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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ROFLMAO, I was going to make a cheap shot on the location... but I don't know if they were with the North or the South... off to google I go.
Can't say what it would be like in the GOM yet, but assuming no land interaction it could easily become a major hurricane while in the NW Caribbean. After that some moderating factors would likely come into play.
Well, then you have two years to practice engineering :)
Actually, I was talking about Tacoman's prediction of a TX landfall being whack. At least, IMHO.
Of course, I've made some whack predictions in my lifetime, so I'm not immune from criticism, either.
Anthony
Yeah and that's what should have folks on the Yucatan very concerned. We're talking potentially feet of rain here if Matthew were to sit around there for just a couple days or more without moving much.
The steering from the high is already starting to break down some and I would not be surprised if the storm were to miss the N coast of Nicaragua / Honduras by a bigger margin than currently forecasted. You can see from the image below how the high has migrated to the East, retreated to the N and suffered erosion of the Western flank.
A track shift to the right is a possibility IMO.
Not good for you:(
I might be getting the hang of this yet... thats what was worrying me also.
what state is that?
Let me send some rain your way...
Here in Trinidad i've got 517mm(20.34inches) for the month of September
120.26 inches since May 14th
who is saying the trough is weak? The forecasted trough is expected to be quite strong and reach into northern Florida
ouch that means i may have a longer time overe water
I don't think the shift will be that dramatic but it may be just enough to allow the storm to benefit from being over that really high TCHP.
Q: at 8PM, how strong will Matthew be?
A. Weak TS (40-50 mph)
B. Moderate TS (51-60 mph)
C. Strong TS (10-70 mph)
D. HUrricane (Cat. 1+)
I vote A.) 50 mph
I won't spend much time on this, what with two named storms swirling about, so I'll just say one thing: while the paper you referenced was received and published in September of 2008, earlier this summer several of that paper's authors retracted their summary and instead noted "The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and [has] became very pronounced over the last three decades...This ice loss appears to be unmatched over at least the last few thousand years and (is) unexplainable by any of the known natural variabilities." (Not that I expect Watts to print that part.)
With that, back to the tropics... ;-)
(P.S. -- That paper--which Watts may not have read--is introduced thusly: "There is clear evidence that over the last 30 years the
Arctic has been experiencing dramatic environmental changes... Most notably, there has been a rapid decline in the
extent and thickness of sea-ice in summer and more recently in winter as well.")
D
Job vacancy obviously filled:
http://www.worshipperiod.com/wp-content/uploads/2010/07/bouncer1.jpg
I agree on all of the points you've made on Matthew. GFS is out on lunch at the moment. I honestly believe the models are not realizing that Matthew could be a stronger system than the model realizes. Models are not good when it comes to intensity, and the SST under Matthew are extremely warm. The stronger this storm becomes, the more WNW or NW movement will occur in my opinion.
I don't like doing the long range thing but if, and I repeat if, this stalls in the Western Caribbean then the West coast of Florida anywhere from the Keys to about two thirds the way to the pan handle is where I would place the cone for now.
Virginia. I will gladly take that rain.
Hey Kman.
Let's hope not...that could end up in a rather potent storm in the NW Caribbean, as the further north the track is, the less land interaction Matthew will have to deal with.
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