Tropical Depression Fifteen forms in the Caribbean
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
Neighbors help a driver to move his vehicle from the flood waters
Reader Comments
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from its previous heading of (9.6degrees west of) WestNorthWest
TS.Mathew's average speed moving between its last 2 reported positions was ~11.3mph(~18.2km/h)
TropicalDepression15
23Sep 06pmGMT - - 13.9n76.2w - - 35mph - - -1007mb - - NHC.Adv.#1
TD.15 becomes TS.Mathew
23Sep 09pmGMT - - 14.0n76.9w - - 40mph - - - 1006mb - - #2
24Sep 12amGMT - - 14.2n77.7w - - 40mph - - - 1005mb - - #2A
24Sep 03amGMT - - 14.0n78.4w - - 45mph - - - 1005mb - - #3
24Sep 06amGMT - - 14.2n79.3w - - 40mph - - - 1005mb - - #3A
24Sep 09amGMT - - 14.3n79.8w - - 50mph - - - 1000mb - - #4
Copy&paste 13.9n76.2w, 14.0n76.9w-14.2n77.7w, 14.2n77.7w-14.0n78.4w, 14.0n78.4w-14.2n79.3w, 14.2n79.3w-14.3n79.8w, pnd, trb, nbw, vqs, 14.3n79.8w-14.96n83.23w into the GreatCircleMapper for a look at the last 12^hours.
Using straightline projection upon the speed&heading averaged
over the 3hours spanning the last two reported positions:
~20hours from now to CaboViejo,Nicaragua
^ The westernmost line-segment is the straightline projection.
As has the Euro and the CMC.
It's possible that the NHC will need to tweak the forecast considerably when they get their new information. They might end up being right all along.
Why I've said since yesterday to keep an eye on the East Pacific (which was skipped over as everyone was so enarmoured with 95L) as that is the low that's travelling in a similar direction to the storm that the models depict.
If you look very carefully at the last few GFS runs, you can see how it transfers. CMC and Euro is harder to pick as it is over 12 hour segments rather than 6, but it does appear similar. You'll note that the low now wants to come over Honduras rather than the Yucatan.
That disorganised area of convection on the East Pacific side could be where the hints are. It's not ITCZ, I don't think. That's much further north according to the Surface Analysis.
Now, it's likely that low - if it forms - will dissipate. However, the energy may not. Whether it's Matthew's remnants which re-fire alone or along with the energy from the East Pacific or it's an entirely new storm (Nicole) is very hard to determine at this point in time.
It's easy to take the line that Matthew will end up being a broad low in the Gulf of Honduras, and perhaps that the easiest line is the correct one. On the other hand, it looks a bit more tricky than that.
You may definitely be on to something there; it'll definitely be interesting to see whether and how your proposed scenario plays out.
Good thinking. Oh, and good morning...
Now, steering current maps, of course, change. We're talking about something that might happen around Monday (at a guess).
However, it's hardly showing a high which would block westward progression which would cause a bounce eastward (as bizarrely shown by the GFDL 12z, for example) and that's if the northward progression was also stopped.
It's unlikely. It'd come from another source.
Neapolitan- I really like the avatar. (smiles) really. (smiles again) (blushes)
So Mathew is following the NFI model this morning. That is the NHC's "low confidence" model. still to far away for us Floridians to use the GI model.
Tick tock tick tock- where's coops and breakfast? Damnit woman a Pup has to EAT!!
Good Morning - was Good Mooning Aqua & ALL
looks like a great day to get the first of the beet seeds in the ground -
watching Matteo like a hawk - be nice if he hit the special box (no land) churned & croaked -- just enough to rock the bouys so some of us could ride Lady of the Gulf or King Neptune (mea culpa, pls. forgive me --sooo addicted to wave)
Matthew??
Pretty good-looking Fella!
Who is Coffee-Monitor, this morning??
(I vote for Surfmom)
Possible, though as I've no idea what the part Matthew will play in it - if it does occur - it'd be harder to show which is him and which is this low (I think the NHC could be aware of it as they're talking about a developing monsoonal low over Central America) than in the case of Hermine where it was relatively straight-forward.
Coalition? That's a new one...
It's harder to see on that one. I've noticed that the non-radiosonde runs have more of a weight towards Matthew continuing as a single entity than the 00z/12z runs. Not by much, but a bit. You can just about see the energy coming over, though.
Low confidence - ompfh
I luv this (sarcastic)
well, makes for a great learning situation
steering by the seat of your pants
or INSTINCT
looks like MaNature is playing Trick or Treat a weee bit early
there's a tweak of amusement when I see humans admit -- they don't know
perhaps - humbling, wow that 4:30Am is showing up already - ODing on Caffiene LOL
Well, it's already happened this year albeit not with a cyclone already there. Matthew's strength will probably play a role as you also see that nothing really ramps him up prior to hitting the Yucatan.
If he strengthens further than expected, he may just end up absorbing whatever's there and continuing on his merry way. If he's around the same weak strength as predicted, that's when the uncertainty comes in.
It's just a theory, after all.
Anything new with Matthew?
some interesting posts this page...poor head - stretching to grasp this stuff...
Latest track has matthew as a TS.
He also seems to be heading WSW into CA, how's he going to become a hurricane there ?
Post some pics of it
Just noticed the last photo on Dr. M's blog, submitted by Trinigirl.
It's been like that, all over Trinidad for quite a while recently.
Looks like we will get a break for a couple of days though.....
Some models keep Matthew moving wnw across the yucatan and into the BOC, and others turn Matthew to the ne just upon approach to the yucatan. The NHC went down the middle of the two with the track... so no models are actually showing the scenario of the current NHC track.
http://raleighwx.easternuswx.com/models/gfs/06zgfs500mbHGHTPMSLtropicalGFSLoop.html
Pottery,
Having seen how your big fish buddy likes to bust your chops, you may want to point him to the last para in this forecast
Morning Pottery! How doth thee fare?
You guys look pretty flooded out.
You and me both. I always go back and read the page or two before. Glad I wasn't on last night.
How's the horses this morning? Beautiful weather here, 73 degrees.
NICE!!
It will give me great pleasure, to point him in that direction.
Matthew has really moved himself along.
Microwave from bout 4 hours ago.
mOrning all
I noticed Trinigirls pictures yesterday, very sad is the state of infrastructure in our country,15 mins or less of haevy rain and its floods.
I vote we start the day with a jigger of your Island supplement in the coffee.... perfect way to great the day
When you feel good & juiced, could you toss a few boulders? Worked the last two times (actually it did)
We've been w/out WAVE for too long..
Though, if Matteo or something, hits the magic box on the map.... our wave drought may end
NASA GEOS-5 Model is close to the NHC scenerio.
Click on the forecast map, select Atlantic at the bottom and then animate.
I got this when clicking your link.
bad bad_referer
Not just bad mind you ;)
True enough!
Unfortunately, the Island is trying to recover from years of Bad Governance. Especially with regard to the maintenance of infrastucture (roads, DRAINS&RIVERS, etc etc).
But we did spend Billions on Bling, (2 Major Summits, several Stadiums, many incomplete glass and concrete super-buildings, and so on)
We have a new Government in place (4 months) and they are struggling to catch-up.
The weather has been unkind....
Good morning. Interesting scenario. I remember one of the models a few days back had pre-Matthew doing what looked like a loop around into the Pacific and then back over Honduras and into the Gulf side again before strengthening and heading north. Very confusting. I had a hard time trying to figure what the heck the model was showing. Well, with this low sitting down below Matthew and the energy in the Pacific, now it makes sense. Good catch.
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