Dangerous Caribbean disturbance 95L close to tropical storm strength

By: Dr. Jeff Masters , 1:57 PM GMT on September 23, 2010

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A tropical wave (Invest 95L), moving westward at 15 mph though the south-central Caribbean, will bring gusty winds and heavy rain squalls to the northern coasts of Colombia and Venezuela this morning, as well as the Netherlands Antilles Islands. This disturbance will bring dangerous flooding rains to the countries bordering the Western Caribbean this weekend, and may also be a threat to the U.S. Gulf of Mexico coast late next week. A hurricane hunter aircraft is in 95L, and found a large region of surface winds of 35 - 45 mph to the east of 95L's center. If they find a closed circulation, 95L will be upgraded to Tropical Storm Matthew today. Satellite loops show that heavy thunderstorm activity has increased markedly in recent hours, with a solid curved band of intense thunderstorms growing to the northeast of 95L's center. Low-level spiral bands are also developing to the southeast of the center, but a closed surface circulation is not yet obvious from satellite imagery.


Figure 1. Morning satellite image of 95L.

Forecast for 95L
An upper-level high pressure system lies to the west of 95L, near the coast of Nicaragua. The clockwise flow of air around this high will bring a moderate 10 - 15 knots of wind shear over 95L today. By Friday, 95L 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, by Friday afternoon. This drop in shear may allow for rapid intensification of 95L as it approaches landfall near the Nicaragua/Honduras border on Friday night and early Saturday morning. NHC is giving the disturbance an 80% chance of developing into a tropical depression by Saturday.


Figure 2. Forecast track of 95L from an ensemble of runs of the GFS model done at 2am EDT this morning.

The future of 95L depends critically upon the storm's interaction with land over the coming days. If 95L 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 Monday, as predicted by last night's 00Z (8pm EDT) run of the GFDL model. However, if 95L spends significant time over Honduras, as predicted by the latest 06Z (2am EDT) run of the GFDL model, the storm will likely stay below hurricane strength. 95L 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 95L to slow and turn more to the north. 95L 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 95L spends significant time over water, the storm could easily develop into powerful and dangerous Hurricane Matthew. If the center remains mostly over land, 95L 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 95L 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 95L northwards across Western Cuba and into Florida. The uncertainties in the long-range fate of 95L are high, and depend strongly on slight variations in its track that determine how much time the storm spends over land. One measure of the uncertainty in 95L's future track can be gained by viewing the ensemble forecast from the GFS model. An ensemble forecast is generated by taking the initial conditions in the atmosphere and making slight variations in the temperature, pressure, and humidity fields. Twenty or so tweaks of the initial conditions are made, and the GFS model run twenty separate times for each new set of initial conditions. The resulting ensemble of model runs gives one an idea of how sensitive the future track of the storm might be to errors in characterizing the initial state of the atmosphere. As one can see from this morning's GFS ensemble run (Figure 2), there are a wide range of possibilities for where 95L might go. The main thing I am confident of at this point is that 95L will generate very heavy rains over Nicaragua, Honduras, Belize, and Mexico's Yucatan Peninsula Friday through Tuesday that will likely 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. There are no other threat areas to discuss, and none of the models is calling for development (except for 95L) over the next seven days.

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 morning. Flood warnings and flood watches are posted for a wide swath of the upper Midwest today, including most of Minnesota, northern Wisconsin, and Michigan's Upper Peninsula. The latest forecast discussion from the NWS office in Minneapolis notes that the forecast amount of moisture in the air this afternoon is similar in magnitude to the all-time record for this time of year (set on September 2, 1953.) These kinds 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 3. Radar estimated rainfall over Minnesota.

Next post
I'll have an update on 95L later today. The timing will depend upon what the Hurricane Hunters find.

