Remnants of Emily could redevelop; Muifa batters Okinawa; Central U.S. roasts
Tropical Storm Emily degraded into an open tropical wave yesterday afternoon, after Hurricane Hunters could no longer locate a center of circulation at the surface. Through the morning yesterday, the storm appeared to lose most of its strong thunderstorm activity on the north side, and mid-level circulation was broad (tropical cyclones need a tight, coherent circulation to maintain themselves). Soon after the Hurricane Hunters took a pass through the storm, the National Hurricane Center demoted Emily from a tropical storm to a remnant low, while continuing to stress the rainfall threat to Hispaniola and eastern Cuba. Today it appears the center of the remnants are located just north of eastern Cuba in the southern Bahamas, although thunderstorm activity continues across eastern Cuba. Hispaniola probably saw rain and thunderstorms again early this morning, the strongest of which were on the eastern side of the island. New thunderstorm activity is starting to develop in the southeast Bahamas. Given Wednesday's rain gauge analysis from CPC, Hispaniola probably saw at least an additional 5 inches of rain yesterday.
Environmental conditions remain pretty much the same as yesterday, but are expected to become more favorable for Emily's remnants, and redevelopment of the storm is possible. Circulation from the low to mid-levels is still broad and tilting to the east with height due to the lingering moderate westerly wind shear. However, this shear is expected to dissipate some over the next 24 hours, and signs of this are already present to the west of the remnants. The dry air that has been following the storm since its inception has dissipated, as well.
Figure 1. Satellite imagery of the remnants of Tropical Storm Emily as they move northwest away from Cuba and Hispaniola and into the Bahamas.
Forecast for Emily's Remnants
Interestingly, the models have come into better agreement on the forecast for former Emily now that it has lost its surface circulation and degenerated into a tropical wave. The ECMWF, which has come out ahead in this forecasting game so far, is optimistic today that Emily will redevelop. Other global models—GFS, CMC, and FIM—also redevelop the storm. Consensus on timing of redevelopment seems to be when the wave reaches the northern Bahamas in 24 to 48 hours. At 12Z (8am EDT), the high-resolution HWRF model run forecasted a track that was furthest to the west of all the models, scraping eastern Florida as it travels northwest. The most probable track and intensity forecast that I see at this point is north-northwest movement over the next 24 to 36 hours, at which point the system will take a fairly sharp turn to the northeast and out to sea. Without an already established, coherent circulation, it appears unlikely that if Emily is reborn it will intensify into anything more than a moderate tropical storm. However, there is some potential as the system moves out to see that it could gain some strength and develop hurricane-force winds before it transitions into an extra-tropical cyclone.
Typhoon Muifa passes to the south of Okinawa, heads into East China Sea
The center of Typhoon Muifa passed to the south of Okinawa earlier this morning (Eastern time) and it continues to batter the islands with high winds and torrential rain. Local radar estimate rainfall rates as high as 80 mm/hour (approx. 3 inches/hour) in the strongest rain bands. Kadena Air Force Base near the city of Okinawa has been reporting sustained winds of 47 mph with gusts up to 72 mph. Muifa is expected to turn northwest today as it enters the East China Sea as a category 1 on the Saffir-Simpson scale, and then intensify into a category 2 as it passes close to eastern China. This morning, the forecast is that Muifa will probably not make landfall anywhere as a typhoon.
Figure 2. Radar imagery from the Japan Meteorological Agency around 1am JST. Scale is in millimeters. Highest rainfall rates appear to be approximately 3 inches/hour.
South-Central U.S. continues to bake
The extreme heat continues again today after 269 high maximum and 250 high minimum temperature records were set yesterday, 19 and 29 of which were all-time records, respectively. 206 of yesterday's records were 110°F or higher. Yesterday, Reuters was reporting that Texas was one power plant shutdown away from rolling blackouts. The forecast today doesn't look any better. Heat index values up to 125° are forecast in eastern Texas and the Lower Mississippi Valley.
