Atlantic Tropical Weather Update 9/1/09

[Update 3:00P MDT]: Tropical Storm Erika has formed.

The NHC had hurricane hunter aircraft investigate the tropical disturbance known as Invest-94 this afternoon.  They have reported that a broad-scale, but closed circulation was found.  Directly sampling the environment, they found sustained wind speeds of 50mph near the “center”.  This means the storm is a Tropical Storm.  The difficulty of ascertaining the storms’ characteristics from satellite data isn’t new – remote sensing will always have its disadvantages to go along with its advantages.

Tropical Storm Erika’s vitals are as follows: center located near 17.2N, 57.3W; moving WNW @ 9mph; maximum sustained winds of 50mph; minimum central pressure of 1007mb.

There isn’t any change in the official track forecast – it takes the storm to the north of the northeast Caribbean Islands the next few days.

Tropical Storm Erika should continue to be a Tropical Storm over the next few days as it fights some wind shear on the western side of the storm.

—–

Invest-94 stubbornly refuses to get enough organization and structure to be classified as a Tropical Depression or Storm.  Meanwhile, it draws closer to land forms in the western Atlantic Ocean.  Here is Invest-94′s vitals as of this morning:

“Center” located near 16.8N, 57.2W; moving WNW @ 9mph.

The tropical disturbance has gone through fits and starts of rather impressive thunderstorm development, but has suffered from a lack of a well-defined closed-off low pressure center.  Some mid-level shear influences are currently thought to be the cause of the lack of organization.

The official track forecast, such as it is, takes Invest-94 to the north of the Caribbean Islands, such as the northern Windward Islands, Puerto Rico and Hispanola.  A wide spread in final position still exists for Days 4 and 5, when the system could be anywhere from north of the Bahamas on it way toward the Carolinas to just north of Hispanola, steering towards the southeastern Bahama Islands.

The official intensity forecast is as muddled as the track forecast.  Models continue to call for intensification, which hasn’t happened the past three or four days when the models were very excited about developing the storm.  Hurricane hunter aircraft are on the way today, and should shed more light on local storm conditions and help pin down exactly what’s spinning over the ocean.

The tropical wave that exited Africa yesterday is centered just east of the Cape Verde Islands.  The NHC has labeled the area of disturbed weather as an area of interest, giving it <30% chance of tropical development in the next 48 hours.

So, a temporary lull in tropical activity in the Atlantic exists while Category 4 Hurricane Jimena bears down on the Mexican Baja peninsula.  Hopefully damage and lives lost are kept to a minimum there.

Atlantic Tropical Weather Update 8/31/09

Invest-94 continues to exhibit increasing organization today, while the banded cloud features are only moderately impressive.  The system still doesn’t have a dominant central low pressure center.  This disturbance is definitely still a tropical wave, not yet a tropical depression.

Invest-94′s general center of circulation is located near 15.6N, 53.4W (~500 miles east of the Windward Islands) ; is moving WNW @ 14mph; and has maximum sustained winds of 30mph.

The disturbance’s movement in the past 12+ hours has taken it more northerly than I thought it would last night.  It should continue its WNW/NW movement throughout the next day or so.  After that, there is considerable divergence of model track solutions.  The NOGAPS keeps moving the storm NW, while the GFS, LBAR and BAMM shift its track to almost due west after Day 2.  The HWRF comes up with a snaking pattern: WNW, W, then WNW again in days 4-5.  The multitudes of track solutions means that anything from no impact on islands is possible, as is a glancing blow to the northern Windward Islands, Puerto Rico and Hispanola.

Continued organization and intensification is also progged by models, but this was the case all day yesterday as well.  The only thing to take from this is that intensification to Tropical Depression status is likely in the next day or so.  SSTs are plenty warm and the system will encounter less wind shear as it continues to travel across the basin.

Much further east, another tropical wave is exiting Africa over the Atlantic.  This wave is fairly far north – about 12.5N or so.  It isn’t that vigorous either.  A wave still over Africa looks a little better on satellite imagery.  It will be many days before either of these disturbances make their mark on the Atlantic basin, if at all.

Atlantic Tropical Weather Update 8/30/09

The Atlantic hurricane season is in medium- to high-gear.  While Tropical Depression Danny was being absorbed by a synoptic low moving off the U.S. coast, a vigorous tropical wave has been moving west across the Atlantic basin.  This wave has slowly grown more organized as it has made its trek westward.

