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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I'm a Crazy Canuck with ya too Orca, I live in Victoria as well. And I'm crazy because every year I believe the Canucks can take home the Stanley Cup *sigh* Here's to another year of disappointment =D
But anyways your secret is safe with me ;)
At least you are not writing it in Kriol, that can get a little hard to decipher. Always interesting reading a news article where someone is interviewed with a quotation in Kriol.
DOOMCON 1 will be triggered when this system stalls and begins wandering aimlessly in the Western Caribbean, growing like a weed in the rainy season and keeping everyone guessing if the bullseye is on their back or not.
All hands on deck this weekend.
That's funny, you tell me to lighten up, but then take on the serious tone. Whatever, happens all the time.
I'm on Terra Ceia Bay just below the mouth of Tampa Bay and can see the Skyway Bridge and the lighthouse beacon from my balcony. I wonder how they will fare in a major storm. Found this on Wikipedia:
"When the first Egmont Key Light was built in 1848, it was the only lighthouse on the Gulf coast of Florida between Key West and St. Marks. In September 1848 a hurricane covered the island with six feet of water and damaged the new lighthouse. The keeper and his family rode out the storm in a small boat tied to a tree. When the keeper saw the damage to the lighthouse, he rowed off to Tampa and never returned. Another hurricane a few weeks later caused more damage, and beach erosion threatened to topple the tower. A hurricane in 1852 again threatened to topple the tower by undermining it."
5:00 PM AST Thu Sep 23
Location: 17.5°N 28.6°W
Max sustained: 40 mph
Moving: Stationary
Min pressure: 1001 mb
Thank you, Reed. You are good at this and I appreciate it.
Awesome find! Thanks for posting.
As in Central America.
LOL, I understand what REED meant now, I see how he meant CA is Central America in reference to Alex (i.e. had Alex tracked further south). Gotcha.
LOL
Location: 17.5°N 28.6°W
Max sustained: 40 mph
Moving: Stationary
Min pressure: 1001 mb
Central America actually.
POSITION ACCURATE WITHIN 20 NM
PRESENT MOVEMENT TOWARD THE WEST OR 280 DEGREES AT 14 KT
ESTIMATED MINIMUM CENTRAL PRESSURE 1006 MB
MAX SUSTAINED WINDS 35 KT WITH GUSTS TO 45 KT.
34 KT....... 30NE 0SE 0SW 30NW.
12 FT SEAS.. 30NE 0SE 0SW 30NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
He thought someone was ordering eggs when they named him so he had to do a flip.
015L/TS/M
MARK
13.25N/76.56W
I made the same mistake earlier, Tropical Storm Lisa actually.
yup
The high in the Atlantic is soo strong, should keep TD15 along the coastline after entering the East Coast, if it gets there. Who knows, could hit the Panhandle of the trough is weak.
Yes, SCOOORE! This is what I said this morning on my blog:
"I believe Lisa will be a tropical cyclone through the forecast period despite recently weakening to a tropical depression. It has redeveloped some thunderstorms recently, and could regain tropical storm status"
Yes, my 95L and Lisa forecasts this morning are going great. Sorry to celebrate, but I had a recent string of bad luck in forecasting with Igor, Julia, and Karl.
nop we have Tropical Storm MATTHEW all so it say so on the nhc site
It's a TS now...winds at 40 mph.
TROPICAL STORM CENTER LOCATED NEAR 14.0N 76.9W AT 23/2100Z
POSITION ACCURATE WITHIN 20 NM
PRESENT MOVEMENT TOWARD THE WEST OR 280 DEGREES AT 14 KT
ESTIMATED MINIMUM CENTRAL PRESSURE 1006 MB
MAX SUSTAINED WINDS 35 KT WITH GUSTS TO 45 KT.
34 KT....... 30NE 0SE 0SW 30NW.
12 FT SEAS.. 30NE 0SE 0SW 30NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
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