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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Julia & Lisa - Still following the NFI tracks
TS Matthew - track is uncertain... intensity uncertain... trying to scare the bejezzus out of Florida and Texas.
AOI
TS BUSTED FORECAST ALIBI
Actually, it CAN be so because the cut-off low will be setting up near AR/MS, and that combined with the cold front moving through LA/MS next week should block anything from coming to TX or LA or even MS.
Maybe.....MAYBE...if the HWRF materializes and Matthew makes it into the BOC, it MAY attempt a run at Northern/N-Cen MX, but even then it's far more likely to drift WSW into old MX or get absorbed into whatever new system forms out in the Western Caribbean.
Far more likely is the original two scenarios: goes into CenAM and weakens and throws its energy to a secondary system, or stalls just at landfall in Belize/Honduras, then drifts N-NE along the Yucatan border and blows up there. Either way, more than likely, it's going to be either a W FL/FL Panhandle hit (probably more N of Tampa to Big Bend area) or a SE FL rake up the East Coast.
You are entitled to your opinon, of course...and we are just as entitled to say how whack it is, based on the evidence.
Anthony
so, your comment about being over Honduras at 144 hours with the energy back in the picture.
Since I am ignorant on this issue, what does this mean for EGOM? Thanks
+1. As a part time engineer and part time politician, I learned a long time ago about not letting words bother one... get into a heated debate about anything but keep your cool... respect. That's where it's at. Respect. End of lecture.
Great image, Bordonaro. If/once the storm can wrap around and keep that dry air at bay, there is not much standing in the way of RI. It seems to be making good progress on that front.
And a stronger storm, in turn, suggests poleward motion ... i.e. missing Honduras and shooting the gap into the GOM.
This has become a sarcastic crap-flinging blog instead. Where people go to chastise other people for their opinions instead of discussing weather.
Oh wait I am sorry, I'm wrong. It is ok for more and more people to act like jerks on here, but it is not okay to be unhappy about it.
Well firstly, just so we're all clear, I'm no professor lol.
Secondly, all that means is we're just back where we started. The GFS runs a circle and then ends up back where it should have been, but it looks like a bit later in the forecast run. That's why it sits down there even longer and hasn't even moved by Day 10. The runs of the GFS now are starting to become radically different from one-another, making them not very trustworthy. I'll be continuing to watch to see when it finally starts to figure it out.
There very well could be a 2nd system that tries to get involved from behind Matthew, but I doubt the scenario depicted by the GFS.
Part time, So I guess you figured out a way to make people believe what you say? (sorry had to joke with ya!)
Evening everyone!
This is how bad we need the rain.
Is it just me...or do a lot of the early and late models have this thing sitting off Belize/Cancun for days?
I am not 100% sure where Matthew is going, he will move over the highest TCHP in the Caribbean, this will be a big problem,!!
Where is "we" ... I have to much rain... your welcome to it.
When I said we, I was refering to we Virginians, especially here in Richmond.
Where is Roatan if you don't mind me asking?
I admit it, I had to look up Roatan. :) Could be a long rough road for you. Be safe!
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.
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