Tropical weather analysis - July 30, 2013

By: KoritheMan , 1:23 AM GMT on July 31, 2013

Share this Blog
8
+

Gil

Tropical Storm Gil quickly formed today. As of the latest NHC advisory (new one is due out in just under two hours), the following information was posted on the cyclone:

Wind: 40 mph, with higher gusts
Location: 12.7°N 116.1°W
Movement: WNW at 15 mph
Pressure: 1005 mb

The satellite presentation of Gil is fairly impressive, with a large curved band to the west. Microwave data throughout the day has suggested a formative mid-level eye feature with the possibility that a primitive eyewall could be attempting to form aloft. However, this feature has not been readily apparent in conventional satellite images. Convection has increased near the center, possibly signifying the beginnings of a central dense overcast.



Figure 1. Latest infrared satellite image of Tropical Storm Gil. Image credit: NOAA's Satellite Services Division (SSD).

For the most part, environmental conditions appear conducive for continued intensification, with very warm waters, weak vertical shear, and the small size of the circulation. One potential negative factor -- probably why the guidance is not forecasting rapid intensification -- is an area of dry air to the west of Gil on water vapor imagery; the airmass becomes particularly dry near 125W. One additional factor supporting the possibility of rapid intensification with Gil (in addition to the microwave passes) is an upper low to the north of the circulation moving west in tandem with the tropical cyclone. This ridge is forecast by the GFS to move westward in tandem with Gil for the next 48 hours while gradually weakening; the distance of the upper low is such that it will act less to shear the cyclone and more to assist in aiding its outflow. The SHIPS rapid intensification index as of 18z shows a 40% chance of an increase of 30 kt in the next 24 hours. None of the guidance forecasts to Gil to become anything more than a minimal hurricane, and even those appear to be confined to the outlying statistical guidance. Closer to the SHIPS guidance, which seems reliable in this case, my forecast assumes Gil will reach a peak of 70 kt in 72 hours; however, the intensity forecast at longer ranges could be conservative if the eye feature observed on microwave images translates down to the surface, leading to the formation of an inner core. Beyond day three, the models show westerly shear increasing, and sea surface temperatures will begin to cool. Gradual weakening is forecast at that time.

Gil is south of a mid-level ridge, and is moving west-northwestward. A blend of satellite and microwave fixes show that the cyclone more or less remains on track with the 2100Z NHC track prediction. The synoptic pattern ahead of Gil appears straightforward, with an upper low off the coast of British Columbia diving southeastward, bringing its trailing mid-level trough with it. The global models respond to this pattern by forecasting a general west-northwest motion for the next 72 hours, after which time the trough is forecast to lift and Gil is expected to turn toward the west. There could be a weak mid-level perturbation northeast of the Hawaiian Islands near the end of the period that could be capable of turning Gil northward closer to the state, but it is too early to be confident of its strength and potential impacts on the cyclone's poleward motion at those times.

Intensity forecast and positions

INITIAL 07/30 2100Z 12.7°N 116.1°W 35 KT 40 MPH
12 hour 07/31 0600Z 13.3°N 118.2°W 45 KT 50 MPH
24 hour 07/31 1800Z 13.9°N 120.6°W 50 KT 60 MPH
36 hour 08/01 0600Z 14.5°N 122.8°W 55 KT 65 MPH
48 hour 08/01 1800Z 15.3°N 125.3°W 65 KT 75 MPH
72 hour 08/02 1800Z 16.4°N 129.5°W 70 KT 80 MPH
96 hour 08/03 1800Z 16.6°N 132.4°W 60 KT 70 MPH
120 hour 08/04 1800Z 16.7°N 136.8°W 50 KT 60 MPH

Track forecast



Figure 2. My 5-day forecast track for Gil.



Invest 90E

An area of low pressure centered a few hundred miles east of Tropical Storm Gil is also quickly organizing. Satellite images show evidence of convective banding to the north, and previous microwave data hinted at this as well.



