4:01 AM
5AM
The hurricane hunters have sufficient data to upgrade tropical depression 17 in to tropical storm Paloma. Some of the surfaces winds measured were over 50 Kt, however, these winds lacked consistency . The surface pressure has dropped from 1005 to 1000 MB, indicating that Paloma is strengthening gradually. The overall poleward outflow channel at the northern quadrant has increased substantially over the past 12 hours, and thunderstorm activity is still consolidating near the center of circulation, indicating vigorous lower level convergence and upper level divergence. A developing anticyclone near Florida will provide further aid to Paloma. The anticyclone is expected to remain there for about 48 hours, helping Paloma to distribute its energy with greater efficacy. Furthermore, vertical wind shear is expected to remain at relatively low levels over the next 72 hours. Some of the computer models expect this system to go through a rapid intensification phase about 36-72 hours from now. The forecast peak intensity at the moment is still unknown, However, I am leaning more towards NHC’s conservative forecast.
Due to the ambiguity of the model consensus, the forecast track for this system is very inaccurate for the time being. The 00Z GFS mode run expects this system curve towards the northeast as a result of a synoptic scale trough of low pressure that will exit the U.S. Subsequently, the GFS model expects to stall, and hit Florida as a feeble cyclone. We may see significant change on the NHC’s forecast track because trough may not be strong enough to pull this system. A large synoptic scale anticyclone is expected to develop of the Eastern United states about 100 hours from now. Depending on where Paloma is located during that time frame will greatly affect its track. The building anticyclone over the Eastern U.S. may cut off the weakness created by the trough , and resume a westward motion. Nonetheless, it is best to remain conservative and observe this system for the time being.
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FUTUREMET
5:02 PM
Brief Analysis
Numerous showers and thunderstorm activity are in association with a weak area of low pressure located just east of Belize, and are enhanced by a weak frontal system near the Florida Keys. This system has been producing copious rain in the Southwestern Caribbean, and will continue to do so over the next 36 hours. Furthermore, this system has been trying to organize itself over the past, however failed sustain itself due to little or no anticyclonic flow to help its lower level convergence. A ridge of high pressure is currently building over southern U.S., and will provide more favorable conditions over the next couple days. Regardless if this system develops or not, residents in the Mesoamerican countries should expect excessive rainfall from this system. Once the high sets up completely, it will steer this system toward Central America.
Elsewhere in the tropics:
A tropical wave associated with an upper level low located near the Windward Islands has been increasing its convection today. I do not think this system will develop any time soon for two reasons: the upper level is creating unfavorable wind shear over the northern part of the convection mass. On the other hand, wind shear is limited over the southern convection mass, however, it is somewhat too close to the equator to feel the effects of the Coriolis force sufficiently to establish rotation.
Nonetheless, if this system manages to sustain its convection, we will have to watch the SW Caribbean over the next couple of days, as it continues to move west.
4:25 AM
The tropical Atlantic is still in a lull state today. However, there are two areas that captivate me this afternoon.
Southwestern Caribbean
Numerous showers and thunderstorms activity located in the southwestern Caribbean enhanced by a weak area of low pressure near the Florida Keys has gotten better organized this afternoon. This system has failed sustain itself over the past couple days, as its thunderstorm activity increases during the daytime hours and decreases overnight****1. This primarily because, the atmospheric pressure around it is too low to support its lower level convergence and upper level divergence, which are momentous necessities for tropical cyclone development. Look at the 12z sea level pressure map. You will notice that there is no anticyclone nearby to support its lower level convergence, and that is the way it has been over the past few days. Nevertheless, a dynamic anticyclone is expected to build over the eastern U.S. about 72 hours from now. This will provide a more favorable environment for this system, and we may see possible tropical cyclone development indicated by NAM model.
Brief Tutorial
You may wonder why I said that “anticyclones help provide better lower level convergence”, since most people say that “anticyclones help provide “upper level divergence”. Yes, that is correct, but technically, an anticyclone helps provide better lower level convergence, which in turn provide good upper level divergence.
Let me explain how this works.