Jeff Masters

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1223. hydrus
2:26 AM GMT on September 24, 2010
Lisa is struggling.
Member Since: September 27, 2007 Posts: 1 Comments: 21086
1222. hydrus
2:25 AM GMT on September 24, 2010
Member Since: September 27, 2007 Posts: 1 Comments: 21086
1221. hydrus
2:24 AM GMT on September 24, 2010
Member Since: September 27, 2007 Posts: 1 Comments: 21086
1220. hydrus
2:23 AM GMT on September 24, 2010
Some green in ther..
Member Since: September 27, 2007 Posts: 1 Comments: 21086
1219. HurricaneHunterJoe
8:49 PM GMT on September 23, 2010
TD#15 LOOKING HEALTHY
Member Since: September 18, 2010 Posts: 0 Comments: 5220
1218. HurricaneHunterJoe
8:41 PM GMT on September 23, 2010
Ithink it has
Member Since: September 18, 2010 Posts: 0 Comments: 5220
1217. HurricaneHunterJoe
8:38 PM GMT on September 23, 2010
I have come to understand that a hurricane that moves very slowly or stalls usually weakens due to upwelling of cooler waters from below. Question. If a hurricane were to stall over an area where the depth of warm water is very very deep, would the upwellinf effect cause it ti weaken,maintain,or strengthen itself?? Thank You
Member Since: September 18, 2010 Posts: 0 Comments: 5220
1215. betapaul
8:14 PM GMT on September 23, 2010
Quoting ConchHondros:


You mean to say it caters to the lowest common denominator? Sweet sign me up! Oh wait, I have a degree...never mind.


And you're sooo wise because of it...
Quoting swlavp:
1072. betapaul

There are some very knowledgable people on here..But to hang on every word anybody says in a weather blog is rather irresponsible I would think..


I wouldn't call it irresponsible. Maybe putting a little bit too much faith into one man, but I can see what you mean.

I just like how he didn't say anything without backing it up with solid data and an explanation that us without degrees (which apparently are made fun of) can understand.

There are several VERY knowledgeable people that comment, but very few really explained their comments to a degree that noobs could comprehend.

He wasn't quick to state facts like he knew it all, but instead offered his opinion based on the data acquired at that time. That's rare here...

I don't even know what happened so I'm just spouting off what I DO know (which isn't much).
Member Since: September 4, 2009 Posts: 0 Comments: 13
1214. xcool
8:03 PM GMT on September 23, 2010
newwwwwwwwwwwww blogggggggggggggggggggggggggggggggggggggggg
Member Since: September 26, 2009 Posts: 2 Comments: 15649
1213. HurricaneHunterJoe
8:02 PM GMT on September 23, 2010
LIKE BATHTUB WATER
Member Since: September 18, 2010 Posts: 0 Comments: 5220
1212. Orcasystems
8:00 PM GMT on September 23, 2010
Complete Update


AOI
AOI AOI AOI

AOI AOI AOI

TS BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
1211. islander101010
7:59 PM GMT on September 23, 2010
just checking in for the reed forecast bring it on
Member Since: September 11, 2010 Posts: 1 Comments: 4533
1210. AnthonyJKenn
7:50 PM GMT on September 23, 2010
Oh...and time to refresh, folks. New blog entry now up.


Anthony
Member Since: September 20, 2005 Posts: 0 Comments: 206
1209. TropicalBruce
7:48 PM GMT on September 23, 2010
It looks like Honduras/Yucatan may take the brunt of Matthew-to-be. If this were mid-October or later, I'd say that Florida would have to watch this one closely, but the troughs aren't quite as strong in late September as they will be later in the year. Unless this system slows down in forward speed soon and with a trough not settling into the east coast of the U.S. until Sunday, I would tend to think that Florida will be bypassed in favor of points further south.
Member Since: May 10, 2009 Posts: 0 Comments: 114
1208. AnthonyJKenn
7:48 PM GMT on September 23, 2010
Quoting atl134:
On that plot Dr. Masters posted of the GFS ensemble... is the white line the GFS ensemble forecast or is it the... base one from which all the other initializations are altered from? I'm wondering since I sorta would expect it to be near the middle of the ensemble cluster, at least for the first couple days.


The white line is actually the official operational GFS model run forecasted path.

The other ensemble model paths are alterations to the operational run based on tweaks to particular data information being off from the original. They are there mostly to compare if something deviates from the original forecasted model path.


Anthony
Member Since: September 20, 2005 Posts: 0 Comments: 206
1207. pinehurstnc
7:47 PM GMT on September 23, 2010
Quoting Tazmanian:




lol
seems all the smart ones are left,,too bad reno,, tell me when the last hurricane hit reno?
Member Since: August 13, 2009 Posts: 0 Comments: 59
1206. unf97
7:47 PM GMT on September 23, 2010
Good afternoon everyone.