At this time, Invest-94 is located 850 miles east of the Windward Islands.  It loosely looks like a tropical storm with the stirrings of potential rain bands moving around a central low pressure site.

Invest-94′s center is located near 12.6N, 48.3W; is moving WNW @ 11mph; and has maximum sustained winds of 30mph.

Invest-94 should continue moving WNW or NW over the next few days.  This expected path would put it near the northern Windward Islands in two to three days.  It has the potential to impact Puerto Rico in days 4-5.  It could also just as well steer north of the islands and remain over the Atlantic, like Bill did earlier this season.

Invest-94 is forecasted to continue to organize and strengthen over the next 3-5 days, becoming a tropical depression in the next day, a tropical storm a day or so after that and even a hurricane in the last part of the forecast period.  Water temperatures are more than warm enough to sustain a hurricane – over 28C waters now, 29C waters in days 2-5.  Wind shear is expected to remain minimal over the next few days, so Invest-94 should have nothing in its way to prevent it from strengthening.

Atlantic Tropical Weather Update 7/20/08

Well, systems are starting to come together after a long stretch of non-genesis.  Yesterday, Tropical Storm Cristobal formed off the South Carolina coast.  Today, Tropical Storm Dolly formed in the western Caribbean.  Meanwhile, Betsy has been downgraded to a Tropical Storm again as she continues to move across the Atlantic.  Let’s take a look at all the vitals:

Betsy: 51.3N, 35.7W; maximum sustained winds of 70mph; moving NE @ 35mph; minimum pressure of 987mb.  Betsy has been caught up in the westerlies.  She has about one day left in her before she interacts with Iceland.  She has had quite the history.

Cristobal: 34.5N, 76.4W; maximum sustained winds of 50mph; moving NE @ 6mph; minimum pressure of 1007mb.  Cristobal is having slight impacts on South and North Carolina’s coasts.  Some rains have been heavy at times as well as convective cells move inland due to Cristobal.  Cristobal’s movement should remain toward the north-east.  His speed will increase as a mid-level trough accelerates him in front of it.  I still expect, as does the NHC, Cristobal to impact Newfoundland sometime Tuesday.

Dolly: 18.4N, 84.2W; maximum sustained winds of 45mph; moving NW @ 17mph; minimum pressure of 1011mb.  Dolly is forecasted to move across the Yucatan Peninsula (not Belize, as I had misidentified earlier) probably later tonight.  She is expected to re-emerge over the Gulf of Mexico Monday during the day.  Thereafter, the track becomes important but highly variable.  There is a small chance Dolly could track a little more north thanf west and impact southern Texas.  Most model solutions keep Dolly further to the south and give Dolly a second landfall over Mexico.

The National Hurricane Center is also keeping an eye on a small area of low pressure 325 south-east of Bermuda.  Development is not expected to take place due to inhibatory environmental factors.  Another tropical wave is emerging form over Africa.  It is broad and disorganized, but will keep an eye on it as it makes its way across the Atlantic.

Atlantic Tropical Weather Update 7/19/08

How ironic is it that I wrote about unexpected things happening in the tropics two days ago? Tropical Storm Bertha regained Category 1 hurricane strength yesterday. She maintains that strength today as she continues to spin away in the middle of the Atlantic. Remember, this storm formed on July 3rd, or 16 days ago. Cape Verde storms are more likely to be long-lived.

Invest-95 is no more, having moved over Nicaragua and Central America yesterday.

Invest-96 has organized more over the last day and has recognized as Tropical Depression 3 for the 2008 Atlantic season. It could organize further into Tropical Storm Cristobal later today. It has affected South Carolina with heavy rains and increased beach surf. It will continue to affect North Carolina today. Track forecasts vary: it could move over North Carolina or stay out to sea and continue to gather strength and organization. Keep an eye out if you’re in that part of the country.

Invest-94 has moved further across the Caribbean. I really expected this system to form into a T.D. or T.S. by now. It still has a high likelihood of doing so. For what it’s worth, the track forecast continues to show it moving across Belize and into the Bay of Campeche in the extended time-frame.

***

[Update 1:30P CDT]:

Tropical Storm Cristobal has formed off the coast of the United States. It is centered at 32.8N, 78.3W; maximum sustained winds of 40mph; moving NE @ 7mph; minimum pressure of 1007mb.

