the coast where IVAN hit in alabama. i know there is still a chance of a hit in alabama now but how much of a chance to you think?

regarding disney, hopefully with it being 16 days out, think the most that will happen in orlando might be rain?
Member Since: September 11, 2010 Posts: 0 Comments: 24
2838. breald
1:41 PM GMT on September 24, 2010
Quoting cat5hurricane:

Yeah, we're keeping an eye on the Gulf Coast, Central America, and NOW perhaps the Mid-Atlanic down the road. Let's hope not any of the three!

I personally do not see him surviving his run-in with the rugged terrain of Hunduras; but by no means am I letting my guard down for anybody just yet.



Me either. Only time will tell.

Member Since: May 28, 2008 Posts: 38 Comments: 5303

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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.