Air flows from an area of high pressure to low pressure (one of the most fundamental laws in weather). To give you a vivid imagery of this, imagine a bathtub where water is sinking into a draining hole, you will notice that the water will flow towards the area where it is the lowest (the hole). Sinking air from a high pressure system will move towards an area of low pressure in an attempt to fill it up. The sinking air will gradually become unstable as it nears the low pressure system, and eventually it will be forced to rise. As the air rises, it will condense at higher altitudes which generates the stormy cumulonimbus clouds, and that is lower level convergence ladies and gentlemen. Now as the air condenses, it will release latent heat, and allow itself to rise even farther in to the atmosphere. When the air reaches the apex altitude, it will finally condense into tiny ice particles (cirrus clouds) and diverge. This is why it always looks like that the white buzz saw shaped clouds always moving away from a Hurricane in satellite imagery, and that is upper level divergence. The diverging air will then converge on top of the high pressure system (it will no condense ort form clouds because it has already lost its moisture) and sink. Subsequently, the sinking air will diverge at the surface and moves towards the area of low pressure, thus repeating the process.
Please note that this is my opinion….if you have any questions, do not hesitate to ask me.
Another reason why I believe it is important to have an adjacent anticyclone nearby is because the sinking air warms adiabatically as it sinks from an anticyclone. That warmer air when flowed toward a cyclone, provide an extra boost. On the contrary, when a trough of low pressure is nearby produces rain, thus cooling the air, which proves to be a burden to the tropical cyclone. So, that is probably one of the reasons why the system in the SW Caribbean is incapable of sustaining itself. However if it does develop, it will likely be in the vicinity of Belize and Honduras.
Central Atlantic
A tropical wave located along 40 degrees west has gotten a bit more organized this afternoon, further development if any will likely be slow to occur over the next couple of days. This system will gradually moves towards the west-northwest over the next couple days. About 120 hours (5 days) from now, it will encounter a trough of low pressure, and might recurve out to sea depending on its intensity, or the potency of the trough. Regardless if this system develops or not, it is best to remain conservative and observe closely for the time being.
***1 I have been noticing thatsome systems actually get better organized during the day, and lose their thunderstorm activity during the night. Thi happened with invest 93L (Kyle), the system in the SW Caribbean, and the weak area of low pressure in the Gulf Of Mexico (GOM) a couple days ago. This kept happening numerous times, and I cannot understand why…..Anyone mind writing a Phd on this one?
4:41 AM
Winds: 100 MPH
Gusts: 120 MPH
Min.Pressure: 946 MB
Location: 25.5N 88W
Movement: WNW 9 MPH.
5AM EDT
Indeed, Ike has the potentially to be a catastrophic hurricane for the United States. Hurricane Ike has been growing in size and strength over the past few days, and now it is a Pseudo-Hurricane Katrina. Hurricane Ike has been going through an eye replacement cycle the previous day, which hindered substantial intensification. As of this morning however, the eye replacement cycle is complete and significant strengthening is likely today. According to the latest satellite imagery, Thunderstorm activity has increased over the past hours or so, and this means that the eye will be fully visible soon. When numerous dynamic cumulonimbus clouds form near the eye, they act as a channel for fast rising air. As the air rises, it cools and condenses releasing latent heat to fuel the Hurricane further. When the rising air reaches the apex altitude, it will diverge, and some of that diverging air will sink into the eye. The current environmental conditions are favorable for further intensification because, sea surface temperatures are sufficiently warm to enhance vertical motion and lower level convergence, Upper level winds are low enough not to disrupt the circulation, and there is anticyclone over it to provide upper level divergence. I will no longer say that "there is an anticyclone" over it because it can give people the wrong impression, since the high pressure system is not directly on top of the hurricane, rather adjacent to it. Air travels from high pressure to low pressure areas, and the velocity of which the air travels depends on the pressure gradient, or the pressure difference between the cyclone and the anticyclone. As the air sinks from a high pressure system, it will move toward areas of lower presser, in an attempt to fill up the low pressure center. To get a vivid idea, imagine water draining in a bath tub hole, the water will flow toward the draining hole, since the water level is lowest there. As the sinking air from the anticyclone nears the cyclone, it itself will lose its density and begin to rise. As it rises it will condense at the mid levels, and this is lower level convergence. When it reaches the extreme top, it will diverge, sinking to areas of higher pressure. So yes technically anticyclone provides good lower level convergence, which in turn provides good upper level divergence. Hurricane Ike, has great upper level divergence on all four quadrants, and great equatoward and poleward outflow can easily be seen in satellite imagery. It is very possible that Hurricane Ike will make landfall near Houston and Galveston Texas as a powerful 4 some time during early Saturday morning. A hurricane of this magnitude and strength will cause serious damage to these areas. A storm surge of over 20 feet is very likely, and capable topping Galveston's sea wall. I know this may seem like the worst case scenario, but that is what likely to happen. It is strongly recommended that residents in these areas evacuate. Hurricane Ike will be steered primary by WNW by a high pressure system north of it. Subsequently as it reaches the ridge axis, a trough of low pressure will cause it to move more to the northwest.