Well, TD 15 on satellite imagery is looking very impressive this afternoon. This cyclone is really spinning up very quickly, which was always my biggest concern as the system is now really drawing and tapping that deep tropical moisture from the SW Caribbean and now the Eastern Pacific. This is going to become a very large cyclone and my heartfelt prayers go out to the people of Honduras, Nicaragua, Belize and the Yucatan Peninsula as the threat of severe flooding looms big in those countries this weekend. Matthew will slow to a crawl this weekend dumping copious amounts of flooding rains especially in the mountainous terrain of the Central America region.

For the first time this season, the Gulf coast and the Florida peninsula especially really have to start thinking about making preparations of a significant tropical cyclone affecting the region. We still have about a week at least before any possible CONUS impact. But suffice to say, this hurricane season is indeed living up to the pre-season expectations of being an active one indeed. I am afraid that we probably will have at least 3-4 other cyclones to develop later into October into the November. But, we will cross that bridge when it occurs.


We just now have to monitor closely what future Matthew will do in the coming days and follow the golden rule: Pray and hope for best, but prepare for the worst.

Member Since: September 25, 2007 Posts: 0 Comments: 1193
1204. CosmicEvents
7:45 PM GMT on September 23, 2010
YOU'RE IN THE WRONG BLOG!!!!!!
NEW BLOG!
Member Since: August 3, 2005 Posts: 10 Comments: 5562
1203. seflagamma
7:43 PM GMT on September 23, 2010
Quoting mx3gsr92:
I asked this yesterday but was not successful in getting any feedback. I'm heading to Cozumel/Cancun for a week vacation starting Sunday. Could someone give me an idea of what to expect? Should I not go? Anybody have a similar experience? Sorry for asking again. Thanks.


not sure if anyone has answered you yet but sounds iffy to me, but if the storm misses that area there is no need to miss your vacation.
just wait and watch a few more days.. this storm could possibly fizzle out, who knows at this point. Most resorts will allow you to cancel at the last minute if they go under a warning.
Member Since: August 29, 2005 Posts: 298 Comments: 40901
1202. ecflweatherfan
7:42 PM GMT on September 23, 2010
NWS MLB 7-day forecast: this is for next Thursday, and note they had alotted for some increase in the pressure gradient (denoting "Breezy" conditions).

Thursday...Partly cloudy with a chance of showers and a slight chance of thunderstorms. Breezy. Highs in the upper 80s. Chance of rain 40 percent.
Member Since: March 19, 2010 Posts: 0 Comments: 1147
1201. Fla55Native
7:41 PM GMT on September 23, 2010
Thanks for the link Bordonaro. I found the same info while I was waiting. A bit lazy on my part. I had never heard of the Hebert Box before.
Member Since: August 25, 2008 Posts: 0 Comments: 65
1200. caribouqueen
7:41 PM GMT on September 23, 2010
Levi, I'm a big fan of your blog - usually hide in the background and just watch (I live in FL so I always worry about another hit) and learn - but thanks - I am learning a lot from you!
Member Since: August 26, 2010 Posts: 0 Comments: 2
1199. StormChaser81
7:41 PM GMT on September 23, 2010
Quoting Max1023:


I mean the wee hours of the morning, right before sunrise. D-Min is right around sunset, so about 4-5am Est.


Understood and I agree. =)
Member Since: August 11, 2008 Posts: 0 Comments: 2315
1198. kshipre1
7:40 PM GMT on September 23, 2010
all will be fine Jeff. your wedding will be great. in reality though, just be careful of the tropical systems as we all know how October can be in Florida.

Good luck!
Member Since: July 12, 2010 Posts: 0 Comments: 1130
1197. Cotillion
7:39 PM GMT on September 23, 2010
Quoting Tazmanian:



i think they will upgrade it too Matthew at 8 or 11pm


11pm's probably a good bet.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
1196. HurricaneHunterJoe
7:39 PM GMT on September 23, 2010
WHO KNOWS?
Member Since: September 18, 2010 Posts: 0 Comments: 5220
1195. Stormchaser2007
7:38 PM GMT on September 23, 2010
Member Since: June 9, 2007 Posts: 4 Comments: 15884
1194. kwgirl
7:38 PM GMT on September 23, 2010
Quoting usa777:


"the sea was angry my friend"
And our anchor dragged!
Member Since: March 28, 2008 Posts: 0 Comments: 1532
1193. Patrap
7:38 PM GMT on September 23, 2010
TD-14 RGB

Member Since: July 3, 2005 Posts: 423 Comments: 127975
1192. Bordonaro
7:38 PM GMT on September 23, 2010
Quoting BaltOCane:


look at the lat/long..... that's Lisa.