Particularly toasty heat index values from yesterday:
• Mobile, Alabama: 120°
• Arkadelphia, Arkansas: 121°
• Bay St. Louis, Mississippi: 121°
• Memphis, Tennessee: 122°
Figure 3. Heat index forecast from the ECMWF for today. Scale is in degrees Fahrenheit. You can plot model forecasts using Wundermap by choosing the "Model Data" layer.
Angela
Reader Comments
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 — Blog Index
Thanks, but do you know what loses angular momentum though? If the storm gains angular momentum, something else must lose it. To me it would have to be the Earth somehow.
Hence, your name! :)
Remily? LOl You have got to submit that to the NHC. It could be a new form of naming ex-storms.
He wants to sell you a credit default swap? Don't do it.
By the way, the storm does gain energy by the release of latent heat from the condensing water vapor. So your guess is correct. You've been paying attention during class.
ME: YEAH, I work at the NHC.
MR.SMITH: Cool, what do you do there?
ME: I rename dead storms, pretty cool huh?
Hmm 2008 did and up having some Caribbean cruisers, and brought us gustav and paloma, this year seems like 2010 with systems moving N before the western Caribbean
HA I got the most cookies!
THUNDERSTORM ACTIVITY ASSOCIATED WITH THE REMNANTS OF TROPICAL
STORM EMILY HAS CHANGED LITTLE IN ORGANIZATION DURING THE PAST
SEVERAL HOURS. IN ADDITION...THE SURFACE WIND CIRCULATION HAS
BECOME LESS WELL DEFINED...AND THE SURFACE PRESSURES ARE RELATIVELY
HIGH IN THE AREA. UPPER-LEVEL WINDS ARE CONDUCIVE FOR SOME
DEVELOPMENT...AND A TROPICAL DEPRESSION COULD STILL FORM DURING THE
NEXT DAY OR TWO AS THE SYSTEM MOVES TOWARD THE NORTHWEST OR NORTH
AT 10 TO 15 MPH. THIS SYSTEM HAS A HIGH CHANCE...60 PERCENT...OF
REGENERATING INTO A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. AN
AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE THE SYSTEM LATER TODAY...IF NECESSARY. INTERESTS IN THE
CENTRAL AND NORTHWESTERN BAHAMAS SHOULD MONITOR THE PROGRESS OF
THIS SYSTEM. REGARDLESS OF DEVELOPMENT...THIS DISTURBANCE WILL
PRODUCE GUSTY WINDS AND LOCALLY HEAVY RAINFALL OVER PORTIONS OF THE
CENTRAL AND NORTHWESTERN BAHAMAS TODAY.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
Was skimming the internets and this site looks the touch on the answer some. It seems to be saying that because a storms is at a lower pressure than the surroundings the surrounding air tries to rush into to fill it in. This is based on The ageostrophic wind theory. If the circulation is strong enough it turns this tangental air into angular velocity. Or geostrophic wind that is in balance. Again this is me speculating at now 1:51am after being up since 6am so my brain is beginning to shut down.
Link
Thanks, but that link is incredibly hard to follow. It also doesn't mention latent heat either. Appreciate the effort though.
It was a great attempt though.
The hurricane gains angular momentum from the increase in average angular velocity generated by steeper air pressure gradients, due to the latent heat release. Since hurricanes do not form on the equator, some of their vorticity occurs about the Earth's axis, and thus the Earth must lose some angular momentum to satisfy the law of conservation of angular momentum.
You could also think about this: If the hurricane has a uniform wind field and the Earth's surface beneath it has a constant coefficient of friction, then the westerlies on the southern side of the storm exert a greater torque on the Earth than the easterlies do on the northern side, because the distance from the Earth's axis of rotation is greater on the south side of the storm. Thus, under the conditions above, the net effect is a gain in angular momentum of the atmosphere, which requires a decrease in the AM of the Earth.