Landfall Intensity:
Category 1: 5%
Category 2: 20%
Category 3: 30%
Category 4: 35%
Category 5: 10%
5:04 AM
Hurricane Ike
Winds- 135 MPH
Gusts- 160 MPH
Minimum Pressure- 948 MB
Location- 20N 73W
Movement- West/14 MPH
5AM EDT
Hurricane Ike has gained momentum Saturday afternoon, and it is now a powerful category 4 Hurricane. The moderate shear that was hindering its intensification has slacken, and further strengthen is expected until it reaches Cuba. A clearly visible eye was able to form Saturday evening as more thunderstorms formed near the center of circulation. Some of the diverging air from the top of the thunderstorms sinks into the center of circulation. As the air sinks however, it warmed adiabatically****, making the eye warmer than anywhere else in the cyclone and rain free. However at the moment, dry stable air from its northwest is trying to penetrate at the northwestern quadrant. This is the same dry air mass that prevents Hanna from strengthening substantially, and it will likely prohibit any rapid intensification from Ike. A series of strong subtropical anticyclones will cause Ike to move in a general westward motion. Despite the fact that there will be weaknesses between them, it will not be significant enough for Ike to feel the effects. As a result, residents along the Gulf Of Mexico will have to watch Ike closely, specifically those in Galveston and New Orleans.
Josephine’s Remnants
Tropical Storm Josephine has been torn apart by strong upper level winds, and now it is nothing more than a weak area of low pressure. However it took advantage of the maximum diurnal phase and managed to build some convection primarily north of the circulation. Wind shear is levels are moderate over its center of circulation, so further organization today is possible. Nonetheless, there is one last patch of high upper level winds about 80 miles to its northwest. If it does move into that unfavorable wind shear patch, the chances of it reinvigorating itself will decrease. I do not think that it will reach that patch of high upper level winds in time to weaken, since the patch of high shear is expected to move towards the northeast hastily at about 20 MPH. Wind shear will be very low by Tuesday, and Josephine may regenerate itself to a tropical cyclone by then. The NOGAPS, and the CMC are in general agreement in this like case scenario.
Another area I am watching is a tropical wave located about 50 miles east of the southern Lesser Antilles. I do not expect it to develop over the next 48 hours for two reasons. As it continues to move west, the outflow from Ike will stifle its development. Furthermore, it is inconvenient for it acquire some spin due to its proximity to the equator. Overall this is a pretty impressive system; it has been sustaining convection for the past couple of days.
****ADIABATIC WARMING AND COOLING.
Adiabatic warming and cooling is also known as compression heating, and expansion cooling. Furthermore, adiabatic warming and cooling has nothing to do with the air surrounding it. Reply to me if you want to know how this works. If you do, I will post a tutorial about it.
8:15 PM
TROPICAL STORM HANNA
WINDS: 65 MPH
GUSTS : 75 MPH
MINIMUM PRESSURE: 987 MB
MOVEMENT: NW 13 MPH
LOCATION: 26N 76W
8PM EDT
The overall structure of tropical storm Hanna has not changed very much during the past few hours, since dry air continues to wrap itself around Hanna's southern quadrant. As a result, lower level convergence is limited at the southern quadrant and that will hinder substantial intensification. However, environmental conditions are marginal for development and slow strengthening is expected as continues to move towards the northwest. In fact, it is possible that it will become a category one hurricane before making landfall between North and South Carolina. The winds and storm surge will be felt far from the center circulation due to its wide wind field, primarily at the northern quadrant. Thus, residents along the Carolina coastlines should monitor Hanna closely.
