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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Any further southward deviation would impact circulation greatly... unfortunately Honduras and Nicaragua should start experiencing quite a bit of rain soon and mudslides especially in Honduras as the day progresses due to the convection being sheared to the W/SW by the E shear.
Once it gets to about 85W shear should decrease:
Don't panic ! Don't Panic !.
AL, 12, 2010092412, , BEST, 0, 309N, 431W, 25, 1012, LO, 34, NEQ, 0, 0, 0, 0, 1015, 200, 60, 0, 0, L, 0, , 0, 0, JULIA, S,
IMO it's very hard for models to deal with land interaction. Does anyone know what level of topographic detail is programmed into the models? I imagine it's fairly precise, but do the models "know" about every peak and valley on Hispaniola or in Honduras?
Indeed... pretty much whole E CONUS is pretty much rain deprived due to the Bermuda placement for the past weeks keeping us dry.
Not to be nit picky... (As I make mistakes too!)
But I believe it is Brian Norcross and not Bob.
120930 1436N 08035W 8431 01518 0039 +173 +123 159040 041 035 003 03
14.6
80.6
Earlier run showed another low in the Bahamas.
from its previous heading of (10.9degrees west of) WestNorthWest
TS.Mathew's average speed moving between its last 2 reported positions was ~20mph(~23km/h)
TropicalDepression15
23Sep 06pmGMT - - 13.9n76.2w - - 35mph - - -1007mb - - #1
TD.15 becomes TS.Mathew
23Sep 09pmGMT - - 14.0n76.9w - - 40mph - - - 1006mb - - NHC.Adv.#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
24Sep 12pmGMT - - 14.3n80.7w - - 50mph - - - 1000mb - - #4A
Copy&paste 13.9n76.2w, 14.0n76.9w, 14.2n77.7w-14.0n78.4w, 14.0n78.4w-14.2n79.3w, 14.2n79.3w-14.3n79.8w, 14.3n79.8w-14.3n80.7w, pnd, trb, nbw, vqs, 14.3n80.7w-14.29n83.23w into the GreatCircleMapper for a look at the last 12*hours.
Using straightline projection upon the speed&heading
over the 3hours spanning the last two reported positions:
~8hours from now to Auastara,Nicaragua
* The westernmost line-segment is the straightline projection.
I believe that is Bryan LOL
Going you one further, it's actually Bryan.
The local "hero" of Andrew, but gone downhill since IMO.
Steady as she goes.
hydrus, that is one scary image!!
(~ 29.56 inHg)
Who has it 14.6, ILwthrfan? It was still 14.3 a few minutes back at the NHC's 12Z.
I'll be in my quarters.
For the GFS:
New orography data sets are constructed based on a United States Geological Survey (USGS)
global digital elevation model (DEM) with a horizontal grid spacing of 30 arc seconds
(approximately 1 km). Orography statistics including average height, mountain variance,
maximum orography, land-sea-lake masks are directly derived from a 30-arc second DEM for a
given resolution. Computed global orography data sets are available for three resolutions of 8, 4,
and 2 minutes which correspond to approximately 16, 8, 4 km, respectively.
Link
Were you also saying that next week whether it be Matthew or Nicole might hit Florida?
I do understand your point that the global model consenus shows a tropical system affecting Florida next week, just wondering
I was going to say 14.6 didnt look right , thx for the correction.
NICARAGUA
Wunderground
Bluefields (South of mid coast) not reporting
and Puerto Cabeza (North Coast) not reporting
NOAA -
Bluefields most current 9/23 6pm (EDT)
Puerto Cabeza most current 9/23 6pm (EDT)
HONDURAS
Wunderground
Puerto Lempira (Soutwest coast) not reporting
NOAA
Puerto Lempira most current 9/23 8pm (EDT)
Closest Buoy
Station 42057 - Western Caribbean 16.834 N 81.501 W
I thought you just told IKE to trust the models? Models indicate the panhandle is in at least as much danger as the peninsula, probably more. Check out the AEMN. I guess we only are to trust the models when they indicate what we're already wishing for...
Thanks. That's pretty good resolution. I guess it's a complex interaction to model even if the background inputs are as precise as this.
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