That's what I thought, but what is the coupling force between them? Another words the angular momentum must be transferred by a force or a torque. Is it some sort of friction between the storm and the Earth.
Thanks! What you just added answered in my question.
Correct. That is why the Earth and its atmosphere are considered as one system.
Also, on average, the Earth's rotation is not affected that much because in the southern hemisphere, cyclones rotate opposite so the integrated affect of all cyclones on the Earth is about zero, correct?
It changes. The atmosphere's total angular momentum is always fluctuating. A product from ESRL tracks it with NCEP reanalysis data. AAM is instrumental in observing changes in the ENSO, which occurs along the equator and has a large effect on the total AAM.
Ok, but if you integrate the last graph it's about zero.
Posted the wrong one by accident lol. That one wasn't total AAM. This one integrates to a negative number (fixed in original post).
Damn... it's not zero anymore. :) What about over a longer time period though... like five or ten years?
Again we see a large period of fluctuation with embedded noise. This is likely due to the Pacific Decadal Oscillation. Notice the increased AAM from 1976-2005, consistent with a positive PDO and thus increased westerlies at the equator, yielding greater AAM.
I don't see why they would use any other axis of rotation. The maps I posted were anomaly maps based on the average, which is always positive, which is consistent with the Earth's axis being the one in use here.
Thanks... it looks like it integrates pretty close to zero though. Also, this looks a plot of the AAA anomaly. How is the anomaly defined? With respect to the some average angular momentum?
The anomaly is defined with respect to the 1968-1997 climatology. Given this, the integration of the graph will naturally be close to zero.
Well for instance, the angular momentum of a hurricane would come from two axis. One about the center of the hurricane and one from it's movement around the surface of the Earth. The total angular momentum from the hurricane is not parallel or anti-parallel with the angular momentum axis for the Earth... it's skewed due to the component normal to the Earth from it's spin around it's center or eye.
Thanks again. You're like an encyclopedia. :)
Yes, but that hurricane has a certain angular momentum relative to the Earth's axis, and that is what is factored into the maps I posted. It is the entire vertically-integrated AAM about the Earth's axis, for the entire atmosphere, hurricanes and all.
I'm just citing the info that they have on their page for their product :P
Wish I understood it all a little better though
Yes, and the friction/drag constants obviously change everywhere. The entire Earth and the fluid atmosphere around it are considered one system. The Earth's surface won't be uniform, but the entire glob is considered as one entity. And then, nothing is a fully isolated system as long as we are within the universe, of course. It's darn close for practical purposes, though, as they apply to meteorology.
Do you know how the other component of the angular momentum is conserved, due to the spin of the hurricane about its center? Since you're here, I figure I'd ask. :)
Believe me... it's an excellent approximation.
jk
I'm sure you know that you could pick any arbitrary axis in the universe for which to calculate the hurricane's angular momentum relative to that axis. As I mentioned earlier, since hurricanes do not form exactly on the equator, some of their angular momentum is always about the earth's axis, which is balanced by a loss in AM from the Earth itself. Here, we are just applying the law of conservation of angular momentum to the earth-atmosphere system about the Earth's axis of rotation. We could pick the hurricane's axis of rotation for the entire earth-atmosphere system instead, and still apply the law, and come out with exactly the same results.
Am I seeing the LLC and MLC finally beginning to become vertically stacked near/over Andros Island? Kinda appears that way, with the LLC slightly to the SW of the MLC... decent convection around it and looking on the IR2 channel, it seems to be bringing itself together a little more with good spiraling around the circulation. Anyone with a take on this like to explain or correct me if I am wrong.
Yes is is becoming very interesting to see how it is quite well organizing a this time, as you said, I see some convection trying to get going around that area and moving to the west, lets see what the visible image shows on the mroning.
Viewing: 2001 - 2051
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 — Blog Index