HURRICANE IKE
WINDS: 135 MPH
GUSTS: 160 MPH
MINIMUM PRESSURE: 945 MB
MOVEMENT: WNW 13 MPH
LOCATION: 23.6N 58.2W
Hurricane Ike has been a powerful category 4 hurricane for nearly 24 hours now, and still looks impressive in satellite imagery. Hurricane Ike is a relatively small compact tropical cyclone with tropical storm force winds only extending about only about 100 miles in diameter, and hurricane force winds extending about 30 miles. The small magnitude of Ike enabled it to intensify rapidly last night after building a complete eyewall. Smaller tropical cyclones require less energy from their environment to intensify and also conserve more angular momentum. Nevertheless, Ike has been weakening slowly today due to higher upper level winds. The majority of the computer models expect it to weaken slowly over the next couple of days as vertical shear increases. Once it reaches the Bahamas however, the environment will be more conductive for significant development. An anticyclone will build over it to support its upper level divergence, sea surface temperatures are will be sufficiently warm to provide great vertical motion, and wind shear will be adequately light to not interfere with the circulation. The model forecast tracks are in harmony with each other until Sunday, when a trough of low pressure exiting the U.S coast will cause a weakness on the ridge. The model tracks vary greatly beyond Sunday, due to the fact that it is very uncertain how strong that weakness on the ridge will be. The ECMWF initialized at 12z almost seems to ignore the fact that there will be a weakness on the ridge, and forecast Ike to make landfall in Louisiana. On the contrary, the GFS model initialized at 12z indicates that there will be a major weakness on the ridge, and take Ike out to sea. For the moment, it is best to consider these models as outliers. Despite the uncertainty of Ike's path, it is best to prepare to for it now if you are in the cone of uncertainty, and that includes, Florida's east coast, Cuba, and northern Haiti. Hurricane Ike's magnitude should increase as it continues to move west, where vorticity is more abundant. Throughout the day, the spiral bands that were embedded in the main circulation mass have been spreading outward. Ike's overall magnitude has increase nearly 10 percent since 5AM this morning. Therefore if this keeps up, Ike may become as wide as Gustav by Monday.
2:07 PM
8:41 AM
5:06 PM
5:33 AM
5:32 AM
5:30 AM
5:27 AM
5:01 AM
Invest 95L has been upgraded to tropical depression number 8, with winds sustained at 35 MPH with higher gust, and is moving west-northwest about 5 MPH. According to satellite imagery, this system has a robust outflow, which indicates the efficacy of its low level convergence, and upper level divergence. An anticyclone will build over it and steer back west, and maybe even west-southwest depending on the potency of that ridge. Residents in Florida should closely monitor this.
I will post a more detailed update this afternoon.
6:51 PM
5:51 PM
A well defined area of low pressure about 200 miles northeast of the Lesser Antilles will have to be watched for potential development. The European model (ECMWF) develop this system into a substantial tropical cyclone
*I will post a special tutorial about how divergence helps cyclones sometime in the future.
7:58 AM
7:14 AM
Invest 92L has gotten better organized this morning, the center of circulation is now completely closed according to the latest quickscat scan. Around 3 AM EDT this morning, dynamic convergence near the invest 92L's circulation caused to some vigorous thunderstorms to flare up. As more thunderstorms flare up, the instability continues increase and more air will rise. Strong upper level winds are abundant where 92L is located, however, the wind shear will not be a threat. This primarily because of the strong anticyclonic flow from the Azores high pressure system that helps provide this cyclone robust upper level divergence. This system seems to be forming some good poleward outflow, and some slight equatoward outflow caused by good lower level convergence and upper level divergence, and that indicates this is a "breathing" system. The computer models track are in good harmony with each other because, they all agree on generally west-northwest path. Unfortunately, that puts areas such as the northern Lesser Antilles, Bahamas, and even south Florida at risk. Residents living in these areas should monitor this cyclone closely.
Elsewhere in the tropics, I am also closely monitoring another vigorous system. The models have been shifting their forecast track gradually southward, thus, this system will have to be watch closely.
6:54 AM
The computer models unanimously forecast a substantial tropical cyclone near 30-40 degrees west about 48-60 hours from now. The environment will allow the tropical cyclone to grow more dynamic, symmetrical, and well established poleward and equatoward outflow due vigorous convergence and divergence. The sea surface temperatures are sufficiently warm to cause robust convection, upper level winds are low enough to keep the center of circulation intact, and the anticyclonic flow from the Azores high will provide great upper level divergence. Indeed, this kind of environment is where tropical cyclones thrive and "breathe", and thus significant intensification is a possibility.
Yet, where will this system go? Should be one of the momentous questions that should be asked right now. This system is right beneath the Azores high, consequently it will move generally towards the west and west-northwest during the next 7 days. Nevertheless beyond that, the forecast path possibility becomes to ambiguous to be considered efficient.
For a long time now, the jet stream dipped far to the south and has been stuck like that. As a result troughs of low pressures dig farther south than usual for this times of year. This does explain tropical cyclone Edouard form last week. When the jet streams dips that far south, the likelihood of tropical cyclones curving out to sea is much higher, but how long will that pattern last?
During the previous runs by the GFS model, it has been indicating that this "dip" in the jet streams will not be present about 10-16 days from now. At the end of that period, the GFS forecast it to far north.
The best thing we can do now is watch the tropics closely.
It should be noted that the GFS develops another tropical cyclone after this system develops.
$$
Jean-Baptiste