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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instead of looking at the models, look at how the system develops
if it becomes a stronger system than forecast, it will move more north and east than forecasted, because it would feel the upper level wind pattern and the trough much easier..
if it doesn't become much of anything, it will likely continue to feel the easterlies at the surface, and continue to move westerly, eventually the trough will grab it and push it a little to the north, but if there's not much of anything, it wont really turn..
models latch on to a TS/CAT 1 mostly, so they are taking a scenerio between those two..
if matthew becomes a monster, everyone in the SE U.S may be threathened as the chances of it turning NE should increase dramatically..
AL, 15, 2010092400, , BEST, 0, 141N, 777W, 40, 1005, TS, 34, NEQ, 30, 0, 0, 30,
South tip of fla
This is excellent. Although I would go further out into probable land and say western GOM at less risk than Eastern GOM AS ridge is not expected to relax north of Yucatan hence the 20deg high risk line. so Mathew will stall until front/trough comes and pushes him and whatever comes or forms east of him NE.
If the ridge relaxes over the weekend or is forecast to relax shut it down. If Mathew stay over water until Sat and becomes a CAT II shut it down.
Indeed the storm is intensifying.
As with EWRF, from what i remember, they have been somewhat consistent with their runs. The situation here is complicated due to the entity responsible for that eventual north to north east movement. A cut off low is not teh same as a strong front sweeping through, as was the case with Wilma, making Matthew 's trajectory incomparable.
yep as I suspected, it's going to rapidly intensify tonight.. the conditions are absolutely PERFECT
weak anticylone formed near the center, properly ventilated, over near 90 degree waters, a lot of moisture/energy to work with, a tight core circulation, nothing should stop it from intensifying quickly tonight, NOTHING
Best thing is to simply watch and see, and heed the advisories issued by the NWS, NHC, and your locals.
I'd think that Port Fourchon/Grand Isle would be safe from a direct hit, since everything points to either MX/CentAM or FL...but anything going from, say, the mouth of the Mississippi to Applachicola/Pensacola could bring some nasty gales and high seas over there. I'm still betting on that cold front passing through to protect TX/LA/MS from any real impacts, other than some fresh NE breezes and maybe some squally weather in the deeper waters to our E-SE.
Still, one cannot take any chances, and preliminary plans to evacuate the rigs just in case things do change -- even though it's still quite unlikely -- is a darn good move.
Anthony
That's true, but a surface front is expected to develop with the cut off low, and dig down into North florida.. which is what is eventually expected to turn a stronger system towards the North east
The front wont be as strong as the front that hit wilma, since that was a full fledged arctic front
Make sense,thanks for the info!
Could be 50mph at 11pm if this keeps up.
yep
Plenty of warm water... but that ULL either destroy Matthew... or re-enforce the outflow ?
Oh, you're welcome. I'm glad someone is reading them... ;-)
ATLANTIC REQUIREMENTS
1. SUSPECT AREA
FLIGHT ONE -- TEAL 70 FLIGHT TWO -- TEAL 71
A. 24/1200,1800Z A. 25/0000,0600Z
B. AFXXX 0215A CYCLONE B. AFXXX 0315A CYCLONE
C. 24/0830Z C. 24/1945Z
D. 14.8N 80.3W D. 15.3N 83.0W
E. 24/1130Z TO 24/1800Z E. 24/2330Z TO 25/0600Z
F. SFC TO 15,000FT F. SFC TO 15,000 FT
Thank you. We do have a link to the NHC and we get regular updates. I just like coming on here and reading what people have to say about it. Sometimes I get a better understanding of what's going on here. The blog was going in a bad direction, so i asked the question trying to get some answers on tropical weather. And yo answered me and i thank you for that. When we do evacuate, There are 3 of us that are the last ones to leave. We are also the first people back. It does really take 2 to 3 days to get rigged down and ready to leave. Then a few hours getting anywhere from 50 to 75 men off of this rig.
I do, and I'm almost certain that it will become a hurricane tonight
TFP's are available.
Yeah I did notice forecast temps for next week is ten degrees less in tallahassee, florida. Just don't know the extent to which a storm changes direction with respect to the orientation of a trough.
I would say the latter... far enough away and when he gets under the upper level H, will have near zero affect.
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