Cristobal is still expected to move toward the north-east and affect South and North Carolina over the next couple of days. He will affect the northeastern United States thereafter, while continuing to move out over the open Atlantic. Newfoundland, Canada could be impacted in the extended future (>5 days).

So far, three storms this year.

Invest-94 continues to have winds that keep it just under Tropical Storm strength.

Bertha has maintained Hurricane strength, even though she is more than 40N (higher latitude than Denver, CO) and is over cooler waters.  She should become extratropical in a day or so.

Atlantic Tropical Weather Update 7/18/08

Invest-94 looks better organized this morning than it did last night. Satellite imagery is pretty impressive. The NHC is giving it a high likelihood of developing into a Tropical Depression again today. It’s life-cycle across the Atlantic has been characterized by a cyclical chance of further development. It has winds at just below Tropical Storm strength. If a central area of closed low pressure develops, we’ll see T.S. Cristobal. Its forecasted path would take it over or just to the north-east of Belize into the Gulf of Mexico. This is one system that bears further watching.

***

[Update 11:30A CDT]:

The NHC released a special tropical disturbance statement about an hour ago.  Invest-94 and Invest-96 could become tropical depressions or storms later today.  They’re sending a hurricane hunter later this afternoon to Invest-94, centered about 400 miles south-east of Jamaica to determine its organization.  A second hunter is also scheduled to take a look at Invest-96 this afternoon.  This system would have a more immediate effect on the U.S. as its just off-shore from Georgia and South Carolina.  Heavy rains would be the primary threat.  So we could see T.S. Cristobal and T.S. Dolly form shortly.

Bertha continues to spin in the Atlantic and won’t have a direct affect on land for some time.

Tropical Storm Bertha Update & Tropical Atlantic Overview 7/17/08

This year’s Atlantic tropical season to date is one reason why I love weather: things never happen quite the way you expect them to.  Between Bertha and a few other areas of interest, things keep changing.

Okay.  Bertha is still northeast of Bermuda, just sort of spinning away.  She was centered at 34.2N, 57.4W this morning.  Her movement is ESE @ 9mph, with maximum sustained winds of 60mph and an estimated minimum pressure of 997mb.  Nothing exciting, and not too much has changed since yesterday.

There are officially three Invest storms in the Atlantic right now.  I’ve been writing about Invest-94 as it has made its way across the Atlantic.  I really expected this storm to get its act together by now, but it just hasn’t happened.  It’s in the Caribbean, it still has convection associated with it.  It just hasn’t gotten organized.  As of this afternoon, it’s less likely to get organized than it was yesterday afternoon.  This system should move northwesterly across the Caribbean and impact Belize later this week or early next week.  Whether it’s a Tropical Depression or Storm or anything else at that point is way up in the air.  But even lots of rain can cause destruction.

Invest-95 is the system further west, and is about to affect Nicaragua.  It has a broader area of convection, but is similarly having trouble getting organized, thought that’s mostly due to interactions with land to its west as it spins over warm water.

The third system is now Invest-96.  It is associated with an upper level low that is slowly moving toward the east.  This system moved over Florida yesterday and is sitting just off the East Coast as it meanders toward the north, north-east.  My thoughts with this system is interaction with the mainland U.S. should prevent tropical development, but we’ll see how it turns out.

Tropical Storm Bertha Update & Tropical Atlantic Overview 7/16/08

Is she still out there kicking?  Sure enough.  Bertha has been at least a Tropical Storm for 13 consecutive days now.  She’ll likely last a few more days as well.  Here are her vitals:

36.1N, 60.5W; moving southeast now at 5mph; maximum sustained winds still just below Category 1 hurricane strength at 70mph; minimum central pressure of 995mb.

She’s forecasted to track further to the southeast through tomorrow, then head back toward the northeast thereafter.  With today’s updated track information, she isn’t expected to impact Europe.  The big question in my mind now is how long can she retain tropical characteristics?

***

Tropical Atlantic: The wave I’ve been watching the past few days, Invest-94, looks a little better organized.  The NHC thinks so as well, giving it a high likelihood of forming a Tropical Depression.  In fact, they sent out a Hurricane Hunter to investigate the system.  There isn’t a single predominant low level circulation present, just a number of smaller features that are fighting for dominance.  The system is centered approximately at 200 miles east of the Windward Islands.  Again, sea surface temperatures are plenty warm enough to support a Depression, but the remainder of the environment isn’t quite right.