Sorry, I corrected my original post everyone..
Member Since: August 25, 2009 Posts: 20 Comments: 6785
1191. robert88
7:37 PM GMT on September 23, 2010
The Caribbean and GOM season has just begun. Be prepared for a roller coaster ride for the next 4 weeks with the MJO coming on strong in that region. Even if TD 15 doesn't hit the US.. it won't be last storm down there.
Member Since: May 22, 2010 Posts: 0 Comments: 907
1190. reedzone
7:37 PM GMT on September 23, 2010
REED Forecast Model Run is in process right now...
Member Since: July 1, 2008 Posts: 13 Comments: 7365
1189. BaltOCane
7:37 PM GMT on September 23, 2010
Quoting Bordonaro:

Welcome TS Matthew. Please behave and do no harm..


look at the lat/long..... that's Lisa.
Member Since: May 19, 2009 Posts: 0 Comments: 481
1188. Bordonaro
7:37 PM GMT on September 23, 2010
Quoting Fla55Native:
Thanks for the answer Victoriahurricane, but the question remains, what is a Hebert Box, please?

Hebert Box link below :O):
Link
Member Since: August 25, 2009 Posts: 20 Comments: 6785
1186. victoriahurricane
7:36 PM GMT on September 23, 2010
Quoting GoodOleBudSir:


Now that is harsh!..LOL


Damn freaking typo lol, sorry sammy that's an oops on my part.
Member Since: October 16, 2008 Posts: 0 Comments: 544
1185. CosmicEvents
7:36 PM GMT on September 23, 2010
NEW BLOG!!!!!
Member Since: August 3, 2005 Posts: 10 Comments: 5562
1184. Greyelf
7:36 PM GMT on September 23, 2010
Quoting Fla55Native:
Thanks for the answer Victoriahurricane, but the question remains, what is a Hebert Box, please?

Google or Wiki works great for questions such as this.
Member Since: June 5, 2007 Posts: 18 Comments: 838
1183. victoriahurricane
7:35 PM GMT on September 23, 2010
Quoting Fla55Native:
Thanks for the answer Victoriahurricane, but the question remains, what is a Hebert Box, please?


It's just an imaginary box where most hurricanes need to pass through to hit florida, there is no real scientific explanation, it's just a term that's used.
Member Since: October 16, 2008 Posts: 0 Comments: 544
1182. Max1023
7:35 PM GMT on September 23, 2010
Quoting atmoaggie:
I *think* he means late, late tonight to early morning...?


I mean the wee hours of the morning, right before sunrise. D-Min is right around sunset, so about 4-5am Est.
Member Since: July 22, 2008 Posts: 1 Comments: 286
1181. Tazmanian
7:35 PM GMT on September 23, 2010
Quoting Cotillion:
AL, 15, 2010092318, , BEST, 0, 139N, 762W, 30, 1007, TD, 34, NEQ, 0, 0, 0, 0, 1010, 130, 30, 0, 0, L, 0, , 0, 0, FIFTEEN

No Matthew yet.

Be calm people, be calm...



i think they will upgrade it too Matthew at 8 or 11pm
Member Since: May 21, 2006 Posts: 5091 Comments: 114988
1179. ILwthrfan
7:35 PM GMT on September 23, 2010
Quoting Grothar:


what pressure is on that model???? 950mb???
Member Since: February 2, 2010 Posts: 0 Comments: 1515
1177. Grothar
7:34 PM GMT on September 23, 2010
Member Since: July 17, 2009 Posts: 71 Comments: 26055
1175. atmoaggie
7:34 PM GMT on September 23, 2010
Quoting StormChaser81:


I thought D-Max is in the morning.

It's going into D-Min and that wont help it.
I *think* he means late, late tonight to early morning...?
Member Since: August 16, 2007 Posts: 6 Comments: 12461
1174. Fla55Native
7:34 PM GMT on September 23, 2010
Thanks for the answer Victoriahurricane, but the question remains, what is a Hebert Box, please?
Member Since: August 25, 2008 Posts: 0 Comments: 65
1173. Cotillion
7:33 PM GMT on September 23, 2010
AL, 15, 2010092318, , BEST, 0, 139N, 762W, 30, 1007, TD, 34, NEQ, 0, 0, 0, 0, 1010, 130, 30, 0, 0, L, 0, , 0, 0, FIFTEEN

No Matthew yet.

Be calm people, be calm...
Member Since: August 23, 2008 Posts: 7 Comments: 5300

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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