Figure 3. Latest infrared satellite image of Invest 90E. Image credit: NOAA's Satellite Services Division (SSD).

The development potential/intensity forecast for this disturbance are rather mixed. None of the guidance suggests significant intensification, and several of the global models -- including the GFS -- fail to initialize or develop it. The ECMWF, which seems to rarely develop cyclones, does show development eventually. I don't see much evidence of vertical shear over the system at the moment, but the GFS assumes that there could be some northwesterly shear in the next couple of days, likely emanating from Gil's outflow. Complicating matters further is the possibility of a Fujiwhara interaction between this disturbance and Gil. Although the circulation of Gil is small, so this one, and the former's circulation envelope appears to be healthier overall, so I presume Gil will ultimately prevail.

Regardless, conditions do appear favorable for the present time, and I expect this disturbance to become a tropical cyclone in the next 24 hours. Preliminary track guidance suggests a motion to the west-northwest, which seems consistent with current trends and the large-scale pattern.

Probability of development in 48 hours: 60%

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 10 - 1

Page: 1 — Blog Index

10. WunderAlertBot (Admin)
3:19 AM GMT on August 01, 2013
KoritheMan has created a new entry.
9. nigel20
2:55 AM GMT on July 31, 2013
Thanks Kori!
Member Since: November 6, 2010 Posts: 11 Comments: 8133
8. Astrometeor
2:12 AM GMT on July 31, 2013
Quoting 6. SuperStorm093:
Well if thats true, people might need to lower the amount of storms we have this year.


I can almost here TropicalAnalystwx13 now:

"How many times do I have to say this: People, it's still July".

June averages 1 storm per every two years, July two every three years. And with the active seasons that Kori provided, you can see why we have such a long ways to go before the end of the season, and why nobody will be revising down their numbers.
Member Since: July 2, 2012 Posts: 101 Comments: 10327
7. KoritheMan
1:54 AM GMT on July 31, 2013
Quoting 6. SuperStorm093:
Well if thats true, people might need to lower the amount of storms we have this year.


Really?

1998

2004

2010

Examine those years and get back to me. This season won't bust, and the numbers will still be even above the 1995-2012 climatological mean.
Member Since: March 7, 2007 Posts: 583 Comments: 20802
6. SuperStorm093
1:49 AM GMT on July 31, 2013
Well if thats true, people might need to lower the amount of storms we have this year.
Member Since: July 31, 2013 Posts: 0 Comments: 925
5. Doppler22
1:48 AM GMT on July 31, 2013
Quoting 4. KoritheMan:


I don't really think things will take off in the Atlantic until the fourth week of August.

Why does Mother Nature make us wait?!
Member Since: February 13, 2012 Posts: 11 Comments: 3768
4. KoritheMan
1:35 AM GMT on July 31, 2013
Quoting 2. SuperStorm093:
If only we had a storm to track in the Atlantic Basin, but hey, we might have to wait a good two weeks before we do.


I don't really think things will take off in the Atlantic until the fourth week of August.
Member Since: March 7, 2007 Posts: 583 Comments: 20802
3. Tropicsweatherpr
1:30 AM GMT on July 31, 2013
It will be interesting to watch if there is interaction between Gil and 90E.
Member Since: April 29, 2009 Posts: 75 Comments: 14310
2. SuperStorm093
1:28 AM GMT on July 31, 2013
If only we had a storm to track in the Atlantic Basin, but hey, we might have to wait a good two weeks before we do.
Member Since: July 31, 2013 Posts: 0 Comments: 925
1. Doppler22
1:26 AM GMT on July 31, 2013
I have a feeling Gil will become stronger then just Cat 1... but we'll see :)
Member Since: February 13, 2012 Posts: 11 Comments: 3768

Viewing: 10 - 1

Page: 1 — Blog Index

Top of Page

About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.

Local Weather

Scattered Clouds
82 °F
Scattered Clouds