Interestingly, there is a wave to I-94′s west, just east of Nicaragua.  It looked more impressive on satellite yesterday than I-94 did.  It still looks a little better today, but is much closer to a major landmass than I-94 is.  Development of the system shouldn’t occur too quickly, if at all.

A third area of interest is found just to the west of the Florida panhandle.  It’s characterized by broad area of low pressure and some convection over Florida.  This area is the least likely to develop into a Tropical Depression.

Tropical Storm Bertha Update & Tropical Atlantic Overview 7/15/08

Tropical Storm Bertha continues to spin away in the central Atlantic.  Her effects on Bermuda have pretty much ended as she has moved off to its northeast.  Bertha’s vitals:

35.6N, 62.7W; maximum sustained winds of 70mph; moving NNE @ 11mph; minimum central pressure of 995mb.

Bertha will continue to turn to the right, eventually to the southeast tomorrow and then turn back toward a westerly heading in a few days.  Some strengthening in that time-frame could occur.  Thereafter, Bertha’s track should take her northeast across the Atlantic and impact Europe in more than a week.

***

The tropical wave moving toward the Lesser Antilles isn’t expected to acquire Tropical Depression status for another day or longer.  Any strengthening thereafter is forecasted to be slow.  The system, Invest 94, is experiencing less than favorable environmental conditions that are inhibiting development.  Sea surface temperatures (and likely a fairly deep layer underneath) are more than warm enough to support a system.  The forecasted track hasn’t changed since yesterday: all of the models I’ve looked at indicate a path over the middle of the island chain, as I-94 continues to move WNW.  It’s sustained winds are estimated at 28mph.  There is a good deal of convection associated with the wave, but a center of rotation is difficult to pick out.  Future impacts to the southern portion of Hispanola or Jamaica are possible in four days or more from now.

***

A second tropical wave is located about 8N, 33W.  A good deal of convection is present with this system.  Development isn’t likely to occur with this system.

A third wave is about to move off the west coast of Africa also.

Tropical Storm Bertha Update 7/14/08

Not a lot of change since yesterday. Bertha is starting to move a little faster, but no major changes in her future are expected. Her vitals:

32N, 63.8W; maximum sustained winds of 65mph; moving N @ 6mph; minimum central pressure of 990mb.

A turn toward the NE and then E is expected in the next couple of days. After that, a turn toward the SE is likely. In the extended time-frame (4-5 days+), Bertha should be caught up in a westerly system and move back toward the NE and the North Atlantic.

Bertha will affect Bermuda more than I thought yesterday. The island is under a Tropical Storm Warning as Bertha slowly makes her way to its east.

***

Onto Invest-94, the tropical wave I discussed yesterday. This system is now 1300 miles east of the Lesser Antilles, centered approximately at 12N, 43W. Its winds are estimated to be sustained at 28mph, below Tropical Storm status. It currently lack the organization to even be classified as a Tropical Depression. That shouldn’t be the case much longer, however. Model solutions point toward a steady strengthening for the next few days. It could (should?) achieve Tropical Storm status sometime in the next 24 hours. If it does, it would be given the name Cristobal.

I spent some time yesterday discussing the track forecast patterns. Two of the models yesterday were indicating a more northwesterly course while three were predicting a more westerly course. The two models have come into more agreement with the three in showing a westerly, west-northwesterly track. This is both good and bad. From a scientific viewpoint, its good to see agreement between model solutions. It lends confidence to the forecasted track, which is one thing that modelers work toward. Its bad from a human impacts perspective. The current predicted track will take the system across the Lesser and Greater Antilles and into the Caribbean Sea. While the extended track (4-5 days) has a much higher degree of uncertainty, it looks right now like the system could track toward the northern part of the Sea. Thus, it could impact Hispanola (Dominican Republic and Haiti) and/or Jamaica. This storm will definitely warrant significant attention.

Invest-94 is trying to develop banded clouds and a center of rotation. It currently has convection on its northern and southern quadrants. The eastern and western are convection-free and relatively cloud-free for now.

***

[Update 4P MDT]:

Tropical Storm Bertha has strengthened ever so slightly from this morning.  Further strengthening is forecasted to occur.  Her current maximum sustained winds have increased to 70mph.  Bertha could become a Category 1 hurricane again in the next 12-24 hours as she continues to spin over warm waters.